The evolutionary history of Drosophila buzzatii. XXIV. Second chromosome inversions have different average effects on thorax length

Abstract

We demonstrate a genetic correlation between rearrangements of the second chromosome of D. buzzatii and thorax length, as a measure of body size. The results indicate that 2j and 2jz3 arrangements are correlated with large size, whereas 2st arrangement is correlated with small size. Some inversions (2st and 2jz3) show dominant effects and others (2j/f3) exhibit overdominance. These results show that at least 25 per cent of body size variation may be accounted for by the studied karyotypes. The possible integration of the genotypic, phenotypic and fitness levels, and also the possible implications to life-history evolution theories, are discussed. These results suggest that, under moderate to high heritability values, some kinds of chromosomal endocyclic and/or balancing selection may be valuable mechanisms for maintenance of body size variation.

The Role of the Use of Different Host Plants in the Maintenance of the Inversion Polymorphism in the Cactophilic Drosophila Buzzatii

“…Flies carrying derived arrangements of the 2j phylad tended, on average, to be larger and to have longer DTs than 2st carriers (Ruiz et al 1991;Hasson et al 1992a;Norry et al 1995;Betrán et al 1998;Rodríguez et al 1999). However, we detected significant differences among derived arrangements, an effect that was also implicit in the marginally significant differences among karyotypes carrying arrangements of the 2j phylad presented in Table 1 of Betrán et al (1998).…”

Correlations among size-related traits are affected by chromosome inversions in an adaptive polymorphism in Drosophila buzzatii

“…This finding does not imply that R is independent of environmental deviations, but supports the hypothesis that homokaryotypic variation in CP-R is not only an environmental variation, but partially genetic. Nonadditive effects of the second chromosome inversions, on the other hand, would be apparently very weak on sizerelated traits in D. buzzatii, as most of the phenotypic variance among karyotypes is explained by a linear regression of trait on chromosome dose (Ruiz et a!., 1991;Hasson et a!., 1992;Norry et a!., 1995b).…”

“…19), it is of interest to detect factors affecting genetic correlations among traits phenotypically correlated with fitness components. Chromosomal inversions could be one of such factors in D. buzzatii, because the second chromosome inversions affect body size and morphometric traits correlated with it (Ruiz et a!., 1991;Hasson et al, 1992;Norry et aL, 1995b). This hypothesis is examined in the present study.…”

“…size (Ruiz et al, 1991;Hasson et a!., 1992;Norry et al, 1995b). However, although size-related selection is substantial in wild D. buzzatii populations, the selection response depends, not only on the heritabilities of traits considered singly, but also on the genetic correlations among all the traits of which the phenotype is composed (Lande, 1979;Falconer, 1989).…”

The evolutionary history of Drosophila buzzatii. XXXIII. Are Opuntia hosts a selective factor for the inversion polymorphism?

“…Research work in D. buzzatii has shown a significant relationship between the inversion polymorphism and body size Hasson et at., 1992a) and other morphometric traits (Norry et at., 1995). The analysis of these traits in original and colonized populations may provide the genetic framework to test the hypothesis of a genetic reorganization after the founder event.…”