In this study we screened for sequence polymorphisms at one mitochondrial (Cytochrome Oxidase subunit I) and one nuclear (Internal Transcribed Spacer 1) gene 33 populations of the cave cricket genera Diestrammena, Paradiestrammena, Eutachycines and Paratachycines from Southern China (three Provinces: Jiangxi, Guangdong and Guizhou), Laos and Thailand. Twenty-five of these populations were assigned to the genus Diestrammena, subgenus Gymnaeta, while the remaining eight belonged to the genera Paradiestrammena (3), Eutachycines (3) and Paratachycines (2). The degree of troglomorphosis varies among them; some populations are blind and depigmented, some have fully developed eyes, while some others show intermediate characteristics. Phylogenetic searches carried out on the two gene partitions separately revealed multiple cases of incongruence but only three of them were statistically significant and were hence removed from the subsequent analyses based on the combined data set. Our data do not support Diestrammena as monophyletic while representatives of Paradiestrammena, Eutachycines and Paratachycines were clustered together; the validity of some nominal species was confirmed molecularly but we also revealed a large number of deeply divergent lineages. Populations with the same degree of troglomorphosis do not cluster together. We identified five major clades; divergence among them (and in a few circumstances also within them) is always higher than the DNA barcode threshold for intraspecific comparisons in insects. In two circumstances, the same clades (III and V) are co-distributed in geographically distinct areas (Provinces). This geographical distribution might be explained by envisioning an evolutionary scenario based on zones of secondary admixture following epigean dispersal among lineages that diverged in allopatry.
