Shrews previously recognized as Sorex monticolus were classified
into two species (one with 14 subspecies, the other monotypic) on
the basis of a morphometric analysis of 3610 individuals from
throughout their range. Sorex m. neomexicanus has been recognized
previously as a subspecies of Sorex monticolus but is recognized
herein as a distinct species. This taxon occurs in the Sacramento
and Capitan mountains of New Mexico. This region possibly acted as
a boreal-forest refugium for S. monticolus-type shrews during the
Pleistocene glaciation, and during the warmer interglacial period,
after the most recent glaciation, the valleys became too arid for
survival and these shrews survived in forested, montane regions of
New Mexico. These mountains are sufficiently isolated from other
mountainous regions in the state to reduce or eliminate gene flow
between these populations of shrews. S. monticolus as defined
herein exhibits relatively little morphometric variation. Even
among nominate races, the only obvious morphometric variation is a
north-south cline in greatest length of skull. There is a general
trend of increasing size from south to north. The southern
subspecies restricted to isolated mountains (S. m. monticolus and S.
m. parvidens) have the shortest skull lengths of all S. monticolus.
The subspecies found in the northern coastal and insular areas of
southeast Alaska and British Columbia (S. m. longicaudus, S. m.
prevostensis, S. m. malitiosus, S. m. insularis, S. m. calvertensis,
S. m. alascensis, and S. m. elassodon) have the longest skulls. S.
m. setosus, S. m. isolatus, S. m. soperi, S. m. obscurus and S. m.
shumaginensis all have skulls of intermediate length. Insular and
coastal populations of S. monticolus have longer skulls than the S.
monticolus that occupy the mainland. Shrews with long skulls that
occur on the mainland (S. m. longicaudus and S. m. alascensis) also
occur on some islands, and the mainland portion of their
distributions are restricted to a narrow band along the coasts of
Alaska and British Columbia. The southernmost subspecies of S.
monticolus with short skulls are restricted to small montane
islands. The morphometric variation among nominate races is
sufficient to warrant continued separation at the subspecies level
of all taxa except S. m. calvertensis and S. m. elassodon. Were it
not for differences in pelage color, based on my morphometric
analysis, S. m. calvertensis and S. m. elassodon should be
synonomyzed. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35822 |
| Date | 31 March 1994 |
| Creators | Alexander, Lois F. |
| Contributors | Verts, B.J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0019 seconds