Global change effects on ant-mediated seed dispersal

Seed dispersal mutualisms, including seed dispersal by ants, are critical to the assembly of communities and the function of ecosystems. However, the consequences of human-caused global change factors, such as habitat fragmentation and climate change, for the future of these mutualisms are not fully understood. My dissertation consists of five chapters that investigated the effects of habitat fragmentation and climate change on ants and their seed dispersal mutualisms. Chapter 1 is an introduction that provides background information on habitat fragmentation and anthropogenic climate change and their impacts on biodiversity. In Chapter 1, I also introduce my study system of ant-mediated seed dispersal mutualisms, myrmecochory. My next two chapters (Chapters 2 and 3) explored the effects of reconnecting fragmented habitat patches with corridors in restored longleaf pine savanna systems in South Carolina. We used a landscape scale experiment to investigate how reducing isolation affects the assembly of ant communities over time (Chapter 2) and seed dispersal of the myrmecochorous forb, Piriqueta cistoides (Chapter 3). For Chapter 2, we found evidence that both habitat connectivity and edge effects underly the effects of corridors on ant communities over time. We found that connected patches accumulated ant species faster than isolated patches over time suggesting that corridors function by facilitating colonization. We also found evidence that edge effects play a role with greater ant functional group diversity in patches with higher edge than patches with lower edge amounts. For Chapter 3, we also found evidence of corridor and edge effects with ants dispersing seeds of P. cistoides longer distances in patches connected via corridors than isolated patches, but only in the center of patches. In Chapter 4, we investigated the effects of predicted climate change scenarios for seed dispersal mutualisms in eastern deciduous forests. For this chapter, we conducted a mesocosm experiment in which we crossed temperature with altered precipitation magnitude and frequency. Our mesocosms contained a common spring ephemeral wildflower, Sanguinaria canadensis, and whole colonies of their mutualist seed disperser, Aphaenogaster rudis. This design allowed us to collect high-resolution data on how ants interacted with seeds under different climate change scenarios that incorporated warming temperatures and altered precipitation. We found that warming effects depended on the precipitation treatment with negative effects of warming on the collection of seeds by ants under historical precipitation regimes and positive effects of warming under simulated precipitation conditions altered under predicted climate change. Finally, Chapter 5 describes my general conclusions from this body of work. Taken together, the research making up my dissertation provides valuable insights into how changing environmental conditions under habitat fragmentation and climate change may alter ant seed dispersal mutualisms. Importantly, we often found that the impacts of global change were context dependent and that our experiments were important tools in disentangling that context dependency. Further, this work demonstrates the value of understanding the basic ecology of the interactions among organisms. Understanding the natural history of organisms across changing environmental conditions will benefit the ways in which we conserve and restore ecosystems in a fragmented and warmer world.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Biological Sciences

Department dc:contributor.department

Biological Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2024

Author dc:creator

• Burt, Melissa Ann

Chair dc:contributor.committeechair

• Whitehead, Susan

Committee members dc:contributor.committeemember

• Mims, Meryl C.
• Reid, John Leighton
• Brown, Bryan Lyle

• myrmecochory
• ant seed dispersal mutualisms
• climate change
• habitat fragmentation

Statement dc:rights

• Creative Commons Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:40520

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/119033