Differential responses to thermal variation between fitness metrics

Temperature is a major factor affecting population abundance and individual performance. Net reproductive rate (R(0)) and intrinsic rate of increase (r) differ in their response to different temperature regimes, and much of the difference is mediated by generation time (Tg). Here, we evaluate the effects of thermal mean and variability on R(0), r and Tg, at four population densities in Drosophila melanogaster. The results show that R(0), r and Tg present differential responses to thermal variation. Although temperature effects on R(0) and Tg are non-linear, r response was negligible. R(0) and Tg comprise a generational time scale, while r is at a chronological time scale. Thus, we argue that individuals growing under different thermal environments perform similarly on a chronological scale, but differently on a generational scale.