Distributional patterns of endemic, native and alien species along a roadside elevation gradient in Tenerife, Canary Islands

Abstract

Abstract:Invasion by alien plant species may be rapid and aggressive, causing erosion of local biodiversity. This is particularly true for islands, where natural and anthropogenic corridors promote the rapid spread of invasive plants. Although evidence shows that corridors may facilitate plant invasions, the question of how their importance in the spread of alien species varies along environmental gradients deserves more attention. Here, we addressed this issue by examining diversity patterns (species richness of endemic, native and alien species) along and across roads, along an elevation gradient from sea-level up to 2050 m a.s.l. in Tenerife (Canary Islands, Spain), at multiple spatial scales. Species richness was assessed using a multi-scale sampling design consisting of 59 T-transects of 150 m × 2 m, along three major roads each placed over the whole elevation gradient. Each transect was composed of three sections of five plots each: Section 1 was located on the road edges, Section 2 at intermediate distance, and Section 3 far from the road edge, the latter representing the "native community" less affected by road-specific disturbance. The effect of elevation and distance from roadsides was evaluated for the three groups of species (endemic, native and alien species), using parametric and non-parametric regression analyses as well as additive diversity partitioning. Differences among roads explained the majority of the variation in alien species richness and composition. Patterns in alien species richness were also affected by elevation, with a decline in richness with increasing elevation and no alien species recorded at high elevations. Elevation was the most important factor determining patterns in endemic and native species. These findings confirm that climate filtering reflected in varying patterns along elevational gradients is an important determinant of the richness of alien species (which are not adapted to high elevations), while anthropogenic pressures may explain the richness of alien species at low elevation.

Evaluating Hypotheses of Plant Species Invasions on Mediterranean Islands: Inverse Patterns between Alien and Endemic Species

“…Alien and endemic species distributions have been shown to differ along a longitudinal gradient in rivers in another Mediterranean island (Sardinia), with endemic species more common in natural upper parts and alien species more common in lower and middle parts, the latter linked to human impact and agriculture (Angiolini et al, 2013). In Tenerife (Canary islands) altitude was the most important factor determining (inverse) patterns in endemic and native species along roadsides (Bacaro et al, 2015). Altitude itself is likely to be masking several long-term acting processes regarding endemism: the increased proportion of Cretan endemics with altitude is regarded as being due to diversification linked to the Cretan mountains (especially midaltitude areas), driven by altitudinal-driven ecological isolation (Trigas et al, 2013).…”

“…Altitude itself is likely to be masking several long-term acting processes regarding endemism: the increased proportion of Cretan endemics with altitude is regarded as being due to diversification linked to the Cretan mountains (especially midaltitude areas), driven by altitudinal-driven ecological isolation (Trigas et al, 2013). Climate filtering reflected in varying patterns along altitudinal gradients is an important determinant of the richness of alien species (which are not adapted to high altitudes), while anthropogenic pressures may explain the richness of alien species at low elevation (Bacaro et al, 2015). Higher elevations have an interaction effect between area and habitat diversity: area since in small islands land surface area extends with elevation, and components of habitat diversity, such as more heterogeneous topography, a broader selection of microhabitats, and a reduced effect of the sea are related with elevation (Panitsa et al, 2006).…”

Recognizing and interpreting vegetational belts: New wine in the old bottles of a von Humboldt's legacy

“…(e.g. Bacaro et al, 2015;Callaway et al, 2002;Kikvidze et al, 2005;Körner, 2007Körner, , 2012Le Roux & McGeoch, 2010). For example, in the Himalayas, due to the extent of the elevational gradient, extremely large environmental variations occur within a relatively short horizontal distance, making this mountain range an excellent place for testing macroecological and biogeographical hypotheses (Acharya, Vetaas, & Birks, 2011;Miehe, Pendry, & Chaudhary, 2015).…”

Determinants of native and non‐native plant community structure on an oceanic island

“…, Bacaro et al. ) and/or high levels of soil OM and NH 4 close to roads (Appendix ) that are likely exploited by non‐native species (Sardans et al. ).…”