Phenotypic plasticity in the energy metabolism of a small Andean rodent: Effect of short‐term thermal acclimation and developmental conditions

Abstract

The study of phenotypic variation within species in response to different environments is a central issue in evolutionary and ecological physiology. Particularly, ambient temperature is one of the most important factors modulating interactions between animals and their environment. Phyllotis xanthopygus, a small Andean rodent, exhibits intraspecific differences along an altitudinal gradient in traits relevant to energy balance that persist after acclimation to common experimental temperatures. Therefore, we aim to explore geographic variations in energetic traits of P. xanthopygus and to assess the contribution of phenotypic plasticity to population differences. We compared metabolic rate and thermal conductance in response to different acclimation temperatures in animals collected at distinct altitudes (F0 generation) and in their offspring, born and raised under common-garden conditions (F1 generation). We found intraspecific differences in resting metabolic rate (RMR) of animals collected at different altitudes that were no longer evident in the F1 generation. Furthermore, although both generations showed the same pattern of RMR flexibility in response to acclimation temperature, its magnitude was lower for the F1 individuals. This suggests that developmental conditions affect the short-term acclimation capacity of this trait during adulthood. On the other hand, thermal conductance (C) showed irreversible plasticity, as animals raised in the laboratory at stable warm conditions had a relatively higher C than the animals from the field, showing no adjustments to thermal acclimation during adulthood in either group. In sum, our results support the hypothesis that the developmental environment shapes energetic traits, emphasizing the relevance of incorporating ontogeny in physiological studies.

Behavioral responses of two small‐sized rodents, Phyllotis vaccarum and Abrothrix andina, to energy challenges of high‐altitude habitats in the Andes Mountains

“…On the other hand, contrary to predictions, the activity pattern of P. vaccarum was invariably nocturnal, in line with previous studies in both natural (Kelt, 1994) and experimental conditions (Ruperto et al, 2020; Sassi et al, 2015). The bigger body size of this species (i.e., the lower surface/volume ratio) coupled with the lower thermal conductance than expected for its body size (Menéndez et al, 2022) favors the body heat accumulation (Tattersall et al, 2012), which could confer advantages to face the thermal compromises of being active under the cold at night. These characteristics, plus its high thermogenic capacity (Nespolo, 2000) and the possibility of entering torpor (Bozinovic & Marquet, 1991), could underlie its consistently nocturnal activity pattern by offsetting the relatively higher thermo‐energetic cost with a relatively lower predatory risk.…”

“…However, they differ in physiological attributes that are key to maintaining thermal and energetic balance (Rezende & Bacigalupe, 2015). While P. vaccarum displays adjustments in its resting metabolic rate under experimental temperature variations (Menéndez et al, 2022) and changes in its thermal conductance at different elevations (Sassi & Novillo, 2015), in A. andina , these traits do not vary with altitude (Bozinovic et al, 1999). Moreover, the thermogenic capacity (i.e., maximum possible increase in metabolic rate in response to an acute decrease in temperature) of P. vaccarum by far exceeds that of A. andina (Nespolo, 2000).…”

Assessment of the distribution of Pseudoryzomys simplex (Cricetidae, Sigmodontinae) in the Pampean region, central-east Argentina, in the late-Holocene

“…the last 5000 years) are mainly observed in islands in the case of rodents (Cucchi et al, 2014; Pergams and Ashley, 2001; Van der Geer, 2020). Some cases of local adaptation and phenotypic plasticity in inland areas have been observed in several rodent species at short time scales (Bittner et al, 2021; Menéndez et al, 2022) so that it cannot be ruled out that there may have been populations of P. simplex with different climatic preferences. Nonetheless, there is no reliable data to confirm the presence of phenotypic plasticity related with P. simplex .…”