The interactive effects of environmental warming and habitat fragmentation on the structure of experimental protist communities

Abstract

Global biodiversity is threatened by substantial and increasing human activity, such as human-induced environmental warming and habitat fragmentation. The effects of warming and fragmentation on biodiversity have been carefully studied, yet their potential interactive effects are less understood. Using freshwater protist communities subject to warming and fragmentation, I present the first experimental evidence of the interactive effects of warming and fragmentation on biodiversity. Somewhat unexpectedly, I found that fragmentation positively affected biodiversity. The magnitude of the effects of fragmentation, however, varied with the warming treatments. In one of our experimental communities (Combination B), fragmentation showed a much stronger positive effect on protist richness when warming was not conducted, but it showed a weaker but significant positive effect under a warming scenario. In other communities (from Combination C), however, fragmentation showed a stronger positive effect on richness when warming was present than when it was absent in experimental treatments. I further show that these long-term effects may be due to the alternation of individual species growth rate affected by warming, fragmentation and their interaction in short-term projections. Moreover, these findings of positive effects of fragmentation and interactions with warming can be useful for understanding conservation strategies, especially in areas where biodiversity is currently threatened or will be in the future.