“Bioinvasion triggers rapid evolution of life-histories in freshwater snails”

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Elodie Chapuis, Thomas Lamy, Jean-Pierre Pointier, Nicolas Juillet, Adeline Ségard, Philippe Jarne, and Patrice David

For the first time, a study tries to measure rapid evolution in coexisting, close invasive, and native species at the same time

Aplexa marmorata, a freshwater snail native to certain Caribbean islands. The photo was taken in one of the sites monitored in Guadeloupe, French West Indies.
(Credit: J.-P. Pointier, 2005)

Biological invasions are a major threat to biodiversity, but at the same time they have been recognized as unique field settings to observe evolutionary and ecological processes. A major issue is to evaluate how invasive species and native species evolve in the course of an invasion. Invaders and natives face different evolutionary challenges, since introduced species may not invade if they do not tolerate well interactions with natives, while the reverse is not necessarily true. Therefore, traits in natives should be selected to minimize negative impacts of invaders, while trait evolution in invasives should rather be constrained by colonization dynamics, reflecting selection for colonizing ability and/or transient mutation accumulation at the colonization front (the so-called expansion load).

These ideas are tested by Chapuis and colleagues in a collaborative work between researchers from IRD Montpellier and La Réunion and from the CNRS-CEFE in Montpellier, by comparing populations invaded at different times in two competing related species, one invasive and one native. The authors apply this approach through a common-garden experiment in two freshwater snails competing in the pond network of a tropical island. In agreement with their hypothesis, they find evidence of rapid evolution of life-history traits in the native species in a way that favours coexistence with the invasive, while trait changes in the invasive species reflect slightly decreased performances at the invasion front as predicted by the expansion load hypothesis.

This study not only adds to a growing number of examples of well-documented rapid evolution, but is also the first to measure evolution in coexisting, related invasive and native species at the same time. It also illustrates how the evolution of life history traits may play a role in promoting species coexistence in a guild, as suggested by recent ecological theory. Read the Article