Recent or relic distribution? The nudibranch Glossodoris sedna in the Caribbean

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Invasive species are an increasing problem for many parts of the world, and will continue to be as global climate change advances. Although the majority of introduced species do not cause major anthropogenic problems their influence on other endemic species can be difficult to determine. It can be difficult to distinguish between newly invading species, and those that have previously not been detected by baseline surveys. This is particularly pertinent for small marine invertebrates.

Glossodoris sedna is a sea slug that is widespread in the tropical east Pacific, occurring from Mexico to the Galapogos Islands. The first records of Glossodoris sedna in the Caribbean were reported by Bertsch (1988) from Tavernier Key and Key Largo. Humann (1996) indicated a number of specimens from the Biscayne Bay area, but the spate of recent records on the Sea Slug Forum ( indicate that both of these locations support permanent populations of G. sedna. The relatively recent records of G. sedna in the Caribbean has led people to conclude that its occurrence there is the result of human-induced activities, such as shipping. However, there is another chromodorid nudibranch species that also occurs naturally on both sides of the Isthmus of Panama (Tyrinna evelinae).

This is one of the few opportunities to directly determine if a recently discovered population actually represents a marine introduction. This is possible only because the east Pacific and Caribbean are separated by a geological barrier to gene flow. It is imperative that the identity of the Caribbean specimens is determined in a rigorous manner, as it is still possible to control the 'invasion', if that is what the records truly represent.

The project will conduct a phylogeographic study on Glossodoris sedna, and examine DNA sequences from all parts of its range. Analyses will uncover genetic parameters that enable us to detect levels of relatedness and gene flow between populations. This will, in turn, allow us to infer patterns of historical distribution.

Contact Information

Dr. Nerida Wilson
Scripps Institute of Oceanography
(%00 Gilman Drive
La Jolla, CA 92093-0202