Scaling temperature‐dependent dispersal rates to metacommunity dynamics: An experimental test

Abstract Changes in community structure under shifting thermal regimes depend on how both local population dynamics and regional dispersal respond to temperature. Processes underlying dispersal, such as movement speed and demographic density dependence, are constrained by temperature‐dependent metabolic rates; however, the temperature dependence of population dispersal rate, and effects of this relationship on local and regional diversity patterns, have received little attention in the metabolic scaling literature. Here, we propose and experimentally test a framework that relates temperature effects on individual dispersal probability, to thermal performance curves (TPCs) for population dispersal rates, to colonization dynamics in metacommunities. Using multi‐patch well plate microcosms, we measured TPCs for dispersal rate in several naturally co‐occurring ciliate species at different monoculture densities and in polyculture metacommunities. In monoculture metapopulations, the functional form of dispersal thermal responses differed at low (a few individuals) versus high (carrying capacity) population densities, and the strength of density‐dependent effects on dispersal rates varied unimodally with temperature. This may suggest distinct temperature effects on the density‐independent (individual movement speed and dispersal probability) and density‐dependent (quorum‐sensing and resource competition) components of population dispersal rate. In polyculture metacommunities, interspecific variation in dispersal TPCs explained differences in colonization dynamics and diversity patterns across temperature treatments. Species' dispersal rate TPCs differed from their growth rate TPCs; as a result, species with higher dispersal thermal optima had higher‐than‐expected per capita population growth at the regional scale compared with predictions from standard growth TPCs measured in single‐patch monoculture. Together, these results suggest that ignoring temperature‐dependent dispersal can yield an incomplete understanding of biodiversity change in spatially structured systems exposed to warming. Read the free Plain Language Summary for this article on the Journal blog.