High genetic diversity in an invasive population of mussels

What is it about?

This work was part of my dissertation research, and was an investigation using nuclear microsatellite markers, comparing invasive and native populations in terms of genetic variation. There is a long standing theory that invasive species undergo population bottlenecks and founder events, and thus tend to have diminished genetic variation relative to the geographic source population. The findings here go counter to many decades of invasion genetics theory, essentially overturning the assumption that source populations have higher genetic diversity than invading populations. This was not the case, as no reduction in genetic variation was detectable, suggesting that a very large number of propagules, in this case larval marine mussels, have been translocated and released in the Gulf of Mexico.

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Why is it important?

This is important because this species was introduced via ballast water release from a bulk carrier, in this case a commercial oil tanker from Venezuela. Many releases of non-native species are unsuccessful, and the reasons can be multifaceted, but one of the main factors often invoked is decreased genetic diversity. This study showed that ballast water release can deliver sufficient numbers of small organisms to offset any genetic bottleneck, or decrease in genetic diversity, providing the invasive species its full compliment of genetic diversity, which is of course the raw material that allows organisms to adapt to different environments.

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