Peromyscus sonoriensis (LeConte)

Hesp [eromys] sonoriensis Le Conte, 1853:413 .

Hesperomys austerus Baird, 1855:336 .

Mus bairdii Hoy and Kennicott, 1857:92 .

Hesperomys sonoriensis var. nebrascensis Coues, 1877:79 .

Hesperomys leucopus arcticus Mearns, 1890:285

Hesperomys leucopus nebrascensis Mearns, 1890:285 .

Hesperomys leucopus deserticolus Mearns, 1890:287 .

Hesperomys leucopus rufinus Merriam, 1890:65 .

Peromyscus texanus nebrascensis J. A. Allen, 1896:251 .

Sitomys americanus artemisiae Rhoads, 1894:260 .

Sitomys insolatus Rhoads, 1894:256 .

Peromyscus michiganensis pallescens J. A. Allen, 1896:238 .

Peromyscus texanus saturatus Bangs, 1897:75 .

Peromyscus texanus subarcticus J. A. Allen, 1899:15 .

Peromyscus akeleyi Elliot, 1899:226 .

Peromyscus maniculatus arcticus Osgood, 1900:33 .

Peromyscus oreas rubidus Osgood, 1901a:193 .

Peromyscus perimekurus Elliot, 1903:156 .

Peromyscus oresterus Elliot, 1903:159 .

Peromyscus luteus Osgood, 1905:77 .

Peromyscus maniculatus artemisiae Osgood, 1909:58 .

Peromyscus maniculatus saturatus Osgood, 1909:61 .

Peromyscus maniculatus hollisteri Osgood, 1909:62 .

Peromyscus maniculatus austerus Osgood, 1909:63 .

Peromyscus maniculatus rubidus Osgood, 1909:65 .

Peromyscus maniculatus rufinus Osgood, 1909:72 .

Peromyscus maniculatus nebrascensis Osgood, 1909:75 .

Peromyscus maniculatus luteus Osgood, 1909:77 .

Peromyscus maniculatus bairdi Osgood, 1909:79 .

Peromyscus maniculatus pallescens Osgood, 1909:83 .

Peromyscus maniculatus sonoriensis Osgood, 1909:89 .

Peromyscus maniculatus borealis Mearns, 1911:102 .

Peromyscus maniculatus nebrascensis Mearns, 1911:102 .

Peromyscus maniculatus osgoodi Mearns, 1911:102 .

Peromyscus maniculatus angustus Hall, 1932:423 .

Peromyscus maniculatus ozarkiarum Black, 1935:144 .

Peromyscus maniculatus gunnisoni Goldman, 1937:224 .

Peromyscus maniculatus alpinus Cowan, 1937:215 .

Peromyscus maniculatus georgiensis Hall, 1938:455 .

Peromyscus maniculatus serratus Davis, 1939:290 .

Peromyscus maniculatus inclarus Goldman, 1939:355 .

Peromyscus maniculatus bairdii McCabe and Cowan, 1945:197 .

Peromyscus maniculatus saxamans McCabe and Cowan, 1945:198 .

Holotype. —United States National Museum (catalog number 146); adult, sex unknown, skin and skull .

Type locality. — Mexico; Sonora; Santa Cruz; collected on 28 September 1851 by J. H. Clark.

Subspecies. —Although we were not able to examine all of the recognized subspecies that potentially are referable to P. maniculatus, we tentatively assign the following 15 subspecies recognized in Hall (1981) and Hogan et al. (1993) to P. sonoriensis: alpinus, artemisiase, austerus, borealis, hollisteri, inclarus, luteus, nebrascensis, ozarkiarum, pallescens, rubidus, rufinus, saturatus, saxamans, serratus, and sonoriensis .

Diagnosis. —Coloration varies greatly between subspecies ( austerus darker in color whereas pallescens is much paler than other subspecies), however, most adults are ochraceous buff (Osgood 1909). Size small for species group, especially relative to length of the tail; measurements obtained from Osgood (1909) for several of the subspecies now assigned to P. sonoroensis, indicated a total length averaging 151 mm; (range 126–176 mm) and tail length averaging 65.5 mm (range 56–75 mm). Tail tends to be more thickly haired and more sharply bicolored (Osgood 1909) than other species in the group.

