Chromosomal inversions effect body size and shape in different breeding resources in Drosophila buzzatii.

P J Fernández Iriarte,F M Norry,E R Hasson

doi:10.1038/sj.hdy.6800280

Abstract

The cactophilic Drosophila buzzatii provides an excellent model for the study of reaction norms across discrete environments because it breeds on rotting tissues (rots) of very different cactus species. Here we test the possible effects of second chromosome inversions on body size and shape (wing loading) across suitable natural breeding substrates. Using homokaryotypic stocks derived from several lines homozygous for four naturally occurring chromosomal inversions, we show that arrangements significantly affect size-related traits and wing loading. In addition, karyotypes show differing effects, across natural breeding resources, for wing loading. The 2st and 2jz(3) arrangements decrease and the 2j arrangement increases wing loading. For thorax length and wing loading, karyotypic correlations across host plants are slightly lower in females than in males. These results support the hypothesis that these traits have a genetic basis associated with the inversion polymorphism.

Highlights

Several studies have shown that inversion polymorphisms in Drosophila affect size-related traits (Ruiz et al, 1991; Hasson et al, 1992a) and body shape (Bitner-Matheet al, 1995)
The cactophilic species Drosophila buzzatii provides an excellent model for the study of reaction norms across discrete environments because it breeds on rotting tissues of very different cactus species that coexist within a given locality (Hasson et al, 1992b)
In O. ficus-indica, D. buzzatii express the biggest size and increase wing loading, whereas in O. vulgaris and T. terschekii there is not a clear trend. In the former D. buzzatii express intermediate values for thorax length (TL), head width (HW) and TL/wing length (WL) ratio while in T. terschekii intermediate values are observed for WW, WL and face width (FW)

Summary

Introduction

Several studies have shown that inversion polymorphisms in Drosophila affect size-related traits (Ruiz et al, 1991; Hasson et al, 1992a) and body shape (Bitner-Matheet al, 1995). Other studies have shown that body size (Thomas and Barker, 1993; Nunney and Cheung, 1997), wing shape (Cavicchi et al, 1991; BitnerMatheand Klaczko, 1999) and a composite trait related to flight ability, wing loading (Stalker, 1980), respond to environmental variation in complex ways (Loeschcke et al, 1999), suggesting that reaction norms in these traits may be part of an adaptive exophenotypic response in Drosophila. The cactophilic species Drosophila buzzatii provides an excellent model for the study of reaction norms across discrete environments because it breeds on rotting tissues (rots) of very different cactus species that coexist within a given locality (Hasson et al, 1992b). Adaptive strategies in cactophilic Drosophila may be related to the temporal and spatial predictability of different cactus species (Etges, 1993; Fanara and Hasson, 2001). Given the potential importance of the maintenance of the genetic variation in heterogeneous environments, it is of considerable interest to test whether or not particular genotypes respond differentially to these discrete environments

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