Genetic variation of desiccation resistance in natural populations of Drosophila buzzatii

PAOLA L. SASSI; ESTEBAN HASSON

Punta del Este, Uruguay

Congreso; 150 years of Darwin's Evolutionary Theory: a South American celebration; 2009

The analysis of genetic variation in stress-resistance characters, such as desiccation-resistance, is essential to understand adaptation and biogeographic patterns in organisms, which are often exposed to seasonal variation in resource availability. Our aim is to investigate intra and interpopulation variation in desiccation resistance in the desert inhabitant Drosophila buzzatii. Desiccation resistance was measured in isofemale lines derived from collections in 4 natural populations sampled at different sites along a longitudinal and precipitation gradient across Northern Argentina. Ten isofemale lines were studied from each population. Flies were tested for survival time, under 2 desiccation treatments with silica gel and a control condition. The essay was conducted for each sex separately. The results showed, as expected, that 1) desiccation treatments had a significant effect on survival, 2) there were significant differences in survival among populations and 3) a significant interaction between these factors. Furthermore, our results also showed a clear sexual dimorphism, with females being significantly more resistant than males. The sex by population interaction was also significant, indicating that the magnitude of the sexual dimorphism varied among populations. Surprisingly, our results did not reveal any clear clinal trend in variation in desiccation resistance along the precipitation gradient. Nevertheless, we detected significant variation among isofemale lines (within populations), indicating that variation in desiccation resistance has a genetic basis. Interestingly, the degree of within population variation was higher in populations living in more humid environments, suggesting that genetic variation could be eroded under stressful conditions faced by flies in more arid areas.