Modeled Shifts in Polylepis Species Ranges in the Andes from the Last Glacial Maximum to the Present

Brian Zutta,Philip Rundel

doi:10.3390/f8070232

Abstract

Polylepis woodlands, the dominant high-elevation woodland species of the Andes of South America, are an increasingly important focus of conservation and restoration efforts as a buffer to the regional effects of climate change. However, the natural extent of these woodlands before the arrival of human populations is still debated. One significant approach to this question is an assessment of the change in woodland extent from a hypothetical peak at the time of the Last Glacial Maximum (LGM) to the present where distributions have been altered by both Holocene climate oscillations and anthropogenic pressures of pre-Colombian and modern communities. LGM and present distributions for 21 Polylepis species were modeled using Maxent with environmental data obtained from the WorldClim database. Overall, potential woodland extent is 36% smaller today than at LGM, however a few species have experienced a projected increase in potential range of 180%. This has occurred at the interface of the southern Amazonian Basin with the Altiplano where Polylepis species richness is highest. Bioclimatically stable areas for each species averaged 20 ± 4% of the modeled range and mostly occurred in disjunct pockets from central Peru to northern Argentina and Chile.

Highlights

The high-elevation Polylepis (Rosaceae) woodlands of the Andean Cordillera of South America are an ecologically significant but highly vulnerable ecosystem
Present georeferenced point localities for 21 species of Polylepis were obtained from an extensive review of online herbarium databases (Association of Andean Ecosystems—ECOAN, TROPICOS, GBIF), published research conducted from April 2006 to January 2008, and by field surveys by BRZ in
Paleoeclimatic records from the Quaternary indicate that major fluctuations in elevational changes in climate have occurred, the absence of species level paleoecological data have limited our understanding of Polylepis species response to changes in glacial extent and climate

Summary

Introduction

The high-elevation Polylepis (Rosaceae) woodlands of the Andean Cordillera of South America are an ecologically significant but highly vulnerable ecosystem. Known to support many endemic species, these species form an integral part of cloud forests and treeline landscapes at high-elevation tropical and subtropical Andean ecosystems [1,2,3]. Their presence in often otherwise treeless alpine landscapes make Polylepis woodlands a driver of biodiversity by providing sheltered, richly-structured woodlands for a variety of animal and plant species [3,4]. There has long been a major controversy as to the original natural extent of Polylepis woodlands and whether the current highly fragmented distribution of these stands are the result of widespread pressure from thousands of years of human populations in the Andes or instead abiotic limiting factors [2].

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