Natives and non‐natives plants show different responses to elevation and disturbance on the tropical high Andes of Ecuador

Abstract

The aim was to assess patterns of plant diversity in response to elevation and disturbance in a tropical mountain. The study area was located in north‐central portion of the Eastern Cordillera of the Ecuadorian Andes, on a road from 1,150 m a.s.l. (Osayacu) to 4,000 (Papallacta). Along a mountain road spanning a wide altitudinal gradient, at 20 elevations we sampled three plots: one at the roadside and two perpendicular to the roadside. The relationship between elevation and species richness was assessed using linear and quadratic regressions, the effect of disturbance on species richness was determined by ANCOVA and a t test with parameters obtained from quadratic equations. Similarity of species composition among the roadside and sites distant was evaluated with the Chao‐Jaccard and classic Jaccard similarity indices, the distribution of non‐native species according to their origin were analyzed with linear and quadratic regression. The native species showed a linearly monotonic decrease with elevation, whereas non‐natives showed a quadratic distribution. Disturbed areas had the greatest number of non‐native species and lower native species richness, showing also a high floristic similarity; less disturbed areas showed the opposite. The non‐native species of temperate origin were more numerous and showed unimodal elevational distribution, while species of tropical origin were few and decreased linearly with elevation. We conclude that in a tropical highland mountain range, native and non‐native plant species respond differently to elevation: native species exhibit a monotonically linear decrease, and non‐native species show a unimodal trend. Disturbance positively affects non‐native species showing higher richness and fewer species turnover. In addition, the non‐native species are located along of the elevational gradient in relation to their biogeographic origin.

Local trampling disturbance effects on alpine plant populations and communities: Negative implications for climate change vulnerability

“…It can determine distributional patterns, such as in the cases of recurring fires (Sousa, ) or through changes in landscape patch structure (Pickett & White, ; p. 309). Anthropogenic disturbances can broaden the range in which non‐native species can grow (Lembrechts et al., ), favor invasive species richness (Sandoya, Pauchard, & Cavieres, ), and cause distributional shifts in invasive species (e.g., McKenzie, Yoshida, & Unsworth, ). Given its influential role in invasive species range expansion, it is therefore surprising that disturbance is often left out of most studies of native species range limits.…”

Establishment dynamics of native and exotic plants after disturbance along roadsides

“…Soil disturbance not only decreased the number of native species, but also reduced total biomass and increased the percentage of bare ground at the end of the growing season, thereby creating potential opportunities for exotic invaders. Frequently disturbed communities that are poor in native species are expected to be more vulnerable to invasions (Pauchard et al, ; Sandoya et al, ). Reduced biomass and plant cover can positively influence species richness of exotics (McDougall et al, ), as competition with the re‐growing native vegetation in the disturbed plots is lower than in non‐disturbed ones (Lembrechts et al, ).…”

“…However, we found only a weak positive effect of disturbance on exotic‐species richness. Areas directly next to roads are often characterized by high rates of disturbance as compared to semi‐natural habitats (Sandoya et al, ); we selected study sites having a medium‐high level of disturbance, also at higher elevations. For this reason, even the undisturbed control areas may already be saturated with all the exotic species occurring at the local scale.…”

“…Most exotic plants have been introduced in the lowlands, where human settlements are concentrated and exotic propagule pressure is greatest (Marini, Gaston, Prosser, & Hulme, ; Alexander et al, ; Marini et al, ; Dainese, Kühn, & Bragazza, ). Mountain roads subsequently facilitate exotic invasions along elevation gradients by acting as corridors for dispersal, and being reservoirs of exotic propagules (Parendes & Jones, ; Pauchard et al, ; Dainese et al, ; Lembrechts et al, ; Sandoya, Pauchard, & Cavieres, ; Haider et al, ). Exotic species often originate from warm, lowland regions, and are therefore expected to have a restricted elevational range in the invaded temperate mountain areas (Pyšek, Sádlo, Mandák, & Jarošík, ).…”

“…Soil disturbance plays an important role in determining site invasibility (Chytrý et al, ; Boscutti, Sigura, Simone, & Marini, ; Seipel, Rew, Taylor, Maxwell, & Lehnhoff, ), and, independently of temperature, disturbed areas are more prone to establishment of exotic species than natural habitats (Parendes & Jones, ; Lembrechts et al, ; Sandoya et al, ; Haider et al, ). Soil disturbance facilitates plant invasions by providing colonization opportunities that allow the establishment of exotic species by seeds (Latzel, Mihulka, & Klimešová, ; Milbau, Shevtsova, Osler, Mooshammer, & Graae, ; McDougall et al, ; Seipel et al, ).…”