Analysis of morphological differences in the male genitalia of Drosophila buzzatii, D. koepferae and their hybrids

SOTO, IGNACIO; VALERIA CARREIRA,; JOSÉ FANARA, JUAN; ESTEBAN HASSON,

Florianopolis, Brasil

Congreso; 50° Congresso Brasileiro de Genética; 2004

Sociedad Brasilera de Genética

The shape of an organ is a trait with a complex quantification. Drosophila buzzatii and Drosophila koepferae are otherwise sinmorfic species only distinguishable by their characteristic male genitalia morphology (aedeagus). Recent studiesrevealed the existence of gene flux between this species via fertile hybrid females providing an excellent model for the study of the genetic basis of speciation. We are reporting the first study of the genetic structure underlying the aedeagus morphology variability and its intra and interespecific differences. Due to the lack of reliable homologous landmarks we utilized elliptic Fourier descriptors (EFDs) for the description andquantification of aedeagi of both species and F1 interespecific hybrids. This procedure provides a descriptive function that can reproduce the original outline of the organ at any desire degree of precision, just depending on the number of estimated variables (coefficients). This coefficients were use in a Principal Components analysis in order to asses the morphological variability of the sample. Multivariate Analysis of Variance detected significant morphological differences of shape among species and hybrids. Discriminant factors recognized both species in all cases and hybrids in an important proportion suggesting that the EFDs contains enough information of the original organ shape. Regarding hybrid genitalia morphology, regressions suggest a complex scenario ofdominance that mainly depends on the particular interspecific cross under study. Size of the organ positively correlates with wing length and widthbut this traits do not correlate with the main shape factor of the organ. This results will allow the study of aedeagus as a quantitative trait thus performing the search of genes involved in the differential development of this organs among species with the consequent improvement on the comprehension of the speciation mechanisms.