Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta-network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta-network. To address this question, for an empirical meta-network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta-network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta-network was more robust to the loss of old (i.e. long-fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta-network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long-lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies.

No 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.

No abstract

No abstract

In mountain environments, both temperature and food availability vary strongly with altitude, leading to a major challenge to the thermo‐energetic balance of organisms. In this sense, the behavioral repertoire is crucial for animals' adequacy because it implies a short‐term response in the face of environmental changes. In this paper, we explored the behavioral versatility of Phyllotis vaccarum and Abrothrix andina (Rodentia: Cricetidae), two of the mammal species with the highest altitudinal distribution worldwide. By radiotelemetry, we analyzed the activity pattern, home range, and microhabitat selection in populations of both species inhabiting at 2300 and 3100 m altitude in the Central Andes of Argentina. We found that A. andina was diurnal at 3100 m and cathemeral at 2300 m a.s.l., while P. vaccarum was nocturnal at both elevations. Moreover, home range size was larger in A. andina males at 3100 m in contrast to females at identical altitude and males at 2300 m; while, in P. vaccarum, there were no differences according to altitude or sex. Furthermore, we recorded a complex and species‐specific microhabitat selection pattern at different altitudes. Finally, the magnitude of behavioral variability was higher in A. andina than in P. vaccarum for all the traits analyzed. These results are discussed with emphasis on the impact of behavioral traits and their plasticity for species adequacy in high‐altitude environments.