_D. obscurus_, which extends northward into British Columbia, and a
Rocky Mountain species, _D. fuliginosus_, that is found in the Sierra
Nevada and northward along the coast and Cascades into British
Columbia. Although the two kinds have at times been considered
conspecific, they differ in voice, hooting mechanism, and characters
of the downy young, and so far no actual intergradation between the
two has been shown (Grinnell and Miller, 1944:113). These grouse thus
seem to offer additional evidence for a Pleistocene, possibly
Wisconsinan, separation of the boreal fauna into a Rocky Mountain and
a Pacific coastal segment.
A notable sidelight on these data is the frequency with which species
in the Sierra Nevada have their closest relatives in the Rocky
Mountains, rather than in the geographically nearer Cascades or
coastal areas. This similarity in fauna of the Sierra Nevada and the
Rockies was noted long ago by Merriam (1899:86).
RELATIONSHIPS WITH OTHER SPECIES
During the Sangamonian interval, isolated segments of the once
widespread ancestral _Sorex vagrans_ quite possibly persisted in such
places as the Sierra Nevada, coastal southern California, the
mountains of Arizona, New Mexico, and southern Mexico, and in the
Black Hills (see fig. 6). One might expect that by Wisconsinan time
these populations would have become reproductively isolated from their
parent stock. They would therefore have remained specifically distinct
when Wisconsinan _Sorex vagrans_, reoccupied these outlying areas, and
may still be found isolated in places peripheral to the range of the
ancestral species.
[Illustration: FIG. 10. Probable distribution of
_S. veraepacis_, _S. longirostris_, and the _S. ornatus_ group
(stipple) and of their Wisconsinan ancestors (lines). Heavy
line indicates limits of Wisconsinan glaciation.]
In fact, we do find species closely related to _Sorex vagrans_ in just
such places today (fig. 10). Probably _Sorex ornatus_, including
members of the _ornatus_ group such as _S. trigonirostris_, _S.
sinuosus_, _S. willeti_, _S. tenellus_, and _S. nanus_, and also _S.
veraepacis_, arose by separation from the ancestral _vagrans_ stock in
Sangamonian time. Probably the eastern _S. longirostris_ arose in a
like manner. The ancestor of _S. ornatus_ may have been isolated in
southwestern California during Sangamonian time, spread north and
south during the Wisconsinan age, and afterward given rise to _S.
trigonirostris_ and the modern _S. ornatus_ complex of California and
Baja California. In at least one place reproductive isolation between
_ornatus_ and the invading _S. vagrans_ has broken down (Rudd, 1953);
the place is a salt marsh along San Pablo Bay, where a hybrid
population between _S. vagrans_ and _S. sinuosus_, an _ornatus_
derivative, has formed. _Sorex tenellus_ may have been isolated in the
Sierra Nevada in the Sangamonian interval, moved into the valleys
east of the mountains during the Wisconsinan age, and become
restricted to its present range since the retreat of the last ice.
_Sorex nanus_ may have occurred in the Black Hills and isolated
mountains of Arizona and New Mexico during the Sangamonian interval
and remained in these general areas during the Wisconsinan age. Its
present range is peripheral to the main body of the Rockies and the
Colorado Plateau.
The eastern species _Sorex longirostris_ has many similarities with
shrews of the _ornatus-vagrans_ stock. _S. l. longirostris_ is close
in many ways to _S. nanus_. Indeed, the differences between the
species _S. nanus_, _S. ornatus_, and _S. longirostris_ seem to me to
be of the same magnitude and indicate a similar period of
differentiation from a common ancestor. The ancestor of _S.
longirostris_ may have gained access to the eastern United States in
the Illinoian Age _via_ the northern Great Plains south of the glacial
boundary (fig. 7). The ancestor of _Sorex veraepacis_ of southern
Mexico probably reached that area in Illinoian time as part of the
ancestral _vagrans_ stock and probably attained its differentiation
during the Sangamonian interval.
All the kinds of shrews so far discussed, including the _S. vagrans_
complex, might thus be thought of as having had a common ancestor in
the Illinoian Age. This entire group of shrews has the third unicuspid
smaller than the fourth, a pigmented ridge from the apex to the
cingulum of each upper unicuspid, and, in most individuals, lacks a
post-mandibular foramen in the lower jaw (Findley, 1953:636-637). The
pigment is not always prominent in _S. longirostris_.
