Abstract
The origin of biota and dispersal routes in eastern Taiwan have long intrigued scientists. The Loxoblemmus appendicularis complex (LAC) is a group of common crickets that inhabit grasslands and woodlands in the low hills of Taiwan. Because of their limited flight capability, the genetic diversification of LAC crickets may have been affected by geographic isolation imposed by mountains and rivers, as well as by historical Pleistocene climatic fluctuations. In this study, we conducted phylogeographic analyses of Southeastern LAC crickets to investigate their patterns of differentiation, possible refugia, and dispersal routes. Results from mitochondrial 16S rRNA gene and amplified fragment length polymorphism (AFLP) suggest that LAC crickets likely dispersed to southeastern Taiwan through low hills and lower mountains in southern Taiwan approximately 0.21 million years ago (Mya) during the middle Pleistocene, highlighting the isolating effects of the Central Mountain Range. Two subsequent northward dispersals, originating from a southern population and crossing major rivers, were estimated to have occurred around 0.12-0.14 Mya. These findings indicate that major rivers did not consistently impede the dispersal of Southeastern LAC lineage. These populations may have experienced recent expansion following isolation in refugia during the late Pleistocene. Genetic homogeneity and higher genetic diversity suggests the existence of three potential refugia for the Southeastern LAC. Moreover, STRUCTURE analysis based on AFLP data revealed varying levels of genetic admixture between two genetic clusters, suggesting recent divergence or possible gene flow between northern and southern populations. Overall, this study demonstrates how geographic barriers, such as mountains and rivers, and Pleistocene glaciations have shaped the current phylogeographic patterns and genetic diversification of LAC crickets in southeastern Taiwan.