Temperature and clinal variation in larval growth efficiency in Drosophilamelanogaster

Geographic dines in ectotherm species including Drosophila melanogaster hav e been found throughout the world, with genetically larger body size and sh orter development time occurring at high latitudes. Temperature is thought to pray a major role in the evolution of this clinal variation. Laboratory thermal selection has effects similar to those seen in geographical clines. Evolution at low temperatures results in more rapid development to larger adult flies. This study investigated the effects of geographical origin and experimental temperature on larval growth efficiency in D. melanogaster. L arvae from populations that had evolved at high latitudes were found to use limited food more efficiently, so that the overall adult body size achieve d was larger. Larvae reared at a lower experimental temperature (18 degrees C) used food more efficiently than those reared at a higher temperature (25 degreesC). The increases in growth efficiency found in populations from hi gh latitudes could explain their increased body size and more rapid develop ment.