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Aim The aim of the present study was to describe the diversity patterns along elevational gradients that are crucial for conservation management and for understanding diversification processes in montane environments. This article analyses the distributional range and elevation patterns of endemic and non-endemic (NE) vascular plants living on a unique set of Neotropical table mountains ( tepuis). To investigate the potential causes of the high degree of diversity and endemism we tested the role of elevation, area and the mid-domain effect (MDE). We also aimed to discuss the origin of the current tepuian biota. Location The Guayana Highlands (northern South America). Emphasis is placed on the mountaintops above 1500 m elevation, which form the highly biodiverse Pantepui biogeographical province. Methods We examined the distribution patterns of vascular plant species richness in relation to elevation, area, and the MDE using generalized additive models. We used Range Model for the MDE. Results We found that regional endemics richness show a hump-shaped curve in relation to elevation. Single-tepui endemics (STE) increase with elevation, whereas NE and total species richness decrease. Area and MDE influence this pattern for Pantepui and STE, but not for NE. We also observed that the spatial distribution of endemic richness displays a left-skewed distribution pattern due to the dominance of STE. Main conclusions Our results demonstrate that a combination of elevation, area and MDE provide a basic explanation for the diversity of vascular plants in Pantepui. In addition, the present study indicates that maxima of STE are located at the highest altitudes, where the possibility of biotic connection (via migration) and gene flux has been minimal, even during glacial phases when most migration pathways amongst the tepui mountains were open. We also suggest that climatic filtering due to the extreme conditions atop the tepuis and low dispersal capacity stand out as the main drivers of the decline in NE species richness with elevation. [ABSTRACT FROM AUTHOR]

Abstract: Current global average temperatures are 2°C cooler than during the last interglacial period. The expected increase in temperature during the 21st century will be most stressful for cold-adapted and stenothermic mountain species, forcing them to migrate upwards, and eventually to concentrate into either large areas with favourable climates (refugia) or small stands under locally favourable microclimates (microrefugia). We investigate potential refugia in the neotropical Guayana Highlands mountain biome (Pantepui), consisting of ∼50 isolated table mountains (tepuis), to develop strategies for conserving biodiversity during future global warming. We predict the amount of loss of altitudinal habitats of endemic vascular flora of 26 tepuis and evaluate potential threats to these taxa with respect to species extinction, habitat loss, habitat connectivity and the degree of isolation. We compare past, present and future Pantepui landscape configurations through fragmentation analysis and identify potential in situ refugia. Spatial analysis forecasts more species isolation and declining biodiversity at the end of this century relative to current and past levels. Habitats are predicted to experience >80% loss, with the disappearance of 38 habitat patches. One large patch (Chimantá massif) accounts for 46% of the predicted remaining habitat. This patch can be considered a potential refugium for future vascular flora, as it is predicted to contain some present-day resistant species from lower altitudinal levels and other species eventually persisting in microrefugia. The easternmost Pantepui district, containing the Chimantá massif and other tepuis, seems to be the most suitable for the application of in situ conservation strategies. [Copyright &y& Elsevier]