Despite the intensive use of the Leptopilina genus and its drosophilid hosts as model-systems in the study of host-parasitoid interactions, the diversity and distribution of the species occurring in the Asian region remain elusive. Here we report the phylogeny of Japanese Leptopilina species attacking frugivorous drosophilid flies, japonica occurring in Japan, and L. j. formosana occurring in Taiwan. According to these results, we discuss the evolution, speciation and colonization history of Japanese Leptopilina species.

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The phylogeny of Colocasiomyia (Drosophilidae) is analysed using data for 70 morphological characters, many of which are re‐evaluated from or added to those used previously, for an expanded taxon sample of 24 Colocasiomyia ingroup species. A special focus is put on three species, of which two have remained unresolved for their relationships to other Colocasiomyia species, and the other is a newly discovered species. The analysis results in a single, most parsimonious cladogram, in which a clade comprising the three focal species is recognized along with other clades recovered for the known species groups of Colocasiomyia. Based on this, a new species group—the gigantea group—is established, including Colocasiomyia gigantea (Okada), C. rhaphidophorae Gao & Toda, n.sp. and C. scindapsae Fartyal & Toda, n.sp. These species of the gigantea group breed on inflorescences/infructescences of the subfamily Monsteroideae (Araceae) exceptionally among Colocasiomyia species, most of which use plants of the subfamily Aroideae as their hosts. Colocasiomyia gigantea uses Epipremnum pinnatum (L.) Engler, C. rhaphidophorae uses Rhaphidophora hookeri Schott and C. scindapsae uses Scindapsus coriaceus Engler as their hosts. The host plants of the gigantea group are epiphytes and differ in the structure of spadix and the fruiting process from those of the Aroideae. To understand how the species of the gigantea group adapt to properties of their host plants, their reproductive ecology—most intensively that of C. gigantea—is investigated. The lifecycle of C. gigantea is characterized by its relatively slow embryonic development (taking approximately 6 days), the very long duration of the full‐grown first instar within the egg capsule (approximately three months) until dehiscence of host infructescence, and its relatively fast larval and pupal development (taking approximately 11 or 12 days). Some morphological adaptations and the reproductive strategy in terms of ‘egg size vs. number’ trade‐off are discussed in relation to their reproductive habits and peculiar lifecycles.

The diversity, abundance and association of frugivorous drosophilids and their parasitoids were studied in Bogor, Indonesia (the tropical region), and compared with the results in Iriomote-jima (the subtropical region) and Tokyo (the temperate region).In the collections of adult drosophilid flies by traps baited with banana in wooded areas, the number of commonly observed frugivorous drosophilid species (i.e. species that occupied more than 0.5% of total drosophilid samples) was 10 in Bogor and nine in Iriomote-jima, more than in Tokyo (six species), probably reflecting the high diversity and abundance of fruits. The rate of parasitism was very high in Bogor, especially in species of the Drosophila ananassae and immigrans species groups. The diversity of parasitoids attacking frugivorous drosophilids was higher in Bogor and Iriomote-jima than in Tokyo, possibly due to the high species diversity of host drosophilids.Parasitoids generally showed wider latitudinal distributions than drosophilids. No remarkable difference was observed in the host range among tropical, subtropical and temperate parasitoids.

The phylogeny of the Colocasiomyia cristata species group is reconstructed as a hypothesis, based on DNA sequences of two mitochondrial and six nuclear genes and 51 morphological characters. The resulting tree splits this species group into two clades, one of which corresponds to the colocasiae subgroup. Therefore, a new species subgroup named as the cristata subgroup is established for the other clade. Within the cristata subgroup, three subclades are recognized and each of them is defined as a species complex: the cristata complex composed of five species (including three new ones: C. kinabaluana sp. nov., C. kotana sp. nov. and C. matthewsi sp. nov.), the sabahana complex of two species (C. sabahana sp. nov. and C. sarawakana sp. nov.), and the xenalocasiae complex of five species (including C. sumatrana sp. nov. and C. leucocasiae sp. nov.). There are, however, three new species (C. ecornuta sp. nov., C. grandis sp. nov. and C. vieti sp. nov.) not assigned to any species complex. In addition, breeding habits are described for four cristata-subgroup species, each of which monopolizes its specific host plant. And, data of host-plant use are compiled for all species of the cristata group from records at various localities in the Oriental and Papuan regions. The evolution of host-plant selection and sharing modes is considered by mapping host-plant genera of each species on the phylogenetic tree resulting from the present study.

