Species colonization history and environmental heterogeneity interact to drive metacommunity assembly

Background/Question/Methods

Ecologists have long recognized that both habitat environmental conditions and species colonization history can influence the structure of ecological communities. Yet, the question of how these two factors combine to influence community assembly remains empirically unexplored. To answer this question, we established experimental metacommunities of bacterivorous protists and manipulated the order of species colonization and ambient temperature for local communities. Two types of metacommunities were created: one characterized by environmental heterogeneity in which each local community was subjected to a different ambient temperature (heterogeneous metacommunities), and the other without environmental heterogeneity where all local communities experienced the same temperature (homogenous metacommunities). Microcosms were sampled periodically to estimate species abundance over time.

Results/Conclusions

Our results revealed considerable variation in the structure of local communities, due both to the variation in species colonization history and the difference in environmental temperature among these communities. Strikingly, differences in species colonization history led to alternative community states in only heterogeneous, but not homogenous metacommunities, suggesting that environmental heterogeneity promotes historical contingencies of ecological communities. Our study demonstrates the importance of the interactions between species colonization history and environmental heterogeneity for structuring metacommunities.