Global gene flow releases invasive plants from environmental constraints on genetic diversity

Abstract

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata. Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.

Genetic analyses reveal complex introduction histories for the invasive tree Acacia dealbata Link around the world

“…and can contribute to a lack of clear genetic structure (Cristescu, 2015;Smith et al, 2020), as was evident in both ranges. Admixture between previously isolated populations can have an important influence on the invasion success of a species (Dlugosch et al, 2015).…”

“…While our ABC modelling approach did not clearly support a specific introduction scenario for Chile and Madagascar, our Bayesian assignment analyses suggest that these populations exhibit patterns consistent with admixture between different sources following multiple introductions. Such a geographic reshuffling of genetic diversity is generally considered as being beneficial for maintaining high diversity levels and can contribute to a lack of clear genetic structure (Cristescu, 2015; Smith et al., 2020), as was evident in both ranges. Admixture between previously isolated populations can have an important influence on the invasion success of a species (Dlugosch et al., 2015).…”

MetaPopGen 2.0: A multilocus genetic simulator to model populations of large size

“…The recursion equations of MetaPopGen 2.0 are based on the frequency‐based approach of MetaPopGen , which greatly reduces computation time and memory needs to simulate populations with large numbers of individuals. This advantage has made MetaPopGen an useful tool to explore the processes shaping the genetic structure of species with abundant populations, such as marine fish and invertebrates (Handal et al., 2020; Marandel et al., 2018) and terrestrial plants (Smith et al., 2020). Memory needs and computation time increase with the number of loci simulated, because the numbers of possible unique gametes and genotypes increase geometrically with the number of loci and alleles per locus (Box 2), and increasing the number of classes entails a parallel increase in computation time.…”

Trait differentiation between native and introduced populations of the invasive plant Sonchus oleraceus L. (Asteraceae)

“…However, as has been shown in some recent studies (e.g. Smith et al 2020), genetic structure amongst introduced plant populations is often weaker than amongst native populations due to multiple introductions (whereby propagules are sourced from multiple sites across the native range), resulting in subsequent genetic admixture and expression of novel genotypes. Such novel genotype expression in introduced S. oleraceus populations might have resulted in the observed divergence in phenotypic responses to novel climate.…”