Biology and Biomedical Sciences: Evolution, Ecology and Population Biology
Date of Award
Doctor of Philosophy (PhD)
Chair and Committee
Understanding factors that limit species distributions within restored habitats has been a longstanding goal of restoration ecology, particularly with respect to differences between rare and widespread species. Numerous mechanisms have been proposed to contribute to rarity, including species traits, propagule limitation, ecological requirements, and population level processes such as demographic and environmental stochasticity. Yet, our understanding of species rarity remains limited since few studies have examined how these factors act in concert. This dissertation examines how these mechanisms may interact to influence the distribution and population establishment of plant species in restored xeric glades in the Missouri Ozarks: USA). First, I used a trait analysis of species in restored glades to determine whether traits related to niche breadth, persistence, or dispersal ability are related to species distributions. The results from this study suggest that several traits may interact to allow species to become widespread in this restored xeric habitat, including habitat specialization of open canopy environments, perennial or clonal life histories, and adaptations to arid conditions such as short plant height. To follow up these observations, I experimentally tested the degree to which propagule limitation, competitive environment: competitors present, burned, or removed), and abiotic stress: precipitation of typical dry, average and wet years) differentially limit the seedling establishment of 32 rare versus widespread species. I found that rare species established as well as widespread species in all treatments, suggesting that dispersal, rather than differences in stress tolerance or competitive ability, is the predominant limiting force for species distributions. This suggests that propagule introductions may be sufficient to increase rare species distributions. To examine how the success of propagule introduction might be influenced by propagule pressure: i.e., a single large versus several small introductions) versus habitat management during introduction: i.e., creating favorable conditions for seedling establishment), I conducted a meta-analysis with demographic modeling. My results indicate that habitat management during introduction has a much greater effect on long-term population establishment compared to propagule pressure. In summary, this dissertation demonstrates the importance of dispersal for limiting species distributions in restored habitats and also provides recommendations on how to best reintroduce rare species.
Kroiss, Steven James, "Regional Rarity: Consequences of Dispersal Limitation and Strategies for Reintroduction" (2012). All Theses and Dissertations (ETDs). 965.