# Community-Level Phenotypic Adaptations of Small Mammals Under Rain-Shadow Dynamics in Baima Snow Mountain, Yunnan

## TL;DR

This study examines how small mammals in Baima Snow Mountain adapt to environmental changes, finding that their body and organ traits vary in complex ways influenced by climate and habitat.

## Contribution

The study provides new insights into how community-level phenotypic adaptations in small mammals respond to rain-shadow dynamics and environmental gradients.

## Key findings

- Body size decreased with increasing temperature, aligning with Bergmann's rule.
- Appendage size allometry violated Allen's rule but showed partial consistency with productivity.
- Renal traits did not correlate negatively with water availability, suggesting microhabitat and zoogeographic influences.

## Abstract

Community-level functional traits reflect species’ responses to environmental factors and their contributions to ecosystem functions. The contribution of energy can directly reflect how species in an ecosystem utilize resources, interact, and impact the environment in response, which in turn affects the structure and function of ecosystems. This study evaluates the associations between environmental factors and community-aggregated trait values in the Baima Snow Mountain, Yunnan, China, to examine the classic Bergmann’s and Allen’s rules, as well as renal phenotypic variations accounting for the local aridity gradient resulting from the intensive rain-shadow dynamic. A total of 807 small mammal individuals were recorded belonging to four orders, eight families, and 24 species. A dataset of traits corresponding to temperature, productivity, and water availability was compiled. Ordinary least squares (OLS) regressions were employed to determine the associations between community-weighted mean trait values and selected environmental predictors. We performed Mantel tests to assess the strength of the influence of transition of species compositions, which is measured as the Bray–Curtis dissimilarity index, on community-level trait variations. We found that, at the community level, variations in body sizes were consistent with Bergmann’s rule, while variations in appendage allometry violated Allen’s rule but were partly explained by productivity and habitat conditions. Surprisingly, we found that renal morphology relating to osmoregulatory capacity did not align with the expectation of water constraint, but its converse.

The adaptation strategies of species to local environments are reflected in phenotypic variations, which could be expressed as trait patterns across the community level. Here, we compiled a dataset of small mammal traits to evaluate the classic ecological rules and to assess predictions related to drought resistance. In June 2017, July 2023, and May–June 2024, a field survey was conducted in Baima Snow Mountain, southwest China, using standardized methods to capture small mammals. Traits potentially corresponding to variations in temperature, productivity, and water availability were measured in the field or calculated in the laboratory. We applied ordinary least squares (OLS) linear regressions to determine the community-level trait variations along the gradients of environmental factors influenced by rain-shadow effects of the mountain system. Results showed that (1) body size decreased with increasing temperature, aligning well with conventional prediction; (2) the proportion of appendage size attributable to allometry decreased with temperature but increased slightly with productivity, thereby violating Allen’s rule while being partly consistent with the resource rule; (3) the renal features did not support the expected negative association concerning water availability but its converse, which may be explained by microhabitat conditions and broad-scale zoogeographic influences within the local community. We conclude that community-level phenotypic variations in small mammals result from complex influences, including climate, productivity, habitat characteristics, and adaptive strategies operating at both micro and macro scales.