Shifting metacommunity assembly rules: how do nonnative fishes affect metacommunity assembly in ephemeral wetland habitats?

Background/Question/Methods

The question of how communities assemble continues to be a central theme in ecology. In recent decades, through the development of metacommunity theory, ecologists have begun to investigate the role of spatial processes on assembly rules, leading to an improved understanding of the relative importance of local and regional processes. However, the influence of non-native species on the assembly of metacommunities is still largely unknown. In the karst habitat of the southern Everglades solution holes serve as refuge habitats when surrounding marshes dry and fish communities in these holes reassemble each year at the onset of marsh drying. At the same time, this region of the Everglades is one of the most  invaded habitats in the Greater Everglades, with as high as 50% of fish present being nonnative, which provides an opportunity for studying how the presence of nonnatives alters assembly processes in these refuge habitats? We sampled 41 solution holes communities at first assembly, via a combination of visual surveys and electroshocking to depletion to obtain a presence/absence matrix and ask if this assembly process is non-random and what factors 

Results/Conclusions

Previous work in this region has shown fish community assembly to be a random process, with no significant deviation from a null distribution. However, results from this analysis indicate that assembly is more determinist, showing evidence of species aggregation. In the time between these studies there have been two major events that may explain a shift in assembly rules: Florida’s most severe cold event of the past century, and the introduction of a nonnative micropredator (African jewelfish). Additional sampling is needed to sort between the effects of these two events, but at minimum our data suggest a change in the way communities are assembled over time.