Patterns of native and aline plant species distribution along roads and trails on an altitudinal gradient of a tropical mountain forest

Abstract

The aim of this work was to assess the distribution patterns of alien and native species richness along altitudinal gradient, the alien community similarity between higher and lower altitudes, and the response of alien species to disturbance and public use intensity along trails and roads in a tropical mountain forest. The work was done in the Itatiaia National Park, located in the Atlantic Forest biome, south-eastern Brazil. The plant species, herbaceous, herbs and grasses, were recorded in 67 sampling points, distancing 500 m from each other, with three plots each along four elevational gradients. To test if the richness pattern between native and alien species varied along the elevation, we used a quadratic function in a generalised linear model. The alien species communities along the gradient were analysed with a PERMANOVA and a nestedness analyses. And the alien species response to disturbance and public use intensity were assessed with the product of the response variables in a generalised linear model with negative binomial distribution. Native and alien species richness patterns differed with increasing elevation. Native species showed a hump-shaped pattern with species peaking around 1,750 m while alien species presented a bimodal pattern with higher richness below 1,000 m and above 2,000 m. The alien species community in higher elevations are not a subsample from lower elevations species pool and nestedness was not observed. And the disturbances and public use intensity favours the occurrence of alien species in plots closer to roads and trails. Native species richness pattern may be a response to local environmental characteristics as ecotonal areas. The alien species are occurring at the most visited areas of the park and are reaching high-elevation environments. The high-altitude alien species community are probably formed due to ecological filters acting from low to high altitudes, shaping an exclusive alien species community. In addition, plots proximity to roads and trails favours the occurrence of a higher number of alien species.