Re-defining historical geographic range in species with sparse records: Implications for the Mexican wolf reintroduction program

Abstract

Reintroduction is often the only remaining option for recovery of extirpated species. According to the U.S. Endangered Species Act, species should be reintroduced to suitable habitats within their probable historical range. However, accurately defining historical range often proves difficult, especially for taxa with limited historical information, and may represent a significant impediment for successful recovery. Here, we combine ecological modeling methods with morphometric and phylogenetic data from museum specimens to define a more biologically realistic historical distribution. We apply this approach to the Mexican wolf (Canis lupus baileyi), the most endangered and genetically distinct wolf subspecies in the New World. Our model substantially increases the potential geographic range of the Mexican wolf to include areas in southern California and Baja California, areas not previously recognized as part of the historical range. Motivated by this prediction, we reanalyzed morphometric data and genetically typed the only historical specimen known from southern California, which was previously assigned to another wolf subspecies. We found that the specimen was in fact of pure Mexican wolf ancestry and fell within our predicted range for this subspecies. Our findings provide an impetus for reconsidering reintroduction sites for the Mexican wolf and highlight how critical taxonomic assignment can be to reintroduction programs and species recovery. Re-analysis of potential range in other extirpated species that have ranges defined by antiquated taxonomic approaches used on a limited number of specimens could enhance the success of future reintroduction programs and restore historical processes such as admixture that can preserve the adaptive legacy of endangered species.