Two other species of North American shrews,_ Sorex palustris_, the
water shrew, and _Sorex bendiri_, the marsh shrew, show these three
characters to a greater or lesser degree, and it seems that these two
species and the _vagrans-ornatus-veraepacis_ group had a common
ancestor, probably before Illinoian time for reasons stated beyond. I
judge, however, that far from being subgenerically distinct as they
have been considered to be, _S. palustris_ and _S. bendiri_ are
actually closely related species of the same subgenus and may have
differentiated from one another because of separation into eastern
(_palustris_) and western (_bendiri_) segments in the Sangamonian
interval, much as has been postulated concerning the eastern and
western stocks of _Sorex vagrans_. Indeed, Jackson (1928:192) has
noted that in the Pacific northwest the characters of the two kinds
approach one another and become differences of degree only.
The widespread species _Sorex cinereus_ resembles all the foregoing
species in the ridges on the unicuspid teeth and in the lack of a
post-mandibular foramen, but differs from those other species in
having the third upper unicuspid larger than the fourth. The
subspecies _S. cinereus ohionensis_, however, often has the sizes of
these teeth reversed. With _S. cinereus_ I include _S. preblei_
(eastern Oregon) and _S. lyelli_ (Sierra Nevada), both obviously
closely related to _cinereus_ as Jackson (1928:37) recognized when he
included them in the _cinereus_ group. _Sorex milleri_ (Coahuila and
central western Nuevo Leon) seems to me to resemble _S. cinereus_ more
than it does other species of North American _Sorex_, and I judge that
it also belongs to the _cinereus_ group. _Sorex cinereus_ and its
close relatives seem more closely related to the species which have
thus far been discussed than they do to such other North American
species as _S. arcticus_, _S. fumeus_, _S. trowbridgii_, _S. merriami_,
and the members of the _S. saussurei_ group; most of these five
species last mentioned possess a post-mandibular foramen, lack
pigmented unicuspid ridges, and have the third unicuspid larger than
the fourth. Because of the morphological resemblances mentioned
above, it seems likely to me that _S. cinereus_ and the
_vagrans-ornatus-veraepacis-palustris_ complex had a common ancestor
in early Pleistocene time. _Sorex cinereus_ has recently been
considered to be conspecific with the Old World_ S. caecutiens_
Laxmann (Van den Brink, 1953) which name, being the older, would apply
to the circumpolar species.
Hibbard (1944:719) recovered _S. cinereus_ and a species of _Neosorex_
(a name formerly applied to the water shrew) from the Pleistocene
(late Kansan) Cudahy Fauna. This indicates that the ancestors of the
modern _S. cinereus_ and of the water shrew had diverged from one
another before that time. Brown (1908:172) recorded _S. cinereus_ and
_S. obscurus_ from the Conard Fissure in Arkansas. These materials
were deposited probably at a later time than was the Cudahy Fauna. The
_S. obscurus_ from Conard Fissure probably represents the ancestral
_S. vagrans_ stock which I think reached eastern United States in
Illinoian time and gave rise to _S. longirostris_. The Conard Fissure
material was deposited at a time (Illinoian?) when northern faunas
extended farther south than they do today.
All of the species mentioned as having structural characters in common
with _S. vagrans_ seem to have arisen from a common ancestor which had
already differentiated from the ancestor of such species as _S.
arcticus_, _S. saussurei_, and others. Consequently all are here
included in a single subgenus. The oldest generic name applied to a
shrew of this group, other than the name _Sorex_, is _Otisorex_ DeKay,
1842, type species _Otisorex platyrhinus_ DeKay, a synonym of _Sorex
cinereus_. The subgenus can be characterized as follows.
Subgenus =Otisorex= DeKay
1842. _Otisorex_ DeKay, Zoology of New York, pt. 1, Mammalia, p. 22,
and pl. 5, fig. 1. Type, _Otisorex platyrhinus_ DeKay (= _Sorex
cinereus_ Kerr).
