The landscape of the Florida Everglades has changed dramatically in the past century. To understand the effects of these changes on aquatic species, it’s necessary to quantify the extent to which dispersal is limited by environmental factors. We compared landscape structure and aquatic animal beta diversity to illustrate the level of neutral and niche drivers in metacommunity dynamics. A high correlation between landscape heterogeneity and community beta diversity suggests environmental (niche) drivers, while a low correlation supports spatial (neutral) drivers. We used a spatially extensive sampling design to obtain data on small fish and macroinvertebrate communities, which are a critical food resource for wading bird populations. We monitored 144 sampling sites spread over 50,000 square kilometers by sampling annually from 2005 to the present. Community samples are collected each wet season between September and December using a 1-m2throw trap. Landscape coverage type was determined using spectral data from WorldView 2. Hydrological data was obtained through the Everglades Depth Estimation Network (EDEN). Community dissimilarity was measured using the Sorenson index of dissimilarity, which is based on the ratio between gamma (regional) and alpha (local) diversity.
Results/Conclusions
The dataset contained 4991 total samples with an average of 525 samples per year. The monitoring area was divided into 22 landscape units by quantifying differences in hydrological cycle, land cover, and heterogeneity. Metacommunities in all landscape units were dominated by Eastern Mosquitofish, Gambusia holbrooki, found in 69.88% of samples; Least Killifish, Heterandria formosa, in 62.67% of samples; and Bluefin Killifish, Lucania goodei, in 51.12% of samples. Dominant macroinvertebrates included riverine grass shrimp, Palaemonetes paludosus, in 67.57% of samples; and creeping water bugs, Pelocoris femoratus, in 52.85% of samples. Gamma diversity, measured as species richness at the landscape unit level, ranged from a low of 35 species to a high of 90 species. Alpha diversity, measured at each sampling site, ranged from 2 to 22 species. The Sorenson index of beta diversity was between 0.004 and 0.873 with a mean of 0.035. Lower beta diversity scores were correlated with long hydroperiod and homogeneous landscape cover, while high beta diversity scores were correlated with landscape heterogeneity and short hydroperiods. These results suggest that aquatic animal metacommunities are structured by niche processes. The overall range of beta diversity found in the monitoring area is reflective of the heterogeneous nature of the landscape.