How insects evolve resistance or counter-resistance against antagonists is a basic issue in the study of host-parasitoid coevolution. One of the factors that affect their coevolution is fitness costs of resistance and counter-resistance. Here, we assess fitness costs of resistance against the parasitoid Leptopilina victoriae in Drosophila bipectinata on the basis of selection experiments. We made a base population by mixing three geographic fly populations that differed in resistance. After six generations of free mating, the base population was divided into four populations, two for selection of resistance against a L. victoriae population and two for control. Resistance increased rapidly in response to selection and reached a very high level within four generations in the two replicated selected populations, while resistance of the control populations remained low at least for 20 generations. High resistance of the selected populations was maintained at least for 10 generations even if selection was stopped. Comparison of life history and stress tolerance revealed that both selected populations had lower female longevity than the two control populations, and at least one of the selected populations had shorter thorax length and lower female desiccation tolerance and adult heat tolerance than both or either of the control populations. On the other hand, selected populations had higher male starvation tolerance and longevity than control populations.There were no significant differences in resistance against another population of L. victoriae and two other parasitoid species between the selected and control populations.These results suggest that the resistance against the L. victoriae population in D.bipectinata may incur some but not so high costs and act parasitoid-species-and/or parasitoid-population-specifically. 3 Key wordsArtificial selection • coevolution • specificity • trade-offs 4 IntroductionAll insects have immune systems to defend themselves from infection of pathogens or parasites. However, their immune systems are not always effective, because some pathogens and parasites have means to avoid being detected by the host immune systems or suppress host immune responses (Edison et al. 1981;Shelby and Webb 1999; Eleftherianos et al. 2007). To cope with such enemy's adaptations, host insects often intensify their immune responses or modify their immune systems (Strand and Pech 1995; Carton et al. 2008). One of the important factors that affect such parasitoid-host coevolution is the costs of resistance and counter-resistance (Doebeli 1997;Sasaki and Godfray 1999). A powerful tool to examine these costs is the study of correlated responses to artificial selection. Kraaijeveld and Godfray (1997) tabida compared with the control populations (Fellowes et al. 1999). Thus, the resistance mechanism of D. melanogaster has parasitoid-species-or parasitoid-population-specific components.The above selection studies were based on within-population genetic variation.Resistance and counter-resistance aga...

For successful parasitism, parasitoid females must oviposit and the progeny must develop in individual hosts. Here, we investigated the determinants of host acceptance for oviposition and host suitability for larval development of Drosophila parasitoids from Bogor and Kota Kinabalu (≍1,800 km northeast of Bogor), Indonesia, in tropical Asia. Asobara pleuralis (Ashmead) from both localities oviposited frequently (>60%) in all of the drosophilid species tested, except the strain from Kota Kinabalu oviposited rarely (10%) in Drosophila eugracilis Bock & Wheeler. Leptopilina victoriae Nordlander from both localities only oviposited frequently (>77%) in species from the Drosophila melanogaster species group except D. eugracilis (<3.7%), whereas Leptopilina pacifica Novković & Kimura from Bogor oviposited frequently (>85%) only in species from the Drosophila immigrans species group. Thus, host acceptance appeared to be affected by host taxonomy, at least in Leptopilina species. Host suitability varied considerably, even among closely related drosophilid species, which suggests that the host suitability is at least in part independent of host taxonomy and that it has been determined via parasitoid-host coevolutionary interactions (i.e., arms race). Host acceptance did not always coincide with host suitability, i.e., parasitoids sometimes oviposited in unsuitable host species. Geographic origin strongly affected the host acceptance and suitability in the A. pleuralis-D. eugracilis parasitoid-host pair, whereas it only weakly affected the acceptability and suitability in other parasitoid-host combinations.

Flies of the Colocasiomyia toshiokai species group depend exclusively on infl orescences/infructescences of the aroid tribe Homalomeneae. The taxonomy and reproductive biology of this group is reviewed on the basis of data and samples collected from Southeast Asia. The species boundaries are determined by combining morphological analyses and molecular species delimitation based on sequences of the mitochondrial COI (cytochrome c oxidase subunit I) gene. For the phylogenetic classifi cation within this species group, a cladistic analysis of all the member species is conducted based on 29 parsimony-informative, morphological characters. As a result, six species are recognised within the toshiokai group, including one new species, viz. C. toshiokai, C. xanthogaster, C. nigricauda, C. erythrocephala, C. heterodonta and C. rostrata sp. n. Various host plants are utilised by these species in different combinations at different localities: Some host plants are monopolized by a single species, while others are shared by two or three species. C. xanthogaster and C. heterodonta cohabit on the same host plant in West Java, breeding on spatially different parts of the spadix. There is a close synchrony between fl ower-visiting behaviour of fl ies and fl owering events of host plants, which indicate an intimate pollination mutualism.