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The southern pocket gopher, Thomomys umbrinus, currently contains 17 subspecies distributed from southeastern Arizona and southwestern New Mexico southward into the Trans-Mexico Volcanic Belt (TMVB) of central Mexico. Here we reevaluate relationships within this species, which, based on previous studies, is composed of 3 genetically divergent clades. Multilocus phylogenetic analyses uphold these clades (Northern Desert, Central Plateau, and TMVB) as well as the monophyly of T. umbrinus with respect to the 3 other species in the T. umbrinus complex ( T. atrovarius, T. nayarensis, and T. sheldoni). Reanalysis of published allozyme data shows a pattern of isolation by distance consistent with the hypothesis of gene flow among the 3 T. umbrinus clades. Species tree analyses of these clades reveal 4 divergent lineages (2 within the TMVB clade), which we recognize herein at the subspecies level. Cranial morphometrics show a moderate level of morphological separation among these clades in multivariate space. The present center of diversity of the T. umbrinus species group is in the southern Sierra Madre Occidental, which also appears to be the center of origin of the T. umbrinus complex. A synonymy of T. umbrinus is provided. La tuza sureña, Thomomys umbrinus, actualmente esta compuesta de 17 subespecies distribuidas desde el sureste de Arizona y suroeste de Nuevo México hacia el sur hasta el Cinturón Volcánico Trans-Mexicano (TMVB) en el centro de México. Aquí reevaluamos las relaciones dentro de esta especie, la cual, basados en estudios previos, esta compuesta de 3 clados genéticamente divergentes. Análisis filogenéticos multilocus sostienen estos 3 clados (Desierto del Norte, Altiplanicie Central, y TMVB), asi como la monofilia de T. umbrinus en relación con las otras 3 especies en el complejo T. umbrinus ( T. atrovarius, T. nayarensis, y T. sheldoni). El reanálisis de datos de alozimas publicados muestran un patrón de aislamiento por distancia, el cual es consistente con la hipótesis de flujo génico entre los 3 clados de T. umbrinus. Los análisis de árbol de especie de estos clados revelan 4 linajes divergentes (2 dentro del clado del TMVB), los cuales reconocemos aquí a nivel subespecie. La morfometría craneal muestra un nivel moderado de separación morfológica entre estos clados en el espacio multivariado. El centro actual de diversidad del grupo de especies de T. umbrinus es en el sur de la Sierra Madre Occidental, que también parece ser el centro de origen del complejo T. umbrinus. Una sinonimia para T. umbrinus se provee. [ABSTRACT FROM AUTHOR]

Historically, a large number of taxonomic forms has been recognized within Nearctic pikas (Lagomorpha: Ochotonidae; Ochotona), including up to 13 species and 37 subspecies. After 1965, 2 species and 37 forms have been recognized: the monotypic O. collaris of Alaska, British Columbia, Yukon, and Northwest Territories, and O. princeps, with 36 subspecies spread throughout western Canada and the western United States. The 36 subspecies of O. princeps have been distinguished by subtle differences, particularly in pelage coloration and body size, within the highly fragmented distribution of the species on isolated "islands" of cool, rocky habitat. However, molecular phylogenetic studies (allozyme electrophoresis and sequencing of both mitochondrial and nuclear genomes) indicate the existence of 5 phylogenetic lineages within O. princeps. The cohesiveness of each lineage has been reinforced during glacial stages by introgressive hybridization among currently isolated populations within each lineage. In contrast, the low level of cranial variation and lack of consistent differentiation in cranial characters, pelage coloration, or body size among the 5 lineages indicates idiosyncratic interlocality variation due to high inbreeding within highly isolated populations, genetic drift, and possibly selection for common traits. Examination of allozymic, morphological, and nuclear DNA data indicates previous introgressive hybridization among several of the lineages, probably associated with contact during the Last Glacial Maximum. Herein we characterize morphometric variation between and among O. collaris (n = 164) and O. princeps (n = 1,999) and revise the subspecific taxonomy of O. princeps to 5 subspecies based on molecular phylogenetic lineages, at least 3 of which are known to possess a unique dialect in the short call: O. p. princeps (Northern Rocky Mountains), O. p. fenisex (Coast Mountains and Cascade Range), O. p. saxatilis (Southern Rocky Mountains), O. p. schisticeps (Sierra Nevada and Great Basin), and O. p. uinta (Uinta Mountains and Wasatch Range of central Utah). These 5 subspecies represent evolutionarily meaningful units for consideration of possible management applications if populations of O. princeps are imperiled by human activities. [ABSTRACT FROM AUTHOR]