Third unicuspid usually smaller than fourth; upper unicuspids usually
with pigmented ridge extending from apices medially to cingula,
uninterrupted by antero-posterior groove; post-mandibular foramen
usually absent. Includes the species _S. cinereus, S. longirostris, S.
vagrans, S. ornatus, S. tenellus, S. trigonirostris, S. nanus, S.
juncensis, S. willeti, S. sinuosus, S. veraepacis, S. palustris, S.
bendiri, S. alaskanus_, and _S. pribilofensis_.
[Illustration: FIGS. 11-14. Characters of the subgenera _Sorex_
and _Otisorex_.
FIG. 11. Medial view of right ramus of _Sorex (Otisorex)
vagrans_. x 14.
FIG. 12. Medial view of right ramus of _Sorex (Sorex)
arcticus_. x 14.
FIG. 13. Anterior view of left second upper unicuspid of _Sorex
(Otisorex) vagrans_. x 45.
FIG. 14. Anterior view of left second upper unicuspid of _Sorex
(Sorex) arcticus_. x 45.]
Other species of _Sorex_ now occurring in North America differ from
_Otisorex_ in having the 3rd unicuspid usually larger than 4th, in
lacking a pigmented ridge from the apices to the cingula of the upper
unicuspids, and in usually possessing a well-developed post-mandibular
foramen. Exceptions to the last mentioned character are _S. fumeus_
and _S. dispar_. The subgenus _Sorex_ in North America should include
only the following species: _S. jacksoni_, _S. tundrensis_, _S.
arcticus_, _S. gaspensis_, _S. dispar_, _S. fumeus_, _S. trowbridgii_,
_S. merriami_, and all the members of the Mexican _S. saussurei_
group.
The subgenera _Otisorex_ and _Sorex_ probably separated in early
Pleistocene or late Pliocene. _Sorex_ is unknown in North America
earlier than the late Pliocene (Simpson, 1945:51).
In the genus _Microsorex_ the characters of the subgenus _Otisorex_
are carried to an extreme; the unicuspid ridges are prominent and end
in distinct cusplets, and the 3rd unicuspid is not merely smaller than
the 4th, but is reduced almost to the vanishing point. In addition,
the post-mandibular foramen is absent. Although it is closer
structurally to _Otisorex_ than to _Sorex_, the recognition of
_Microsorex_ as a distinct genus seems warranted.
Figure 15 is intended to represent graphically some of the
relationships discussed above. It must be re-emphasized that much of
it is purely speculative, especially as regards actual time when
various separations took place. It will be noted that I have indicated
most separations as having taken place in interglacial ages. They are
generally regarded as periods of warmth and aridity and, therefore,
probably are times of segmentation of the ranges of boreal mammals and
hence times exceptionally favorable to the process of speciation.
Glacial ages, characterized by extensive and continuous areas of
boreal habitat, probably were times of relatively unrestricted gene
flow between many populations of boreal mammals and hence not
favorable to rapid speciation.
=Sorex vagrans=
Wandering Shrew
The size of the wandering shrew varies from small in the subspecies
_monticola_ and _vagrans_ to large in the subspecies _pacificus_. The
tail makes up from a little more than a third to almost half of the
total length. The color pattern ranges from tricolored through
bicolored to almost monocolored. Color ranges from reddish (Sayal or
Snuff Brown) to grayish in summer pelage and from black to light gray
in winter. Diagnostic dental characters include: 3rd upper unicuspid
smaller than 4th, and unicuspids, except 5th, with a pigmented ridge
extending from near apex of each tooth medially to cingulum and
sometimes ending as internal cusplet. _S. vagrans_ differs from
members of the _ornatus_ group in less flattened skull, and in more
ventrally situated foramen magnum that encroaches more on the
basioccipital and less on the supraoccipital. The wandering shrew
differs from _S. trowbridgii_ and _S. saussurei_ in the dental
characters mentioned above. These dental characters also serve to
distinguish _S. vagrans_ readily from _S. cinereus_, _S. merriami_,
and _S. arcticus_ which may occur with _vagrans_. The large marsh
shrew and water shrew, _S. palustris_ and _S. bendiri_, can be
distinguished at a glance from _S. vagrans_ by larger size and darker
color.
[Illustration: FIG. 15. Diagrammatic representation of the
probable phylogeny of _Sorex vagrans_ and its near relatives.]
In the following treatment of the 29 subspecies of _Sorex vagrans_,
the subspecies are arranged in geographic sequence, beginning with the
southernmost large subspecies on the California coast and proceeding
clockwise, north, east, south, and then west back to the starting
point.
