Two new species of Peromyscus (Cricetidae: Neotominae) from the Transverse Volcanic Belt of Mexico.

Specimens of the Peromyscus boylii species group distributed in the western and northeastern montane regions of Michoacán, México, historically have been assigned to P. levipes. Previous studies indicated that these specimens possessed mitochondrial DNA haplotypes that were distinct from both P. levipes and P. kilpatricki, a recently named species in the P. boylii species group from northeastern Michoacán and western Morelos. Herein karyotypic, DNA sequence, and morphological data were analyzed from those populations to evaluate their taxonomic affinity. Karyotypic data indicated that individuals from western Michoacán (Dos Aguas and Aguililla) and from a newly discovered population in northeastern Michoacán (Zinapécuaro) were chromosomally similar to P. carletoni (FN = 68) but distinct from other taxa assigned to the P. boylii species group. Analyses of cranial characteristics indicated that, relative to other species in the P. boylii species group, two morphologically distinct groups were present that corresponded to the Dos Aguas/Aguililla and Zinapécuaro populations, respectively. The latter population, although represented by a small sample size (n = 5 specimens), appeared to exhibit some trenchant morphological distinctions compared with other cryptic species in the P. boylii group. Phylogenetic analyses (parsimony, Bayesian, and likelihood) of DNA sequences obtained from the mitochondrial cytochrome-b gene indicated that although the individuals from Dos Aguas/Aguililla and Zinapécuaro formed a sister group relationship, they formed monophyletic clades that differed genetically (2.54%)-a level approaching that seen between other sister species of Peromyscus. Further, the Dos Aguas/Aguililla and Zinapécuaro clade was more closely aligned with a clade containing representatives of P. carletoni and P. levipes instead of with those from closer geographic proximities (P. kilpatricki) located in eastern Michoacán. Together, these results indicated that these two populations seemingly represent two undescribed species in the P. boylii species group for which we propose the names Peromyscus greenbaumi for populations in western Michoacán (circa Dos Aguas and Aguililla) and Peromyscus ensinki for populations in northeastern Michoacán (circa Zinapécuaro).

Los especímenes del grupo de especies de Peromyscus boylii distribuidos en las regiones montañosas occidentales y el noreste de Michoacán, México, históricamente fueron asignados a P. levipes. Sin embargo, estudios previos han indicado que estos especímenes poseen haplotipos de ADN mitocondrial que son distintos de P. levipes y P. kilpatricki, una especie recientemente nombrada en el grupo de especies P. boylii del noreste de Michoacán y el oeste de Morelos. Los datos cariotípicos indicaron que los individuos del oeste de Michoacán (Dos Aguas y Aguililla) y de una población recién descubierta en el noreste de Michoacán (Zinapécuaro) eran cromosómicamente similares a P. carletoni (FN = 68), pero distintos de otros taxones asignados al grupo de especies P. boylii. Los análisis de las características craneales indicaron que en relación con otras especies del grupo de especies P. boylii, dos grupos morfológicamente distintos estaban presentes, y que correspondían a las poblaciones de Dos Aguas/Aguililla y Zinapécuaro, respectivamente. Aunque representada por un tamaño de muestra pequeño (n = 5 especímenes), esta última población pareció exhibir algunas diferencias morfológicas en comparación con las otras especies crípticas en el grupo P. boylii. Los análisis filogenéticos (parsimonia, inferencia bayesiana y verosimilitud) de secuencias de ADN obtenidas del gen mitocondrial citocromo-b, indicaron que, aunque los individuos de Dos Aguas/Aguililla y Zinapécuaro tienen una relación de grupo hermano, estos forman clados monofiléticos que difieren genéticamente (2.54%), nivel que se acerca al observado entre otras especies hermanas de Peromyscus. Además, el clado de Dos Aguas/Aguililla y Zinapécuaro está más estrechamente alineado con un clado que contenía representantes de P. carletoni y P. levipes en lugar de aquellos de proximidades geográficas más cercanas (P. kilpatricki) ubicados en el este de Michoacán. Estos resultados indicaron que estas dos poblaciones aparentemente representan dos especies no descritas en el grupo de especies P. boylii para las cuales proponemos los nombres Peromyscus greenbaumi para poblaciones en el oeste de Michoacán (hacia Dos Aguas y Aguililla) y Peromyscus ensinki para poblaciones en el noreste de Michoacán (circa Zinapécuaro).

Molecular and morphologic data reveal multiple species in Peromyscus pectoralis.

DNA sequence and morphometric data were used to re-evaluate the taxonomy and systematics of Peromyscus pectoralis. Phylogenetic analyses (maximum likelihood and Bayesian inference) of DNA sequences from the mitochondrial cytochrome-b gene in 44 samples of P. pectoralis indicated 2 well-supported monophyletic clades. The 1st clade contained specimens from Texas historically assigned to P. p. laceianus; the 2nd was comprised of specimens previously referable to P. p. collinus, P. p. laceianus, and P. p. pectoralis obtained from northern and eastern Mexico. Levels of genetic variation (~7%) between these 2 clades indicated that the genetic divergence typically exceeded that reported for other species of Peromyscus. Samples of P. p. laceianus north and south of the Río Grande were not monophyletic. In addition, samples representing P. p. collinus and P. p. pectoralis formed 2 clades that differed genetically by 7.14%. Multivariate analyses of external and cranial measurements from 63 populations of P. pectoralis revealed 4 morpho-groups consistent with clades in the DNA sequence analysis: 1 from Texas and New Mexico assignable to P. p. laceianus; a 2nd from western and southern Mexico assignable to P. p. pectoralis; a 3rd from northern and central Mexico previously assigned to P. p. pectoralis but herein shown to represent an undescribed taxon; and a 4th from southeastern Mexico assignable to P. p. collinus. Based on the concordance of these results, populations from the United States are referred to as P. laceianus, whereas populations from Mexico are referred to as P. pectoralis (including some samples historically assigned to P. p. collinus, P. p. laceianus, and P. p. pectoralis). A new subspecies is described to represent populations south of the Río Grande in northern and central Mexico. Additional research is needed to discern if P. p. collinus warrants species recognition.