NESPOLO, RF; BACIGALUPE, LD; BOZINOVIC, F: On the heritability of body temperature in endotherms: a study in leaf eared mice

Natural selection acts over additive genetic variation. Consequently, its measurement is a requisite for any statement about the evolutionary significance of a trait. The evolution of endothermy is a long-standing issue in which body temperature plays a central role. We determined heritability in a small mammal species, the leaf-eared mouse (Phyllotis darwini). In this wild species we performed a full sib / half sib analysis to determine narrow-sense heritability (h²) of body rectal temperature (T_b). Offspring were isolated at weaning, and night and day T_b were measured in adults. We used the animal model approach to estimate components of variance and h². Statistically significant values of h² were 0.58 (SE=0.24) and 0.72 (SE=0.25) for day and night T_b, respectively. In addition, the genetic correlation between both measures was high, r_A = 0.90 (SE=0.18), and the contribution of maternal effects was not significant (X² = 0.6, P > 0.05). We conclude that T_b in this species could potentially respond evolutionarily to selection. These results suggest that the direct selection on higher T_b cannot be disregarded so far as a potential target for natural selection in the origin and evolution of visceral endothermy.