Seasonal variation in microhabitat of salamanders: environmental variation or shift of habitat selection?

Enrico Lunghi,Raoul Manenti,Gentile Francesco Ficetola

doi:10.7717/peerj.1122

Abstract

Relationships between species and their habitats are not always constant. Different processes may determine changes in species-habitat association: individuals may prefer different habitat typologies in different periods, or they may be forced to occupy a different habitat in order to follow the changing environment. The aim of our study was to assess whether cave salamanders change their habitat association pattern through the year, and to test whether such changes are determined by environmental changes or by changes in preferences. We monitored multiple caves in Central Italy through one year, and monthly measured biotic and abiotic features of microhabitat and recorded Italian cave salamanders distribution. We used mixed models and niche similarity tests to assess whether species-habitat relationships remain constant through the year. Microhabitat showed strong seasonal variation, with the highest variability in the superficial sectors. Salamanders were associated to relatively cold and humid sectors in summer, but not during winter. Such apparent shift in habitat preferences mostly occurred because the environmental gradient changed through the year, while individuals generally selected similar conditions. Nevertheless, juveniles were more tolerant to dry sectors during late winter, when food demand was highest. This suggests that tolerance for suboptimal abiotic conditions may change through time, depending on the required resources. Differences in habitat use are jointly determined by environmental variation through time, and by changes in the preferred habitat. The trade-offs between tolerance and resources requirement are major determinant of such variation.

Highlights

The use of habitat models to evaluate factors determining species distributions is becoming increasingly prevalent in ecological research (Peterson et al, 2011; Warren, 2012; Stein, Gerstner & Kreft, 2014)
Differences in habitat association patterns may occur through two distinct, non-exclusive processes: the species may select different habitats across their life-time, and environmental features may change through time
We assessed whether the temporal variation in microhabitat occurs because the species selects different environmental features through the year, or because habitat features are affected by seasonal variation

Summary

Introduction

The use of habitat models to evaluate factors determining species distributions is becoming increasingly prevalent in ecological research (Peterson et al, 2011; Warren, 2012; Stein, Gerstner & Kreft, 2014). According to the environmental change hypothesis, temporal variation that exists for the many biotic and abiotic features can affect species distribution (Kearney et al, 2013) Such variation may occur over both short (e.g., variation of vegetation cover or temperature among the seasons) and longer timescales (e.g., climate change, habitat degradation) (Saupe et al, 2014). Both selection changes and environmental changes may influence the possibility of predicting species distribution in different time periods. Evaluating whether habitat association pattern changes through time, and the factors determining such variation, is extremely important to assess the transferability and generality of conclusions drawn from habitat modeling

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