研究者データベース

秋元 信一(アキモト シンイチ)
農学研究院 基盤研究部門 生物資源科学分野
教授

基本情報

所属

  • 農学研究院 基盤研究部門 生物資源科学分野

職名

  • 教授

学位

  • 博士(農学)(北海道大学)

ホームページURL

科研費研究者番号

  • 30175161

J-Global ID

研究キーワード

  • 生物地理学   昆虫   系統学   遺伝   形態   性比   自然選択   分類   系統   進化   biogeography   insect   phylogenetics   

研究分野

  • ライフサイエンス / 多様性生物学、分類学
  • ライフサイエンス / 生態学、環境学

職歴

  • 2007年06月 - 現在 - 北海道大学大学院農学研究院 教授 昆虫体系学研究室
  • 1996年10月 - 2007年 北海道大学農学部 昆虫体系学研究室 助教授
  • 1996年 - 2007年 Associate Professor
  • 2007年 北海道大学大学院農学研究院 准教授
  • 2007年 - Professor
  • 1984年10月 - 1996年09月 北海道大学農学部 昆虫学研究室 助手

所属学協会

  • 個体群生態学会   日本動物行動学会   日本行動学会   日本個体群生態学会   応用動物昆虫学会   日本昆虫学会   日本応用動物昆虫学会   

研究活動情報

論文

  • Li Y, Akimoto S
    Entomological Science 21 1 210 - 215 2018年03月01日 [査読有り][通常論文]
     
    The present study evaluated the effectiveness of an aphid-rearing method devised by Milner in 1981 using Acyrthosiphon pisum and its host plant Vicia faba. In the “agar-leaf method,” excised leaves of V. faba were attached to the surface of 1% agar gel containing nutrient solution, and test aphids were transferred onto the leaves. Excised leaves grew in size and weight on the agar medium. Fecundity, longevity, body size and developmental time to adulthood were compared between aphids reared using the agar-leaf method vs. those reared on V. faba seedlings under the same conditions. No significant difference was detected between the two treatments for any of the four parameters, suggesting that the aphids grew and reproduced on excised leaves as successfully as on V. faba seedlings. This method was also useful for inducing males and oviparous females at lower temperature and in short days. Therefore, the present study confirms the effectiveness of using excised leaves on agar and suggests that this method could be applied to the rearing of other aphids, phytophagous mites, leaf miners and leaf-gall formers.
  • Effects of radiation from contaminated soil and moss in Fukushima on embryogenesis and egg hatching of the aphid Prociphilus oriens
    Shin-ichi Akimoto, Yang Li, Tetsuji Imanaka, Hitoshi Sato, Ken Ishida
    Journal of Heredity 109 199 - 205 2018年 [査読有り][通常論文]
  • Female-female competition leads to female-biased sex allocation and dimorphism in brood sex composition in a gall-forming aphid (in press)
    Tong X, Akimoto S
    Functional Ecology 32 0 - 0 2018年 [査読有り][通常論文]
  • Naoki Matsuda, Takashi Kanbe, Shin-ichi Akimoto, Hideharu Numata
    JOURNAL OF INSECT PHYSIOLOGY 101 1 - 6 2017年08月 [査読有り][通常論文]
     
    DMany aphid species switch reproductive modes seasonally, with the sexual generations appearing in autumn. Sexual generations are induced by short days. It has been reported that the appearance of sexual morphs is suppressed by a transgenerational factor (a seasonal timer) over several generations after hatching from over wintered eggs. The present study examined whether the seasonal timer measures the number of days from hatching or the number of generations from hatching using the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae). Effects of temperature and photoperiod on the seasonal timer were also examined by successive rearing. The ability to produce sexual morphs was strongly suppressed in stem mothers (the foundress generation), and gradually recovered over successive generations produced during a few months. The duration for which the seasonal timer could function depended on the number of days from hatching and temperature, but not on photoperiod or the number of generations from hatching. We thus showed in a single study that the seasonal timer of the pea aphid has all the physiological characteristics shown in separate studies in different aphid species.
  • Y. Li, S. Akimoto
    JOURNAL OF EVOLUTIONARY BIOLOGY 30 7 1347 - 1360 2017年07月 [査読有り][通常論文]
     
    Frequency-dependent selection is a fundamental principle of adaptive sex ratio evolution in all sex ratio theories but has rarely been detected in the wild. Through long-term censuses, we confirmed large fluctuations in the population sex ratio of the aphid Prociphilus oriens and detected frequency-dependent selection acting on these fluctuations. Fluctuations in the population sex ratio were partly attributable to climatic factors during the growing season. Climatic factors likely affected the growth conditions of host plants, which in turn led to yearly fluctuations in maternal conditions and sex ratios. In the process of frequency-dependent selection, female proportion higher or lower than ca. 60% was associated with a reduction or increase in female proportion, respectively, the next year. The rearing of aphid clones in the laboratory indicated that mothers of each clone produced an increasing number of females as maternal size increased. However, the mean male number was not related to maternal size, but varied largely among clones. Given genetic variance in the ability to produce males among clones, selection should favour clones that can produce more numerous males in years with a high female proportion. Population-level sex allocation to females was on average 71%-73% for three localities and more female-biased when maternal conditions were better. This tendency was accounted for by the hypothesis of competition among foundresses rather than the hypothesis of local mate competition. We conclude that despite consistent operation of frequency-dependent selection, the sex ratio continues to fluctuate because environmental conditions always push it away from equilibrium.
  • Yerim Lee, Wonhoon Lee, Mariusz Kanturski, Robert G. Foottit, Shin-Ichi Akimoto, Seunghwan Lee
    PLOS ONE 12 4 https://doi.org/10.1371/journa  2017年04月 [査読有り][通常論文]
     
    Aphids are a species rich group comprising many important pests. However, species identification can be very difficult for aphids due to their morphological ambiguity. DNA barcoding has been widely adopted for rapid and reliable species identification as well as cryptic species detection. In this study, we investigated cryptic diversity in the subfamily Calaphidinae (Hemiptera: Aphididae) based on 899 sequences of cytochrome c oxidase I (COI) for 115 morphospecies (78 species collected in this study and sequences of 73 species downloaded from Genbank). Among these 115 morphospecies, DNA barcoding results of 90 (78.3%) species were identical to results of morphological identification. However, 25 (21.7%) morphospecies showed discrepancies between DNA barcoding and traditional taxonomy. Among these 25 discordances, a total of 15 cryptic species were identified from 12 morphospecies. We also found three morphologically distinct species pairs that sharing DNA barcoding. Based on molecular operational taxonomic unit (MOTU) estimation, we discussed on species delimitation threshold value for these taxa. Our findings confirm that Calaphidinae has high cryptic diversity even though aphids are relatively well-studied.
  • 藤井秀司, 中村吉伸, 秋元信一
    表面技術 68 121 - 126 2017年 [査読有り][通常論文]
  • Daisuke Shimizu, Yoshikazu C. Sugano, Kaori Tsuchiya-Suzuki, Gen Ito, Shin-ichi Akimoto
    ENTOMOLOGICAL SCIENCE 19 4 452 - 457 2016年10月 [査読有り][通常論文]
     
    Several insects exhibit morphological asymmetry in the mouthparts or genitalia. In a part of species with asymmetric genitalia, two mirror-image forms of the genitalia are reported to occur in a population. This dimorphism, called chiral dimorphism, is usually observed in male genitalia, but its examples in female genitalia are very limited. Here, we report that the females of the brachypterous grasshopper Parapodisma mikado are equipped with an asymmetric sclerite in the copulatory bursa, and that two mirror-image forms of the sclerite occur in local populations. This dimorphism was detected in all of seven populations examined, and the ratio of the two forms was approximately 2:1 for the right:left forms. In one population, the ratio of the two forms did not vary among three consecutive years. Thus, chiral dimorphism in the female genitalia is kept almost constant spatiotemporally. Mating experiments indicated that the direction of female genitalia did not affect the direction to which the males twist their abdomen (right or left side) during mating or the duration of mating. We propose two hypotheses, a neutral developmental mechanism and sexual conflict, for the maintenance of chiral dimorphism in the genitalia of P.mikado females.
  • Alexander G. Bugrov, Yury Yu Ilinsky, Anton Strunov, Mariya Zhukova, Elena Kiseleva, Shin-ichi Akimoto, Haruki Tatsuta
    ENTOMOLOGICAL SCIENCE 19 3 296 - 300 2016年07月 [査読有り][通常論文]
     
    The brachypterous grasshopper Podisma sapporensis (Orthoptera: Acrididae) is distributed throughout the Sakhalin, Kunashir and Hokkaido Islands. Karyotypes of this species consist of two major chromosomal races with different sex chromosome systems, XO/XX and XY/XX. Molecular phylogeographic analysis of the chromosome races and subraces confirms the genetic divergence of the races and subraces in P.sapporensis. Here we first report that P.sapporensis is infected with Wolbachia consisting of three variants on wsp locus, while gatB locus was monomorphic. Furthermore, observation of cell tissue of P.sapporensis using electron microscopy confirmed the infection of Wolbachia that was inferred from polymerase chain reaction and revealed the distribution of the bacteria in the head, thorax and abdomen of P.sapporensis embryos. Our finding may shed new light on Wolbachia as a possible agent causing hybrid dysfunction resulting from experimental crosses between chromosome races or subraces of P.sapporensis.
  • K. Muramatsu, S. Akimoto
    JOURNAL OF EVOLUTIONARY BIOLOGY 29 7 1423 - 1436 2016年07月 [査読有り][通常論文]
     
