Biogeography

Executive Summary

This executive summary describes the breadth of the entire Madrean Archipelago (MAR) Rapid Ecoregional Assessment (REA) and illustrates examples from all of the products. It does not summarize methods but instead focuses on products, key findings, and limitations. Because of the breadth and number of assessments, this summary is necessarily longer than a typical executive summary and is intended to give a brief but fairly complete picture of the MAR REA results.

Rapid Ecoregional Assessments: Purpose and Scope

The Monte Desert of Argentina and the Sonoran Desert of North America are very similar in most aspects of their physical environments. The origins and the degree of affinity of thefaunas of three classes of vertebrates in the two deserts are discussed. Heterotherms show high endemism, with 72 0 % of the Monte species either endemic to the Monte or with Monte-Chaco distribution and with 61-4% of the Sonoran Desert heterotherms endemic to deserts of the southwest. Mammals show low endemism and theirdesertinhabitantsgenerallybelongto wide-ranging species.