Aedeagus morphology as a discriminant marker in two closely related Cactophilic species of Drosophila (Diptera; Drosophilidae) in South America

Fernando F Franco,Fábio M Sene,Maura H Manfrin,Luciano F Costa,Pedro R.R Prado

doi:10.1590/s0001-37652006000200002

Abstract

Drosophila serido and D. antonietae are sibling species belonging to the Drosophila buzzatii cluster. Morphologically, they can only be discriminated by quantitative traits. In this paper we analyze the length and equalized average curvature of four regions of the aedeagus of D. antonietae and D. serido. Specimens of D. serido and D. antonietae were classified correctly 96.74% of the time. Based only on the variable that most contributed to the discrimination of the groups (equalized average curvature of the arch IV of the aedeagus), we observed significant intraspecific morphological divergence in D. serido in relation to the D. antonietae, in agreement with other markers. The high morphological divergence in equalized average curvature of the arch IV of the aedeagus shows that this region evolved faster than others, since the divergence of the two species. The importance of the present study to the understanding of the genetic basis that controls the formation of the aedeagus, in the species of the Drosophila buzzatii cluster, is discussed.

Highlights

Morphological characters have been used historically in evolutionary and taxonomic studies
Normal curves obtained by the average and standard deviation of the two groups in relation to the canonical scores are shown in Figure 2, in which we can observe the discrimination between D. antonietae and D. serido
Our data confirm the existence of quantitative differences in morphological characteristics of the aedeagus of the individuals analyzed, making possible the discrimination of the D. serido from D. antonietae

Summary

Introduction

Morphological characters have been used historically in evolutionary and taxonomic studies. The lack of qualitative morphological differences among sibling species makes it difficult to establish the diagnostic morphological characteristics among them. The morphology of the aedeagus (external male genitalia) is of extreme importance in the taxonomic characterization of Drosophila species (Vilela 1983, Silva and Sene 1991, Liu et al 1996, Moreteau et al 2003, Kullikov et al 2004), as well as in other Diptera. Quantitative variations in morphological characteristics of the aedeagus have been used for discrimination of the sibling species of Drosophila (Silva and Sene 1991, Kullikov et al.2004). A marked difference exists in the aedeagi form (shape + size) among them, which is considered the main diagnostic character in the group (Vilela 1983)

Methods

Results

Conclusion