    The measurement of the selection gradient is crucial for understanding the magnitude of selection acting directly on a trait and predicting the evolutionary trajectory of that trait. This study evaluated the selection gradient acting on the morphology of the gall-parasitic aphid Tetraneura sorini during the galling process and compared the strength among populations. Gall formers (first instars) frequently fight with conspecifics or heterospecifics for usurping incipient galls using their well-developed hind legs. First instars that successfully acquired galls were found within galls, whereas those that failed were found dead on leaf surfaces. Selection gradients were estimated using logistic stepwise regression and partial least square (PLS) regression. Calculated selection differentials indicated that first instars that secured galls were larger in body size than failed individuals through all populations. However, selection gradients on weapon traits varied largely among populations or among years in the same population. We confirmed microevolutionary changes in the relationship between traits, which accorded with the expectation from changes in the selection gradients. When gall formers were transferred onto developing buds individually, individuals that successfully induced galls had smaller body size than failed individuals. Available evidence suggests that the selection gradient on body size becomes higher with an increasing proportion of T. sorini in the Tetraneura species community. Thus, we concluded that more intense fighting with conspecifics leads to stronger selective pressure on body size, but that selective pressure for each trait is variable depending on differences in the tactics and species composition among populations.
  • アブラムシに学んだ粉体状粘着剤
    藤井秀司, 中村吉伸, 秋元信一
    現代化学 544 7 46 - 49 2016年 [査読有り][通常論文]
  • 生物規範工学に基づく粉体状粘着剤の開発
    藤井秀司, 中村吉伸, 秋元信一
    工業材料 64 3 46 - 49 2016年 [査読有り][通常論文]
  • Genetic variability of the invasive species Metcalfa pruinosa (Say, 1830) (Hemiptera: Flatidae) in the Republic of Korea
    Chang-Gyu Park, Sujeong Min, Gwan-Seok Lee, Sora Kim, Yerim Lee, Seunghwan Lee, Ki-Jeong Hong, Stephen W. Wilson, Shin-ichi Akimoto, Wonhoon Lee
    Journal of Economic Entomology 109 4 1879 - 1906 2016年 [査読有り][通常論文]
  • Wonhoon Lee, Shin-Ichi Akimoto
    JOURNAL OF ASIA-PACIFIC ENTOMOLOGY 18 2 267 - 275 2015年06月 [査読有り][通常論文]
     
    The mitochondrial COI gene has often been utilized as a molecular marker for species identification. However, it has sometimes caused misidentification for some pairs of closely related species. For detecting complementary barcoding loci, we first screened candidate genes by calculating genetic distances within and between species based on 542 sequences collected from the Genbank by using aphids of the Eriosomatini as an example. Of eight genes analyzed, we selected the ATP6 and ATP8 genes, which exhibited lower intraspecific and higher interspecific genetic divergences than did the COI gene. Secondly, we tested the usefulness of these genes by calculating genetic distances between all the combinations of 44 individuals of 23 eriosomatine species for each of the ATP6. ATP8, and COI genes. In the ATP8 gene, the average intraspecific divergence was lowest (0.6%) and the average interspecific divergence was highest (14.7%). The ATP8 gene evolved more rapidly than did the COI gene if genetic divergence between individuals was sufficiently large, whereas it evolved more slowly than did COI if genetic divergence was less than a threshold (1% in COI distance). As a result, species with intraspecific variation in COI and ATP6 exhibited no genetic variation in ATP8. The pattern of genetic divergence in ATP8 well accorded with the pattern of species delimitation in the present taxonomic system. Thus, we conclude that the use of the ATP8 gene in DNA barcoding could improve the accuracy of species identification in the Eriosomatini and possibly other insect groups. (C) 2015 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All rights reserved.
  • Hereditary effects of radioactive fallout on gall-forming aphids and the subsequent recovery process near the Fukushima Daiichi Nuclear Power Plant
    AKIMOTO Shin-ichi
    Journal of Radiation Research 56 (suppl 1) 2015年 [査読有り][通常論文]
  • Masakazu Sano, Shalva Barjadze, Shin-ichi Akimoto
    ZOOLOGY IN THE MIDDLE EAST 61 1 55 - 63 2015年01月 [査読有り][通常論文]
     
    Zelkovaphis caucasica is a little-known Caucasian species of leaf-rolling aphids on Zelkova carpinifolia, and was not included in a previous morphological phylogenetic analysis of the tribe Eriosomatini. We redescribe little-known emigrants of Z. caucasica and describe first instars borne by the emigrants, with keys to species for these morphs of the genus Zelkovaphis. Based on the present specimens and a previously published description, we added Z. caucasica to a published data matrix for Eriosomatini species, and re-analysed the phylogenetic relationships of the tribe Eriosomatini. Successive weighting analysis indicated that Z. caucasica branched off at the base of the Eriosomatini phylogeny, as well as other leaf-rolling species on Zelkova. It is therefore suggested that, like other leaf rollers on Zelkova, Z. caucasica is a relict that has survived in glacial refugia.
  • Tomoko Watanabe, Izumi Yao, Shin-ichi Akimoto
    ENTOMOLOGICAL SCIENCE 18 1 55 - 65 2015年01月 [査読有り][通常論文]
     
    In this paper, we revised the taxonomy of the Tuberculatus quercicola group, myrmecophilous drepanosiphine aphids that are associated with Quercus dentata and Q.crispula in Japan, based on morphometry and molecular phylogeny. This species group has been recognized as T.quercicola with some junior synonyms. Morphometric analysis of 11 morphological characters divided the group into three clusters: (i) the Q.crispula-associated population; (ii) the central Hokkaido group of the Q.dentata-associated population; and (iii) the eastern Hokkaido group of the Q.dentata-associated population. Most parsimony and maximum likelihood analyses of the mitochondrial cytochrome oxidase subunitI COI gene indicated that samples of the T.quercicola group are separated, with high bootstrap supports, into two monophyletic groups that are associated with either Q.dentata or Q.crispula. However, no genetic differentiation was detected between the central Hokkaido group and the eastern Hokkaido group of the Q.dentata-associated population. These results led us to conclude that populations associated with Q.dentata are genetically and morphologically distinct from those associated with Q.crispula, and thus they are in a full specific status. On the other hand, we treated the two local groups of the Q.dentata-associated population as local races based on morphology. We formally redescribed the Q.crispula-associated and Q.dentata-associated populations under the names T.quercicola and T.macrotuberculatus stat. rev., respectively.
  • Koichi Muramatsu, Shin-Ichi Akimoto
    ECOLOGICAL ENTOMOLOGY 39 5 531 - 538 2014年10月 [査読有り][通常論文]
     
    1. Factors affecting host preference in herbivorous insects are actively discussed. Larval performance, competition and predation on each host, and host abundance are reportedly factors affecting the host preference of ovipositing females. In the present study, chronological changes in female host preference were examined by employing a flea weevil species that uses the original host and a newly introduced host simultaneously. 2. Orchestes hustacheiKlima (Coleoptera: Curclionidae) is an aphidophagous flea weevil that oviposits on aphid galls, and the larvae feed on aphids inside. The weevil's native hosts are galls of the Tetraneura species on Ulmus davidiana, while the novel hosts are galls of an introduced species, Paracolopha morrisoni on Zelkova serrata, an introduced hardwood. Choice experiments were conducted using Tetraneura galls and Paracolopha galls and the results were compared with experiments conducted 10 years ago. 3. More than 90% of ovipositing females selected Paracolopha galls. This result is in marked contrast with the result of the 2002 experiment, in which 66.3% of females selected Paracolopha galls. To explore driving forces of the preference change, mortality factors, pupal mass on the two hosts, and temporal changes in the abundance of the host galls were examined. 4. Abundance of Tetraneura galls decreased gradually throughout the last 26 years. By contrast, weevil survival and performance did not vary significantly between the two hosts. Therefore, it is concluded that temporal changes in the relative abundance of two hosts are main factors of the change in host preference.
  • Wonhoon Lee, Yerim Lee, Hyojoong Kim, Shin-Ichi Akimoto, Seunghwan Lee
    JOURNAL OF ASIA-PACIFIC ENTOMOLOGY 17 3 617 - 627 2014年09月 [査読有り][通常論文]
     
    The mitochondrial cytochrome c oxidase subunit I (COI) gene has been utilized as a molecular marker for aphid species identification. However, this gene has sometimes resulted in misidentification because of low interspecific genetic divergences between some species pairs. In this study, to propose new molecular markers for the family Aphididae, we first screened 2289 sequences of 11 genes (COI, COII, CytB, ATP6, IrRNA, srRNA, ITS1, ITS2, EF1a, 18S, and 28S) collected from the GenBank. Among the 11 genes, ATP6 gene revealed the largest generic divergence among congeneric species with the smallest divergence among conspecific individuals; in contrast, species pairs with low genetic divergences (<1%) were not observed. Secondly, for statistically testing the usefulness of ATP6 gene in species identification, we analyzed genetic distances between all of the combinations of 32 individuals of 20 species for both COI and ATP6 genes. The ATP6 gene showed lower intraspecific (on average 0.08%) and higher interspecific (on average 8.28%) genetic distances than the COI gene (on average 0.19% and 6.24%, respectively) for the same pairs of individuals. This study corroborates the usefulness of the ATP6 gene as a new molecular marker that could improve the misidentification problems that are inherent with the COI gene. (C) 2014 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All right reserved.
  • Wonhoon Lee, Seol-Mae Lee, Chang-Seok Kim, Hong-Soo Choi, Shin-Ichi Akimoto, Kyeong-Yeoll Lee, Gwan-Seok Lee
    FLORIDA ENTOMOLOGIST 97 1 155 - 161 2014年03月 [査読有り][通常論文]
     
    Field surveys for the Bemisia tabaci complex were conducted from 2009 to 2013 in Korea, and the results were compared with published data of the B. tabaci complex. Three species, MED, MEAM1, and JpL, were collected from several provinces. The MED was mainly collected in greenhouses, displacing the earlier invasive species, MEAM1, and the JpL species was collected in the field. JpL is newly confirmed as a unique species of B. tabaci species complex in Korea and Japan.
  • Shin-ichi Akimoto
    ECOLOGY AND EVOLUTION 4 4 355 - 369 2014年02月 [査読有り][通常論文]
  • Wonhoon Lee, Takashi Kanbe, Shin-ichi Akimoto
    ZOOKEYS 417 417 37 - 44 2014年 [査読有り][通常論文]
     
    A new species of the genus Megoura, M. lathyricola sp. n., was collected from Lathyrus japonicus subsp. japonicus (Leguminosae) in seashore areas of northern and southern Japan. This species is described and illustrated, and a revised key to the identification of the world species of Megoura is presented.
  • Wonhoon Lee, Jongsun Park, Gwan-Seok Lee, Seunghwan Lee, Shin-ichi Akimoto
    PLOS ONE 8 5 2013年05月 [査読有り][通常論文]
     
    Bemisia tabaci (Hemiptera: Aleyrodidae) is one of the most important insect pests in the world. In the present study, the taxonomic status of B. tabaci and the number of species composing the B. tabaci complex were determined based on 1059 COI sequences of B. tabaci and 509 COI sequences of 153 hemipteran species. The genetic divergence within B. tabaci was conspicuously higher (on average, 11.1%) than interspecific genetic divergence within the respective genera of the 153 species (on average, 6.5%). This result indicates that B. tabaci is composed of multiple species that may belong to different genera or subfamilies. A phylogenetic tree constructed based on 212 COI sequences without duplications revealed that the B. tabaci complex is composed of a total of 31 putative species, including a new species, JpL. However, genetic divergence within six species (Asia II 1, Asia II 7, Australia, Mediterranean, New World, and Sub Saharan Africa 1) was higher than 3.5%, which has been used as a threshold of species boundaries within the B. tabaci complex. These results suggest that it is necessary to increase the threshold for species boundaries up to 4% to distinguish the constituent species in the B. tabaci complex.
  • Wonhoon Lee, Akiko Otsuki, Shin-ichi Akimoto
    Entomological Science 16 2 243 - 247 2013年04月 [査読有り][通常論文]
     
