Living in two worlds: Evolutionary mechanisms act differently in the native and introduced ranges of an invasive plant

Abstract

Identifying the factors that influence spatial genetic structure among populations can provide insights into the evolution of invasive plants. In this study, we used the common reed (Phragmites australis), a grass native in Europe and invading North America, to examine the relative importance of geographic, environmental (represented by climate here), and human effects on population genetic structure and its changes during invasion. We collected samples of P. australis from both the invaded North American and native European ranges and used molecular markers to investigate the population genetic structure within and between ranges. We used path analysis to identify the contributions of each of the three factors—geographic, environmental, and human‐related—to the formation of spatial genetic patterns. Genetic differentiation was observed between the introduced and native populations, and their genetic structure in the native and introduced ranges was different. There were strong effects of geography and environment on the genetic structure of populations in the native range, but the human‐related factors manifested through colonization of anthropogenic habitats in the introduced range counteracted the effects of environment. The between‐range genetic differences among populations were mainly explained by the heterogeneous environment between the ranges, with the coefficient 2.6 times higher for the environment than that explained by the geographic distance. Human activities were the primary contributor to the genetic structure of the introduced populations. The significant environmental divergence between ranges and the strong contribution of human activities to the genetic structure in the introduced range suggest that invasive populations of P. australis have evolved to adapt to a different climate and to human‐made habitats in North America.

Competition among native and invasive Phragmites australis populations: An experimental test of the effects of invasion status, genome size, and ploidy level

“…Such populations may not be successful in highly productive wetlands in Europe dominated by P. australis (Ellenberg, ) where only competitive populations would survive. This is in accordance with the results of Guo, Lambertini, Nguyen, Li, and Brix (), Guo, Lambertini, Pyšek, Meyerson, and Brix () who showed that the populations invading in North America may have arrived on this continent preadapted from Europe and experience further postintroduction evolution in response to the new environment.…”

Climate outweighs native vs. nonnative range‐effects for genetics and common garden performance of a cosmopolitan weed

“…In addition, the eco‐evolutionary history of nonnative populations is often too short to allow the populations to reach isolation by environment equilibrium (Guo et al. ).…”

“…This may be because the demographic histories of nonnative populations are assumed to be more strongly influenced by stochastic elements than the demographic histories of native populations (e.g., due to more frequent founder events and population admixture; Verhoeven et al 2011). In addition, the eco-evolutionary history of nonnative populations is often too short to allow the populations to reach isolation by environment equilibrium (Guo et al 2018).…”

“…However, surprisingly little is known about whether stochastic demographic processes vs. isolation by environment affect genetic differentiation in a similar or idiosyncratic manner in native as compared to nonnative ranges and how this may ultimately contribute to an understanding of biogeographical variation in the performance of native vs. nonnative populations (Guo et al. ).…”

“…Unraveling how stochastic demographic processes (e.g., founder effects, isolation by distance, admixture) and isolation by environment jointly affect the genetic differentiation of nonnative populations can increase our ability to reconstruct their invasion histories (Keller et al 2009). However, surprisingly little is known about whether stochastic demographic processes vs. isolation by environment affect genetic differentiation in a similar or idiosyncratic manner in native as compared to nonnative ranges and how this may ultimately contribute to an understanding of biogeographical variation in the performance of native vs. nonnative populations (Guo et al 2018).…”