Many plants rely on animals to disperse their seeds. Since the species in a dispersal assemblage may differ in the quality and magnitude of the dispersal services they offer, temporal variation in the dispersal assemblage can contribute to temporal variability in dispersal which can influence the rate at which plant populations can spread across the landscape. The Audubon Society Christmas Bird Count is a long-running citizen science initiative that provides long-term data on bird abundance at a variety of locations. To assess how annual winter variation in the assemblage of avian frugivores varies across southern Florida, we used annual Christmas Bird Count data from 2003-2013 in six Florida locations (Cocoa, Fakahatchee Strand, Ft. Myers, Ft. Pierce, Long Pine Key and Punta Gorda). To examine spatiotemporal patterns between sites and years we constructed hierarchical cluster diagrams using three measures of distance: biological (proportional abundance of each species), geographical (latitude and longitude), and climatic (temperature and precipitation).
Results/Conclusions
Overall, the community of potential dispersers at Cocoa was the most dissimilar from other sites. It was also the most northern site. Cocoa and Fakahatchee had the greatest dissimilarity in the avian assemblage across years, while Punta Gorda’s assemblage of potential dispersers was the most similar across all years. Punta Gorda also had the highest similarity in weather across the years, while Fakahatchee, Ft. Pierce Cocoa and Long Pine Key had a high dissimilarity in weather between years.
These results suggest that the potential disperser assemblage at these sites is fluctuating annually, with regional differences in the suite of potential dispersers. The observed spatiotemporal variation in the composition of the potential disperser assemblages can be a source of variability in dispersal affecting avian dispersed plants, with the magnitude of the variability determined by region-specific contexts.