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Keywords:

  • deformation;
  • hypercephaly;
  • Malaysia;
  • Oriental Region;
  • sexual dimorphism

Abstract

We describe three new species of the Drosophila obscura species group, D. hypercephala, D. hideakii and D. quadrangula Gao & Toda, spp. nov., all discovered from high altitudes (>1500 m) on Mt Kinabalu, Sabah, Malaysia. These are the southernmost distribution records of the D. obscura group in the Oriental Region. The three new species are each morphologically similar to different species of the Old World D. obscura species subgroup. This suggests that they are descendants of different founder species that independently colonized the tropics from the subtropical or temperate zones during the glacial ages. The new species D. hypercephala is hypercephalic not only in males but also, although less distinct, in females, unlike other hypercephalic drosophilid species in which only males are hypercephalic. This new finding of a hypercephalic species from the subgenus Sophophora, of which species are relatively easy to culture in the laboratory and include the model species such as D. melanogaster and D. pseudoobscura, will promote genetic analyses on the development and the evolution of hypercephaly.