    Tetraneura nigriabdominalis (Sasaki, 1899) is a galling aphid that is distributed widely in Eurasia. In the present study, a diagnostic multiplex polymerase chain reaction (PCR) protocol was developed to discriminate two types of the cytochrome oxidase subunitI (COI) sequences in this species, and its usefulness was examined from 25 samples of T. nigriabdominalis. Multiplex PCR and electrophoresis revealed that 10 and 15 samples had one band of 133bp (typeA) and 426bp (typeB), respectively. This discrimination was identical to the division of the 25 samples based on the alignments of COI sequences (511bp), indicating high accuracy of this protocol in distinguishing the two types. This protocol is useful for studying microgeographic distributions of the two types and genetic diversities in T. nigriabdominalis. © 2012 The Entomological Society of Japan.
  • Wonhoon Lee, Shin-ichi Akimoto
    Entomological Science 16 2 248 - 251 2013年04月 [査読有り][通常論文]
     
    Recently, the number of collection records of Pemphigus galls from Populus nigra has been increasing in Japan. To identify the galls on P. nigra, mitochondrial COI sequences were analyzed from galling aphid samples collected on P. nigra in Tokyo and Hokkaido. From the BLAST search and neighbor-joining (NJ) analysis, the aphid samples were identified as Pemphigus bursarius, which has not been recorded from Japan. Two samples from Tokyo and Hokkaido showed a genetic difference of 0.30%. This result suggests that different strains of P. bursarius might have been introduced into the Japanese islands at least twice. © 2012 The Entomological Society of Japan.
  • Assaying Mitochondrial COI Sequences and Their Molecular Studies in Hexapoda, PART I: From 2000 to 2009.
    Wonhoon Lee, Jongsun Park, Shin-ichi Akimoto, Sora Kim, Yang-Su Kim, Yerim Lee, Kwang-Ho Kim, Si Hyeock Lee, Yong-Hwan Lee, Seunghwan Lee
    Korean Journal of Applied Entomology 52 4 395 - 402 2013年 [査読有り][通常論文]
  • Shin-ichi Akimoto, Taiga Murakami
    BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY 66 11 1475 - 1484 2012年11月 [査読有り][通常論文]
     
    Local mate competition (LMC) has been postulated to be the primary factor of female-biased sex allocation. In animals such as aphids that exhibit seasonal alternations of clonal and sexual reproduction, there is a high possibility of intra-clonal mating and LMC. This possibility is more plausible for more fecund clones, but out-breeding is predicted for less fecund clones. We hypothesize that clones that are more fecund will gain higher fitness returns by reducing investment in males because of more intense LMC among clonal males. We tested this hypothesis by elucidating the clonal sex allocation patterns of the galling aphid Kaltenbachiella japonica, in which inbreeding and LMC appear to be common. Winged mothers that emerge from a gall, belonging to the same clone, produced males and sexual females asexually on a branch, without dispersing to other trees. The heavier the gall, the more winged mothers were produced from the gall. Individual mothers produced a constant number of males and a variable number of females. The clonal sex allocation to males was 39.8 %, on average, and decreased with increasing gall weight. This result showed that clones that were more fecund exhibited more female-biased sex allocation and thus supported our hypothesis. Furthermore, our results corroborated Stubblefield and Seger's hypothesis for sex allocation in patch structure rather than Yamaguchi's constant male hypothesis. We conclude that K. japonica clones are able to adjust their sex allocation patterns adaptively depending on the quality of resources in the galls.
  • Kota Ogawa, Asano Ishikawa, Takashi Kanbe, Shin-ichi Akimoto, Toru Miura
    ZOOMORPHOLOGY 131 3 197 - 207 2012年09月 [査読有り][通常論文]
     
    Wing polymorphisms observed in many Insecta are important topics in developmental biology and ecology; these polymorphisms are a consequence of trade-offs between flight and other abilities. The pea aphid, Acyrthosiphon pisum, possesses 2 types of wing polymorphisms: One is a genetic wing polymorphism occurring in males, and the other is an environmental wing polyphenism seen in viviparous females. Although genetic and environmental cues for the 2 wing polymorphisms have been studied, differences in their developmental regulation have not been elucidated. In particular, there is little knowledge regarding the developmental processes in male wing polymorphism. Therefore, in this study, the development of flight apparatuses and external morphologies was compared among 3 male wing morphs (winged, wingless, and intermediate). These male developmental processes were subsequently compared with those of female wing morphs. Developmental differences between the male and female polymorphisms were identified in flight muscle development and degeneration but not in wing bud development. Furthermore, the nymphal periods of wingless and intermediate males were significantly shorter than that of winged males, indicating the adaptive significance of male winglessness. Overall, this study indicates that the male and female wing polymorphisms are based on different regulatory systems for flight apparatus development, which are probably the result of different adaptations under different selection pressures.
  • Tomohiko Aoyama, Shin-ichi Akimoto, Eisuke Hasegawa
    ARTHROPOD-PLANT INTERACTIONS 6 3 461 - 469 2012年09月 [査読有り][通常論文]
     
    Gall-site selection by the aphid Kaltenbachiella japonica was evaluated in relation to leaf position in a shoot, and gall positions within a leaf. First-instar fundatrices induce closed galls on the midribs of host leaves, and several galls were often induced on one leaf. Leaves with many galls were often withered before emergence of sexuparae from the galls. Within a leaf, gall volume was positively correlated with the sum of lateral-vein length in the leaf segment at which the gall was induced. The observed pattern in gall volume among the leaf segments corresponded with that in the lateral-vein length. These results show that a foundatrix selects the most vigorous position within a leaf to produce more offspring. Although distal leaves grew faster than did basal leaves, gall density was highest on leaves at the middle order when a shoot has more than seven leaves. Optimal gall-site selection seems to be constrained by the asynchrony in timing between the hatching of fundatrices and leaf growth within a shoot. These results suggest that the observed gall distribution is affected by both the distribution of suitable galling sites within a leaf and the synchrony with leaf phenology of the host plant.
  • Wonhoon Lee, Sang-Hyun Koh, Won Il Choi, Chan Sik Jung, Il-Kwon Kim, Bong-Kyu Byun, Bong-Woo Lee, Yang-Su Kim, Jongok Lim, Sora Kim, Shin-ichi Akimoto, Seunghwan Lee
    JOURNAL OF ASIA-PACIFIC ENTOMOLOGY 15 3 363 - 368 2012年09月 [査読有り][通常論文]
     
    A total of 103 barcode (mitochondrial COI) sequences were newly provided for 77 forest insect pests from 66 genera belonging to Coleoptera, Hemiptera, and Lepidoptera. All 77 species had distinct COI sequences, revealing low intraspecific genetic divergence (<1.20%) and high interspecific genetic divergence (>7.30%). Among the 66 genera, 32 COI sequences of 25 species belonging to 16 genera were compared with 280 COI sequences of 117 species belonging to the same 16 genera archived in GenBank, showing that most species were clearly distinguished by barcode sequences. Based on these results, we conclude that a DNA barcode is effective for identifying forest insect pest species. (C) Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2012. Published by Elsevier B.V. All rights reserved.
  • Shin-ichi Akimoto, Ryota Mitsuhashi, Tomoko Yoshino
    POPULATION ECOLOGY 54 3 411 - 419 2012年07月 [査読有り][通常論文]
     
    Several aphid species exhibit female-biased sex allocation. Local mate competition (LMC) has been postulated to be the evolutionary factor of the female-biased sex allocation. We estimated individual sex allocation in the eriosomatine aphid Prociphilus oriens and explained the observed pattern of sex allocation based on a hypothesis other than LMC. On the basis of the relationship between maternal body size and brood size, we estimated the cost of producing a female to be 1.85 times the cost of producing a male. The population-wide allocation to males was 22-24 %. Winged mothers exhibited a large variation in the number of male and female embryos they had, including 23-30 % of winged mothers producing only female embryos. There was polymorphism in the sex-ratio expression. Thus, the constant male hypothesis assuming LMC was not supported. Winged mothers that produced an all-female brood contained larger female embryos than did mothers that produced a bisexual brood. Previous studies have indicated that a large sexual female produces a single large egg, which hatches into a first-instar larva containing a larger amount of gonads. Thus, in eriosomatine aphids, maternal investment in daughters directly affects the potential fecundity of granddaughters, whereas investment in sons does not. We propose a hypothesis that higher fitness returns from maternal investment in daughters than in sons may have primarily led to the evolution of highly female-biased sex allocation in P. oriens.
  • Masakazu Sano, Shin-Ichi Akimoto
    SYSTEMATIC ENTOMOLOGY 36 4 607 - 627 2011年10月 [査読有り][通常論文]
     
    Aphids of the tribe Eriosomatini are typically associated with the tree genera Ulmus and Zelkova as the primary host, on which they induce several types of leaf gall. To elucidate evolutionary changes in the aphid-host associations and gall morphology, phylogenetic relationships were inferred using 36 species (28 in the ingroup) and based on 52 morphological characters. Phylogenetic analysis with equal character weighting led to hundreds of most-parsimonious trees, and the strict consensus of these was poorly resolved. However, the successive weighting of characters yielded three most-parsimonious trees. The strict consensus of these supported the monophyly of the Eriosomatini and the monophyly of most genera. Reconstruction of the aphid-host associations on the consensus tree indicated that the ancestral Eriosomatini were associated with Zelkova and that the association with Ulmus evolved twice independently. Ancestral reconstruction suggests that galls of the leaf-roll type are ancestral to those of the completely and incompletely closed pouch type, and that each type of pouch galls evolved independently. It is suggested that despite early diversification of the Eriosomatini on Zelkova species, Zelkova-associated eriosomatines had become extinct or survived as relict parthenogens on the secondary host due to the elimination of Zelkova in most regions since the late Tertiary. In contrast, two large genera in the Eriosomatini, Eriosoma and Tetraneura, are associated with the largest elm section Ulmus whose elements are distributed widely in Eurasia, including boreal regions. Therefore, the available evidence suggests that the present species diversity and distribution patterns of the eriosomatines have been largely affected by the diversification and extinction of their host plants during the late Tertiary and Quaternary.
  • Zenta Nakai, Tetsuya Kondo, Shin-ichi Akimoto
    ARTHROPOD-PLANT INTERACTIONS 5 3 227 - 234 2011年09月 [査読有り][通常論文]
     