In this study, Cyt b sequences indicated that P. sonoriensis differed from P. gambelii, P. melanotis, P. polionotus, P. sejugis, and P. maniculatus (sensu stricto), by 4.55%, 6.02%, 4.71%, 4.42%, and 4.68%, respectively. Genetic differentiation (= 1.27%) based on DNA sequences obtained from 186 individuals of P. sonoriensis . This species exhibited a moderate level of genetic divergence even though it possesses the broadest geographic distribution of the P. maniculatus species group.

Distribution. —Occurs primarily west of the Mississippi River from the Yukon and Northwest Territory southward to northern California and the United States/Mexico border (along Arizona and New Mexico) then eastward across northern Texas to Arkansas. The distribution of P. sonoriensis does not include: 1) the coastal islands and mainlands fromAlaska southward to Oregon; in this area P. keeni may exclude P. sonoriensis or the two species may be sympatric; 2) southcentral California and Baja California and the southwest corner of Arizona where P. gambelii occurs; and 3) southern New Mexico, and southwestern of Texas where P. labecula occurs. Populations of mice that are assignable to P. sonoriensis appear to occur on Isle Royale, Michigan (Dragoo et al. 2006; this study) and in southern Michigan (Lansman et al. 1983); whereas samples from northcentral Michigan are assignable to P. maniculatus (Lansman et al. 1983) . Additional samples are needed from much of the Great Lakes region to resolve this conundrum.

Comparisons. —A member of the P. maniculatus species group. Similar in coloration but smaller in size compared to other members of the P. maniculatus species group. Specimens from the Pacific Northwest are darker in pelage color (more similar to P. keeni) than those occurring in the central and eastern portions of the continent exhibit. Differs from P. keeni in external measurements such as tail length (averaging <100 mm compared to an average length> 100 mm in P. keeni).

Remarks. —Two seventy-two samples examined were assigned to P. sonoriensis . Of these samples, the closest examined herein (Grant County, New Mexico) was approximately 200 km northeast of the type locality in Santa Cruz, Sonora.

Chromosomal data are highly variable for this group with a broad range of FNs (72–86) with some well-studied subspecies, such as P. m. bardii, reported as highly polymorphic (74–85). A trend in the data suggest that lower FNs (72–80) for this species occur in the Pacific Northwest, where populations exist in sympatry with P. keeni (Gunn and Greenbaum et al. 1986; Gunn 1988; Hogan et al. 1993). The FNs reported for P. sonoriensis span the ranges reported for P. gambelii, P. labecula, and P. maniculatus; but differ substantially from those observed for P. melanotis (FN = 62, Hsu and Arrighi 1968; Bowers et al. 1973), P. polionotus (FN = 69–71, Te and Dawson 1971), and P. sejugis (FN = 76, Smith et al. 2000).

Several previous studies (Dragoo et al. 2006, Gering et al. 2009, Kalkvik et al. 2012, Natarajan et al. 2015, Sawyer et al. 2017, and Greenbaum et al. 2017 indicated that populations of P. maniculatus in the eastern regions of the United States were genetically divergent from central and western populations. Similarly, DNA sequence data (Cyt b gene), presented herein, suggest elevation to species status that would include 17 currently recognized subspecies of P. maniculatus . This population encompasses the largest geographic area of any clade recovered in this study. Divergence dates suggest P. sonoriensis last shared a common ancestor with the lineage giving rise to P. polionotus approximately 1.40 mya.

As discussed earlier, P. sonoriensis appears to be sympatric with samples of P. gambelii in western Nevada (NAS Fallon Air Force Base) and at two separate localities in east-central California (one in Mono County and one in Tuolumne County). Further, P. sonoriensis appears to be sympatric with samples of P. labecula in southcentral New Mexico (6.2 mi NW of Timberon). Additional data are need from these areas to determine if these genetic species (see Bradley and Baker 2001; Baker and Bradley 2006) are behaving as biological species (Mayr 1942) as well as genetic species.