Assembly of Invaded Plant-pollinator Communities in a Fire-adapted Pine Rockland in the Lower Florida Keys

Authors

Brittany M. Harris, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Suzanne Koptur

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Sparkle Malone

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Diego Salazar

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Hong Liu

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Michael Ross

Fifth Advisor's Committee Title

Committee member

Keywords

pollination, mutualistic networks, community assembly, invasive species, buzz-pollination, competitive exclusion, fire-suppression, modularity, plant-pollinator interactions, fire regimes

Date of Defense

10-14-2022

Abstract

Most flowering plants rely on pollinators for their long-term survival. Increasing anthropogenic change has caused concern for declining pollinator populations and plant reproduction, yet we lack an understanding of the connection between pair-wise responses and those effects on the broader community. Here, I use a network approach and species-pair responses to understand how biological introductions and altered fire regimes influence plant-pollinator network dynamics, community stability, and plant reproduction in the globally imperiled pine rockland of the Florida Keys.

I analyzed shifts in the pollinator assemblage and reproductive output of an endangered buzz-pollinated plant before and after two tropical buzz-bees invaded the Florida Keys. Permutational multivariate analyses indicated high and sustained community turnover. Exotic orchid bees dominated the post-invasion assemblage, displacing the formerly dominant native buzz-bee, but providing similar pollination services.

Network analysis of the whole plant-pollinator community suggests that the displacement extended beyond the single plant assemblage; however, other buzz-bees viii were unaffected. To understand drivers of coexistence or competitive exclusion, I analyzed network subsets consisting of the whole plant-pollinator community and a buzz-bee subnetwork. The invaded networks were highly modular and specialized, with pollinators strongly partitioning resources compared to null models of abundances. Plant-pollinator co-occurrence and seasonal onset of flowering explained modularity and niche partitioning in the buzz-bee subnetwork but not the overall plant-pollinator network.

Lastly, I analyzed the effects of altered fire regimes on network dynamics and species diversity using a time-since-fire chronosequence in the fire-adapted pine rockland. Both flowering plant and interaction richness decreased with time-since-fire. Networks of recently burned areas were more specialized and modular than expected from null models, and deviation from random decreased with increasing fire return, suggesting that prolonged fire exclusion unravels complex plant-pollinator communities.

Introduced bees can disrupt pollinator communities, but partitioning niches across seasons can promote coexistence. Although invaded networks were modular and specialized, networks became less modular with prolonged fire suppression. Modularity and niche partitioning are thought to increase community resilience by confining disturbances rather than destabilizing whole networks. Therefore, understanding how abiotic and biotic change affects community dynamics and function is essential for reducing negative impacts of anthropogenic change

Identifier

FIDC010947

ORCID

https://orcid.org/0000-0002-0667-4853

Recommended Citation

Harris, Brittany M., "Assembly of Invaded Plant-pollinator Communities in a Fire-adapted Pine Rockland in the Lower Florida Keys" (2022). FIU Electronic Theses and Dissertations. 5168.
https://digitalcommons.fiu.edu/etd/5168