Abstract
One hypothesized invasion strategy (“try-harder”) predicts that invaders exhibit functional traits that are better adjusted to the environment than native species. Alternatively, the “join-the-locals” hypothesis predicts trait convergence between invasive and native species due to environmental filtering with increasing resource limitation. We hypothesized that invasions strategies shift from “try-harder” to “join-the-locals” with increasing elevation. We used an elevational gradient to detect possible trait convergences between alien invaders and native plant species in Asteraceae, Fabaceae and Poaceae. We found a significant trait convergence with elevation only in Asteraceae, suggesting a species-specific pattern, but also an important phenotypic variability of the alien invader. This supports the idea that the more resource-limited the environment, the more it filters out traits substantially diverging from the locally-adapted native community, thereby entailing a shift from “try-harder” to “join-the-locals” strategies. The invasive grass was also more acquisitive but did not exhibit any relation to the native community, supporting the “try-harder” hypothesis. The size of the invasive Fabaceae species decreased with elevation, mirroring the native Fabaceae species, but not the overall native community. Including more replicates and a thorough quantification of environmental conditions, offers a promising avenue for improving the understanding the seemingly idiosyncrasies of invasion pathways.
Highlights
Plant ecological strategies, which can be quantified using a wide array of functional traits, can help to understand the invasion process (Drenovsky et al 2012)
We found a significant trait convergence with elevation only in Asteraceae, suggesting a species-specific pattern, and an important phenotypic variability of the alien invader
The PC1 axis was correlated to traits related to the leaf economics spectrum (SLA, leaf dry matter content (LDMC) and leaf toughness) (Reich 2014), while the PC2 axis was related to plant size
Summary
Plant ecological strategies, which can be quantified using a wide array of functional traits, can help to understand the invasion process (Drenovsky et al 2012). Trait-based theories have been proposed to describe the invasion strategies of alien species in native communities. The “try-harder” hypothesis states that invaders would present traits that are better adjusted to the local environment than native species, be the conditions benign or harsh (Tecco et al 2010). Traits are expected to converge between invasive and native species as a result of to environmental filtering according to the “join-the-locals” hypothesis
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