Meeting Abstract

P2.198  Saturday, Jan. 5  Global population structure of the widely introduced tropical ascidian Botrylloides nigrum SHEETS, E.A.*; RUIZ, G.M.; ROCHA, R.M.; COHEN, C.S.; Romberg Tiburon Center for Environmental Studies and Department of Biology, San Francisco State University; Smithsonian Environmental Research Center; Departamento de Zoologia, Universidade Federal do Paraná; Romberg Tiburon Center for Environmental Studies and Department of Biology, San Francisco State University bethsheets@gmail.com

Studies of marine introductions in tropical regions are extremely limited, and our current understanding of global invasion events is based mainly upon studies in temperate habitats. New surveys are highlighting tropical marine invasion hotspots, and this presents a great need for studies characterizing invasion processes in these areas. Here, we are using a multi-gene approach to investigate global population structure of the broadly introduced tropical ascidian Botrylloides nigrum, by comparing mitochondrial cytochrome oxidase subunit I (COI) with nuclear polymorphic markers. We have currently analyzed a 529-bp region of COI in 181 samples from 12 populations (9 Atlantic and 3 Pacific locations). We have found 3 haplotypes and 12 singletons at this locus, and two of these haplotypes are very abundant, where one is globally distributed and the second appears to be restricted to the Atlantic Ocean. Populations at each entrance to the Panama Canal share the global haplotype, suggesting that the Panama Canal may serve as an invasion corridor between the Atlantic and Pacific Oceans. To date, the highest haplotype diversity (~0.622) is found in the Caribbean region (4 of our sampled populations). We are expanding our sampling with additional locations and loci to test hypotheses about invasion pathways.