Contrasting population genetic structures using allozymes and the inversion polymorphism in Drosophila buzzatii

Abstract

Second chromosome inversion and genotypic frequencies at seven allozyme loci, differentially associated with inversions, were determined in seven natural populations of Drosophila buzzatii. The patterns of variation of allozymes and the inversion polymorphisms were significantly different, indicating the role of adaptive differentiation for the latter. Moreover, the patterns of population structure varied among allozyme loci, suggesting the operation of diversifying selection for certain loci. Differentiation was negligible for Leucyl‐amino peptidase (Lap) and Peptidase‐2 (Pep‐2), low to moderate for Aldehyde oxidase (Aldox), Peptidase‐1 (Pep‐1) and Esterase‐1 (Est‐1) and high for Esterase‐2 (Est‐2) and Xanthine dehydrogenase (Xdh). Significant linkage disequilibria were detected between inversions and Aldox, Est‐1, Est‐2 and Xdh. Multiple regression analyses of inversion and allele frequencies on environmental variables revealed the existence of clines for inversions, Est‐1, Est‐2, Xdh and Aldox along altitudinal, latitudinal and/or climatic gradients. Tests using conditional allele frequencies showed that Est‐1 and Aldox clines could be accounted for by hitchhiking with inversions, whereas natural selection should be invoked to explain the clines observed for Est‐2 and Xdh.

Altitudinal patterns for longevity, fecundity and senescence in Drosophila buzzatii

“…In spite of harsh thermal conditions in winter, D. buzzatii actually overwinters at least as larvae even at the highest elevations sampled in the present study (Table 1; rots support alive larvae during winter at high elevations, F.N. 's personal observation), where neutral markers in sharp contrast to inversion polymorphisms show no association with geography (Rodriguez et al, 2000). Therefore, altitudinal adaptive variation for fitness-related traits can be tested in this species (Dahlgaard, Hasson & Loeschcke, 2001;Sørensen et al, 2005b).…”

Spatial Variation of Genetic Diversity in Drosophila Species from Two Different South American Environments

“…Zapata et al (2000) detected that natural selection is an evolutionary force operating in the allozyme-chromossomic inversion association in D. subobscura. In D. buzzatii, the analysis of allozyme variation in colonizing populations in Australia and Spain suggested a significant role of natural selection shaping the allele frequency distribution for several loci (Barker & East, 1980;Barker et al, 1986;Rodriguez et al, 2000), which are strictly linked to chromossomal inversions rearrangements (Schaffer et al, 1993;Betrán et al, 1995;Rodriguez et al, 2000). In the guarani group would be necessary to verify the association between allozymes and chomossomic inversions that were already detected in some of its species (Brncic, 1953;Salzano, 1954).…”

The conversion of variance and the evolutionary potential of restricted recombination

“…Clines in inversion frequency related to variation in life history, morphological, and fitness-related traits and correlated to different climatic conditions have been characterized in D. suboobscura (Prevosti et al, 1988;Orengo and Prevosti, 1996;Schaeffer et al, 2003), other fruit fly species (Inoue et al, 1984;Rodriguez et al, 2000), and in mosquitoes (Coluzzi et al, 1979). Interestingly, Rodriguez et al (2000) found that only inversions associated with positive effects on trait values or fitness were involved in a latitudinal cline of D. buzzatti; inversions that were associated with neutral and negative effects on trait values or fitness did not show latitudinal patterns.…”