    Hard seeds of some legume species can germinate after seed-feeding insects bore through the seed coat and consequently break seed dormancy. Larvae of bruchine beetles are the main seed feeders attacking many legume species. Boring of the hard seed coat by bruchine beetle larvae enhances the germination percentage of legume species, but consuming too much of a single seed may reduce the chances the seed will survive. We hypothesise that the early mortality of bruchine larvae due to parasitism contributes positively to seed germination because larvae are killed before consuming too large a quantity of the seed. Here, we tested this hypothesis using Lathyrus japonicus seeds and Bruchus loti, the main seed feeder attacking this plant. B. loti larvae were mainly parasitised by two species of idiobiont parasitoids-Pteromalus sp. and Dinarmus sp. The seeds from which Pteromalus wasps emerged germinated more successfully than did the seeds from which B. loti adults emerged. B. loti larvae parasitised by the two wasp species consumed the seeds less intensively than did unparasitised larvae. Thus, the results of experiments supported our hypothesis. However, the germination success varied significantly between the seeds from which Pteromalus and Dinarmus wasps emerged. The difference in the size of seeds the two wasp species chose for parasitism may have influenced the germination percentage.
  • Yoshihiro Hata, Takuto Hashiba, Takashi Nakamura, Masashi Kitamura, Takahide A. Ishida, Shin-ichi Akimoto, Hiroaki Sato, Masahito T. Kimura
    JOURNAL OF FOREST RESEARCH 16 4 309 - 318 2011年08月 [査読有り][通常論文]
     
    Leafminer (Phyllonorycter, Gracillariidae, Lepidoptera) and aphid (Tuberculatus, Aphididae, Hemiptera) composition were studied in three deciduous oak species, Quercus dentata, Q. crispula, and Q. serrata, and their hybrids in Tomakomai Experimental Forest of Hokkaido University, Hokkaido, northern Japan. Identification of trees in this forest was done mainly on the basis of discriminant analysis on leaf morphology with reference to trees in pure Q. dentata and Q. crispula stands and a Q. serrata stand mixed with Q. crispula. The results suggested that hybridization occurred in all combinations (i.e. Q. dentata-Q. crispula, Q. crispula-Q. serrata, and Q. serrata-Q. dentata) and the frequency of hybrids was approximately 10%. The composition of Phyllonorycter and Tuberculatus species differed between Q. dentata and Q. crispula or Q. serrata, but did not differ between Q. crispula and Q. serrata. Thus, Q. dentata could differ from Q. crispula and Q. serrata in chemical properties that determine herbivore host selection, survival, and performance, possibly reflecting eco-physiological differences or phylogenetic distances. The study insects were divided into three groups: species specialized to Q. dentata (three Phyllonorycter and one Tuberculatus species), those to Q. crispula and Q. serrata (six Phyllonorycter and two Tuberculatus species), and a species collected at least from Q. dentata and Q. crispula (one Tuberculatus species). Putative hybrid trees of Q. dentata and Q. crispula harbored both Q. dentata-specific and Q. crispula-specific insects.
  • Yoshikazu C. Sugano, Shin-ichi Akimoto
    BEHAVIORAL ECOLOGY 22 4 701 - 709 2011年07月 [査読有り][通常論文]
     
    We explored why interpopulation crosses often yield mating asymmetry in the grasshopper Podisma sapporensis. Previous studies show that when local populations are crossed, mating frequency differs significantly between the 2 types of heterotypic mating. Mating asymmetry has been explained by 3 hypotheses: female choice, sexual conflict, or the consequences of bottlenecking events (Kaneshiro's hypothesis). The present study assessed which hypothesis best explained the observed mating patterns. Each test population was crossed with populations used in the previous studies. Of the 10 combinations of interpopulation crossing, 6 exhibited significant asymmetry in the frequency of heterotypic mating, 2 had marginal P values, and 2 exhibited symmetry. The mating frequency of one sex of a test population was mainly determined by the mating propensities of 2 crossed populations, but no interactions were detected between the populations. Conspicuous mating asymmetry arose when the 2 populations had greatly different mating propensities (i.e., the combination of vigorous males in 1 population and receptive females in the other population). In contrast, when 2 populations with similar female receptivity were crossed, the mating tended to be assortative. The results of crossing of ancestral and derived chromosomal races do not support Kaneshiro's hypothesis. Furthermore, the finding that mating propensities for both sexes vary greatly among populations does not agree with the female choice hypothesis. In conclusion, our results are consistent with the sexual conflict hypothesis, which postulates that mating vigor/receptivity varies geographically due to antagonistic coevolution between the sexes.
  • Juan M. Nieto Nafria, Colin Favret, M. Pilar Mier Durante, Masakazu Sano, Shin-Ichi Akimoto, Sebastiano Barbagallo, Samiran Chakrabarti, Gary L. Miller, Nicolas Perez Hidalgo, Ge-Xia Qiao, Andrey V. Stekolshchikov, Piotr Wegierek
    ZOOTAXA 2410 2410 65 - 68 2010年03月 [査読有り][通常論文]
  • Debora K. Suzuki, Yukiharu Fukushi, Shin-ichi Akimoto
    ARTHROPOD-PLANT INTERACTIONS 3 4 241 - 247 2009年12月 [査読有り][通常論文]
     
    Some aphid species induce leaf galls, in which the fundatrix parthenogenetically produces many nymphs. In order to ensure high performance, galls have to provide the aphids with sufficient nutrients, in particular, amino acids as a nitrogen source. We tested this hypothesis using six Tetraneura aphid species that induce closed galls. We extracted free amino acids from the whole gall tissues of unit weight and quantified the concentration of each amino acid. There were large differences in the total amino acid concentrations among galls of the Tetraneura species. Tetraneura species in which higher concentrations of total amino acids were found in the gall tended to produce larger numbers of offspring. Of the amino acids found, asparagine was predominant in the gall. The asparagine concentration in T. yezoensis galls was several hundred times as high as in control leaves. We discussed why such a high level of asparagine accumulates in aphid galls.
  • Yoko Matsumura, Shin-ichi Akimoto
    ENTOMOLOGICAL SCIENCE 12 2 215 - 217 2009年06月 [査読有り][通常論文]
     
    The criocerine leaf beetle Lema coronata Baly has extremely long genitalia that reach more than twice the body length in both sexes. We observed mating behavior of this species in the laboratory and inspected the male genital morphology using a scanning electron microscope. The males did not perform pre-copulatory courtship and post-copulatory guarding of the mates, and copulation lasted only for about 30 min. The surface of male genitalia is smooth without any special structures at the tip. A fragment of broken male genitalia was detected in the spermathecal duct of one female. We discuss the adaptive significance of male genital damage and the selective factor of elongated genitalia.
  • Takashi Kanbe, Shin-Ichi Akimoto
    MOLECULAR ECOLOGY 18 5 801 - 816 2009年03月 [査読有り][通常論文]
     
    Many aphid species exhibit geographical variation in the mode of reproduction that ranges from cyclical parthenogenesis with a sexual phase to obligate parthenogenesis (asexual reproduction). Theoretical studies predict that organisms reproducing asexually should maintain higher allelic diversity per locus but lower genotypic diversity than organisms reproducing sexually. To corroborate this hypothesis, we evaluated genotypic and allelic diversities in the sexual and asexual populations of the pea aphid, Acyrthosiphon pisum (Harris). Microsatellite analysis revealed that populations in central Japan are asexual, whereas populations in northern Japan are obligatorily sexual. No mixed populations were detected in our study sites. Phylogenetic analysis using microsatellite data and mitochondrial cytochrome oxidase subunit I (COI) gene sequences revealed a long history of asexuality in central Japan and negated the possibility of the recent origin of the asexual populations from the sexual populations. Asexual populations exhibited much lower genotypic diversity but higher allelic richness per locus than did sexual populations. Asexual populations consisted of a few predominant clones that were considerably differentiated from one another. Sexual populations on alfalfa, an exotic plant in Japan, were most closely related to asexual populations associated with Vicia sativa L. The alfalfa-associated sexual populations harboured one COI haplotype that was included in the haplotype clade of the asexual populations. Available evidence suggests that the sexuality of the alfalfa-associated populations has recently been restored through the northward migration and colonization of alfalfa by V. sativa-associated lineages. Therefore, our results support the theoretical predictions and provide a new perspective on the origin of sexual populations.
  • Several nomenclatural clarifications on genus-group names in the Aphididae (Hemiptera Sternorrhyncha).
    Nieto Nafría JM, Favret C, Akimoto S, Barbagallo S, Chakrabarti S, Mier Durante MP, Miller GL, Perez Hidalgo N, Qiao G-X, Sano M, Stekolshchikov AV, Wegierek P
    Redia 72 3 119 - 123 2009年 [査読有り][通常論文]
  • Seasonal changes in the genetic structure of an aphid-ant mutualism as revealed using microsatellite analysis of the aphid Tuberculatus quercicola and the ant Formica yessensis
    Yao I, Akimoto S
    Journal of Insect Science 9 9 1 - 18 2009年 [査読有り][通常論文]
  • Elzbieta Warchalowska-Sliwa, Haruki Tatsuta, Shin-Ichi Akimoto, Anna Maryanska-Nadachowska, Marek Kowalczyk, Alexander Bugrov
    EUROPEAN JOURNAL OF ENTOMOLOGY 105 2 185 - 196 2008年 [査読有り][通常論文]
     
    The distribution patterns of the X0/XX and neo-XY/neo-XX chromosome races, subraces, and "hybrids" between subraces of the grasshopper P. sapporensis were analyzed. The origin of the observed variation is Robertsonian translocations between a sex chromosome and an autosome, and chromosome rearrangements. The fixation levels of inversions varied depending on geographic regions. No hybrid population is known implying that a strong reproductive isolation system exists in hybrids between the different chromosomal races. The probable reasons for the purity of X0 and neo-XY chromosome races and high chromosome polymorphism in contact zones between chromosomal subraces are discussed. The presence of isolating barriers between chromosome races indicates a review of the taxonomic structure of P. sapporensis is required. It is proposed to divide P. sapporensis into two sibling species, which differ in the chromosome mechanisms of the sex determination system. The analysis of the distribution of chromosomal races and subraces of P. sapporensis allows a reconstruction of the history of this species in the Okhotsk sea region.
  • Elzbieta Warchalowska-Sliwa, Alexander G. Bugrov, Yoshikazu Sugano, Anna Maryaska-Nadachowska, Shin-ichi Akimoto
    EUROPEAN JOURNAL OF ENTOMOLOGY 105 1 45 - 52 2008年 [査読有り][通常論文]
     
