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.
Highlights
Mountain habitats cover 5% of the Earth’s land-area, harboring ca. 10,000 vascular plant species (Körner, 1999; Nagy & Grabherr, 2009).despite their small area, mountain habitats harbor a great diversity of plant species and supply many important ecosystem services including clean water (Körner, 1999)
We found that along a wide elevational gradient located in a tropical continental area of South America, native and non-native plant species showed different distributional patterns that differ from what has been reported for temperate areas
The diversity of native species was higher than that of non- native species along the entire tropical elevational gradient studied, non-n ative species were present in all sites, especially along roadside habitats
Summary
Mountain habitats cover 5% of the Earth’s land-area, harboring ca. 10,000 vascular plant species (Körner, 1999; Nagy & Grabherr, 2009). The large majority of the studies describing the elevational distribution of non-native species have been conducted in temperate areas creating an important gap for understanding these processes in other biomes such as tropical mountains (e.g., Alexander et al, 2011; Becker et al, 2005; Marini et al, 2011; Pauchard & Alaback, 2004; Seipel et al, 2012; Siniscalco, Barni, & Bacaro, 2011). While monotonic decreases with elevation have been reported for non-native species in temperate areas (e.g., Alexander et al, 2011; Marini et al, 2011; Seipel et al, 2012), hump-shaped distributions have been found in the tropical islands (Arévalo et al, 2005; Pauchard et al, 2009). We assessed: 1) the distributional pattern of native and non-native species with elevation; 2) the variation in richness and composition of native and non-native species with respect to disturbance (distance to road) along an elevational gradient; and 3) the distribution of non-native species along the elevational gradient respective to its biogeographic origin
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