Island biogeography extends to small-scale habitats: low competitor density and richness on islands may drive trait variation in nonnative plants

Abstract

Previous island biogeography studies have quantified species richness on the scale of entire islands rather than smaller scales relevant to plant-toplant competitive interactions. Further, they have not accounted for density compensation. Using mainland and island sites along the New England coast, we asked two questions. First, are both richness and density lower in small-scale habitats within islands than in similar mainland habitats? Second, do differences in competitor richness and density drive postestablishment trait variation in nonnative plant species? We used field surveys and individual-based rarefaction to estimate richness and density in 100-m 2 plots and demonstrated that island sites have significantly fewer species and individuals per unit area than mainland sites. We then conducted a field study in which we removed competing neighbors from nonnative plant individuals and found that when competitors were removed, individuals in low-competition environments demonstrated a lesser increase in vegetative growth but a greater increase in reproductive effort and herbivore tolerance relative to mainland individuals whose neighbors were also removed. We found that the central concept of island biogeography, i.e., that islands host fewer species than comparable mainland habitats, can be extended to smaller-scale habitats and that this difference in competitive pressure between mainland and island habitats can act as a driver of trait variation in nonnative plants.

Quantifying the landscape influence on plant invasions in Mediterranean coastal habitats

“…Classical works suggested that islands tend to be more heavily invaded than their mainland counterparts (Elton 1958;Lonsdale 1999;Pyšek and Richardson 2006). However, other studies confirm our findings supporting that communities in non-oceanic islands tend to be less invaded by non-native plants than in the mainland (Teo et al 2003;Atwood and Meyerson 2011). Furthermore, even when islands were found to be more invaded these differences could be explained by other factors not directly linked to insularity, but to differences in anthropic disturbances (Yiming et al 2006).…”

Potassium: a neglected nutrient in global change

“…Islands are among the areas most threatened by the success of invasive plants (Denslow et al, 2009;Atwood & Meyerson, 2011). Current literature relates alien success in islands to several variables linked to humans, such as population density (Atwood & Meyerson, 2011;Traveset et al, 2014), the level of human impact (MacDonald et al, 1991;Monty et al, 2013), ecological traits such as genetic diversity (Hardman et al, 2012;Traveset et al, 2014), differences in phylogeny with native species (Bezeng et al, 2013), island area (Traveset et al, 2014), isolation and distance to the nearest continent (Traveset et al, 2014) and climate change (Yamashita et al, 2000). The possible relationship between bedrock K 2O concentrations and alien plant success remains mostly unexplored.…”

Biology of Invasive Plants 3.Vincetoxicum nigrum(L.) Moench andVincetoxicum rossicum(Kleopow) Barbarich

“…Greenhouse and growth chamber experiments have shown that competition against A. syriaca , Canada goldenrod ( Solidago canadensis L.), and quackgrass [ Elymus repens (L.) Gould] can substantially reduce Vincetoxicum performance (Blanchard et al 2010; Jackson and Amatangelo 2021; Milbrath et al 2019a; Sanderson and Antunes 2013). Research on V. nigrum has demonstrated that competitive responses are shaped by competitive environments over evolutionary time (Atwood and Meyerson 2011). Competitive environments also matter at smaller, more ecological spatiotemporal scales: in general, plant community invasibility depends on numerous determinants of resource supply and demand (Davis et al 2000).…”