Seasonal Differences in Diet Specialization, Frugivory, and Seed Dispersal in a Subtropical Population of Gopher Tortoise

Authors

Adrian Figueroa, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Earth Systems Science

First Advisor's Name

Hong Liu

First Advisor's Committee Title

Committee co-chair

Second Advisor's Name

Joel T. Heinen

Second Advisor's Committee Title

Committee co-chair

Third Advisor's Name

Clinton N. Jenkins

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Steven M. Whitfield

Fourth Advisor's Committee Title

Committee member

Keywords

Niche variation, individual specialization, frugivory, seed dispersal, ecological networks

Date of Defense

11-8-2023

Abstract

This dissertation is the culmination of a 1.5-year research project into the unique ecology of gopher tortoises (Gopherus polyphemus) at the southeasternmost extent of the species’ range. This study population occupies the globally imperiled pine rockland ecosystem of Miami-Dade County, Florida, USA, of which >98% no longer exists outside Everglades National Park. My research unveiled a seasonal shift in the diet of the gopher tortoise population where individuals became more specialized in the wet season (June to November) than in the dry season (December to May). This temporal difference in diet specialization coincided with a shift toward frugivory. As frugivory increased, so did diet specialization even after accounting for seasonal effects in the analysis. I subsequently quantified the temporal patterns of frugivory and how different fruit species contributed to the frugivorous diet of the gopher tortoise. Out of the 16 fleshy-fruited plant species consumed, five explained >95% of the variation in frugivory by the tortoises. I then found that as frugivory increased, so did the number of fleshy-fruited species being dispersed, alluding to a potential broadening in the partner plant species whose seeds the gopher tortoises disperse as they become more frugivorous. Lastly, I used network theory to construct and analyze an intra-specific seed dispersal network and further examined how morphological traits, seasonality, and the endozoochory (i.e., fleshy fruit) dispersal syndrome shape seed dispersal interactions in this population. Carapace length was the strongest predictor for how specialized the tortoises were in their seed dispersal interactions and how diverse their range of partner species were. As carapace length increased, tortoises were more generalized and more diverse in the partner plant species whose seeds they would disperse. Further analyses revealed that wet and dry season networks were very different from one another due to network rewiring, which I confirmed was the result of both seasonality and the dispersal syndrome of fleshy-fruited plants in the network. This demonstrated that the functional role of the gopher tortoise shifts intra-annually to become more frugivorous not only through its diet, but by interacting with and dispersing the seeds of many fleshy-fruited species during the wet season.

Identifier

FIDC010977

ORCID

0000-0001-8361-0653

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Recommended Citation

Figueroa, Adrian, "Seasonal Differences in Diet Specialization, Frugivory, and Seed Dispersal in a Subtropical Population of Gopher Tortoise" (2023). FIU Electronic Theses and Dissertations. 5143.
https://digitalcommons.fiu.edu/etd/5143