Most ecological studies of species interactions have focused on negative consequences such as competition, predation, and parasitism. However, different species also can interact in nature so as to enhance each other?s ability to reproduce, grow, or survive. The intensity and consequence of these mutualisms is hypothesized to be dependent on environmental conditions. This project will address that hypothesis through a study of a common interaction among fish species in North American rivers and streams. Nest association is a phenomenon whereby one or more species deposit their eggs in the nest of a host species and leave the care of the nest to the host. Although mostly considered mutually beneficial to the species involved, current understanding of nest association lags critically behind other mutually beneficial interactions known in nature. This research project will focus on Bluehead Chub and Mountain Redbelly Dace, a pair of fish species commonly found in the New River basin in Virginia. How species trade services in terms of egg production and nest maintenance to benefit each other?s reproduction and survival of offspring will be examined through in-stream experiments. In particular, this research will determine how important this trade is to each species when nesting material is scarce and when there is high threat from other fish that may eat eggs on the nest. Previous research suggests that nest association may be one of the key mechanisms by which many stream fishes continue to survive degradation to stream quality caused by urban and agricultural development.

The results of this project will help resource managers working to maintain fish species diversity in stream habitats subject to disruption through various land uses and invasive species. This project will provide research experiences for undergraduate students from groups underrepresented in biology and ecology, including students from the University of Arkansas at Pine Bluff, an under-resourced university with over 90% African American student enrollment.

Project Report

Intellectual Merit The results found in this study were mostly consistent with predictions of the biological markets model borrowed from the field of economics. Mountain redbelly dace did not reproduce in the absence of the bluehead chub, implying an obligate mutualistic relationship for the dace. In scare substrate conditions, both the chub and dace reproduced more successfully when the other species was present. Similarly, in the presence of a large number of predators, reproduction was more successful for both species in the presence of each other. One prediction of this research was that egg predators will cause an overall lower success of reproduction for both species, but results turned out to the contrary, and further investigation of this phenomenon is called for. As a relatively new model for understanding mutualism in ecology, this study is the first application of the biological markets model to vertebrate communities that we know. This study, thus, contributes significantly to the development of mutualism theory, not only in freshwater systems but also in vertebrate community ecology in general. The emerging paradigm of context dependency of the outcome of interactions among species requires rigorous testing in a variety of systems. The model system used in this study (nest-spawning stream minnows) is rich in opportunities for developing the theory because minnows are common in the eastern United States and many parts of the world, streams are relatively accessible systems, and our knowledge base is increasing about how to successfully study the system in an experimental way. This study has contributed many techniques for studying nest-spawning minnows as a mutualistic system. Broader Impacts Previous research suggests that nest association may be one of the key mechanisms by which many stream fishes continue to survive drastic changes caused to streams by urban and agricultural development and the spread of non-native fishes. The results of this project, along with other projects of the PI's lab support continuing development of tools to manage streams, to maintain the keystone chub and its mutualist network in the ecosystem, and to increase the public's appreciation for the connections among the species they love and the ecosystems they like to see around for future generations. This project, although grounded in basic science, has thus added to knowledge that has significant conservation implications. The public understands the role of nature in the health of communities and support research that seeks to help maintain functioning ecosystems for current and future generations. As a result, natural resource users were involved in this project in a variety of ways. Generous private land owners and the town of Blacksburg gave their lands for this research because of their expectation that the research will contribute to better management of streams and native fish species. The project took advantage of its strategic locations (by main roads and public parks) to educate the public about conservation when individuals of the public inquired. This project offered more than 20 students spanning high school to doctoral studies the opportunity to develop professionally. Most of the students who were transitioning (high school to college or college to graduate studies) have made it to the next stage, bringing with them vital skills from the project that have made them better students and professionals. All these students will eventually become academics, trainers and resource managers/conservationists, thus multiplying the effect of this project on science. Notably, several individuals of underrepresented groups benefited from research experience for undergraduates (REU) and other training opportunities on this project. Also worthy of special mention, a high school student was trained on this project and transitioned to Virginia Tech and she is now a sophomore in the Honors College and Department Fish and Wildlife Conservation ( ) This project reached out to stakeholders from the outset and involved several local organizations. Numerous presentations have been made at conferences to communicate results to the scientific community. Manuscripts have also been written and submitted for publication in a timely fashion. Several non-technical presentation of this work have also been published, including the award-winning American Fisheries Society student writing contest article by the PhD student on this project, a Virginia Tech university profile of the PI and this research in the university Research Magazine (, and Virginia Department of Game and Inland Fisheries highlighting of this project and their collaboration in the agency newsletter. The PI and graduate students on the project made presentations about the project to groups, including Virginia Master Naturalists program (a group of volunteers, educators, citizen scientists, and stewards engaged in conservation efforts in Virginia), and Catawba Landcare (a conservation oriented riparian landowner association whose members provided access to the North Fork Roanoke river for the experiments. Another one of the experiments was carried out at the Catawba sustainability center in furtherance of Virginia Tech’s conservation and outreach efforts.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Alan James Tessier
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