Phylogenetic position of Chinese endemic Drosophila curviceps species subgroup in the Drosophila immigrans group.

In order to investigate the phylogenetic position of Chinese endemic Drosophila curviceps species subgroup within the D. immigrans group on DNA molecular level, the ITS1 region of ribosomal DNA and part of Adh gene for 12 species represented all the five subgroups in D. immigrans group were sequenced. Molecular phylogenetic trees were constructed by using parsimony and neighbor-joining methods based on ITS1, Adh and combined sequences. In the molecular trees, species of the D. curviceps subgroup cluster together, strongly supporting establishment of a separating subgroup suggested in an initial morphologic study. This subgroup is the sister taxa of the D. quadrilineata subgroup. They are the younger subgroups, splitting about 3.4 Mya. The D. hypocausta subgroup is located at the base of the molecular tree, diverged first in this group about 9.2 Mya. Taking the geographic distribution into account, we can conclude that D. curviceps subgroup originated from tropic zones, agreeing with the previous morphologic and biogeographic suggestions. The position of D. neohypocausta was also discussed in this report and it seems that it is closer to the D. immigrans subgroup than to the D. hypocausta subgroup.