Mismatch Between Ectotherm Thermal Preferenda and Optima for Swimming: A Test of the Evolutionary Pace Hypothesis

摘要

A continuing issue in evolutionary thermal biology is the mismatch between preferred body temperatures (T (pref)) and optimal temperatures (T (opt)) for whole-animal performance. Using phylogenetic comparative analyses, I examined the hypothesis that a difference in the rates at which T (pref) and T (opt) evolve causes the mismatch in a lineage of European newts. In a laboratory thermal gradient, newts maintained body temperatures that were on average 8 A degrees C below T (opt) for maximum swimming velocity. The lower boundary of the T (pref) range evolved faster than the mean T (pref), the upper boundary of the T (pref) range, and T (opt). The strong evolutionary co-variation between mean T (pref) and its boundaries prevented the shift of mean T (pref) away from T (opt). This suggests that the variation in evolutionary rates has a limited potential to modify the disparity between thermal optima and preferenda.