Abstract
Key evolutionary events associated with invasion success are traditionally thought to occur in the introduced, rather than the native range of species. In the invasive ant Wasmannia auropunctata, however, a shift in reproductive system has been demonstrated within the native range, from the sexual non-dominant populations of natural habitats to the clonal dominant populations of human-modified habitats. Because abiotic conditions of human- modified habitats are hotter and dryer, we performed lab experiments on workers from a set of native and introduced populations, to investigate whether these ecological and genetic transitions were accompanied by a change in thermotolerance and whether such changes occurred before establishment in the introduced range. Thermotolerance levels were higher in native populations from human-modified habitats than in native populations from natural habitats, but were similar in native and introduced populations from human-modified habitats. Differences in thermotolerance could not be accounted for by differences in body size. A scenario based on local adaptation in the native range before introduction in remote areas represents the most parsimonious hypothesis to account for the observed phenotypic pattern. These findings highlight the importance of human land use in explaining major contemporary evolutionary changes.
Highlights
Most recent studies trying to decipher the reasons for the success of invasive species have explicitly focused on the introduced range of invasive species (Richardson et al 2000; Sakai et al 2001; Colautti and MacIsaac 2004)
We have previously shown that abiotic conditions differ considerably between the natural and human-modified environments of W. auropunctata in its native range (Orivel et al 2009)
The pairwise FST values calculated among all populations sampled in the distribution range of W. auropunctata showed that our focal introduced populations used for thermotolerance experiments were genetically closer to native Guianese populations than to any other sampled native populations (Brazil and Costa Rica; Fig. S2)
Summary
Most recent studies trying to decipher the reasons for the success of invasive species have explicitly focused on the introduced range of invasive species (Richardson et al 2000; Sakai et al 2001; Colautti and MacIsaac 2004) This is logical given that post-introduction ecological and evolutionary challenges are likely to be more important than those occurring before long-distance dispersal. After their introduction into a new area, founding individuals generally have to cope with new demographic and/or environmental conditions when compared to their native habitats.
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