Biodiversity, the variety of different species living in a particular geographic region, is important to the functioning of local ecosystems and provides for many of humanity's needs. There is a pressing need in ecology and conservation biology to better understand the underlying processes leading to species extinction with the goal of developing predictive models for local, regional, and ultimately global extinctions. Although general threats to biodiversity are well-documented, there is less consensus about why one species may go extinct while others persist in response to one particular disturbance or threat. This suggests that the key question to understanding modern biodiversity loss is not what causes extinctions, but why do some species go extinct, while others survive? This study examines the loss of species from aquatic and terrestrial environments due to a variety of disturbances. These disturbances will include the loss of habitat area, and the introduction of predators and novel species. Mathematical models will be developed to predict and test for different outcomes. Of key interest is determining the degree to which the loss of species is due to chance events alone and the degree to which the characteristics of species that make some more susceptible to being lost than others. This work will engage undergraduate students in the development, design and implementation of each stage of the project. This research training of undergraduates in experimental design and theory and the use of modeling approaches will prepare the next generation of scientists to address pressing environmental issues.
Empirical data and perspectives provide conflicting evidence as to whether species extirpations and extinctions are best explained by random chance or by selective trait-based processes. This proposal uses artificial aquatic and terrestrial mesocosm environments to test a framework for clarifying when probability alone or ecological determinism, acting through species identity and traits, predict and explain patterns of local and regional extinctions. Through a combination of manipulative experiments, modeling and null analyses, this study will 1) test the prediction that local extinctions caused by habitat loss will be explained by species rarity alone; 2) determine whether delayed extinctions (extinction debt) after habitat loss are the function of random chance or selective, deterministic processes; and 3) test whether ostensibly selective disturbances, such as predator addition and habitat homogenization, may overwhelm the importance of random chance and rarity in explaining patterns of local and regional extinction. Understanding how and why species go extinct will allow for the prediction and prevention of extinctions, which is essential for the successful management and conservation of biodiversity.