    Experimental hybridization of X0 and XY chromosome races of the brachypterous grasshopper P. sapporensis did not reveal pre-zygotic reproductive isolation. However, a partial zygotic barrier was found between the X0-standard race from Shimokawa and XY-standard chromosome race from Akan. Approximately 40% of embryos from females crossed with males from other chromosome races developed parthenogenetically, the remaining embryos were normal heterozygotes. Adult F, males and females from crosses of this type had properly developed testes and ovaries. Non-sister associations and other irregularities in meiosis were not observed in male meiosis. Crossing experiments demonstrated that hybrids between X0 and XY races occur to some extent. The absence of a hybrid zone between the X0 and XY chromosome races may be the result of selection against heterozygotes. Crosses between the XY-Tanno and X0-standard (Teine) subraces resulted in F-1 and F-2 generations in spite of the many chromosome differences between them such as a X-A translocation and fixed pericentric inversions in four pairs of autosomes. These results do not support the hypothesis that chromosomal differences play a key role in restricting gene flow between the X0 and XY races of P. sapporensis.
  • Effects of body size and shape on mating frequency in the brachypterous grasshopper Podisma sapporensis
    Sugano, Y. Sasaki, Y, Akimoto S
    Journal of Orthoptera Research 17 243 - 248 2008年 [査読有り][通常論文]
  • Jun-ichi Takahashi, Tadaharu Yoshida, Toshiyuki Takagi, Shin'ichi Akimoto, Kun S. Woo, Sureerat Deowanish, Randall Hepburn, Jun Nakamura, Mitsuo Matsuka
    APIDOLOGIE 38 4 335 - 340 2007年07月 [査読有り][通常論文]
     
    Genetic variation among Apis cerana japonica isolates from Japan and Apis cerana isolates from the neighboring areas of Russia, South Korea, and Taiwan was determined from DNA sequences of the mitochondrial DNA non-coding region ( between tRNA leu and COII). Three haplotypes were identified among 470 colonies samples at 47 Japanese sites. All isolates from the main Japanese Islands of Honshu, Shikoku, and Kyushu belonged to a single haplotype, a previously reported Japan 1 haplotype. Two new haplotypes were found on the far southern Japanese islands of Amami-Oshima and Tsushima ( the Japan 3 and Japan 4 haplotypes, respectively). The A. cerana from Russia and South Korea were the Japan 1 isolate, the A. cerana from Taiwan was the previously known Taiwan haplotype. Our studies showed little genetic variation in the mtDNA of A. cerana japonica, indicating that this genomic region is of limited use for detecting genetic variation among closely related populations of A. cerana.
  • Haruki Tatsuta, Katsufumi Fujimoto, Koji Mizota, Klaus Reinhardt, Shin-Ichi Akimoto
    BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY 90 4 573 - 581 2007年04月 [査読有り][通常論文]
     
    Recent comparative studies have revealed that the rapid diversity of genitalia is closely related to sexual selection and that genital development interacts with the development of different body parts. Hypotheses about developmental stability due to selection to genital parts were tested by estimating allometric relations in a sexually dimorphic stag beetle Prosopocoilus inclinatus. All genital parts of males scaled to body size with a slope of less than 1 and all but the median lobe (male intromittent organ) showed smaller variability than other body parts. This supported the 'one-size-fits-all' hypothesis, which suggests broad copulation opportunity by males of any size with females within a population. Nevertheless, we found large variation among different genital parts in coefficients of variation and in values of the switch point where the allometric relations varied significantly. These results strongly support the view that developmental trajectories of genital traits are not necessarily integrated. Among the genitalic traits, male intromittent organ and female genitalia exhibited large variability, suggesting a high responsiveness to the selective regimes and physical interaction during copulation. This may account for rapid diversification of genital morphology, even in closely-related populations in beetle species. (c) 2007 The Linnean Society of London.
  • Yasuyoshi Fukunaga, Shin-ichi Akimoto
    ENTOMOLOGICAL SCIENCE 10 1 45 - 53 2007年03月 [査読有り][通常論文]
     
    Larvae of the ladybird Harmonia axyridis are reported to suffer high mortality when they are fed with the aphid Aulacorthum magnoliae associated with the elder Sambucus sieboldiana. In the present study we first examined whether aphid toxicity to H. axyridis was altered when the aphids were reared on different host plants, and second whether some ladybird families could adapt specially to the toxic aphids. Ladybird larvae from each egg batch were divided into two groups; one group was fed with A. magnoliae reared on potato, and the other group was fed with A. magnoliae reared on elder. The ladybird larvae fed with elder aphids suffered significantly higher mortality and grew more slowly than did larvae fed with potato aphids. This result indicates that A. magnoliae aphids absorbed toxic substances or their precursors from S. sieboldiana. We suggest that host association of A. magnoliae with the primary host plant S. sieboldiana has been maintained because of the advantage of deterring predation. Significant and positive correlation was detected across H. axyridis sib families between the mean weight of larvae fed with elder aphids and the mean weight of larvae fed with potato aphids. The hypothesis that some ladybird families adapt specially to the toxic aphids was not supported. However, the available evidence showed that a large amount of genetic variance in performance is maintained in a wild population of the ladybird H. axyridis.
  • Yoshikazu C. Sugano, Shin-ichi Akimoto
    ETHOLOGY 113 3 301 - 311 2007年03月 [査読有り][通常論文]
     
    Crossing of genetically differentiated populations often results in assortative mating within populations. However, asymmetric sexual isolation or negative assortative mating has occasionally been reported. Previous studies suggested that sexual selection or sexual conflicts would lead to asymmetric mating when local populations are crossed. In order to evaluate the extent of assortative or disassortative mating in population crosses, we conducted laboratory crosses using the flightless grasshopper Podisma sapporensis. Crossing was conducted for all pairwise combinations of three populations, 150-240 km from one another - Teine, Shimokawa, and Akan. We found evidence for asymmetric mating for all the pairs of the populations. In particular, when the Teine and Akan populations were crossed, mating in the Teine male-Akan female cross was significantly more frequent than mating in both within-population crosses, whereas mating in the Teine female-Akan male cross was significantly less frequent than mating in both within-population crosses. We examined whether these results can be explained by any of the three hypotheses: (1) Kaneshiro's hypothesis, (2) differentiation in attractiveness, or (3) coevolution between male vigor and female receptivity. All the results were consistent with male vigor differing between populations balanced by different female potential to reject males. The available evidence suggests that antagonistic coevolution between the sexes has led local populations to different equilibria and that crossing of populations at different equilibria has resulted in asymmetry in mating frequencies.
  • Izumi Yao, Haruki Tatsuta, Shin-Ichi Akimoto
    MOLECULAR ECOLOGY NOTES 6 4 1067 - 1069 2006年12月 [査読有り][通常論文]
     
    Using the magnetic particles method, we isolated six polymorphic microsatellite loci from an apterous grasshopper, Podisma kanoi Strozhenko, which shows conspicuous structural variation in chromosomes. The isolated loci were polymorphic, with three to 10 alleles among 20 individuals. Expected heterozygosities ranged from 0.23 to 0.90. These loci can be used to examine the history of population fragmentation and the establishment of chromosomal variation.
  • H Tatsuta, S Hoshizaki, AG Bugrov, E Warchalowska-Sliwa, S Tatsuki, SI Akimoto
    ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA 99 3 457 - 462 2006年05月 [査読有り][通常論文]
     
    The brachypterous grasshopper Podisma sapporensis Shiraki (Orthoptera: Acrididae) consists of two major chromosomal races with different sex chromosome systems. In the X0/XX race, the diploid number of chromosomes is 2n = 23 (X0) in males and 2n = 24 (XX) in females. In the XY/XX race, the diploid number is 2n = 22 (XY) in males and 2n = 22 (XX) in females, owing to Robertsonian fusion between an autosome and the X chromosome. The X0/XX and XY/XX races are allopatrically distributed, and each race contains geographical populations characterized by different chromosomal inversions. A previous hypothesis suggested that the XY/XX race was derived from the X0/XX race. To test this hypothesis, we examined mitochondrial DNA (mtDNA) sequence variation in two regions (cytochrome oxidase subunit II and 16S ribosomal DNA) among 29 P. sapporensis individuals representing five X0/XX and 12 XY/XX populations. The maximum parsimony tree of mtDNA indicated that neither of the two chromosomal races was monophyletic. Northern populations of XY/XX race did not join a clade consisting of more southern XY/XX populations but were included in a clade consisting of X0/XX populations. On the basis of these results, we propose two hypotheses for the differentiation between the northern and southern XY/XX populations. First, the XY/XX karyotype may have occurred more than once. Second, introgression of mtDNA may have occurred across adjacent populations possessing different karyotypes.
  • S Akimoto
    EVOLUTION 60 1 77 - 86 2006年01月 [査読有り][通常論文]
     
    Trade-offs are potentially common among two or more traits whose development is dependent on the same resources. To detect genetic trade-offs, the techniques of quantitative genetics, pedigree analyses, and selection experiments have been used. This study demonstrates genetically based trade-offs between gonads and appendages in hatched larvae of the aphid Prociphilus oriens by focusing on enlarged variance among the families of selfed progeny. The selfed and outbred families were compared in respect to the size of morphological traits, gonad volume, and hatch dates as well as egg volume. Selfing not only increased the among-family variance component in all larval traits examined. but it also increased the mean size of all the morphological traits significantly. In contrast, gonad volume, a fitness component, was reduced with selfing. Calculation of the allometry (log-transformed regression) of larval traits to egg volume indicated that in the outbred group, morphological traits grew slowly relative to egg volume with slopes below 0.25, whereas gonads exhibited isometric growth. With selfing, most morphological traits had significantly steeper slopes. whereas the slope for gonads was greatly decreased. When the effect of egg volume was statistically removed from the means of selfed families, significant negative correlation was detected between the adjusted means of gonad volume and those of tibia length. This result suggests genetic trade-offs between gonad volume and tibia length. Thus, the evidence implies that at the loci governing the development of appendages, the dominant alleles function to canalize the development of tibiae into an optimal size, irrespective of egg volume. It is hypothesized that increased homozygosity of the deleterious recessive alleles reduced gonad volume through increasing the resource allocation to tibiae. The hypothesis of the gonad-appendage trade-off could be applied to explain the phenotypic evolution in some aphid species.
  • K Futami, S Akimoto
    ETHOLOGY 111 12 1126 - 1138 2005年12月 [査読有り][通常論文]
     
