High Genetic Variance in Life-History Strategies within Invasive Populations by Way of Multiple Introductions

Abstract

Biological invasions represent major threats to biodiversity as well as large-scale evolutionary experiments. Invasive populations have provided some of the best known examples of contemporary evolution [3-6], challenging the classical view that invasive species are genetically depauperate because of founder effects. Yet the origin of trait genetic variance in invasive populations largely remains a mystery, precluding a clear understanding of how evolution proceeds. In particular, despite the emerging molecular evidence that multiple introductions commonly occur in the same place, their contribution to the evolutionary potential of invasives remains unclear. Here, by using a long-term field survey, mtDNA sequences, and a large-scale quantitative genetic experiment on freshwater snails, we document how a spectacular adaptive potential for key ecological traits can be accumulated in invasive populations. We provide the first direct evidence that multiple introductions are primarily responsible for such an accumulation and that sexual reproduction amplifies this effect by generating novel trait combinations. Thus bioinvasions, destructive as they may be, are not synonyms of genetic uniformity and can be hotspots of evolutionary novelty.

Invasions and extinctions through the looking glass of evolutionary ecology

“…When adaptive variants from a genetically distinct population introgress, natural selection can act on this enhanced standing variation without waiting for new mutations to arise de novo [57]. For these reasons, and because invasive species frequently experience novel selective environments in their introduced range, admixture has been implicated as a potential factor fuelling rapid evolution and the generation of novel invasive genotypes [33,48,58]. Nevertheless, direct evidence of a link between introgressed variation and the evolution of invasiveness is largely lacking to date.…”

Changes in phytophagous insect host ranges following the invasion of their community: Long‐term data for fruit flies

“…Invasive species can also trigger horizontal reorganizations of food webs, by altering competitive relationships between species at the same trophic level through competition for resources, apparent (i.e., predator‐mediated), or interference competition. Such horizontal reorganizations may even lead to successions of invaders, with each new invader replacing the previous one as the dominant species (Facon, Pointier, Jarne, Sarda, & David, 2008). …”

Genetic admixture and heterosis may enhance the invasiveness of common ragweed

“…Several population genetic studies have revealed mixed ancestries of invasive populations reflecting genetic admixture of multiple divergent native source populations (e.g., Kolbe et al., 2004; Rosenthal, Ramakrishnan, & Cruzan, 2008; Chun, Fumanal, Laitung, & Bretagnolle, 2010; Stephen R. Keller, Gilbert, Fields, & Taylor, 2012). Moreover, some studies also provide evidence for phenotypic changes and effects on fitness associated with admixture (Kolbe, Larson, & Losos, 2007; Facon, Pointier, Jarne, Sarda, & David, 2008; S. R. Keller & Taylor, 2010). However, although these observational studies suggest a strong link of genetic admixture and invasion success, it remains difficult to disentangle the direct effects of genetic admixture (e.g., heterosis) from long‐term effects of increases in genetic variation (evolutionary potential), as well as other confounding effects such as propagule pressure that may be associated with multiple introductions.…”