Taxonomy, Phylogeny And Reproductive Ecology Of The Colocasiomyia Gigantea Species Group From Yunnan

The gigantea species group is one of the six species groups of the genusColocasiomyia. All the three previously described species of this group are knownbreeding on the inflorescence and infructescence of the subfamily Monsteroideae, thusexhibiting peculiar reproductive habits. In this study, Colocasiomyia flies collected frominflorescence/infructescence in Baihualing, Baoshan, Yunnan were identified based oneither morphological characters or DNA barcodes (partial sequence of the mitochondrialcytochrome c subunit I, i.e., COI gene), and as a result, four new species belonging to thegigantea group were recognized. Diagnostic nucleotide sites in the COI alignment wererecognized for species identification. We also determined partial coding (i.e, exon)sequences of two nuclear genes (alphaTub84B and Ef2b), and reconstructed thephylogenetic relationship among all the seven species of the gigantea group with theconcatenated sequences of the three genes COI, alphaTub84B and Ef2b, using the Bayesianinferring and maximum likelihood methods. Then, the four new species, C.longifilamentata Li&Gao, sp. n., C. longivalva Li&Gao sp. n., C. hailini Li&Gao sp. n.,and C. yini Li&Gao, sp. n. were described, and a morphological key was provided for theidentification of species in the gigantea group. In addition, the reproductive ecology of thenew species C. hailini and C. longifilamentata were investigated via either field orlaboratory methods; two discrete egg phenotypes, which were assumed to be conspecific(of C. hailini) based on morphological and barcode information, were confirmed. Theadaptive significance of the seasonal egg dimorphy (a kind of polyphenism) was discussedfrom a view point of evolutionary ecology. Finally, we discussed the geographicaldistribution and host selection of the gigantea group in light of the distribution of the hostplant lineage (the Rhaphidophora clade), and also discussed the importance of the giganteagroup in study of evolution of the pollination mutualism between Colocasiomyia flies andaroid plants.