Phenotypic variability of wild living and laboratory grown Drosophila: Consequences of nutritional and thermal heterogeneity in growth conditions

(1) Wild living Drosophila simulans were collected in two different seasons and their progeny grown at 14 and 21 °C. Several morphometrical traits were measured on parents and offspring.(2) Body size was on average smaller in nature than in the laboratory, and much more variable. Other traits were also more variable in nature, but significantly less than size. For the two symmetrical traits (sternopleural bristles and ovarioles) the fluctuating asymmetry indices were similar in nature and in the laboratory.(3) Phenotypic correlations among traits were also greater in nature. This difference is attributed to heterogeneous natural breeding sites, differing in food quality and temperature.(4) From biometrical data, it is possible to infer the average developmental temperature in nature.(5) A significant genetic difference in abdomen pigmentation was found between the flies collected at different seasons, in agreement with the result of a selection produced by cold in winter.