Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Quantitative Biology
Department
Biology
First Advisor
Luke Frishkoff
Abstract
Understanding what forces determine species occurrence is central to studies of community ecology. Species interact with each other and their environment, and these interactions scale up to shape global patterns of diversity. In my first chapter, I examined how predation might shape patterns of Anolis lizard species richness and abundance across landscapes on islands in the Greater Antilles. I quantified predatory bird occurrence by using thousands of observations from an online citizen science database (eBird). I then obtained estimates of anole abundance and diversity by conducting local field surveys and using mark-resight methods. While predators could negatively impact anole abundance and diversity, they may also promote species coexistence by reducing the competitive dominance of any one species. While my data showed some evidence for reduced abundance in areas where predation is high, lizard diversity tended to increase with predator occurrence. Both predator occurrence and lizard abundance and diversity were predicted by climate, suggesting bottom-up drivers of species occurrence. In my next chapter, I examine the relative roles of competition and resource availability in driving dietary niche expansion in mainland and island Anolis lizards. I used DNA metabarcoding to determine the dietary niche breadth of hundreds of anole individuals at sites in mainland Ecuador and the island of Puerto Rico. This system is useful in that local anole species richness on islands tends to be higher than on the mainland, contrary to many other systems. I found that populations of species with more competitors present had narrower dietary niche breadths and lower intraspecific diet overlap. Population-level diet breadth was also narrower at sites with more insect biomass, but this niche contraction was a result of less intraspecific diet overlap, in contrast to niche expansion as a result of competitive release. In my fourth chapter, I scale up from communities to geographic distributions. Specifically, I identify potential mechanisms by which precipitation may limit species ranges. The Texas spiny lizard Sceloporus olivaceus has a range that corresponds to high and low mean annual precipitation. While precipitation might be limiting the species directly, I predicted that it may be doing so indirectly through its effects on temperature, which is known to be critical in shaping the life history of reptiles. I collected critical thermal maximum (CTmax) and thermal preference (Tsel) data for S. olivaceus. I also obtained 20 months of microclimate data along a precipitation gradient at sites within and outside the range of the lizard. While the driest site had a suitable proportion of temperatures within the thermal preference of S. olivaceus, temperatures in the summer were at times 100% above their CTmax. Conversely, the wettest site experienced very few temperatures above the CTmax, but also had a restricted window of time in the year where temperatures were within the preferred temperature range. This highlights the ways in which precipitation can limit ranges, not directly through moisture availability, but indirectly through effects on thermal quality of the habitat.
Keywords
diversity, thermal biology, lizards, anolis, sceloporus, predation, competition, community ecology, dietary niche, Texas
Disciplines
Biology | Ecology and Evolutionary Biology | Life Sciences
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Folfas, Edita, "INTERSPECIFIC INTERACTIONS AND RESOURCE AVAILABILITY AS DRIVERS OF SPECIES OCCURRENCES" (2025). Biology Dissertations. 229.
https://mavmatrix.uta.edu/biology_dissertations/229
Comments
Degree granted by The University of Texas at Arlington