Meeting Abstract
Geographical parthenogenesis refers to the common association of widely dispersed asexual populations with more narrowly distributed sexual populations. Some research supports the adaptive advantages of temporary or facultative asexuality as a colonization strategy. Other work points to a non-adaptive rationale for the association of asexuality to habitat margins, because parthenogens frequently display hybrid ancestry, genome duplications often precede parthenogenetic ability, and admixture of sexuals and asexuals within populations is expected to be rare. We explore support for these hypotheses in two Japanese species of harvestmen, Leiobunum manubriatum and Leiobunum globosum. Reproduction in these species proceeds with or without male fertilization, and female-biased localities are common in high-latitude and elevation habitat margins. Karyotypic and cytometric work indicates L. globosum is entirely tetraploid, while L. manubriatum has both diploid and tetraploid lineages. Using next-generation sequence data, we estimated genetic differentiation, diversity, and mitonuclear discordance in females collected at high and low latitude and elevation in order to evaluate genetic indicators of adaptation in specimens from marginal habitat. Our results point to northward expansion of L. manubriatum, coupled with support for increased male gene flow. Specimens from localities in the Tohoku and Hokkaido regions were indistinct, particularly in L. globosum, potentially due to little mitochondrial differentiation or haplotypic variation. Ongoing molecular work will serve to elucidate reproductive mode within and potential for hybridization between these putative populations.
