Preadapted for invasiveness : do species traits or their plastic response to shading differ between invasive and non-invasive plant species in their native range?

Abstract

Aim: Species capable of vigorous growth under a wide range of environmentalconditions should have a higher chance of becoming invasive after introductioninto new regions. High performance across environments can be achieved eitherby constitutively expressed traits that allow for high resource uptake underdifferent environmental conditions or by adaptive plasticity of traits. Here we test whether invasive and non-invasive species differ in presumably adaptiveplasticity.Location: Europe (for native species); the rest of the world and North America inparticular (for alien species).Methods: We selected 14 congeneric pairs of European herbaceous species thathave all been introduced elsewhere. One species of each pair is highly invasiveelsewhere in the world, particularly so in North America, whereas the otherspecies has not become invasive or has spread only to a limited degree. We grewnative plant material of the 28 species under shaded and non-shaded conditionsin a common garden experiment, and measured biomass production andmorphological traits that are frequently related to shade tolerance and avoidance.Results: Invasive species had higher shoot–root ratios, tended to have longer leafblades, and produced more biomass than congeneric non-invasive species bothunder shaded and non-shaded conditions. Plants responded to shading byincreasing shoot–root ratios and specific leaf area. Surprisingly, these shadeinducedresponses, which are widely considered to be adaptive, did not differ between invasive and non-invasive species.Main conclusions: We conclude that high biomass production across differentlight environments pre-adapts species to become invasive, and that this is notmediated by plasticities of the morphological traits that we measured.