Energetic constraints on mammalian distribution areas

Abstract

Energy is a universal resource essential for all life functions. The rate of transformation of energy into an organism, and the energetic investment into reproduction, determines population and ecological‐level processes. Several hypotheses predicted that the ecological expansion and size of the geographic distribution of a species are shaped by, among other factors, metabolic performance. However, how organismal energetic characteristics contribute to species geographic range size is poorly understood. With phylogenetic comparative methods whether energetic maintenance costs (basal metabolic rate, BMR), aerobic capacity (maximum exercise metabolic rate, VO2max), summit thermoregulation (summit metabolic rate, VO2sum) and the ability to sustain energy provisioning (daily energy expenditure, DEE) determine the distribution of mammalian species range sizes was tested. Both basal and maximum exercise metabolic rates (accounting for body mass), but not summit thermogenic metabolic rate, were positively associated with species range sizes. Furthermore, daily energy expenditure (accounting for body mass) was positively associated with species ranges. Body mass (accounting for energetic maintenance) was negatively related to range sizes. High aerobic exercise capacity, aiding mobility such as running and dispersal, and high sustained energy provisioning, aiding reproductive effort such as pregnancy, lactation and natal dispersal, can facilitate the establishment of large mammalian geographic ranges. Consequently, the pace of organismal physiological processes can shape important ecological and biodiversity patterns by setting limits to species’ range sizes.

Energetic dissociation of individual and species ranges

“…Thus, it is expected that it governs individual and species ranges [20,22,57]. Previous studies considered ranges separately [22,24,57,58] and/or were restricted only to one limit of metabolic rate to range sizes ( [21,22]; but see [19,23]). Thus, the potential energetic dissociation between ranges has never been resolved.…”

“…We compiled mammalian species range (SR, in km 2 ) and individual (home) range sizes (HR, in km 2 ), trophic level, aerobic capacity (measured during physical exercise; VO 2 max ; ml O 2 h −1 ) and maintenance metabolism (measured during rest at thermoneutral conditions, on post-absorptive, non-reproducing animals; BMR; ml O 2 h −1 ) data from previous studies ([ 19,23,[40][41][42][43]; N = 60; figure 1). We obtained the species phylogenetic relationship from the Global Timetree of Life (http://www.timetree.org/; [44]), which we trimmed to match the studied species.…”

“…the energy available above obligatory maintenance, is needed to sustain large home ranges among competing individuals [19,28]. By contrast, species range sizes were positively related to both aerobic capacity and maintenance metabolism [23,24]. Those results suggest that, apart from mobility (determined by the aerobic capacity), the basic rate of energy absorption and transformation increases species expansion capabilities.…”

“…Energy use, in fact, has been shown to influence the distribution range size of both individuals and species [19][20][21][22][23][24] (previous findings are summarized in electronic supplementary material, table S1). The range size of individuals, the home range, was positively associated with the upper limit of metabolic processes (VO 2 max : maximum metabolic rate or aerobic capacity), which determines the capacity for physical exercise and daily mobility [19,21,25].…”

“…Individual ranges may depend on animals' ability to move and to maintain their daily ranges [19,21]. Species ranges may depend on the species colonization potential, which may also be determined by mobility [23,24]. Thus, we hypothesize that physiological mechanisms optimizing mobility promote large ranges at both scales.…”