=Sorex vagrans sonomae= Jackson
_Sorex pacificus sonomae_ Jackson, Jour. Mamm., 2:162, August
19, 1921.
_Type._--Adult female, skin and skull; No. 19658, Mus. Vert.
Zool.; obtained on July 2, 1913, by Alfred C. Shelton, from
Gualala, on the Sonoma County side of the Gualala River, Sonoma
Co., California.
_Range._--Coastal California from Point Reyes north to Point Arena.
_Diagnosis._--Size large; average and extreme measurements of 3
topotypes are: total length, 141.7 (141-143); tail, 59 (54-63); hind
foot, 17 (17-17). Color reddish in summer, somewhat grayer in winter.
[Illustration: FIG. 16. Probable geographic ranges of 16
subspecies of _Sorex vagrans_.
Guide to subspecies
1. _S. v. shumaginensis_
2. _S. v. obscurus_
3. _S. v. alascensis_
4. _S. v. soperi_
5. _S. v. isolatus_
6. _S. v. setosus_
7. _S. v. bairdi_
8. _S. v. permiliensis_
9. _S. v. yaquinae_
10. _S. v. pacificus_
11. _S. v. sonomae_
12. _S. v. longiquus_
13. _S. v. parvidens_
14. _S. v. monticola_
15. _S. v. neomexicanus_
16. _S. v. orizabae_
]
_Comparisons._--Differs from _S. v. pacificus_, with which it
intergrades to the north, in average smaller size and somewhat darker
color; differs from the sympatric _S. v. vagrans_ in much larger size
and more reddish color in both summer and winter.
_Remarks._--This subspecies inhabits the Transition Life-zone below
300 feet, and occurs on moist ground in forests and beneath dense
vegetation.
_Marginal records._--CALIFORNIA: Point Arena (Grinnell, 1933:82);
Monte Rio (Jackson, 1928:144); Inverness (Grinnell, 1933:82).
=Sorex vagrans pacificus= Coues
_Sorex pacificus_ Coues, Bull. U. S. Geol. and Geog. Surv.
Terr., 3 (3):650, May 15, 1877.
_Sorex pacificus pacificus_, Jackson, Jour. Mamm., 2:162,
August 19, 1921.
_Type._--Adult, sex unknown, skin and skull; No. 3266 U. S. Nat. Mus.;
date of capture unknown; received from E. P. Vollum and catalogued on
March 8, 1858; obtained at Ft. Umpqua, mouth of Umpqua River, Douglas
Co., Oregon.
_Range._--Coast of California and Oregon from Mendocino north to
Gardiner.
_Diagnosis._--Size large, largest of the species; average and extreme
measurements of 8 specimens from Orick, Humboldt Co., California, are:
total length, 143.1 (134-154); tail, 65.5 (59-72); hind foot, 17.5
(16-19). Color reddish in summer, browner or grayer in winter.
_Comparisons._--See account of _S. v. sonomae_ for comparison with
that subspecies; averaging larger in all dimensions than _S. v.
yaquinae_ with which it intergrades to the north; much larger and has
more reddish than the sympatric _S. v. vagrans_.
_Remarks._--This subspecies occurs in the Canadian and Transition
life-zones below 1500 ft. where there is found moist ground in or
adjacent to heavy forests.
_Specimens examined._--Total number, 76.
OREGON: _Douglas Co._: Umpqua, 1 BS. _Coos Co._: Marshfield, 1 BS;
Myrtle Point, 1 BS. _Josephine Co._: Bolan Lake, 1 SGJ.
CALIFORNIA: _Del Norte Co._: Smith River, 2 BS; Gasquet, 4 BS;
Crescent City, 17 BS. _Humboldt Co._: Orick, 13 BS; 1 mi. N Trinidad,
18 FC; Trinidad Head, 1 BS; Carson's Camp, Mad River, Humboldt Bay, 5
BS; Arcata, 3 BS; Cape Mendocino, 2 BS; 5 mi. S Dyerville, 1 BS.
_Mendocino Co._: Mendocino, 6 BS.
_Marginal Records._--OREGON: Marshfield; Umpqua. CALIFORNIA: Gasquet;
5 mi. S Dyerville; Mendocino, thence up coast to point of beginning.
