Energetic constraints on mammalian distribution areas

Morphological Variation in the Striped Field Mouse Across Three Countries

We examined the morphological variation in the striped field mouse (Apodemus agrarius) along south-north and west-east geographic gradients in Europe (Slovakia, Lithuania, and Estonia). Data collected over several decades (1980s-2020s) were analyzed, focusing on five traits: body mass, body length, tail length, hind foot length, and ear length, with GLM models assessing the influence of latitude, longitude, age, sex, and decade. Results revealed strong adherence to ecogeographic rules. Findings suggest that body size increased toward the north, following Bergmann's rule, which links larger size to better heat conservation in colder climates. Conversely, appendage sizes (e.g., tail, ear) decreased, aligning with Allen's rule to minimize heat loss. Longitudinal gradients revealed reductions in body length and appendages toward the east, potentially reflecting climatic and habitat variability. Temporal trends highlighted dynamic changes in body size, with increases in Slovakia and mixed trends in Lithuania and Estonia. Sex-based dimorphism varied by country and decade, with females often heavier and males displaying longer appendages. The findings underscore the influence of geographic and temporal factors on morphological variation, providing critical insights into the adaptability of A. agrarius. These results contribute to understanding species' ecological plasticity and evolutionary responses.

Flight performance and wing morphology in the bat Carollia perspicillata: biophysical models and energetics

Studies on functional performance are important to understand the processes responsible for the evolution of diversity. Morphological trait variation within species influences the energetic cost of locomotion and impacts life history traits, with ecological and evolutionary consequences. This study examined wing morphology correlates of flight performance measured by energetic expenditure in the Seba's short-tailed bat, Carollia perspicillata. In the flight experiments, nature caught bats (59 females, 57 males) were allowed to fly for 3 min in a room. After each flight, thermographic images were taken to measure body temperature, and biophysical models were used to calculate sensible heat loss as a measure of energetic expenditure. Wing morphological traits were measured for each individual and associated with heat loss and power required to fly on performance surfaces. Wing morphological traits explained 7-10% of flight energetic cost, and morphologies with the best performance would save the energy equivalent to 9-30% of total daily requirements. The optimal performance areas within the C. perspicillata morphospace were consistent with predicted selection trends from the literature. A trade-off between demands for flight speed and maneuverability was observed. Wing loading and camber presented sexual dimorphism. These morphological differences are likely associated with more economical but less maneuverable flight in females, leading them to fly more often in open areas along the forest edge. Our findings demonstrate how small scale changes in wing morphology can affect life history strategies and fitness.

Energetic dissociation of individual and species ranges

The use of energy is universal to all life forms and all levels of biological organization, potentially linking processes operating at variable scales. Individual and species ranges might be energetically constrained, yet divergent metabolic limitations at both scales can disassociate these individual and species traits. We analysed comparative energetic and range data to unravel the mechanistic basis of the dissociation between individual and species range sizes observed among mammalian species. Our results demonstrate that basal, or maintenance, metabolism negatively correlates with individual ranges, but, at the same time, it positively correlates with species ranges. High aerobic capacity, i.e. maximum metabolic rate, positively correlates with individual ranges, but it is weakly related to species range size. These antagonistic energetic constraints on both ranges could lead to a disassociation between individual and species traits and to a low covariation between home and species range sizes. We show that important organismal functions, such as basal and maximum metabolic rates, have the potential to unravel mechanisms operating at different levels of biological organization and to expose links between energy-dependent processes at different scales.