    Semelparity is prevalent in arthropod species that exhibit maternal care. Previous hypotheses postulated that long-term maternal care constrains future reproduction in females, leading to the evolution of semelparity. Nevertheless, females may occasionally lose all or part of their offspring because of predation or other causes. Where females lose the first egg mass for any reason, the potential for females to produce an additional egg mass could be adaptive. This potential may be found widely among semelparous arthropods as a conditional strategy. We tested this hypothesis using the crab spider Lysiteles coronatus whose females guard their egg mass against predators. L. coronatus females did not consume food during the 40-d guarding period; this resulted in a 30.2% loss in their weight. When the females were separated from their eggs immediately after oviposition and were provided with food, they resumed feeding and their ovaries redeveloped. Dissection of guarding females indicated that their ovaries developed temporarily during egg guarding and that the developed ovaries were subsequently reabsorbed. These results suggest that the females maintain the potential to produce a second egg mass in case of egg loss, but that this potential declines towards the end of the guarding period. Field observations showed that a small fraction of the females oviposited in late July, when most females had completed egg guarding. The size of the late broods was similar to the oocyte numbers that we found in the females fed in the laboratory. This result suggests that a few females produced a second egg mass after they had lost the first one. Thus, we suggest that facultative second oviposition in L. coronatus females has evolved as an adaptation to egg loss, and that the development of ovaries during the guarding period is intrinsically programmed for compensatory oviposition.
  • M Sano, SI Akimoto
    JOURNAL OF NATURAL HISTORY 39 4 337 - 349 2005年 [査読有り][通常論文]
     
    Aphids of the genus Colopha are represented by three bisexual and three unisexual species. The bisexual species are associated with two Ulmus species that are most closely related, being distributed disjunctively in Europe and eastern North America on the host plants. A new unisexual species of Colopha, collected from Setaria chondrachne (Poaceae) in Japan, is described under the name Colopha setaricola sp. nov. The distribution of the three unisexual species is discussed in relation to aphid-plant associations and historical changes in the distribution of the host plants. It is suggested that these unisexual species have persisted on the secondary hosts through parthenogenetic reproduction since the extinction of the primary host plants, Ulmus species section Blepharocarpus. Therefore, the unisexual species in Colopha exemplify Mordvilko's hypothesis that unisexual species on the secondary host plants have remained as relics in the region where the primary host was once distributed but then became extinct.
  • BUGROV Alexander G, BUGROV Alexander G, WARCHALOWSKA‐SLIWA Elzbieta, AKIMOTO Shin‐ichi
    Entomological Science 8 1 85 - 90 2005年 [査読有り][通常論文]
  • Y Koyama, Yao, I, SI Akimoto
    ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA 113 1 35 - 44 2004年10月 [査読有り][通常論文]
     
    The nutrition hypothesis for the adaptive significance of insect gall formation postulates that galls accumulate higher concentrations of nutritive compounds than uninfested plant tissue, resulting in a high performance of the gall former. This hypothesis has been supported by some taxa of gall insects, but not by taxa such as cynipid wasps. Aphid galls are expected to require higher levels of nitrogen than other insects' galls with a single inhabitant, because aphid galls are required to sustain a number of aphids reproducing parthenogenetically over two generations. The present study tested this hypothesis by evaluating aphid performance and amino acid concentration in phloem sap, using the aphid Rhopalosiphum insertum (Walker) (Homoptera: Aphididae), which establishes colonies on leaves of Sorbus commixta Hedlund or in galls of the aphid Sorbaphis chaetosiphon Shaposhnikov (Homoptera: Aphididae). We prepared the gall and non-gall treatments on trees of S. commixta, in which R. insertum fundatrices were reared and allowed to reproduce. In S. chaetosiphon galls, R. insertum colonies propagated more rapidly, and the second generation grew larger and more fecund than on ungalled leaves. The amount of amino acids exuding from cut galled leaves was fivefold that in ungalled leaves; however, there was no significant difference in the amino acid composition between galled and ungalled leaves. In the intact leaves, total amino acid concentration in the phloem sap declined rapidly from late April to late May; however, the galls retained this high amino acid concentration in developing leaves for 1 month. These results indicate that the improved performance in R. insertum is ascribed to the increased concentration of amino acids in galled leaves. We suggest that S. chaetosiphon galls function to promote the breakdown of leaf protein, leading to an increased performance of gall-inhabiting aphids.
  • T Kurokawa, Yao, I, SI Akimoto, E Hasegawa
    MOLECULAR ECOLOGY NOTES 4 3 523 - 524 2004年09月 [査読有り][通常論文]
     
    Using the magnetic particles method, we isolated six polymorphic microsatellite loci from the pea aphid, Acyrthosiphon pisum (Harris), which feeds on a wide range of legume species. The isolated loci were polymorphic, with three to six alleles in 40 aphids. Expected heterozygosities ranged from 0.12 to 0.65. These loci can be used to quantify clonal diversity and compare genetic population structure between sexual and asexual populations.
  • R Tomisawa, S Akimoto
    ENTOMOLOGICAL SCIENCE 7 1 21 - 30 2004年03月 [査読有り][通常論文]
     
    Although larvae of flea weevils (Curculioninae: Rhamphini) have been known to be leaf miners, larvae of the rhamphine weevil Orchestes hustachei have been found in aphid galls of four Tetraneura species on Ulmus davidiana and in galls of Paracolopha morissoni on Zelkova serrata. This study clarified the feeding habits of O. hustachei larvae and evaluated gall selection by ovipositing females to test the hypothesis of host race formation on their hosts, Tetraneura and Paracolopha galls. When weevil larvae were placed in half-cut galls, they always fed on aphids rather than on gall tissue. When given gall tissue only, all larvae failed to reach adulthood. The number of aphids surviving in a parasitized gall decreased significantly with the development of the weevil larvae. These results suggest that O. hustachei larvae use aphids as their major food source. In the field, ovipositing females did not discern between four Tetraneura species on U. davidiana, in spite of a large difference in suitability as food. Paracolopha morrisoni was introduced into Hokkaido approximately 100 years ago, together with the host plant Z. serrata. It is probable that P. morrisoni has recently come to be used as a host by O. hustachei in Hokkaido. Host choice experiments using Tetraneura sp. O and P. morrisoni galls indicated that female weevils from Z. serrata preferred P. morrisoni to Tetraneura sp. O galls, while females from U. davidiana selected the two types of gall randomly. On Z. serrata, female weevils selected larger P. morrisoni galls, while on U. davidiana, females did not show a preference for gall size. These results suggest that a host shift to P. morrisoni galls may have led to an initial stage of host race formation between the weevil population using Tetraneura galls on U. davidiana, and that using P. morrisoni galls on Z. serrata.
  • AG Bugrov, E Warchalowska-Sliwa, Y Sugano, S Akimoto
    FOLIA BIOLOGICA-KRAKOW 52 1-2 39 - 45 2004年 [査読有り][通常論文]
     
    The results of experimental hybridisation between some chromosome subraces belonging to the X0 and XY chromosome races of the brachypterous grasshopper P. sapporensis are presented. Pre-zygotic reproductive isolation mechanisms in experimental pairs were not confirmed. In crossings of XY-standard x X0-standard and XY-standard x X0-Naganuma chromosome subraces, a zygotic barrier has been found. All embryos of XY-standard x X0-standard crosses and the vast majority of embryos of XY-standard x X0-Naganuma crosses were obtained from female diploid or haploid/diploid cells as a result of parthenogenesis. In very rare cases, when the zygotic barriers had been surmounted, normal embryo heterozygotes and a F1 hybrid generation were obtained in XY-standard x X0-Naganuma crosses. On the contrary, crosses between the XY-Tanno and X0-standard subraces gave viable offspring in spite of many chromosome differences such as a X-A translocation and fixed pericentric inversions in four pairs of autosomes. The results obtained do not support the hypothesis that chromosomal differences play a key role in restricting gene flow between X0 and XY races of P. sapporensis. The presence of crossing barriers explains the phenomena of the purity of the X0 and XY chromosomes races.
  • Akimoto, S, Yamaguchi, Y
    Aphids in a New Millennium. Proceedings of the VIth International Symposium on Aphids 201 - 206 2004年 [査読有り][通常論文]
     
    Sexuparae (autumnal migrants) of the Pemphiginae produce sexual males and females at once, and the sexuals mature without food intake. Hence, sex ratio and the size of sexuals are completely determined by the mothers (sexuparae). This study examined variation in sex ratio among species of Tetraneura and its allied genera. The relative size of sexuals to sexuparae (mothers) varied greatly among species. In species with relatively small sexuals, each sexupara produced both males and females; the number of males was constant and the number of females tended to increase in larger sexuparae. Sex allocation in these species can be explained by Yamaguchi (1985)'s model. In contrast, in species with relatively large sexuals, a considerable fraction of sexuparae produced sexual females alone. Rearing experiments in T. sp. O showed that sexuparae from one clone produced sexual females only, while those from other clones produced both males and females. In species with relatively large sexuals, the relative investment in both sexes was highly female-biased. Local mate competition has been assumed to be responsible for female-biased sex allocation. However, this comparative study suggests that sex allocation is also affected by the relative size of sexuals. The size of sexual females is highly correlated with that of first instar fundatrices (gall makers). Therefore, it is suggested that advantage of larger size in fundatrices, for example in fighting, has led to larger body size in sexual females and more highly female-biased sex allocation.
  • Takahashi, J., Akimoto, S., Martin, S.J., Tamukae, M. and Hasegawa, E. Mating structure and male production in the giant hornet Vespa mandarinia (Hymenoptera: Vespidae). Applied Entomology and Zoology, 39: 343-349, 2004*
    2004年 [査読無し][通常論文]
  • AG Bugrov, E Warchalowska-Sliwa, Y Sugano, S Akimoto
    FOLIA BIOLOGICA-KRAKOW 52 1-2 39 - 45 2004年 [査読有り][通常論文]
     
    The results of experimental hybridisation between some chromosome subraces belonging to the X0 and XY chromosome races of the brachypterous grasshopper P. sapporensis are presented. Pre-zygotic reproductive isolation mechanisms in experimental pairs were not confirmed. In crossings of XY-standard x X0-standard and XY-standard x X0-Naganuma chromosome subraces, a zygotic barrier has been found. All embryos of XY-standard x X0-standard crosses and the vast majority of embryos of XY-standard x X0-Naganuma crosses were obtained from female diploid or haploid/diploid cells as a result of parthenogenesis. In very rare cases, when the zygotic barriers had been surmounted, normal embryo heterozygotes and a F1 hybrid generation were obtained in XY-standard x X0-Naganuma crosses. On the contrary, crosses between the XY-Tanno and X0-standard subraces gave viable offspring in spite of many chromosome differences such as a X-A translocation and fixed pericentric inversions in four pairs of autosomes. The results obtained do not support the hypothesis that chromosomal differences play a key role in restricting gene flow between X0 and XY races of P. sapporensis. The presence of crossing barriers explains the phenomena of the purity of the X0 and XY chromosomes races.
  • Ohno, S., Hoshizaki, S., Ishikawa, Y., Tatsuki, S., and Akimoto, S Allometry of male genitalia in a lepidopteran species, Ostrinia tatipennis (Lepidoptera: Crambidae). Appl. Entomol. Zool. 38: 313-319, 2003*
    2003年 [査読無し][通常論文]
  • Takahashi J., Akimoto S., Nakamura J. and Hasegawa E. Mating frequency and genetic relatedness of workers in the hornet Vespa analis (Hymenoptera: Vespidae). Entomological Science, 6, 119-123, 2003*
    2003年 [査読無し][通常論文]
  • Takahashi J., Nakamura J., Akimoto S. and Hasegawa E. Kin structure and colony male reproduction in the hornet Vespa crabro (Hymenoptera:Vespidae). Journal of Ethology, 22:43-47, 2003*
    2003年 [査読無し][通常論文]
  • Yao, I, SI Akimoto
    ECOLOGICAL ENTOMOLOGY 27 6 745 - 752 2002年12月 [査読有り][通常論文]
     
