Grantee Research Project Results

Alternative Reproductive Strategies and Group Dynamics in a Facultatively Eusocial Paper Wasp

EPA Grant Number: U916186
Title: Alternative Reproductive Strategies and Group Dynamics in a Facultatively Eusocial Paper Wasp
Investigators: Gunnels, Charles W.
Institution: University of Florida
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $154,844
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Entomology

Objective:

Behavior is critically important to population viability, although the effect of behavior on population dynamics is scantily studied. The growth and decline of a population is determined largely by how individuals respond to constraints found in a particular location, and cooperative breeding may indicate a response to an environmental disturbance. In times of stress, populations may remain viable if individuals exhibit behavioral modifications that allow them to respond to the new pressure. This observation led to the development of the Ecological Constraints Model, which noted that cooperative breeding vertebrates retain reproductive opportunities by engaging in social interactions during periods of environmental stress. The switch from solitary to cooperative nesting may provide for the maintenance of the population in otherwise inhospitable environments. Because of this relationship between environmental stress and cooperative breeding, cooperative breeding vertebrates are frequently at risk of extinction (e.g., Florida Scrub Jay and Red-Cockaded Woodpecker). Because of this association between cooperation and stress, we need a model system to examine environmental effects on the reproductive decision of cooperative breeding animals.

The objective of this research project is to study the alternative reproductive strategies in the facultatively eusocial paper wasp, Mischocyttarus mexicanus. In the past decade, it has become increasingly clear that facultatively eusocial wasps and cooperatively breeding birds and mammals exhibit analogous life histories that may be predicted by the Ecological Constraints Model. In addition to solitary nesting, two or more reproductively viable adults may care cooperatively for young that are not all direct descendents. Similar to the "helpers at the nest" observed in cooperatively breeding vertebrates, individual female wasps retain reproductive potential, although some forgo direct reproduction to help others raise young.

Approach:

Our understanding of social groups requires that we experimentally manipulate animals to isolate influential factors and their consequences, which is frequently difficult to accomplish with threatened or endangered vertebrate taxa. Additionally, theory developed within the social insect literature may generate predictions for at-risk cooperative breeding vertebrates, including age polyethism (i.e., adoption of age-specific roles and/or tasks within a group). Because M. mexicanus is locally abundant; easy to artificially rear; observe, mark, and manipulate; and exhibits life history variability within and among populations, they are model organisms for understanding the formation and maintenance of social groups. General patterns and predictions derived from this study could help us evaluate social behavior in at-risk cooperatively breeding vertebrates. In addition, I expect that the study will elucidate some important connections between individual behavior and population dynamics.

Supplemental Keywords:

fellowship, behavior, population dynamics, Ecological Constraints Model, eusocial paper wasps, Mischocyttarus mexicanus, cooperative breeding.

Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 358KB, about PDF)

Progress and Final Reports:

2003

2004

Final