Species interactions can regulate a population’s density and therefore can act as a selective force on that population. Such
evolutionary responses have the potential to feedback and change ecological interactions between species. For species that compete for
resources, the interaction between ecological and evolutionary dynamics will regulate the stability of the species interactions, determining
whether competing species can coexist. The outcome of competition between species is determined by two factors: (1) niche overlap, or the
similarity in how species use resources and are affected by their environment, and (2) fitness differences, or differences in how efficiently
each species uses resources in their environment. Decreasing niche overlap will decrease competitive interactions, thereby stabilizing
coexistence. Decreasing fitness differences makes species more equal in their competitive abilities, facilitating coexistence. In the absence
of evolutionary constraints, both niche overlap and fitness differences among species are subject to change as a consequence of evolution
among competitors, and thus ecological dynamics between two species will also change. In this dissertation, I develop a broader understanding
of (1) how niche overlap and fitness differences between species change after evolution in response to competition, (2) how changes in niche
overlap and fitness differences are mediated through changes in resource use of protists, and (3) what role evolutionary history plays in
shaping ecological and evolutionary dynamics. I address these goals with a suite of approaches including theoretical models, an experimental
lab system, and comparative methods. I constructed a quantitative genetic model of trait evolution, where the trait of a species determined
its resource use, and found that species are prone to change in their niche overlap as well as their fitness differences as a result of trait
evolution. However, the magnitude of changes in niche overlap and fitness differences were determined by the resource availability within the
environments. When resources were broadly available, species changed more in their niche overlap, whereas when resources were narrowly
available, species changed more in their fitness difference. To test these predictions, I developed a system in the laboratory where protists
competed for a bacterial resource. Species were allowed to evolve in either monoculture or a two-species mixture; the effects of evolution on
competition, niche overlap and fitness differences were quantified using parameterized models. In general I found that species tended to
converge in their niche as a result of evolution, however, changes in fitness differences between species were larger and more influential on
coexistence than changes in niche differences. Both increases in niche overlap, and increases in fitness differences decreased coexistence
among species pairs. By describing the bacterial communities associated with these protists before and after selection I determined that
protists tended to converge or not change in which bacteria they were consuming as a result of selection. Additionally, for eleven protist
species, I determined whether traits or relatedness predicted competitive ability by placing species on a molecular phylogeny and conducting
pairwise competition experiments for all pairs. I found no correlations, suggesting neither traits, nor evolutionary history was informative
for explaining current ecological and evolutionary interactions in this deeply divergent clade. There are two major conclusions from this
dissertation: (1) when species evolve in response to competition, changes in fitness differences may often be more important than changes in
niche overlap, (2) evolution can, and may be likely to, decrease the ability of species to coexist through increases in niche overlap and
increases in fitness differences. This work suggests that one must simultaneously consider the role of evolutionary and ecological processes
to understand community processes. Specifically, when researchers are attempting to explain mechanisms of coexistence between species, they
must consider how evolutionary dynamics may change the ecological interactions within communities of competitors. / A Dissertation submitted to the Department of Biological Science in partial fulfillment of the requirements
for the degree of Doctor of Philosophy. / Summer Semester 2017. / August 4, 2017. / Coexistence, Competition, Evolution, Fitness Difference, Niche Overlap, Selection / Includes bibliographical references. / Thomas Miller, Professor Directing Dissertation; Richard Bertram, University Representative; Brian
Inouye, Committee Member; Scott Steppan, Committee Member; Alice Winn, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_605001 |
| Contributors | Pastore, Abigail I. (Abigail Ilona) (author), Miller, Thomas E. (professor directing dissertation), Bertram, R. (Richard) (university representative), Inouye, Brian D. (committee member), Steppan, Scott J. (committee member), Winn, Alice A. (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Biological Science (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (105 pages), computer, application/pdf |
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