Dispersal is key for maintaining biodiversity at local and regional scales in metacommunities. Theory has shown that an intermediate level of dispersal is optimal for maximizing diversity at these spatial scales. This hump-shaped diversity-dispersal relationship has been investigated for fragmented patches unperturbed by other environmental change. However, little is known about the interacting effects of environmental change and dispersal on biodiversity. Global warming, in particular, is expected to strongly impact the environment and species persistence. In this study, we aimed to understand the combined effects of temperature change and of varying dispersal rates on the diversity in metacommunities from early- and late- successional stages. In order to answer our question experimentally, we used the inquiline protozoan communities of a carnivorous plant, Sarracenia purpurea. We conducted a laboratory factorial design experiment with four dispersal levels and four temperature treatments, which were applied to communities from two different successional stages.
Results/Conclusions
We found that with increased dispersal, the hump shape of the diversity-dispersal relationship was observed, but only in late-succession communities. Increased temperature did not flatten this relationship, but instead decreased diversity globally. In early-succession communities, diversity increased monotonically with dispersal, and these communities were less affected by temperature. For late communities, the absence of flattening and the decrease in species gamma-diversity was due to higher extinction rate with temperature, which mostly affected small-bodied species. Our results indicate that temperature increase may not affect local diversity through a disruption of the diversity-dispersal relationship, but merely by increasing rates of extinctions at both local and global scales. These results are, however, dependent on the successional stage of the community.