Processes at multiple scales affect richness and similarity of non‐native plant species in mountains around the world

Abstract

Aim To investigate how species richness and similarity of non-native plants varies along gradients of elevation and human disturbance.Location Eight mountain regions on four continents and two oceanic islands. MethodsWe compared the distribution of non-native plant species along roads in eight mountainous regions. Within each region, abundance of plant species was recorded at 41-84 sites along elevational gradients using 100-m 2 plots located 0, 25 and 75 m from roadsides. We used mixed-effects models to examine how local variation in species richness and similarity were affected by processes at three scales: among regions (global), along elevational gradients (regional) and with distance from the road (local). We used model selection and information criteria to choose best-fit models of species richness along elevational gradients. We performed a hierarchical clustering of similarity to investigate human-related factors and environmental filtering as potential drivers at the global scale. ResultsSpecies richness and similarity of non-native plant species along elevational gradients were strongly influenced by factors operating at scales ranging from 100 m to 1000s of km. Non-native species richness was highest in the New World regions, reflecting the effects of colonization from Europe. Similarity among regions was low and due mainly to certain Eurasian species, mostly native to temperate Europe, occurring in all New World regions. Elevation and distance from the road explained little of the variation in similarity. The elevational distribution of non-native species richness varied, but was always greatest in the lower third of the range. In all regions, non-native species richness declined away from roadsides. In three regions, this decline was steeper at higher elevations, and there was an interaction between distance and elevation. Main conclusionsBecause non-native plant species are affected by processes operating at global, regional and local scales, a multi-scale perspective is needed to understand their patterns of distribution. The processes involved include global dispersal, filtering along elevational gradients and differential establishment with distance from roadsides.

Plant invasion at landscape and local scales along roadways in the mountainous region of the Greater Yellowstone Ecosystem

“…Non-native plant abundance tends to decrease away from roadsides (Arevalo et al 2010;Timmins and Williams 1989), and this pattern has been shown to be exacerbated along an elevation gradient within the GYE (Seipel et al 2012). In order to better understand the process of non-native plant invasion along roadways in the GYE, we examined the relationship of elevation and distance from road to non-native plant richness at the landscape scale.…”

Annual monitoring reveals rapid upward movement of exotic plants in a montane ecosystem

“…This is especially true for many exotics that have not yet occupied all suitable regions in their introduced range (Alexander and Edwards 2010). Whether an introduced species will successfully invade a montane ecosystem depends on a range of factors such as species plasticity, local disturbance regime, biotic and abiotic resistance, and propagule pressure McDougall et al 2011;Molina-Montenegro et al 2012;Seipel et al 2012;Van Rensburg et al 2013). The lack of adequate datasets on the distributional range of exotics, however, makes it difficult to disentangle the relative importance of each of these factors.…”

Comparación de la severidad de invasión asociada a caminos con diferentes niveles de perturbación en un bosque templado lluvioso del sur de Chile

“…Esto podría explicarse debido a que ambos sitios corresponden a bordes de caminos, por lo tanto, a pesar de trabajar a escala local (donde probablemente los recursos serían más limitantes y la interacción debería ser negativa), se les está otorgando el espacio disponible para no competir por recursos (Shea & Chesson 2002). De esta manera, tanto las plantas introducidas como las nativas estarían utilizando los nichos disponibles dejados por la fragmentación del hábitat, ya que los caminos son considerados hábitats propicios particularmente para el establecimiento de especies de plantas introducidas (Trombulak & Frissell 2000, Arévalo et al 2005, Seipel et al 2012, pero para este caso, también para especies nativas dada la matriz vegetacional en la que se encuentran estos caminos.…”