Evaluating differences in the shape of native and alien plant trait distributions will bring new insights into invasions of plant communities

Abstract

Failure to quantify differences in the shape of inter‐specific trait distributions (e.g., skew, kurtosis) when comparing co‐occurring alien and native plants hinders the integration of biological invasions and plant community ecology. Within a plant community, understanding the circumstances that lead to the shape of the inter‐specific distribution of one or more functional plant traits being unimodal, bimodal, multimodal or skewed has the potential to shed new light on community vulnerability to invasion, subsequent ecosystem impacts and the selection pressures (e.g., stabilizing, directional or disruptive) acting upon native and alien species. Ignoring differences in the shape of inter‐specific trait distributions of alien and native species could miss important insights into plant invasions, including: the existence of unsaturated native plant communities, empty niches, shifting trait optima of species as a result of environmental change and incomplete colonization–extinction processes following invasion. Future comparisons of functional trait differences between native and alien species should include assessment of the shapes of inter‐specific trait distributions since these may differ even when the mean values of traits are similar for native and alien species. The infrequent application of such approaches may explain the limited generalizations regarding the drivers and consequences of plant invasions in plant communities.

Similarities between invaders and native species: Moving past Darwin's naturalization conundrum

“…The use of trait means may therefore underpredict the invasion potential (Figure b). Recently, comparing the shape and overlap of trait distributions between the alien and native assemblages has been suggested as a way to reduce our reliance on average trait values and better understand whether native and alien species are responding to similar aspects of the environment (Hulme & Bernard‐Verdier, ). Comparing the distribution of trait values within a single alien population to the distribution of traits within the resident community may help identify invasive phenotypes, and thus improve our understanding of invasion.…”

Functional and phylogenetic consequences of plant invasion for coastal native communities

“…() documented changes in functional (but not phylogenetic) diversity on the west coast of Italy. Such context dependency suggests that the invader's effects on the functional and phylogenetic structure of a native plant community will depend on: (1) the phylogenetic and functional features of the native species that are more susceptible to being outcompeted by the invader, which could lead to decreased functional and/or phylogenetic diversity of the recipient community; and (2) the dissimilarity of the functional traits and the phylogenetic relatedness of the invader with respect to the recipient community, which might increase the functional and/or phylogenetic diversity by providing a novel subset of traits and/or evolutionary origins to the recipient communities (Castro‐Díez et al., ; Hulme & Bernard‐Verdier, ; Lapiedra et al., ). These two complementary sources of variation could explain the contrasting patterns that have been reported regarding the impact of invasive plant species on native communities.…”

Functional niche differences between native and invasive tree species from the southern Brazilian mixed forest

“…In recent years, many ecological studies have focused on the functional traits of invasive species (Lai et al , Carmona et al 2016, Funk et al 2016, Cadotte et al 2018. By investigating patterns of functional similarities, these researches have enlightened the knowledge about the paths by which non-native species may become invasive (Cadotte et al 2018, Hulme & Bernard-Verdier 2018. While low functional overlap suggests that invasion occurs in vacant niches (Lambdon et al 2008), a high overlap indicates that species are influenced by the same environmental filters (Carboni et al 2016).…”