Functional redundancy (FR) is commonly invoked as one of the main mechanisms underlying ecological resilience. Despite this, FR is still poorly understood. Little is known about the variation of FR among ecological assemblages at biogeographic scales and its extension from single to multiple-trait systems. We studied 51 assemblages of 121 Eurasian small mammals (orders Rodentia and Soricomorpha) at community, and population scales. We observed their redundancy (FR) for five different functional traits, namely, their diet, habitat preferences, body mass, diel activity, and role as parasite hosts. We used three different metrics (SES mean nearest neighbor similarity, SES mean similarity and the R index) to study the FR of these Eurasian small mammal assemblages along biogeographical gradients. We analyzed the effect of geography, climate, ecosystem productivity, and land use. Importantly, the mammal richness and geographic gradients on our system were decoupled. Additionally, we evaluated the correlation between FR measures for each functional trait to assess the prevalence of redundancy and/or complementarity.
Results/Conclusions
We found that FR mainly varied along geographic gradients. FR for body mass, diel activity and role as hosts increased at higher latitudes, which may be partially due to environmental filtering processes. FR for diet and habitat preferences increased Eastwards. Some of the measures of FR for different traits were highly correlated. Further, we showed that correlations between FR of the mammals’ habitat, body mass, diel activity, and role as hosts were maintained across scales. The redundancy of the mammals’ diet was less related to the rest of the functional traits. The FR of the mammals was generally structured around two main axes defined by either by the combinations of body mass and host role or trophic and habitat preferences. Despite the redundancy and complementarity of some functional traits, our results warn against the generalizations obtained from studying FR for a single functional trait set. We expect that our conclusions will inform future studies about FR.