    1. Mutualistic interactions between aphids and ants are mediated by honeydew that aphids produce. Previous work showed that when attended by the ant Formica yessensis Forel (Hymenoptera: Formicidae), nymphs of the aphid Tuberculatus quercicola (Matsumura) (Homoptera: Aphididae) developed into significantly smaller adults with lower fecundity than did nymphs that were not ant attended. 2. This study tested the hypothesis that this cost of ant attendance arises through changes in the quality and quantity of honeydew. Ant-attended and ant-excluded aphid colonies were prepared in the field. The composition and concentration of amino acids were compared between the honeydew produced by ant-attended colonies and that produced by ant-excluded colonies. 3. The aphids excreted smaller droplets of honeydew, but also excreted them more frequently, in ant-attended colonies than in ant-excluded colonies. The honeydew of ant-attended aphids contained more types of amino acid, and a significantly higher total concentration of amino acids, than did the honeydew of ant-excluded aphids. 4. These results suggest that the increase in the concentration of amino acids in honeydew leads to a shortage of nitrogen available for aphid growth and reproduction, resulting in lower performance under ant attendance. 5. With the advance of seasons, a significant reduction was found in both the total free amino acid concentration in phloem sap and the frequency of honeydew excretion; however the total concentration of amino acids in the honeydew did not vary significantly during the seasons, suggesting that aphids keep the quality of honeydew constant in order to maintain ant visitation.
  • Nectar secretion from damaged shoots in Quercus mongolica and exploitation of the response by ants; herbivory by ants
    H. Yorozuya, S. Akimoto
    Entomological Science 5 275 - 280 2002年 [査読有り][通常論文]
  • Takahashi, J., Akimoto, S., Hasegawa, E. & Nakamura, J. "Queen mating frequencies and genetic relatedness between workers in the hornets Vespa ducalis (Hymenoptera: Vespidae)". Applied Entomology and Zoology, 37: 481-486, 2002*
    2002年 [査読無し][通常論文]
  • Takahashi J., Nakamura J., Sasaki M., Tingek S. and Akimoto S. "New hplotypes for non-coding region of mitochondrial DNA in cavity-nesting honey bees, Apis koschevnikovi and A. nuluensis". Apidologie 33, 25-31, 2002*
    2002年 [査読無し][通常論文]
  • S. Akimoto and Y. Narita. "Alternating temperatures enhance the hatchability of overwintered eggs of the gall- forming aphid Paracolopha morrisoni (Aphidoidea: Eriosomatinae)". Entomological Science, 5:11-18, 2002.*
    2002年 [査読無し][通常論文]
  • Yao, I, S Akimoto
    OECOLOGIA 128 1 36 - 43 2001年06月 [査読有り][通常論文]
     
    Mutualistic interactions between aphids and ants are mediated by the honeydew produced by aphids. Previous work showed that when attended by the ant Formica yessensis, nymphs of the aphid Tuberculatus quercicola developed into significantly smaller adults with lower fecundity than when not ant-attended. This study tested the hypothesis that this cost of ant attendance arises through changes in the quality and quantity of honeydew. Ant-attended and ant-excluded aphid colonies were prepared in the field, and the sugar concentration and sugar composition of the honeydew of ant-attended colonies were compared with those of ant-excluded colonies. The frequency and amount of honeydew excretion were also quantified in the two types of colonies. The aphids excreted smaller droplets of honeydew more frequently in ant-attended colonies than in ant-excluded colonies. There was no significant difference in total sugar concentration between the honeydew of ant-attended aphids and ant-excluded aphids. However, ant-attended aphids produced honeydew containing a significantly lower proportion of glucose and higher proportions of sucrose and trehalose than did ant-excluded aphids. These results suggest that the enhanced rate of honeydew-excretion behavior under ant attendance led to changes in the aphid's physiological status. We suggest that the increase in the proportions of sucrose and trehalose in honeydew leads to a shortage of carbohydrates available for energy metabolism, resulting in lower performance of the aphids under ant attendance.
  • H Tatsuta, K Mizota, SI Akimoto
    ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA 94 3 462 - 466 2001年05月 [査読有り][通常論文]
     
    Males of Lucanus maculifemoratus Motschulsky are markedly variable in size of body and heads. In this study, we investigated the possible causes that affect the development of the male heads and genitalia by comparing variability of weight among body parts and allometry in each part to bed, size. Genitalia varied least in weight among males, and the frequency, distribution of their weight was approximately normal. In contrast, the frequency distribution of head weight exhibited a conspicuous skew. Significant positive allometry was found for heads, whereas genitalia showed significant negative allometry. Heads that are used for fighting are allometrically highly variable, whereas genitalia are highly stable, suggesting variable strategies for obtaining mates M while maintaining equally sexually functional genitalia. The low variability and low allometric coefficient with body size for genitalia may indicate that the development mechanism for genitalia is separated from that for other body parts, as a result of sexual selection.
  • H. Tatsuta , K. Miura and S. Akimoto. Morphological differentiation among neighboring populations in the brachypterous grasshopper Parapodisma subastris (Orthoptera: Acrididae). Entomological Science, 4:315-320, 2001*
    2001年 [査読無し][通常論文]
  • E Warchalowska-Sliwa, AG Bugrov, H Tatsuta, S Akimoto
    FOLIA BIOLOGICA-KRAKOW 49 1-2 63 - 75 2001年 [査読有り][通常論文]
     
    Seven categories of B chromosomes found in the brachypterus grasshopper Podisma sapporensis from Hokkaido populations differ in structure, size, and C-band content. The interchange between B and one autosome from M-3 and sporadically M-7 was observed in most of the populations examined. Such an interaction between standard and non-standard chromosomal set provides an insight into the integration of supernumerary chromosome. In addition, C-hrterochromatin polymorphism was also identified in male karyotypes in some populations. These facts indicate P. sapporensis is a highly polymorphic species from the cytogenetic point of view.
  • Yao, I, H Shibao, S Akimoto
    OIKOS 89 1 3 - 10 2000年04月 [査読有り][通常論文]
     
    The defensive effects of ants against aphid predators have been well documented in the mutualistic relationship of aphids and their attending ants. However, it is not clear whether ant attendance has any direct effect on the aphids' growth and reproduction. Through field experiments, this study evaluates the benefits and, in particular, the costs of ant attendance to aphid colonies, focusing on the drepanosiphid aphid Tuberculatus quercicola which is associated with the Daimyo oak, Quercus dentata, and which is always attended by the red wood ant Formica yessensis. Ant attendance was clearly beneficial to the aphid; the exclusion of ants led to a significant increase in the extinction rate of aphid colonies. However, MANOVA and randomized block ANOVA indicated that in colonies continuously attended by ants, aphids had significantly smaller body size and produced a smaller number of embryos than in colonies isolated from ants when they were reared under homogeneous host conditions free from natural enemies. Thus, ant attendance had a negative influence on the growth and reproduction of the aphids, even though it contributed to the greater longevity of the aphid colonies. We hypothesize that ant-attended aphids are under intense selective pressures that act against aphid clones which fair to attract many ants, so that aphids have developed an adaptive mechanism to allocate a larger fraction of resources to the honeydew when they are requested to do so by the ants in order to ensure the ants' consistent visitation.
  • H. Tatsuta and S. Akimoto. Variability in phenotypic covariance structure of female genitalia in the brachypterous grasshopper, Podisma sapporensis (Orthoptera: Podisminae). Annals of the Entomological Society of America, 93(1):127-132, 2000*
    2000年 [査読無し][通常論文]
  • Distribution pattern of the XO/XX and neo-XY/neo-XX chromosomal races of the brachypterous grasshopper Podisma sapporensis (Orthoptera: Acrididae) in Hokkaido, northern Japan
    A. G. Bugrov, E. Warchalowska-Sliwa, H. Tatsuta, E. A. Perepelov, S. Akimoto
    Entomological Science 3 4 693 - 699 2000年 [査読有り][通常論文]
     
    A. G. Bugrov, E. Warchalowska-Sliwa, H. Tatsuta, E. A. Perepelov and S. Akimoto. Distribution pattern of the XO/XX and neo-XY/neo-XX chromosomal races of the brachypterous grasshopper Podisma sapporensis (Orthoptera: Acrididae) in Hokkaido. Entomological Science, 3(4) :693-699, 2000*
  • H. Tatsuta, G. Ito, A.G. Bugrov, A. Tchernykh and S. Akimoto. Multivariate morphometrics of two Podisma species in Kunashiri Island. Applied Entomology and Zoology, 35(1):1-8, 2000*
    2000年 [査読無し][通常論文]
  • Bugrov, A. G., Warchalowska-Sliwa, E., Ito, G. and Akimoto, S. C-banded karyotypes of some Podisminae grasshoppers (Orthoptera, Acrididae) from Japan. Cytologia 65: 351-358, 2000*
    2000年 [査読無し][通常論文]
  • Akimoto, S.:"Host preference and galling success in closely related aphids, Tetraneura yezoensis and T. radicicola (Pemphigidae: Aphidoidea), associated with the Japanese elm", Applied Entomology and Zoology, 34(1):31-38 (1999)*
    1999年 [査読無し][通常論文]
  • SI Akimoto
    ECOLOGICAL ENTOMOLOGY 23 3 229 - 237 1998年08月 [査読有り][通常論文]
     