=Sorex vagrans yaquinae= Jackson
_Sorex yaquinae_ Jackson, Proc. Biol. Soc. Washington, 31:127,
November 29, 1918.
_Sorex pacificus yaquinae_, V. Bailey, N. Amer. Fauna, 55:364,
August 29, 1936.
_Type._--Adult female, skin and skull; No. 73051 U. S. Biol. Surv.
Coll., obtained on July 18, 1895, by B. J. Bretherton, from Yaquina
Bay, Lincoln Co., Oregon.
_Diagnosis._--Size large for the species; average and extreme external
measurements of 11 specimens from Oakridge, Lane Co., Oregon, are:
total length, 125.3 (11-136); tail, 55.1 (49-61); hind foot, 14.9
(14-16). Color reddish in summer, browner or grayer in winter.
_Comparisons._--See account of _S. v. pacificus_ for comparison with
that subspecies. Larger and more reddish than _S. v. bairdi_ with
which it intergrades to the north and east. Much larger and more
reddish than the sympatric _S. v. vagrans_.
_Remarks._--The name _yaquinae_ actually applies to a population of
intergrades between _pacificus_ and _bairdi_. There is much variation
over the range of the subspecies, and individuals from the western and
southern parts are larger than those from the west slope of the
Cascades. Specimens from Vida and McKenzie Bridge are smaller than
those from Mapleton, Mercer, and the type locality but still seem
closer to _yaquinae_ than to topotypes of _bairdi_. Between Marshfield
and Umpqua on the one hand, and the Columbia River and the Cascade
Mountains on the other, the size of _Sorex vagrans_ decreases quite
rapidly from the large_ pacificus_ to the smaller _permiliensis_. Size
decreases less rapidly northward along the coast than it does eastward
toward the mountains; consequently, at any given latitude, coastal
shrews are larger than mountain shrews. In this area of rapid change
in size it is difficult to draw subspecific boundaries between
_pacificus_, _yaquinae_, and _bairdi_, and this must be done somewhat
arbitrarily.
Jackson (1928:141) remarked upon the possibility that intergradation
between _pacificus_ and _yaquinae_ took place. He noted also the close
resemblance between _yaquinae_ and _bairdi_, and stated (_loc. cit._)
that specific affinity between the two might be demonstrated with more
specimens. He had a series of eight specimens from Vida, Oregon, seven
of which he assigned to _S. o. bairdi_ and one to _yaquinae_. I have
examined these specimens and find no more variation between the
largest and the smallest than would be expected in any normally
variable series of shrews. Vernon Bailey (1936:364) arranged
_yaquinae_ as a subspecies of _pacificus_ without giving his reasons
for so doing.
_Specimens examined._--Total number, 65. OREGON: _Lincoln Co._: type
locality, 2 AW. _Benton Co._: Philomath, 2 BS. _Lane Co._: Mable, 1
OU; Vida, 4 BS, 1 OSC, 3 OU; McKenzie Bridge, 8 OSC, 3 AW, 17 OU, 2
SGJ; Mercer, 1 OSC, 1 OU; Mapleton, 3 BS; Oakridge, 11 OU. _Douglas
Co._: Gardiner, 2 BS; Elkhead, 1 BS. _Klamath Co._: Crescent Lake, 3
OU.
_Marginal Records._--OREGON: Yaquina Bay; _Philomath_; McKenzie
Bridge; Prospect (Jackson, 1928:140); Crescent Lake; Gardiner.
=Sorex vagrans bairdi= Merriam
_Sorex bairdi_ Merriam, N. Amer. Fauna, 10:77, December 31,
1895.
_Sorex obscurus bairdi_, Jackson, Proc. Biol. Soc. Washington,
31:127, November 29, 1918.
_Type._--Adult female, skin and skull; No. 17414/24318, U. S. Biol.
Surv. Coll.; obtained on August 2, 1889, by T. S. Palmer, from
Astoria, Clatsop Co., Oregon.
_Range._--Northwestern Oregon, south to Otis and east to Portland.
_Diagnosis._--Size medium for the species; average and extreme
external measurements of 6 specimens from the type locality are: total
length, 126.3 (124-130); tail, 55.0 (52-57); hind foot, 15.0 (14-15).
