The subgenus Dudaica Strand of the genus Drosophila Fallén has been known to comprise only two species: Drosophila (Dudaica) senilis Duda, 1926 (recorded from Indonesia, Philippines, Vietnam, Bhutan, and India) and D.malayana (Takada, 1976) (recorded from Malaysia). In the present study, this subgenus is revised, with D.malayana redescribed and six new species discovered and described from China, Malaysia, and Indonesia: gracilipalpis Katoh & Gao, sp. n., puberula Katoh & Gao, sp. n., albipalpis Katoh, Toda & Gao, sp. n., qiongzhouensis Katoh & Gao, sp. n., orthophallata Katoh, Toda & Gao, sp. n., and dissimilis Katoh & Gao, sp. n. Both morphological and molecular data (DNA barcodes) are used to distinguish the above species. A key to species of this subgenus is provided.
Our intensive surveys of wild drosophilids in East and Southeast Asia discovered a great species diversity (more than 100 putatively new species) of the genus Dichaetophora, which is currently comprised of 67 formally described species assigned into five species groups, i.e., agbo, tenuicauda, acutissima, sinensis and trilobita. In the present study, we delimited species from a huge amount of samples of Dichaetophora and allied taxa (the genus Mulgravea and the subgenus Dudaica of Drosophila) collected from a wide range of the Oriental and east Palearctic regions. We first sorted all specimens into morpho-species, and representative specimen(s) selected from each morpho-species were subjected to barcoding of COI (the cytochrome c oxidase subunit I gene) sequences. The applied ASAP (Assemble Species by Automatic Partitioning) analysis estimated a total of 166 to 168 MOTUs (molecular operational taxonomic units). Integrating this result with morphological evidence from re-examined, detailed structures of male terminalia, we recognized a total of 144 (109 new and 35 known) species in our sample. Out of them, 83 species representing the supraspecific taxa of Dichaetophora, Mulgravea and Dudaica were selected, along with 33 species from major genera and subgenera of Drosophila in the tribe Drosophilini, as in-group and four species from the tribe Colocasiomyini as out-group for phylogenetic reconstruction based on 12 nuclear gene markers. In the trees constructed by the maximum likelihood and Bayesian inference methods, the three focal taxa (i.e., Dichaetophora, Mulgravea and Dudaica) formed a clade provisionally called the "pan-Dichaetophora". Within this large clade, the agbo, tenuicauda, sinensis and trilobita groups of Dichaetophora, Mulgravea and Dudaica were recovered as monophyletic groups, but Dichaetophora and its acutissima group were regarded as paraphyletic. In addition, two clusters were recognized among ungrouped species of Dichaetophora. Thus, the present study has uncovered some issues concerning the taxonomy of the pan-Dichaetophora. Such issues will be addressed elsewhere in the phylogenetic reclassification of the pan-Dichaetophora, along with descriptions/redescriptions of a large number of new/known species delimited in the present study.