Taxonomic Status of Some Mice of the Peromyscus Boylii Group in Eastern Mexico, with Description of a New Subspecies

In the cloud forests and montane valleys of eastern Mexico, a hidden diversity has persisted for millennia, known only to the mice themselves. Ticul Alvarez undertook the painstaking work of making that diversity legible to science, examining specimens from the highlands of Veracruz, Puebla, and Nuevo León to untangle a taxonomic puzzle that had confounded earlier naturalists. This 1960s monograph systematically reviews prior classifications of the Peromyscus boylii group, then dismantles and rebuilds them with fresh morphological analysis, distinguishing the often-subtle boundaries between species like Peromyscus aztecus and Peromyscus boylii levipes. The result is the formal description of a new subspecies, the diminutive Peromyscus b. ambiguus, along with a revised framework for understanding how these mice have diversified across the region's complex geography. For mammalogists and zoologists, this is foundational work: a rigorous specimen-based argument about where one species ends and another begins, and a testament to the precision required to document biodiversity before it vanishes.