Clarifying historical range to aid recovery of the Mexican wolf

Abstract

ABSTRACTWe assessed historical, morphological, and genetic information on the range of the Mexican wolf (Canis lupus baileyi) to plan the recovery of this endangered subspecies. Early accounts of its range included the Sierra Madre Occidental, Mexico, and southeastern Arizona, southwestern New Mexico, and sometimes western Texas, USA. Such accounts are supported by ecological, physiographic, and morphological data. Recent suggestions to depict a more extensive northern periphery have been based primarily on a fragmented geographic sampling of genetic markers assumed to be diagnostic at subspecies level. Some of these genetic markers, found in extant Mexican wolves, reportedly also occur in a few individuals far to the north of the range defined in early accounts. Extending the historical range northward would necessitate drawing that line far north of transitions in wolf phenotype, breaks in vegetation associations, barriers to gene flow, and differences in prey base. We review morphologic, genetic, and ecological information to illustrate why such historical range extensions are not supported. The historical distribution of the Mexican wolf likely does not correspond to the detected distribution of certain molecular markers. The historical range of the Mexican wolf should not be altered through the identification of similar habitat in other locations, the distribution of inadequately sampled molecular markers, or by theoretical arguments about movement capacity. Rather, it should respect the original descriptions that were made when the animal was still present on the landscape, and which are concordant with ecological relationships, physiography, morphology, and the principles of population genetics. Clarifying the historical range of the Mexican wolf accurately will be foundational to developing a scientifically defensible recovery plan. © 2017 The Wildlife Society.