Abstract
How the macroclimate conditions spatial patterns of plant diversity has been extensively studied in many systems and usually proven a strong relationship, however tropical mountains remain understudied. Because understanding primary drivers of diversity patterns in the Andean paramo is still in its infancy, we focused on evaluating the role of the current macroclimate in form of three complementary hypotheses, energy, seasonality and harshness, in explaining local variation of plant species richness. We relied on 1559 vegetation plots that offered a fine-scale outlook on real species assemblages due to community rules and species’ interactions with their surrounding environment, including climate. Generalized Least Squares (GLS) regression models provided insight on the significance of the different hypotheses in explaining local plant richness, but only the energy and seasonality hypotheses received partial support. The best model was then combined with spatial interpolation Kriging modelling techniques to project species richness for a standardized 25m2 plot throughout the entire paramo biogeographic province. We highlighted a North-South increase in richness with several species-rich areas, potential local biodiversity hotspots, independent of the general gradient: the Amotape-Huancabamba zone, Sangay and Cotacachi areas, and eastern Venezuelan Andes. Our endeavor to finely map local richness is the first effort predicting macroecological patterns in the emblematic Andean paramo and contributes novel biogeographic knowledge useful to further support in-depth research and conservation focus in the northern Andes.
Highlights
Understanding spatial patterns of biodiversity across dimensions, scales, and areas of the world remains one of the greatest challenges in biogeography (Lomolino and Heaney, 2004; Kennedy and Norman, 2005)
The páramo includes all natural and semi-natural ecosystems located above the montane treeline (∼3,000–5,000 m) in the northern tropical Andes of Venezuela, Colombia, Ecuador, and northern Peru (Luteyn, 1999) and presents an astonishing phytodiversity of almost 500 genera and 5,000 plant species, 60–80% of which are endemic (Londoño et al, 2014; RangelChurio, 2015)
Because this study focused on spatial patterns of finescale species richness over a broad area, plots whose descriptive structure and composition explicitly referred to azonal or ecotone vegetation were eliminated, according to the plot’s original authors
Summary
Understanding spatial patterns of biodiversity across dimensions, scales, and areas of the world remains one of the greatest challenges in biogeography (Lomolino and Heaney, 2004; Kennedy and Norman, 2005). With 15% of the world’s total plant richness, the Tropical Andes is a main biodiversity hotspot on earth (Myers et al, 2000; Barthlott et al, 2007), and home to the Andean páramo, a high mountain biogeographical province (Morrone, 2014) known as the most phytodiverse tropical high mountain system worldwide (Sklenár et al, 2014). Macroecological research on broad-scale spatial patterns of species richness in tropical mountain regions and in the páramo is critically lacking to date. When focusing on plant species richness, a decreasing tendency has been highlighted along the elevational gradient of certain páramos (Sklenár and Jørgensen, 1999; Sklenár and Ramsay, 2001) and latitudinal gradients remain generally understudied. Several authors have discussed potential drivers of local species richness and found that human disturbance and several environmental factors, such as annual precipitation and scree, condition plant richness in the high tropical Andes (Sklenár and Ramsay, 2001; Vásquez et al, 2015; Cuesta et al, 2017)
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