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Science/Tech See other Science/Tech Articles Title: Invasive species create dangerous 'genetic hotspots' Invasive species create dangerous 'genetic hotspots' The secret of invasive species' notoriously destructive power may have been discovered. Genetic analysis of an introduced snail suggests that successive waves of invasion create a "hotspot" of evolutionary potential that means conservationists should be even more vigilant against invading species. Patrice David of France’s National Center for Functional and Evolutionary Ecology in Montpellier and colleagues examined key physiological and behavioural attributes, or "life history traits" of an invasive population of freshwater snails (Melanoides tuberculata), found on the French Caribbean island of Martinique. The snails, which are often sold in pet shops, probably arrived on the island in recent decades via plants and gravel used in household aquariums. Multiple invasions David's team sequenced key genes affecting fertility, juvenile size, and age at first reproduction in a number of snails, and found huge differences between them. The findings suggest the invading gastropods have strong potential for evolutionary change. "The genetic variation for life history traits in these snails are among the highest ever observed for any kind of animal," David says. Such genetic variance, he contends, contradicts prior theories suggesting invasive populations are "evolutionary dead ends", lacking enough genetic diversity to evolve in their new environment. The Martinique snails derive from five successive invasions of genetically distinct individuals arriving from different parts of Asia. David says that because of increased human traffic between continents, such multiple introductions from multiple locations are now common for species invasions. "Introductions are not single, chance events but repeated invasions which can accumulate diversity in these invasive populations," David says. "This makes invasive populations really full of evolutionary potential." Renewed vigilance David Lodge of the University of Notre Dame in Indiana, US, says such potential is cause for alarm: "It shows why multiple introductions of an invasive species can contribute to a particularly invasive genotype." Lodge says that when the first few individuals of a given species invade, the group often lacks the genetic diversity needed for the population to thrive in their new environment. As a result, invasive species often languish in small numbers in a localised area after their initial introduction. Lodge says that in showing high levels of genetic diversity after multiple invasions, David's work should be seen as a call for renewed vigilance against invasion. "It provides a reason to limit introduction even if a species is already established in a given environment," Lodge says. "Additional introductions can be just the trigger that causes the invasive to spread like it was shot out of a cannon." Journal Reference: Current Biology (DOI: 10.1016/j.cub.2008.01.063)
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