THE EFFECT OF POLYMORPHIC INVERSIONS ON BODY-SIZE IN 2 NATURAL-POPULATIONS OF DROSOPHILA-BUZZATII FROM ARGENTINA

Previous works in a colonized and an original population of Drosophila buzzatii have shown a consistent relationship between the inversion p olymorphism and thorax length, a measure of body size. However, the po pulations studied in those reports share a close genealogical relation ship as suggested by several lines of evidence. In the present paper, we revisit this issue by analysing the correlation between second chro mosome arrangements and thorax length in two Argentinian natural popul ations (Termas de Rio Hondo and Arroyo Escobar) From different biogeog raphic areas with different host plants. Our findings are: (1) inversi on frequencies were significantly different between populations; (2) t he mean thorax length of flies collected in both populations was not s ignificantly different; and (3) we obtain confirming evidence that fli es carrying 2st, the ancestral gene order, have on average a smaller b ody size than those carrying the derived arrangements (2j and 2jz(3)). These results suggest that the biometrical effect of inversions on bo dy size previously described are due to genetic differences between ar rangements and not to the close historical relationship between the po pulations studied in previous reports.