DIRECT AND CORRELATED RESPONSES TO SELECTION FOR DESICCATION RESISTANCE - A COMPARISON OF DROSOPHILA-MELANOGASTER AND D-SIMULANS

Replicate lines of Drosophila melanogaster and D. simulans originating from the same location in Australia were selected at two selection in tensities (50%, 85% mortality) for increased resistance to desiccation , and scored for correlated responses to see if similar physiological changes were associated with the selection responses. Realized heritab ilities were much higher in D. melanogaster. Selected lines of both sp ecies were more resistant than control lines to starvation and a toxic ethanol concentration. Both species also showed similar correlated re sponses for traits underlying the selection response: selected lines l ost water at a slower rate and had reduced activity levels in a dry en vironment, but they did not differ in wet or dry body weight or in wat er content. For D. Melanogaster, realized heritabilities for lines sel ected at 85% mortality were higher than for lines selected at 50% mort ality, but there was no effect of selection intensity for D. simulans. Comparative studies of this nature may be useful in predicting the ex tent to which species can adapt to stress in the wild.