    1. The performance of gall-forming aphids is largely dependent on the timing of egg hatch relative to host budburst. This study examined the mode of natural selection acting on egg-hatching time and the extent of its genetic variance in a Tetraneura aphid. 2. The budburst time of the primary host of the aphid varied greatly among individual trees. Egg hatch on a host tree was often asynchronous with host budburst. 3. Transplant experiments indicated that egg-hatching time was subject to heterogeneous selective pressures in heterogeneous host environments. 4. Hatching time was compared between half-sib families. Small nymphs in a half-sib family tended to hatch later, and this resulted in large within-family variance in hatching time. 5. Small nymphs that hatched late were likely to be selected out during the galling process. Thus, these nymphs may be produced not as bet-hedging but due to maternal effects. When such maladapted nymphs were not included in analysis, a significant amount of additive genetic variance was detected in hatching time. 6. Heterogeneous selection, coupled with density-dependent regulation of population on respective host trees, probably maintains additive genetic variance in this trait.
  • A. Kanazawa, A.Tozuka, S. Akimoto, J. Abe and Y.Shimamoto: "Phylogenetic relationships of the mitochondrial genomes in the genus, Glycine subgenus Soja." Genes & Genetic Systems, 73(4):255-261 (1998)*
    1998年 [査読無し][通常論文]
  • S. Akimoto: "Soldie-like nymphs in the pemphigid aphid Colophina clematicola (Pemphigidae: Aphidoidea)." Entomological Science,1:33-36 (1998)*
    1998年 [査読無し][通常論文]
  • H. Tatsuta and S. Akimoto: "Sexual differences in the pattern of spatial variation in the brachypterous grasshopper, Podisma sapporensis (Orthoptera: Podisminae)." Canadian Journal of Zoology, 76:1450-1455 (1998)*
    1998年 [査読無し][通常論文]
  • Sakamaki, Y. and Akimoto, S-I. : "Wing shape of gelechiid Moths and its Functions : analysis by elliptioc Fourier transformation", Annals of The Entomological Society of America, 90(4) : 447-452 (1997)*
    1997年 [査読無し][通常論文]
  • Akimoto, S. and Yamaguchi, Y. : "Gall usurpation by the gall- forming aphid, Tetraneura sorini (Insecta Homoptera)", Ethology, Ecology and Evolution, 9(2) : 159-168 (1997)*
    1997年 [査読無し][通常論文]
  • Tatsuta, H. and Akimoto, S. : "Temporal morphological variation of the brachypterus grasshopper, Podisma sapporoensis (Orthoptera : Podisminae)", Applied Entomology and Zoology, 32(3) : 527-529 (1997)*
    1997年 [査読無し][通常論文]
  • S Akimoto
    INSECTES SOCIAUX 43 1 1 - 15 1996年 [査読有り][通常論文]
     
    Colony defense has been reported in a limited number of species of aphids. This paper examines which life-historical traits have promoted the evolution of colony defense using two kinds of deterministic simulation models. These models postulate that first-instar larvae can counterattack predators and that the duration of this instar stage is a variable, subject to selection. Prolonging the first-instar span increases the proportion of defenders in the colony, while it results in a delay in reproduction. By calculating the optimal first-instar span, the optimal defensive effort of a colony under various ecological conditions could be estimated. Simulations based on the general model, which regards the number of adults maturing in a period as performance, predicted that a lower birthrate leads to a longer first-instar span (larger investment in defense). This condition also allowed the evolution of dimorphism in the first-instar span, which may ultimately result in the appearance of soldiers. Where birthrate declines with time, the first-instar span was predicted to be prolonged in later stages. Colony duration had little influence on the optimal first-instar span if the season is long enough to repeat generations. The galling-aphid model that assumes a fixed number of generations predicted that a longer duration of colonies leads to a longer first-instar span, but that birthrate has little influence on the optimal first-instar span. A tendency in defense reported in pemphigid aphids was consistent with the prediction from the galling-aphid model.
  • "Soldier aphids found in the closed gall of Paracolopha morrisoni (Aphidoidea : Pemphigidae)", Japanese Journal of Entomology, 64 : 379-384 (1996)*
    1996年 [査読無し][通常論文]
  • S. Akimoto, K. Ozaki, and Y. Matsumoto : "Production of first-instar defenders by the Hormaphidid gall-forming aphid Hamamelistes cristafoliae living anholocyclically on Betula maximowicziana", Japanese Journal of Entomology, 64 : 879-888 (1996)*
    1996年 [査読無し][通常論文]

書籍

  • 地球と生命の進化学 新自然史科学I
    北大図書刊行会 2008年

その他活動・業績

  • Akimoto S. Phylogeny, evolution and biogeography of gall-forming aphids (Insecta: Homoptera): a case study from the Eriosomatini. In: Mawatari, S. F. & Okada, H. (eds.), Neo-Science of Natural History: Integration of Geoscience and Biodiversity Studi・・・
    2004年 [査読無し][通常論文]
     
    Akimoto S. Phylogeny, evolution and biogeography of gall-forming aphids (Insecta: Homoptera): a case study from the Eriosomatini. In: Mawatari, S. F. & Okada, H. (eds.), Neo-Science of Natural History: Integration of Geoscience and Biodiversity Studies, Proceeding of International Symposium on "Dawn of a New Natural History: Integration of Geoscience and Biodiversity Studies", March 5-6, 2004, Sapporo, pp. 19-26.*
  • アブラムシの生物学<石川統編著>
    東京大学出版会 2000年 [査読無し][通常論文]
  • 『親子関係の進化生態学』<斉藤 裕>
    北海道大学図書刊行会 1996年 [査読無し][通常論文]
  • 『日本動物大百科, 昆虫1』<石井 実, 大谷 剛, 常喜 豊>
    平凡社 1996年 [査読無し][通常論文]

受賞

  • 2005年 日本昆虫学会2005年学会賞
  • 2005年 Award for best paper (Entomological Society of Japan)

共同研究・競争的資金等の研究課題

  • 福島県高線量地域における降下物のアブラムシ集団への遺伝的影響と回復過程の解明(代表)
    日本学術振興会:科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 秋元 信一
  • 短翅性バッタに見られる染色体変異の進化的起源と分布拡大過程の解明(分担)
    日本学術振興会:科学研究費補助金 基盤研究(B)
    研究期間 : 2013年04月 -2017年03月 
    代表者 : 立田晴記
  • アブラムシおよびその他昆虫における無性生殖種の進化的起源:交雑起源説の検証
    日本学術振興会:科学研究費補助金 基盤研究(B)
    研究期間 : 2011年04月 -2015年03月 
    代表者 : 秋元 信一
  • アブラムシにおける性比と性的二型の進化:繁殖集団の遺伝学的分析と系統学的検証
    日本学術振興会:科学研究費補助金 基盤研究(C)
    研究期間 : 2008年04月 -2011年03月 
    代表者 : 秋元 信一
  • アブラムシにおける種分化機構の解明
    日本学術振興会:科学研究費補助金 基盤研究(B)
    研究期間 : 2005年04月 -2008年03月 
    代表者 : 秋元 信一
  • アリ-アブラムシ間相利共生関係の進化的ダイナミックス
    日本学術振興会:科学研究費補助金 基盤研究(C)
    研究期間 : 2003年04月 -2005年03月 
    代表者 : 秋元 信一
  • アブラムシ類における無性生殖集団の起源と系統関係の解明
    日本学術振興会:科学研究費補助金 基盤研究(C)
    研究期間 : 2000年04月 -2003年03月 
    代表者 : 秋元 信一
  • アブラムシ個体群における近親交配の程度とそれが発生・形態におよぼす影響
    日本学術振興会:科学研究費補助金 基盤研究(C)
    研究期間 : 1998年04月 -2000年03月 
    代表者 : 秋元 信一
  • 寄主植物の多様性がゴール形成アブラムシの集団に与える進化的影響
    日本学術振興会:科学研究費補助金 基盤研究(C)
    研究期間 : 1995年04月 -1997年03月 
    代表者 : 秋元信一
  • insect-plant interactions Genetic differentiation of local populations Speciation in aphids Taxonomy of aphids

教育活動情報

主要な担当授業

  • 昆虫系統進化学演習
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 農学院
    キーワード : 種分化、量的遺伝学、進化学、系統学、最節約原理、遺伝的多様性、共進化
  • 生物共生科学
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 農学院
    キーワード : 共生理論、生物間の捕食連鎖、共生関係、植物の根圏機能、持続的生態系、共生の代謝生理、共生的農業システム Theory for Symbiosis, Predatory Chain among Organism, Symbiotic Relationship, Sustainable Eco-system, Physiology of Symbiosis, Agro-system enhansing Symbiotic Mechanism
  • 生物共生科学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 農学院
    キーワード : 共生理論、生物間の捕食連鎖、共生関係、植物の根圏機能、持続的生態系、共生の代謝生理、共生的農業システム Theory for Symbiosis, Predatory Chain among Organism, Symbiotic Relationship, Sustainable Eco- system, Physiology of Symbiosis, Agro-system enhansing Symbiotic Mechanism
  • 生物生態・体系学総論Ⅰ
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 農学院
    キーワード : 系統学、進化、最節約原理、系統樹、最尤法、距離法、ネットワーク、分類群、博物館、標本、多様性データベース
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 地球生命史, 生物進化, 地球環境変化, 気候変動, 生物大量絶滅, 生物多様性, 古生物科学, 地質年代
  • 多様性生物学概論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 理学院
    キーワード : 生物多様性,進化,絶滅,種分化,動物,植物,統計モデリング
  • 生物生態・体系学総論Ⅱ
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 農学院
    キーワード : 野生動植物の生態・進化と保全, 生物多様性
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 系統学、進化、最節約原理、系統樹、最尤法、距離法、ネットワーク、分類群、博物館、標本、多様性データベース
  • 環境昆虫学概論
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 農学部
    キーワード : 昆虫、環境、進化、生態、系統、共進化、生活史、適応、自然選択、性選択、形態、交尾器、総合的害虫管理、薬剤抵抗性、有機農業、天敵、生物農薬
  • 生物学Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 分類、系統、進化、有性生殖、生物の多様性、遺伝、集団、植物の生理、生態、繁殖、種、生物の形態,生命活動の多様性
  • 動物学夏季実習
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 農学部
    キーワード : センサス、フィールド科学センター、野外実習、密度、多様性
  • 動物生態学概論
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 農学部
    キーワード : 生態、進化、適応、遺伝、保全、生物多様性
  • 教科教育法(農業I)
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 教育学部

大学運営

委員歴

  • 2017年01月 - 現在   一般社団法人 日本昆虫学会   学会長
  • 2015年04月 - 現在   北海道環境影響評価審議会   北海道環境影響評価審議会委員
  • 2014年01月 - 2015年12月   日本昆虫学会   編集委員長
  • 2013年01月 - 2014年12月   日本昆虫学会   評議員
  • 2010年01月 - 2011年12月   日本昆虫学会   評議員   日本昆虫学会
  • 2006年 - 2008年   日本昆虫学会   庶務幹事   日本昆虫学会


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