Peromyscus gambelii (Baird)

Bradley, Robert D., Francis, James Q., Platt II, Roy N., Soniat, Taylor J., Alvarez, Daysi & Lindsey, Laramie L., 2019, Mitochondrial Dna Sequence Data Indicate Evidence For Multiple Species Within Peromyscus Maniculatus, Special Publications of the Museum of Texas Tech University 70, pp. 1-59 : 16-18

Peromyscus gambelii (Baird)

Hesperomys gambelii Baird, 1857:464 .

Sitomys americanus thurberi J. A. Allen, 1893:185 .

Peromyscus texanus clementis Mearns, 1896:4 .

Peromyscus texanus medius Mearns, 1896:446 .

Peromyscus leucopus coolidgei Thomas, 1898:145 .

Peromyscus cineritius J. A. Allen, 1898:155 .

Peromyscus geronimensis J. A. Allen, 1898:156 .

Peromyscus exiguus J. A. Allen, 1898:157 .

Peromyscus dubius J. A. Allen, 1898:157 .

Peromyscus catalinae Elliot, 1903:10 .

Peromyscus maniculatus gambelii Osgood, 1909:67 .

Peromyscus maniculatus coolidgei Osgood, 1909:94 .

Peromyscus maniculatus margaritae Osgood, 1909:95 .

Peromyscus maniculatus clementis Osgood, 1909:96 .

Peromyscus maniculatus catalinae Osgood, 1909:97 .

Peromyscus maniculatus dubius Osgood, 1909:98 .

Peromyscus maniculatus geronimensis Osgood, 1909:99 .

Peromyscus maniculatus cineritius Osgood, 1909:100 .

Peromyscus maniculatus magdalenae Osgood, 1909:101 .

Peromyscus imperfectus Dice, 1925:123 .

Peromyscus maniculatus assimilis Nelson and Goldman, 1931:305 .

Peromyscus maniculatus streatori Nelson and Goldman, 1931:531 .

Peromyscus maniculatus santacruzae Nelson and Goldman, 1931:532 .

Peromyscus maniculatus exterus Nelson and Goldman, 1931:532 .

Peromyscus maniculatus elusus Nelson and Goldman, 1931:533 .

Peromyscus maniculatus martinensis Nelson and Goldman, 1931:534 .

Peromyscus maniculatus dorsalis Nelson and Goldman, 1931:535 .

Peromyscus maniculatus hueyi Nelson and Goldman, 1932:51 .

Peromyscus maniculatus sanctaerosae von Bloeker, 1940:173 .

Peromyscus maniculatus anacapae von Bloeker, 1942:161 .

Peromyscus maniculatus exiguus Miller and Kellogg, 1955:485 .

Holotype.— Osgood (1909) determined that an individual type was not dedicated by Baird (1857), however, one of Baird’s original specimens (catalog number 369 deposited in the United States National Museum) was designated by Allen (1893) as the type for P. gambelii . This specimen was an adult; however, the specimen was reported to be in poor condition and the sex was unreported .

Type locality.— United States: California; Monterey .

Subspecies.— Includes P. g. coolidgei and P. g. gambelii based on the findings of Greenbaum et al. (2017), as well as P. m. margaritae according to the phylogenetic relationships of samples examined herein. Although we were not able to examine many of the subspecies that potentially are referable to P. gambelii , we tentatively assign the following 15 subspecies recognized by Hall (1981) to P. gambelii : anacapae, assimilis, catalinae , cineritius , clementis, coolidgei, dorsalis, dubius , elusus, exiguous, exterus, gambelii , geronimensis , hueyi, magdalenae, margaritae, sanctaerosae, santacruzae, and streatori.

Diagnosis.— Sides and upperparts ochraceous or ochraceous buff mixed with dusky coloration; underparts white; ears dusky; tail short to medium in length and bicolored (brown to dusky on top and white below). Medium sized for species group but possessing a longer than normal tail; measurements obtained from Osgood (1909), for several of the subspecies now assigned to P. gambelii , indicated a total length averaging 171.5 mm; (range 148–195 mm) and tail length averaging 84.5 mm (range 64–105 mm). Skull slightly smaller than that found in nearby populations of P. maniculatus and P. sejugis ( Burt 1932) .

