Author: Christopher Seth RichardsonPublisher:
ISBN:
Category :
Languages : en
Pages : 530
Book Description
Abstract: I examined regulatory nonshivering thermogenesis (NST), basal metabolic rate (BMR), and plasma levels of thyroid hormone (T3), leptin and cortisol in the big brown bat, Eptesicus fuscus, at seven maternity colonies in Massachusetts (MA) (northern population) and two maternity colonies in Alabama (AL)/Georgia (GA) (southern population) in 1997 and 1998 to test the hypothesis that these traits vary geographically. After accounting for effects of body mass and stage of pregnancy and within-population variation, I found that bats from the northern population did not differ significantly from those in the southern population for NST, BMR, T3, leptin and cortisol. For all traits, except for cortisol, the test for differences among all colonies from both populations was significant. For NST, colonies did not differ significantly within MA, whereas bats from the AL colony tended to have greater NST than all other colonies of bats examined. For BMR, colonies differed significantly within MA, whereas bats from the AL colony had significantly greater BMR than those from the GA colony. Moreover, the AL colony tended to have greater BMR than all other colonies of bats examined. For T3, leptin and cortisol, colonies did not differ significantly within MA, whereas bats from the AL colony had significantly greater T3, lower leptin and lower cortisol than those in the GA colony. Additionally, bats from the AL colony tended to have greater T3, lower leptin and lower cortisol than all other colonies. Thus, for NST, BMR, T3, leptin and cortisol, most or all of the variation among colonies cannot be explained by differences between populations (i.e., macro-geographic variation). Clearly, the absence of any predicted population differences along a clinal (adaptive) direction rules out evolutionary adaptations of bats to different thermal environments as the primary reason for differences among colonies for NST, BMR and their hormone correlates. However, the clear presence of among-colony, and within-population variation (i.e., micro-geographic) for these traits, suggests that environmental factors (acting recently) may play an important role in shaping the observed intra-specific variation in NST and BMR. Additionally, inter-individual variation and seasonal and sex differences were found for NST, BMR and the hormones.