DISSERTATION RESEARCH: The ax and wedge of competition shapes symbiont diversity

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

The term symbiosis has many technical and non-technical definitions, but here symbiosis simply means that the lives of two species are intimately linked by exchanges of resources and services or provisioning of habitat, such as when one organism lives on or inside another. Most plants and animals are engaged in symbioses. In many cases, organisms cannot live without their symbionts. Moreover, the life of an organism may depend on many kinds of symbiotic interactions with many kinds of symbionts. For instance, human nutrition, development, and immune function depend on interactions with thousands of internal and external bacterial species. However, current symbiosis theories cannot account for the evolution and maintenance of diversity in symbiont communities. The proposed project will explore patterns of ecological and evolutionary similarities among species of worms which live in symbiosis with crayfish to show how competition among symbionts can limit symbiont diversity by excluding less competitive species, but also create diversity by favoring the evolution of new symbiont species. Because symbiont diversity is often necessary for an organism?s survival, an understanding of symbiont diversity is needed to predict the fate of many species in a rapidly changing world. Therefore this work will have far-reaching implications for disparate fields such as conservation, epidemiology, and agriculture. The proposed work includes a collaboration with Dr. Mike Rosenzweig, director of the Seek Education, Explore, and DiScover (SEEDS) program as part of the Virginia Tech Biological Science Outreach. The investigators will disseminate their findings through public lectures and demonstrations at the Price House Nature Center in Blacksburg, Virginia. These activities will raise public awareness of the intriguing symbioses that occur just beyond their back door and provide a first-hand experience with charismatic native species. Competition may play a dual role in shaping local biodiversity; it can limit local diversity through competitive exclusion, or it can create diversity through disruptive selection. Observation of contemporary patterns alone cannot distinguish these processes because both yield similar patterns. The proposed work will extend beyond contemporary patterns of symbiont assemblages to search phylogenetic history for evidence of the evolutionary processes that create and shape symbiont diversity. The researchers will do this by combining ecological data of functional traits and broad scale assessment of patterns in biodiversity with a phylogenetic reconstruction of evolutionary history using genetic sequence data, in order to elucidate the evolutionary processes that create symbiont diversity.