Molecular phylogeny and systematics of the subgenus Oxyphortica Duda from the Oriental region (Diptera: Drosophilidae: Stegana)

Phylogenetic analysis of DNA sequences of three mitochondrial (COI, COII and ND2) and six nuclear (28S, atpA, CAD, EF2, HSPA4 and TUBA1) gene regions recovered a novel lineage (Crypsistegana subgen.n.) and lends support to the monophyly of the subgenus Oxyphortica. Integrating molecular and morphological evidence, we revise the taxonomic status of Oxyphortica, reclassify species of uncertain affinity into four new species groups (adentata, geisson, polystylata and subconvergens) and place five new species discovered from southern China in Crypsistegana subgen.n. and two species groups (geisson and polystylata) of Oxyphortica, respectively. To evaluate the performance of individual genes in phylogenetic inference, the phylogenetic informativeness profiles were generated. The results reveal mitochondrial loci possess much greater phylogenetic signal to resolve species-level relationships, while nuclear loci perform better at the subgenus level within the genus Stegana. In addition, both tectonic and climatic events appear to have played pivotal roles in the diversification of Oxyphortica. The present distribution pattern of this subgenus might have been shaped from a rapid adaptive radiation in Southwest China as a secondary area of endemicity.