Population genetic structure and microendemism in aquatic Empididae (Diptera) in transient tufa biotopes on tropical karst

Abstract

ABSTRACTPopulation genetic structure of an aquatic insect obligately associated with fragmented and temporally unstable tufa formations on tropical karst was investigated using mtCOI sequence data. A median‐joining (MJ) haplotype network calculated from 263 COI sequences of Hemerodromia conspecta Plant (Diptera: Empididae: Hemerodromiinae) sampled from its 12 known sites in Thailand indicated a high level of genetic structure and identified five distinct lineages present in geographically close localities. Haplotype diversity (h), nucleotide diversity (π) and pairwise comparisons of FST suggested considerable differentiation among populations but evolutionary distance judged from the Kimura 2‐parameter was too low (0.98–4.58) to establish any lineage as a discrete species, however, it was considered as evidence of ongoing processes of allopatric speciation. Mismatch distribution analysis and low nucleotide diversity associated with high haplotype diversity in three lineages was consistent with the sudden expansion model but very low haplotype diversity of a fourth lineage provided strong indication that it had historically experienced a profound population bottleneck. Long path lengths in the MJ network suggested prolonged isolation of the four major lineages and mismatch distribution analysis indicated that their populations experienced a late Pleistocene expansion that was complete by the early Holocene, entirely consistent with evidence for a climatically driven period of late Cenozoic tufa deposition followed by late Quaternary decline. The allopatric distribution of geographically fragmented and genetically distinct lineages suggests that vicariant diversification is driving active processes of speciation and microendemism occurring within multiple microrefugia set within a wider matrix of unsuitable habitats.