Widespread native and alien plant species occupy different habitats

Abstract

Theories to explain the success of alien species often assume that they are inherently different from native species. Although there is an increasing body of evidence showing that alien plants tend to dominate in highly human‐modified environments, the underlying reasons why widespread natives might differ in their habitat distribution have rarely been addressed. We used species distribution models to quantify the dominant environmental axes shaping the habitat of 95 widespread native and alien herbaceous species in a highly modified grassland‐dominated landscape in New Zealand. For each species, support vector machines were used to determine 1) the environmental variables that most strongly determined a species’ distribution; 2) the affinity towards a particular position along environmental axes; and 3) tolerance to environmental variation. These three measures were compared among native perennials (n = 31), alien perennials (30) and alien annuals (34). Independent of their origin, species’ distributions were defined by similar environmental variables. Nevertheless, native and alien species occupied different regions of the dominant environmental axes. Perennial natives occupied regions associated with lower human disturbance, while perennial aliens were associated with habitats that had been modified by vegetation clearance, pasture development and livestock grazing. Annual aliens differed from perennials and were associated with both semi‐natural and more intensively managed vegetation. No evidence was found that aliens had broader environmental tolerances than natives that might facilitate invasion into a wider range of environments. Thus, widespread native and alien species differ in the degree to which environmental factors shape their distribution as a result of anthropogenic perturbations to which they respond differently as well as the introduction of functional groups that are capable of exploiting novel environments.

Alien and native plant richness and abundance respond to different environmental drivers across multiple gravel floodplain ecosystems

“…This contrasts with other studies in which alien and native richness have been associated with similar drivers in the same direction (Fridley et al, 2007), or the same variables but in opposite directions (Polce et al, 2011;Greet et al, 2013;Tomasetto et al, 2013;Pouteau et al, 2015). At the broadest scale where we examined average differences in cover and richness among river reaches, no predictors were shared between the New Zealand alien and native plant communities.…”

“…Davis et al, richness and abundance of alien and native species. Yet other studies have found that while alien and native richness are often driven by the same variables, the nature of the underlying relationships can differ (Marini et al, 2009(Marini et al, , 2012Polce et al, 2011;Greet et al, 2013;Tomasetto et al, 2013;Pouteau et al, 2015). These divergent perspectives have been attributed to differences in the spatial scale at which relationships were examined (Fridley et al, 2007), yet, to date, few studies have attempted to assess the drivers of native and alien plant richness or abundance at different spatial scales (Brooks et al, 2013).…”

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

“…The values of a particular trait may be normally distributed across all species in the native assemblage but exhibit significant inter-specific trait divergence (e.g., platykurtosis) among alien species even if no difference in trait means might be found between these two groups ( Figure 2c). An example might be where aliens comprise a wider spectrum of growth forms (e.g., annuals, biennials, short-and longlived perennials) than natives and result in a broader distribution in specific plant traits (Pouteau, Hulme, & Duncan, 2015). Despite mean trait values being similar, the inter-specific trait distributions reveal that aliens occupy under-exploited areas of niche space at the extremes of the trait distribution and this might explain the F I G U R E 2 Schematic to illustrate the importance of accounting for the shape of inter-specific trait distributions when comparing cooccurring native and alien species.…”

ssdm: An r package to predict distribution of species richness and composition based on stacked species distribution models

“…Understanding how local species richness (α‐diversity) is distributed is a critical prerequisite for effective conservation strategies. Richness maps can provide the basis for selecting reserves (Cañadas et al., ; Moraes, Ríos‐Uzeda, Moreno, Huanca‐Huarachi, & Larrea‐Alcázar, ; Murray‐Smith et al., ; Raes, Roos, Slik, Van Loon, & ter Steege, ), prevention of biological invasions (Bellard et al., ; Gallardo, Zieritz, & Aldridge, ; Kelly, Leach, Cameron, Maggs, & Reid, ; Pouteau, Hulme, & Duncan, ), and mitigation of future impacts of climate change (Bellard et al., ; Brown, Parks, Bethell, Johnson, & Mulligan, ; Colombo & Joly, ; Fitzpatrick, Gove, Sanders, & Dunn, ; Midgley, Hannah, Millar, Thuiller, & Booth, ; Ogawa‐Onishi, Berry, & Tanaka, ; Siqueira & Peterson, ).…”