PT - JOURNAL ARTICLE AU - Rodolfo Mei Pelinson AU - Mathew A. Leibold AU - Luis Schiesari TI - Top predator introduction changes the effects of spatial isolation on freshwater community structure AID - 10.1101/857318 DP - 2019 Jan 01 TA - bioRxiv PG - 857318 4099 - http://biorxiv.org/content/early/2019/11/29/857318.short 4100 - http://biorxiv.org/content/early/2019/11/29/857318.full AB - Spatial isolation can differentially affect the distribution of predators and thus affect lower trophic levels by resulting in trophic cascades. Similarly, the introduction of top predators into isolated ecosystems can cause the same cascading effects because they mostly prey upon larger frequently predatory taxa, indirectly benefiting consumers. Here we experimentally tested whether spatial isolation can affect the outcome and strength of the cascading effects caused by fish on macroinvertebrate community structure. We found that fish did reduce the abundance of predators but had no effect on consumers. Spatial isolation, however, did cause trophic cascades, but only in the absence of fish. We believe this happened because fish also preyed upon consumers when they increase in abundance. Additionally, and in contrast with simple theoretical expectations for metacommunities, we found that the difference between ponds with and without fish increased with isolation, probably because fish dampened the cascading effects of spatial isolation.