Color Fuscous to Sepia in summer, darker in winter, underparts buffy.
_Comparisons._--For comparisons with _yaquinae_ see account of that
subspecies. More reddish and larger than _permiliensis_ with which
_bairdi_ intergrades to the east; specimens from Portland show
evidence of such intergradation. Some specimens from southern
Tillamook County show an approach to _yaquinae_.
_Remarks._--_S. v. bairdi_ lives primarily in forests as do _yaquinae_
and _pacificus_.
_Specimens examined._--Total number, 39. OREGON: _Clatsop Co._: type
locality, 12 BS; Seaside, 3 BS. _Tillamook Co._: Netarts, 1 OU;
Tillamook, 2 OSC; Blaine, 1 AW; Hebo Lake, 1 SGJ; 5 mi. SW Cloverdale,
1 AW. _Multnomah Co._: Portland, 6 USNM. _Lincoln Co._: Otis, 7 USNM;
Delake, 1 KU. _Lane Co._: north slope Three Sisters, 6000 ft., 4 BS.
_Marginal Records._--OREGON: type locality; Portland; north slope Three
Sisters; Taft (Macnab and Dirks, 1941:178).
=Sorex vagrans permiliensis= Jackson
_Sorex obscurus permiliensis_ Jackson, Proc. Biol. Soc.
Washington, 31:128, November 29, 1918.
_Type._--Adult male, skin and skull; No. 91048, U. S. Biol. Surv.
Coll.; obtained on October 2, 1897, by J. A. Loring from Permilia
Lake, W base Mt. Jefferson, Cascade Range, Marion Co., Oregon.
_Range._--The Cascade Mountains of Oregon from Mt. Jefferson north to
the Columbia River.
_Diagnosis._--Size medium for the species; average and extreme
measurements of 14 specimens from the type locality are: total length,
117.7 (110-124); tail, 51.9 (45-58); hind foot, 14.0 (14-15). Pale
reddish in summer, darker and brownish in winter.
_Comparisons._--For comparison with _S. v. bairdi_ see account of that
subspecies. Larger than _S. v. setosus_ except tail relatively
shorter. More reddish in summer pelage than _setosus_.
_Remarks._--_S. v. bairdi_ is larger in the southern part of its range
than elsewhere. Specimens from McKenzie Bridge, herein referred to
_yaquinae_, are intermediate in character between _yaquinae_ and
_bairdi_ or between _yaquinae_ and _permiliensis_. The transition
between _yaquinae_ and _bairdi_ is much more gradual than between
_yaquinae_ and _permiliensis_.
_Specimens examined._--Total number, 21. OREGON: _Hood River Co._: Mt.
Hood, 2 BS. _Wasco Co._: Camas Prairie, E base Cascade Mts., SE Mt.
Hood, 1 BS. _Marion Co._: Detroit, 1 BS; type locality, 17 BS.
_Marginal Records._--OREGON: Mt. Hood; type locality; Detroit.
=Sorex vagrans setosus= Elliott
_Sorex setosus_ Elliott, Field Columb. Mus. Publ. 32, zool.
ser. 1:274, May 19, 1899.
_Sorex obscurus setosus_, Jackson, Proc. Biol. Soc.
Washington, 31:127, November 29, 1918.
_Type._--Adult male, skin and skull; No. 6213/238, Chicago Nat. Hist.
Mus.; obtained on August 18, 1898, by D. G. Elliott from Happy Lake,
Olympic Mts., Clallam Co., Washington.
_Range._--Washington from the Cascades west; southwestern British
Columbia west of 120 deg. W Longitude north to Lund.
_Diagnosis._--Size medium for the species; average and extreme
measurements of 20 specimens from the Olympic Mountains, Washington,
are: total length, 117.3 (107-125); tail, 49.8 (41-54); hind foot,
13.4 (12-14). Color dark in both summer and winter.
_Comparisons._--For comparison with _permiliensis_ see account of that
subspecies. Darker, longer-tailed, and somewhat larger cranially than
_S. v. obscurus_ with which it intergrades in southwestern British
Columbia. Smaller in all dimensions, but much the same color as _S. v.
longicauda_ with which it intergrades along the British Columbian
coast north of Lund. Larger, darker, less reddish, and longer-tailed
than the sympatric _S. v. vagrans_.