Meeting Abstract

22.1  Jan. 5  Macro vs. Micro-Geographic Variation in Metabolism and Hormone Correlates in the Big Brown Bat ( Eptesicus fucus ) RICHARDSON, C.S.*; WIDMAIER, E.P.; MARSH, R.L.; KUNZ, T.H.; BOSTON UNIVERSITY; BOSTON UNIVERSITY; NORTHEASTERN UNIVERSITY, BOSTON; BOSTON UNIVERSITY crichard@bu.edu

We examined basal metabolic rate (BMR) and plasma levels of thyroid hormone (T3) and leptin in the big brown bat, Eptesicus fuscus, from 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, we found that bats from the northern population did not differ significantly from those in the southern population for BMR, T3 and leptin. For all traits, the test for differences among colonies from both populations was significant. For BMR, bats differed significantly within MA colonies, and bats from the AL colony had a significantly higher BMR than those from the GA colony. For T3 and leptin, bats from colonies in MA did not differ significantly, whereas bats from the AL colony had significantly higher T3 and lower leptin than those in the GA colony. Thus, for BMR, T3 and leptin, most or all of the variation among colonies cannot be explained by differences between populations (i.e., macro-geographic variation). 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 observed among colonies for BMR and its hormone correlates. However, the 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 intraspecific variation in BMR and its hormone correlates.