Meeting Abstract

99.1  Sunday, Jan. 6  Deciphering the evolutionary history and developmental mechanisms of a complex sexual ornament: the abdominal appendages of Sepsidae (Diptera) BOWSHER, J H*; ANG, Y; FERDERER, T; MEIER, R; North Dakota State University; National University of Singapore; North Dakota State University; National University of Singapore julia.bowsher@ndsu.edu

Male abdomen appendages are a novel trait found within Sepsidae (Diptera). Here we demonstrate that they are likely to have evolved once, were lost three times, and then secondarily gained in one lineage. In order to establish the developmental mechanism for appendage formation, we studied the development of the sternites in males and females for three species with and one species without the appendages. For each species and sex the number of cells in the ventral histoblast nests was counted. The species without appendages has similar cell counts in all sternites regardless of sex. All species with appendages have elevated cell counts for the fourth segment, which gives rise to the appendages. In Perochaeta dikowi, which reacquired the trait, the female also has an elevated cell count on the fourth segment despite the fact that females do not develop appendages. This difference suggests that P. dikowi has evolved a different developmental mechanism for appendage formation.