Shifting metacommunity assembly rules: How do invasive fishes influence the assembly of an ephemeral metacommunity?
Results/Conclusions: Previous work in this region noted the fish metacommunity assembly was a random process, with no significant deviation from a null distribution; however, our meta-analysis indicates that this has shifted toward determinism in the form of aggregation in 2003. Interestingly, this corresponded with the expansion of the African Jewelfish, a non-native micro-piscivore, in to the marsh. This species is now the second most abundant fish in the marsh, and is a significant predictor of species diversity at the local scale (P<0.001, R2=0.368), while regional scale is better predicted by dispersal distance (P<0.001, R2=0.409). We note a similar shift, increased aggregation, following the 2014 expansion of Asian Swamp Eels through this habitat, but not following the introductions of several other fishes. These results, as well as a limited but growing body of literature, suggest that the introduction of an invasive species shifts metacommunity assembly patterns to be aggregative. The mechanism behind this shift however is still unknown, and is the subject of our continuing research.