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 intensities (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 heritabilities were much higher in D. melanogaster. Selected lines of both species were more resistant than control lines to starvation and a toxic ethanol concentration. Both species also showed similar correlated responses for traits underlying the selection response: selected lines lost water at a slower rate and had reduced activity levels in a dry environment, but they did not differ in wet or dry body weight or in water content. For D. Melanogaster, realized heritabilities for lines selected at 85% mortality were higher than for lines selected at 50% mortality, but there was no effect of selection intensity for D. simulans. Comparative studies of this nature may be useful in predicting the extent to which species can adapt to stress in the wild.