Amber Brace

Parasite exposure, which is practically inevitable in the wild, typically results in activation of the innate immune system. While these responses provide rapid detection and elimination of parasites, they are also costly to hosts in many ways including increases in the use of essential amino acids to produce immune proteins. Costs experienced by hosts can sometimes be offset by abundant resources, but in most environments, resources are limited. As a result, immune costs are likely an important influence on many ecological and evolutionary phenomena, such as the diversity of immune defenses that exist among and even within populations. If immune costs are driving variation in immune responses, then it is reasonable to expect that they might also affect how parasites move through communities. If host costs of immunity increase with parasite exposure, then we would expect to see selection for hosts that tolerate infections, rather than clearing them.

Photo by Amber J. Brace

In our study recently published in Functional Ecology, we examined whether increased exposure to Salmonella lipopolysaccharide increased costs of innate immune activation in brown anoles (Anolis sagrei) by tracking allocation of an isotope-labelled amino acid (¹³C-leucine) to the liver and gonads after exposure. We found that costs of immunity are indeed dose-dependent in this introduced population of from Tampa, Florida, but the sexes experienced costs differently; males increased leucine allocation to their livers while females sacrificed allocation to their gonads. Most interestingly, costs were modest even at high doses, suggesting that at high levels of Salmonella exposure, this species may tolerate infection as the costs of resisting a high level of infection may be too great. These results are particularly interesting because they indicate that populations of brown anoles, a successful introduced species in Florida, may have been selected to have decreased costs of immune activation, and therefore increased parasite burdens. This may mean they are substantially contributing to the disease risk of native species by increasing exposure risk of Salmonella to other animals in Florida by maintaining comparatively high burdens, which they shed into the environment.

Amber J. Brace

University of South Florida, Department of Integrative Biology

One of the greatest threats to ecosystems is the continued introduction and spread of invasive species, which are commonly introduced to new areas by humans. Invasive species not only threaten nature preserves, but can harm commerce (such as zebra mussels damaging ships, or lionfish devastating fishing grounds) and pose a threat to public health by spreading disease (such as introduced rodents and mosquitoes). However, despite the problems caused by invasive species, we still know surprisingly little about what makes certain species successful in new ranges.

For my dissertation research in the Martin lab at the University of South Florida, I hope to identify the mechanisms that enable these species to survive and spread following an introduction. By identifying some of these mechanisms, we will be able to focus control efforts in a more effective manner by ascertaining which species have this potential. Specifically, I study Anolis sagrei, the brown anole, which is native to Cuba and the Bahamas, but is widespread across Florida where it has displaced the native green anole. My research aims to address if A. sagrei is able to be so successful in its introduced range in Florida because it changes the way it uses dietary resources as it invades new territory. The results of my study will not only fill a gap in the knowledge that we have on a common invasive species in Florida, but will also provide a stepping stone for future research on invasive species from other taxonomic groups.

The scientific community is no exception to having cope with budget cuts. Many labs that have traditionally depended on funding from federal agencies are finding money for research (especially ecological research) harder to come by. That is where the general public comes in. Crowd funding provides an opportunity for the general public to personally contribute to research projects and allows scientists to reach out and bridge the gap between the public and scientific communities. The support I receive from funders will be used to help me travel to different locations across the introduced range of A. sagrei in Florida and for sample processing at the University of South Florida. I will be sampling from sites close to the point of original introduction (Key Largo and Miami-Dade, FL), as well as sites where brown anoles have been reported for less than 20 years.
Please help to support my research: http://rkthb.co/25521
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Author: Amber Brace

Exposure Determines Costs of Immunity in Brown Anoles

Invasive Anole Research In Florida