Over the past three decades the colonial ascidian Didemnum vexillum has been expanding its global range, significantly impacting marine habitats and aquaculture facilities. What biological features make D. vexillum so highly invasive? Here, we show that juxtaposed allogeneic D. vexillum colony fragments ('ramets') may, initially, form chimeric entities. Subsequently, zooids of the differing genotypes within such chimeras coordinately retreat away from fusion zones. A few days following such post-fusion retreat movements there is further ramet fission and the formation of zooid-depauperate tunic zones. Using polymorphic microsatellite loci to distinguish between genotypes, we found that they were sectorial at the fusion zones and the subsequent ramet movements resulted in further spatial separation of the pairedgenotypes indicating that the fusion events observed did not lead to formation of long-term, stable chimeras. Thus, movements of D. vexillum colony ramets from initial fusion zones lead to progressive segregation of genotypes probably minimizing potential somatic/germ-cell competition/parasitism. We speculate that relatively fast (≤10 mm/day) movement of D. vexillum colonies on substrates along with frequent, and perhaps unrestrained, transient allogeneic fusions play significant roles in this species' striking invasiveness and capacity to colonize new substrates.
Bibliographical noteFunding Information:
This work was funded by the New Zealand Ministry of Business, Innovation and Employment (MBIE) and there was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
© 2018 Fidler et al.
- Invasive species
- Substrate acquisition
ASJC Scopus subject areas
- Neuroscience (all)
- Biochemistry, Genetics and Molecular Biology (all)
- Agricultural and Biological Sciences (all)