A quantitative topographic analysis of the Sky Islands: a closer examination of the topography-biodiversity relationship in the Madrean Archipelago [Abstract]This article is part of a larger document. View the larger document here.
The well-documented relationship between topography and biodiversity is particularly profound in the Madrean Archipelago. However, despite this recognition, most studies of the Sky Island biogeography have used only a first-order qualitative description of the topography (e.g., average vertical relief and mean elevation). Exploiting the availability of high-resolution DEMs (digital elevation models), we have undertaken a rigorous quantitative analysis of the topographic fabric of the region and explored its utility for evaluating the relationship between topography and biodiversity. Using a surface-normal eigenvector analysis of a 1-km-resolution DEM, topographic roughness, strength, orientation, and organization were used for characterization of the topographic fabric. Building on the assumption that land cover diversity is a plausible first-order measure of biodiversity, we compare “predicted” biodiversity (based on weighted topographic quantities) and the “observed” biodiversity (based on land cover information extracted from satellite imagery). We find good fit throughout much of the Madrean Archipelago (in contrast to the neighboring provinces) supporting the conclusion that topography plays a critical role in the biodiversity of sky-island regions.