COS 16-2 - Warming up mutualisms: a case study of an ant–dispersed plant, Sanguinaria canadensis

Monday, August 15, 2022

1:45 PM – 2:00 PM EDT

Location: 516D

Presenting Author(s)

MB

Melissa A. Burt

PhD Candidate
Virginia Tech
Blacksburg, Virginia, United States

Slides (PDF)

Coauthor(s)

AN

Annika S. Nelson

Postdoctoral Associate
Virginia Tech
Blacksburg, Virginia, United States
CK

Charles Kwit

University of Tennessee
Knoxville, Tennessee, United States
SW

Susan R. Whitehead

Assistant Professor
Virginia Tech
Blacksburg, Virginia, United States

Background/Question/Methods

A majority of plants require animals for seed dispersal. To predict how plant distributions will be impacted by anthropogenic climate change, we need to understand how warming affects both partners in these mutualisms. Seed dispersing ants play an important role in structuring plant populations and communities across terrestrial ecosystems. While previous research indicates warming temperatures will impact the plant and ant partners in seed dispersal mutualisms, controlled experiments manipulating the thermal environment of the ants and plants together will give us a better understanding of how warming might affect the process of seed dispersal by ants. We used a greenhouse experiment to test the effects of warming on Aphaenogaster rudis colonies and the ant-dispersed plant Sanguinaria canadensis. During the course of the experiment, we measured ant colony survival and activity. Additionally, in our fully crossed design experiment we conducted a seed dispersal assay where we fed seeds from warmed and ambient plants to the ant colonies in warmed and ambient conditions. With this experiment we asked: (1) How do ant-dispersed plants and their ant mutualists individually respond to warming? and (2) What is the effect of warming on the quantity and quality of the seed dispersal services provided by ants?

Results/Conclusions

We found that colony and worker survival did not differ between warmed and ambient conditions. However, colonies in ambient conditions consumed ~62% more mealworms over the course of the experiment than colonies in warmed conditions. Similarly, we found that ambient colonies removed more seeds during the first six hours of seed placement, although these differences had disappeared by 24 hours. Overall, these results suggest that warming will impact seed dispersal of ant-dispersed plants via effects of warming on ant activity and not through changes to worker or colony survival and abundance. Slower seed dispersal under warming may result in fewer seeds dispersed with the possibility of an increased risk for seed predation. Although, in the absence of seed predators, this may also give more time for neighboring colonies located farther away to move seeds, potentially resulting in less clumped plant distributions. More field-based studies of ant-mediated seed dispersal are needed for a better understanding of the consequences of warming on seed fate. Given that ants influence plant distributions via seed dispersal in terrestrial ecosystems throughout the world, a greater understanding of the impacts of warming on this mutualism is critical to understanding the impacts of warming on ecosystems.