Biodiversity Patterns and Continental Insularity in the Tropical High Andes

Abstract

Alpine areas of the tropical Andes constitute the largest of all tropical alpine regions worldwide. They experience a particularly harsh climate, and they are fragmented into tropical alpine islands at various spatial scales. These factors generate unique patterns of continental insularity, whose impacts on biodiversity remain to be examined precisely. By reviewing existing literature and by presenting unpublished data on beta-diversity and endemism for a wide array of taxonomic groups, we aimed at providing a clear, overall picture of the isolation-biodiversity relationship in the tropical alpine environments of the Andes. Our analyses showed that (1) taxa with better dispersal capacities and wider distributions (e.g., grasses and birds) were less restricted to alpine areas at local scale; (2) similarity among communities decreased with spatial distance between isolated alpine areas; and (3) endemism reached a peak in small alpine areas strongly isolated from main alpine islands. These results pinpoint continental insularity as a powerful driver of biodiversity in the tropical High Andes. A combination of human activities and warming is expected to increase the effects of continental insularity in the next decades, especially by amplifying the resistance of the lowland matrix that surrounds tropical alpine islands.

Acknowledgments

We warmly thank Carlos Boada, Michael Kessler, Santiago Ron, the Herbario Nacional de Bolivia (LPB), and the Missouri Botanical Garden for providing us with unpublished information that consistently improved our database. We are also grateful to James Juvik for inviting Fabien Anthelme to the international conference “Vulnerable Islands in the Sky: Science and Management of Tropical Island Alpine & Sub-alpine Ecosystems” held in Hawai‘i in August 2012. Macek was supported by MSMT LM2010009 CzechPolar.