Morphological analysis of male mating organ in the Drosophila virilis species group: a multivariate approach

Abstract

The shape of the male mating organ differs among 11 closely related species of the Drosophila virilis species group. Multivariate analyses of variation of a suite of 35 morphological traits (indices) describing the phallus shape were carried out in order to characterize interspecies variability of the traits. An overwhelming majority of the traits displayed species-specific variability. The main result of the investigation was the revelation of the differences involved in the traits studied in the evolution of the D. virilis species group. The structure of species-specific variability of some traits was discovered to be in accordance with the generally accepted taxonomy of the species group, while that of other traits required isolation of D. virilis per se from lummei phylad (former virilis phylad), and confirmed separation of montana phylad into three subphylads: montana proper, littoralis and kanekoi. Several subsets of traits having separate variability were determined in different parts of the male mating organ which correspond to spots of evolutionarily significant variability.

Coevolution of male and female reproductive structures in Drosophila

“…Whilst a formal analysis of such relationships is beyond the scope of the present paper, it will be a promising avenue to pursue in future studies for a truly integrated understanding of the evolution of male and female reproductive structures. Kulikov et al (2004) analysed quantitative differences among Drosophila species of the D. virilis group with respect to 35 morphological traits related to the shape of the phallus (aedeagus) which was previously demonstrated as being the best species specific organ (Gornostaev et al 1998). They identified nine independent groups having variation in the shape of the phallus and were able to determine major evolutionary hot spots.…”

“…Clear-cut differences in the structure of the genitalia (or of equivalent structures as the copulatory organs in spiders, Huber 2004) are often found even between closely related species that are otherwise difficult to classify using phenotypic characteristics (Kulikov et al 2004;Franco et al 2006). Within species however, the male genitalia are generally found to be extremely morphologically stable (but see Garnier et al 2005;Franco et al 2006;Reinhardt et al 2007;Andrade et al 2009) even when many other traits may exhibit geographic, and sometimes local variability.…”

Evolution of the male genitalia: morphological variation of the aedeagi in a natural population of Drosophila mediopunctata

“…Our results indicate that inversion DS-PC0 was responsible for localized changes in the aedeagus and global changes, in the wing. This association is promising, since it presumably allows us to initially estimate the direction of the level of population change; and secondly, it detects the parts of both organs submitted to more important evolutionary changes (Kulikov et al 2004). Nonetheless, caution is advisable, as the RW3 withholds only part of the form variation.…”

“…For instance, in the repleta group D. serido and D. borborema are morphologically similar species, but Tidon-Sklorz and Sene (1995) distinguished one from the other based on measurements extracted of the aedeagus outline, applying ''traditional'' multivariate morphometric techniques. Kulikov et al (2004) described the phallus shape, using multivariate analyses of variation, for various closely related species of the Drosophila virilis group.…”

Phenotypic variation of the Aedeagus of Drosophila serido vilela & sene (Diptera: Drosophilidae)

“…For this reason, in the Drosophila genus, as well as other insect taxa, the aedeagus is an important organ for taxonomic purposes (Silva & Sene 1991, Kullikov et al 2004, Franco et al 2006. The D. repleta group, for example, includes more than 100 Neotropical species and the aedeagus morphology has been considered the most important diagnostic character of this group (Vilela 1983).…”