The evolutionary history of drosophila buzzatii. Xxiv. second chromosomeinversions have different average effects on thorax length

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 2jz.3 arrangements are correlated with large size, whereas 2st arrangement is correlated with small size. Someinversions (1st and 2jz3) show dominant effects and others (2j/Jz3) exhibit overdominance. Theseresults show that at least 25 per cent of body size variation may be accounted for by the studiedkaryotypes. The possible integration of the genotypic, phenotypic and fitness levels, and also thepossible implications to life-history evolution theories, are discussed. These results suggest that, under moderate to high heritability values, some kinds of chromosomal endocyclic and/orbalancing selection may be valuable mechanisms for maintenance of body size variation. © 1992 The Genetical Society of Great Britain.