Meeting Abstract
P2.95 Saturday, Jan. 5 Inter-colony fusion in the invasive colonial tunicate Didemnum vexillum VANDER LINDEN, A.*; CLANCY, D.; COHEN, C.S.; Romberg Tiburon Center, San Francisco State University, CA; Romberg Tiburon Center, San Francisco State University, CA; Romberg Tiburon Center, San Francisco State University, CA avanderl@uw.edu
The colonial tunicate Didemnum vexillum has aggressively invaded coastal marine habitats around the globe. Many ecological aspects of this species are not well understood, including the occurrence of fusion between colonies. Fusion is known in other colonial tunicates, most notably Botryllus schlosseri, in which it occurs only between individuals sharing an allele at a highly variable allorecognition locus. In the didemnid family, a genetic basis for fusion was not found in Diplosoma listerianum, but has been suggested for D. vexillum. The exact mechanism of fusion in D. vexillum is still unknown, but if there is a genetic component, we would expect to see higher rates of successful fusions in colonies that are genetically similar. To investigate the phenomenon of fusion within the D. vexillum population of San Francisco Bay, we carried out colony fusion assays at field sites and observed the frequency and details of the fusion process. Self-fusions had an 80% success rate (n=6), and inter-colony fusion occurred in 53% of assays (n=17). Genetic analysis revealed that four different haplotypes were present at the mitochondrial cytochrome oxidase subunit 1 (CO1) locus in the colonies collected for fusion assays. Although CO1 serves as a measure of genetic similarity and does not itself determine fusion, the increased rate of fusion in conjunction with lower genetic diversity when compared to other studies of the native range suggests a genetic component to fusion in D. vexillum. Comparison of CO1 sequences between colonies shows a preliminary trend of higher fusion rate in pairs with identical haplotypes. However, further genetic data from fusion pairs is needed to support this relationship and provide insight into the competitive strategies of invasive populations.
