Genetic and physiological variation among sexual and parthenogenetic populations of Asobara japonica (Hymenoptera: Braconidae), a larval parasitoid of drosophilid flies

Abstract

Abstract. We studied variations in genetic, physiological, and ecological traits, and the phylogenetic relationship among sexual and parthenogenetic populations of Asobara japonica, a larval parasitoid of drosophilid flies, in order to understand how they adapt to local environments and have differentiated. The strain from Iriomote-jima (IR) differed from other Japanese strains in the nucleotide sequences of its cytochrome oxidase subunit I (COI) and in not undergoing diapause and having a shorter preimaginal period and a higher adult tolerance of cold. The strains other than IR showed a low level of nucleotide variation in COI but varied in their mode of reproduction; the strains from the Ryukyu Islands were sexual, whereas those from the main islands of Japan and Ogasawara were parthenogenetic. In addition, strains from higher latitudes generally showed a high incidence of diapause, although there were some exceptions. On the other hand, preimaginal period and adult cold tolerance varied little among the strains excluding IR, and pupal cold tolerance, oviposition preference and incidence of parasitism varied little among the strains including IR. Evolution and environmental adaptations in this species are discussed, particularly focusing on parthenogenetic populations.

Occasional males in parthenogenetic populations of Asobara japonica (Hymenoptera: Braconidae): low Wolbachia titer or incomplete coadaptation?

“…The uninfected arrhenotokous strain from Amami exhibited the same haplotype as two thelytokous strains from Hirosaki and Sendai. More or less the same pattern, based on 645 bp of the mitochondrial CO1 gene, was found by Murata et al (2009).…”

“…The strains were kindly provided by M.T. Kimura from cultures derived from field samples, collected along the entire length of Japan, described in Mitsui et al (2007) and Murata et al (2009). Maps of the sampled locations can be found in both papers.…”

“…Fertile crosses between males and females from Iriomote and Amami, and between (natural and cured) males from Kagoshima and females from Amami indicate that individuals from these strains belong to the same species (Murata et al, 2009;Kraaijeveld et al, 2011b). However, Murata et al (2009) also found indications for weak asymmetrical sexual isolation, suggesting that Iriomote and Amami have been geographically isolated for a long time.…”

“…The mitochondrial variation among the five thelytokous strains suggests that multiple infection events have occurred and that the Wolbachia infection has spread (partly) via horizontal transmission. The five infected thelytokous strains were collected from the two Japanese main islands, with 1580 km distance between the northernmost location Sapporo and the southernmost location Kagoshima (for maps of the locations see Mitsui et al, 2007 andMurata et al, 2009). The distance between the two main Japanese islands is very small (20 km) and the Wolbachia infection probably spread easily between the two islands.…”

Abundance and host associations of parasitoids attacking frugivorous drosophilids on Iriomote-jima, a subtropical island of Japan

“…The presence of drosophilid species resistant to A. japonica may result from longer evolutionary interactions between A. japonica and potential hosts on subtropical Iriomote-jima than mainland Japan. Based on the fact that the main-island populations are parthenogenetic whereas the Iriomote-jima population reproduces sexually, it is assumed that this species origi-nated in the subtropics and that its recent colonization of temperate regions is associated with the evolution of parthenogenesis (Murata et al, 2009).…”