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Several genetic factors are assumed to influence developmental instability (DI). One is the level of heterozygosity, with higher levels often being associated with decreased DI; another is genetic incompatibility in hybrids, which in several cases has been shown to increase DI. The genus Bacillus includes species which have both amphigonic heterozygous reproducing populations and homozygous parthenogenetic reproducing populations (B. rossius rossius and B. r. redtenbacheri). Furthermore, Bacillus includes hybrid parthenogenetic species, which have very high levels of almost fixed heterozygosities (B. atticus, B. whitei, B. lynceorum). We investigated the phenotypic variance (sigma(2)p) and the impact of hybridization and level of heterozygosity on DI in females from these populations and species of Bacillus. DI was estimated as fluctuating asymmetry (FA) for three bilateral traits: the labial palpus, the maxillary palpus and the antenna. For the labial palpus and maxillary palpus we found, in general, a lower level of DI in the amphigonic females compared with parthenogenetic counterparts from the same species and with parthenogenetic females from the three hybrid species. A higher DI of the antenna was found in the hybrid species when compared with both parthenogenetic and amphigonic populations of the nonhybrid species, suggesting that the genes controlling antenna development are located on the sex chromosomes. The development of the investigated bilateral characters in the hybrid species seemed to be affected more by factors relating to genetic incompatibilities as a consequence of hybridization than by the stabilizing force of increased heterozygosity. Only few differences in sigma(2)p were observed, supporting the possibility that the observed differences in DI are related mainly to internal genetic factors. (c) 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 249-259.

Udgivelsesdato: 2005-Jul Maternal effects on progeny wing size and shape in a homozygous parthenogenetic strain of Drosophila mercatorum were investigated. The impact of external maternal factors (heat stress) and the impact of internal maternal factors (different maternal and grand maternal age) were studied. The offspring developed under identical environmental conditions, and due to lack of genetic variation any phenotypic difference among offspring could be ascribed to maternal effects. Wing size was estimated by centroid size, shape was analysed with the Procrustes geometric morphometric method and variation in landmark displacement was visualized by principal component analysis. Both kinds of maternal effects had a significant impact on progeny wing size and shape. Maternal heat stress led to the same pattern of response in size and shape among the progeny, with increased difference between the control group and progeny from heat stressed flies in both size and shape with increased maternal heat stress temperature. The effects of maternal age, however, led to different responses in size and shape between the different progeny groups. The observed variation in landmark displacements was similar, and in both cases mainly associated with shape differences of the posterior part of the wing. Finally, our results suggest that maternal effect has some evolutionary implications by altering the genetic correlations among traits, which can affect the response to selective pressures.