Assessing functional redundancy in Eurasian small mammal assemblages across multiple traits and biogeographic extents

Abstract

Functional redundancy (FR) is commonly invoked as one of the main mechanisms underlying ecological resilience. However, little is known about the extension of FR from single to multiple functions and its variation among ecological assemblages at biogeographic scales. We studied 51 assemblages of Eurasian small mammals (Mammalia: Rodentia and Mammalia: Soricomorpha), analyzing FR across and within assemblages. We quantified FR for trait sets related to five different functions: parasitic interactions, diet, habitat preferences, body mass and diel activity. We then evaluated the relationships between FR based on different functional trait sets across and within mammal assemblages, to determine whether small mammal assemblages and their species are redundant for single or multiple trait sets and thus, whether they are complementary or fully redundant when considering multiple functions. Further, we analyzed the influence of geography, climate, plant productivity and land use on FR. We found that FR based on mammal parasitic interactions, body mass and diel activity were positively correlated, whereas FR based on mammal body mass and habitat preferences were negatively related. These relationships were consistent across and within mammal assemblages. Additionally, FR mainly varied along geographic gradients (latitude and longitude). FR based on parasitic interactions, body mass and diel activity followed similar patterns, increasing at northern latitudes, possibly as a response to environmental filtering processes. FR for diet and habitat preferences increased at easterly longitudes, which may be due to landscape homogeneity in sites across central and eastern Asia. Despite redundancy across multiple functional trait sets, Eurasian small mammal assemblages were complementary when considering all five trait sets. Our results warn against conclusions drawn from the study of FR based on traits related to a single function.