Impacts of climate-mediated vegetation shifts and regional climate change on coastal avian community dynamics across the Gulf of Mexico

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Keyser, Spencer Ryan

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Climate change is considered to be a major threat to extant biodiversity. In addition to direct impacts of changing climatic conditions, poleward shifts in foundation species associated with warming temperatures may exacerbate impacts on higher trophic level species by altering habitat structure and resource availability. Across the Gulf of Mexico (GoM) reductions in severity and duration of winter freezes have facilitated the expansion of mangroves into previously salt marsh dominated habitat. Using birds as model taxa, I investigated the impacts of climate-mediated shifts in foundational species on multiple facets of avian biodiversity. I paired a long-term, standardized avian monitoring dataset (e.g. U.S. Geological Survey Breeding Bird Count) with environmental variables to investigate drivers of avian biodiversity change along coastal sites throughout the GoM and eastern portion of Florida from 1980-2017. Specifically, I was interested in testing whether expansion of mangrove-dominated wetlands and changes in regional climate change (i.e. temperature and precipitation) drive shifts in bird species richness (α-diversity) or elevated rates of bird community turnover through time (temporal β-diversity). I documented changes in α-diversity and temporal β-diversity in both total and wetland bird communities across the GoM. Increases in mangrove cover at fine-spatial scales predicted changes in α-diversity and temporal β-diversity, whereas, coarse-scale changes in temporal β-diversity were predicted by climate. Increasing prevalence of southerly species were associated with faster rates of warming and increased temporal β-diversity, indicating potential poleward shifts in species ranges may be one factor underlying biodiversity change. Modifications in microclimate, biotic interactions, and resource availability associated with mangrove expansion may underlie observed shifts in bird biodiversity. My findings suggest that climate-mediated shifts in foundation species are likely impacting biodiversity of higher trophic level species and may exacerbate biodiversity change driven by the direct impacts of altered temperature and precipitation regimes. As mangrove habitats are predicted to continue to expand across the GoM, integrating data on in foundation species will be crucial for future assessments and adaptive management of climate-mediated changes in avian biodiversity



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