Genetic differentiation in Japanese populations of Drosophila simulans and D. melanogaster. II Morphological variation.

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Abstract
Geographical variation in ten quantitative morphological characters in each sex were studied for seven sympatric populations of D. simulans and D. melanogaster, the former has recently colonized the main islands of Japan. Populations of D, melanogaster showed geographical variation in most of the characters studied (wing size, body weight, thorax length, eye size, ovariole number, and ratio of eye width and wing length). In D. simulans, geographical differentiation was found only in three characters, among which the ovariole number increased with the latitude as was seen in D. melanogaster. Ovariole number was positively correlated with fecundity. Morphological characters appear to be differentiated at various speeds among geographical populations according to their adaptive significance. In both species, Ogasawara population was strikingly different from the other six populations in characters relating body size and eye size. Eye size and ovariole number were highly correlated with body size in D, simulans, but not in D. melanogaster.