Taxonomic status of <i>Chaetodipus lineatus</i> and phylogeography of the <i>Chaetodipus nelsoni</i> species group

Abstract Sequence analysis of mitochondrial DNA from museum study skins, cranial morphometrics, and pairwise niche comparisons are used to clarify the taxonomic status of a problematic species of coarse-haired pocket mouse, Chaetodipus lineatus, and to resolve the systematic status of populations of the Chaetodipus nelsoni species group in eastern Coahuila, Mexico, and southern Texas. Doubts about the species status of C. lineatus are confirmed: it is composed of specimens of C. nelsoni from the Llanos El Salado of San Luis Potosí that have retained the juvenile pelage. Furthermore, there is no niche differentiation between C. lineatus and C. nelsoni. We recommend that C. lineatus be synonymized under C. nelsoni. Most populations of the C. nelsoni species group in eastern Coahuila are morphologically larger forms of Chaetodipus collis mapimiensis, while the northern limit of C. nelsoni is extended farther north. The status of a purported range extension of C. collis in southern Texas is discussed in light of sequence analysis and fieldwork.