Thermal energetics of bats of the family Vespertilionidae: an evolutionary approach

Abstract

O_LIThermal energetics define the way animals spend energy for thermoregulation. In this regard, numerous studies have determined that body mass (Mb) is the most influential morphological trait affecting the thermal traits in different species of birds and mammals. However, most of the studies have been focused on the basal metabolic rate (BMR), while other thermal traits have been less studied. C_LIO_LIWe addressed this gap by examining thermal variables on bats of the family Vespertilionidae. Using open-flow respirometry, we measured BMR, absolute thermal conductance (C), lower and upper critical temperatures (TLC and TUC), and the breadth of the thermoneutral zone (TNZb) of 15 bat species varying in Mb from [~] 4.0 to 21.0 g from central Mexico. We: 1) combined our empirical data with information gathered from the bibliography and conducted phylogenetic analyses to investigate the relationship between Mb and thermal traits, and 2) mapped the thermal energetic values along the phylogeny to explore how they may have evolved. C_LIO_LIWe found a positive relationship between Mb and BMR and absolute C, and a negative relationship between Mband TLC and TUC. However, we did not find a relationship between Mband TNZb in bats. The phylogenetic approach suggested that over the evolutionary history of bats, BMR and C have decreased while TLC and TUChave increased. C_LIO_LIOur results suggest that adaptive changes in Mb and thermal traits may have influenced the geographical distribution and the use of energy-saving strategies of the different species of bats of the family Vespertilionidae. C_LI