Dissertations, Theses, and Capstone Projects

Date of Degree

9-2024

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Lisa L Manne

Committee Members

Richard R Veit

John S Gosnell

Joanna Coleman

José D Anadón

Subject Categories

Biodiversity | Other Ecology and Evolutionary Biology

Keywords

Biodiversity loss, Biodiversity rate of change, Birds, Change in climate and land cover, Habitat loss, Seasonal Areas of Occupancy

Abstract

The current restructuring of species assemblages and global loss of biodiversity result from species-specific responses to anthropogenic changes in climate and land cover. I investigated the effect of these two drivers on the seasonal distribution and biodiversity of birds in the United States and how human-induced habitat loss impacts macroecological patterns such as the species-area and the abundance-occupancy relationships. In Chapter 1, I examined the existence of a correlation between breeding and wintering geographic distributions of birds with different migratory strategies and the effect of changes in climate and the proportion of crop-pasture and urban land cover on this correlation. I selected species whose breeding and wintering ranges lie substantially within the contiguous United States and Mexico. More than half of the species analyzed had a correlation between seasonal areas of occupancy (AOOs). Warmer and wetter winters weakened the correlation between AOOs, while wetter breeding seasons strengthened this relationship. Changes in the proportion of crop-pasture affected the AOO correlation only in short-distance migrant birds. At the assemblage level, this correlation strengthened for residents and weakened for short-distance migrants. In Chapter 2, I quantified the rate of change in species richness and assemblage dissimilarity across five ecoregions in the United States. I analyzed the effect of the rate of change in climate and land cover on these biodiversity metrics within each ecoregion. Across the study period, assemblage dissimilarity (either total beta diversity or its components) changed for 70% of the bird assemblages and species richness (alpha diversity) changed for 50% of them. Rapid declines in richness were associated with rapid biotic heterogenization, while fast increases in richness were associated with high biotic homogenization rates. Most of the assemblages showing higher rates of assemblage dissimilarity change were becoming more different over time, and whether this was due to rapid species loss or rapid species replacement was ecoregion-dependent. Fast increases or decreases in temperature, declines in precipitation, and forest loss were the main predictors explaining the observed assemblage restructuring. Rapid increases in richness were associated with rapidly warming locations, rapid forest gain, and reduction of crops/pasture areas. In Chapter 3, I focused on a novel socioeconomic habitat loss predictor, the House Price Index (HPI), and its impact on the species richness, abundance, and rarity index of woodland, open-habitat, and urban birds at a continental scale. When compared to primary productivity and random habitat loss at the regional level, the HPI predicted higher estimates of richness loss and increase in rarity for open-habitat birds. However, both HPI and primary productivity affected the richness and rarity levels of woodland birds, while the diversity of urban birds was less impacted by habitat loss than the other groups studied. This dissertation advanced conservation research by providing a deeper understanding of the biodiversity patterns of birds in the US and how they are impacted at the population and species assemblage levels by changes in climate and land use land cover, and habitat loss. I have provided new insights into the species-specific correlation between seasonal areas of distribution and how this relationship is impacted by environmental changes, underscoring the importance of inter-seasonal studies in conservation assessments. I have demonstrated that varying rates of change in climate and land cover produce complex and spatially variable changes in biodiversity across scales. Lastly, I have demonstrated the usefulness of a novel socioeconomic variable as a measure of development risk and the relevance of high-development-risk areas in biodiversity conservation. Overall, the findings in this work highlighted the importance of inter-seasonal, multivariate, and multi-index studies. This type of study contributes to a comprehensive understanding of the capacity of species assemblages to respond to anthropogenic environmental change.

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