Invasion of encrusting bryozoans of the genus Watersipora during the past ~50 years has created a significant ecological disturbance to many coastal areas. The occurrence of separate-source introductions and latitudinal clines (observed from mtDNA patterns) suggests that genetic variance and adaptation may be important factors in controlling introductions. Previous studies indicate a rapidly re-arranging complex of cryptic species in harbors. The unique success of Watersipora in this 'fouling' niche on ship hulls evokes a mechanism for invasion, and adaptations (e.g., to temperature or copper anti-fouling paints) that would facilitate transport. Knowing the degree to which invasions are facilitated by genetic adaptation versus propagule pressure alone is critical for understanding, and predicting, the success of exotic species in shallow marine ecosystems.
In this study, genetic variation in the Watersipora complex will be quantified using microsatellite markers, as well as COI gene sequences. In addition, "common-garden" experiments will be conducted to examine the role of past selection events involving two selective agents (temperature and copper anti-fouling paint) in influencing the success of various genotypes in different metapopulations. Focusing on populations in California, a coastline recently experiencing multiple Watersipora invasions, there are three major goals of this research. (i) To use 12 microsatellite loci to identify past or present reproductive barriers in the complex of Watersipora species, both to better define the relevant units of selection, and to reconstruct the dynamics of introductions and spread of these species. (ii) To examine the relationship between colony growth rate, genotype and temperature to determine whether growth rate correlates with genetic lineage or the environment (temperature) of the source population. (iii) To examine larval-stage tolerance to dissolved copper, assessing whether variation in this trait correlates with genetic background; if so, spread of Watersipora into new harbors may depend on antifouling paints (on hulls), as well as on vessel traffic.
Intellectual Merit: These experiments will reconstruct the dynamic sequence of introductions in one of the most remarkably successful groups of invasive species (Watersipora spp.) in marine coastal habitats (harbors and bays) world-wide. The research will shed light on the phylogeny of this genus. A combination of gene-based studies and lab-based experiments will test the influences of propagule pressure, existing phenotypic variation, and evolutionary adaptation (temperature, copper paints) toward understanding the successful traits of this highly invasive species complex.
Broader Impacts: A major goal of this "primarily undergraduate institution" (Evolutionary Processes) proposal is to provide hands-on research experience in ecological genetics for undergraduates from two different institutions within the California State University (CSU) system. The approach and findings from this research also will be integrated into 6 classes (Evolution, Ecological Genetics, Invertebrate Zoology, etc) at both campuses, impacting >150 undergraduate students each year, including those under-represented in science at the Universities. Results of this mechanistic study will have important implications for managing the spread of invasive species in harbors and bays around the world.