Genetically (mitochondrial sequences; Hogan et al. 1997; Walker et al. 2006; Greenbaum et al. 2017; this study), P. gambelii has been shown to differ from other populations from the northwestern and western United States, formerly assigned to P. maniculatus but based on results presented herein (see Table 2 ) have been assigned to P. sonoriensis as well as other regional members of the P. maniculatus species group now assigned to P. keeni . In this study, data from the Cyt b analysis indicated that P. gambelii differed from P. keeni , P. labecula , P. maniculatus , P. sonoriensis , and P. sejugis by 3.71%, 3.80%, 4.90%, 4.55%, and 2.05%, respectively. Genetic differentiation (= 0.98%) based on DNA sequences obtained from 41 individuals of P. gambelii was among the lowest intraspecific values obtained in this study.

Distribution.— Based on data presented herein and from Greenbaum et al. (2017), the distribution of P. gambelii should include northern California (San Francisco Bay Area and San Joaquin Valley) and extreme western-central region of Nevada (west of the Sierra Nevada range), southward along coastal California to the southern tip of Baja California del Sur, Mexico. Further, it appears that samples from the northern portion of the former distribution of P. m. gambelii (as depicted by Hall 1981), specifically those from central Oregon and east-central Washington, should be assigned to P. sonoriensis . Although we were not able to examine many of the insular subspecies occurring along the California and Baja California coasts, presumably based on geographic location, those subspecies would be assignable to P. gambelii .

Comparison.— A member of the P. maniculatus species group. Similar in most characteristics to other members of the P. maniculatus species group; although smaller in size compared to P. keeni and P. sonoriensis . Hooper (1944) noted morphological distinctions between populations P. gambelii and populations north of the San Francisco Bay (now recognized as P. sonoriensis rubidus ); with samples of P. s. rubidus averaging larger than P. g. gambelii in the following measurements: total length, tail length, length of braincase, length of nasals, and length of hindfoot. In addition, Hooper (1944) noted that samples referable to P. s. rubidus were darker and more reddish in color than were individuals referable to P. gambelii .

Remarks.— Forty-six samples were examined in this study that are assignable to P. gambelii . Of these samples, the closest to the type locality, examined herein, was approximately 50 km northeast of Monterey, California, United States.

Chromosomal variation within P. gambelii is extensive as the number of autosomal arms (fundamental number, FN) ranges from 72–86 (Bradshaw and Hsu 1972; Bowers et al. 1973; Calhoun et al. 1988) with P. g. cooledgii being reported as monomorphic (FN = 76; Calhoun et al. 1988) and P. g. gambelii being polymorphic (FN = 72–86; Calhoun et al. 1988). The FNs reported for P. gambelii overlap those reported for P. labecula , P. maniculatus , and P. sonoriensis ; 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).

Although karyotypic, allozymic, and mtDNA restriction fragment length polymorphism datasets ( Lansman et al. 1983; Calhoun et al. 1988) could not distinguish among populations of P. maniculatus from California and Baja California (now referable to P. g. coolidgei, P. g. gambelii , P. s. rubidus, and P. s. sonoriensis ), recent genetic studies ( Hogan et al. 1997; Dragoo et al. 2006; Walker et al. 2006; Greenbaum et al. 2017) indicated that P. g. coolidgei and P. g. gambelii , ranging from central California to Baja California del Sur were species distinct from P. s. rubidus, and P. s. sonoriensis . In addition, P. gambelii presumably was more closely related to P. sejugis and P. keeni than to other populations of P. maniculatus from the western United States ( Avise et al. 1979; Gunn and Greenbaum 1986; Smith et al. 2000; Greenbaum et al. 2017); although Hogan et al. (1997), Chirhart et al. (2005), and this study posited that P. sejugis is sister to P. keeni . Although they did not include samples of P. sejugis , other studies ( Dragoo et al. 2006; Kalkvik et al. 2012) demonstrated a close relationship between samples of P. keeni and P. m. coolidgei and postulated that coastal populations of P. maniculatus might represent a distinct genetic form. In addition, Kalkvik et al. (2012) reported that populations of P. maniculatus from southern California and Baja California (= P. gambelii ) occupy significantly different climatic niches and ecozones than do populations of P. maniculatus from north of the San Francisco Bay (= P. sonoriensis ). Herein, samples of P. gambelii exhibited extremely low genetic distance value with P. sejugis compared to other species examined. Estimated divergence times indicated that P. gambelii last shared a common ancestor with members of the P. keeni /P. sp clade approximately 1.55 mya. Further it appears that the P. gambelii / P. sejugis / P. keeni lineage diverged from other taxa formerly assigned to P. maniculatus ( P. labecula , P. maniculatus , P. polionotus , and P. sonoriensis approximately 1.80 mya.

As discussed earlier, P. gambelii appears to be sympatric with samples of P. sonoriensis in western Nevada (near NAS Fallon Air Force Base) and at two separate localities in east-central California (one in Mono County and one in Tuolumne County). 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.