Gene Hunn wrote:

>While it may be that the east side Orange-crowneds and Wilson's are
>subspecifically distinct from west side populations and more closely
>related to Rocky Mountain forms, this is not necessarily the case. A
>large number of bird, herp, and plant species illustrate a distribution
>pattern in which northern Rocky Mountain populations are connected to
>Pacific Coastal slope populations and isolated from central and southern
>Rocky Mountain pops, suggesting a post glacial expansion of coastal pops
>eastward through the forests of northern Washington and southern British
>Columbia. This would seem the best explanation for the "Western
>Flycatcher" distribution, Nashville Warblers, Varied Thrushes,
>Chestnut-backed Chickadees, etc. Might it also apply to OCs and Willies?

No, these two really are different subspecies, breeding east of the
Cascades range, but there may need to be more study of populations on the
east side of the Cascades themselves. The situation as portrayed in Jewett
et al's Birds of Washington State is certainly inadequate for
Orange-crowned and perhaps inadequate for Wilson's.

Actually, just speaking for vertebrate animals, I think those distribution
patterns Gene mentions aren't the mode but the exception. There are
actually rather few good examples in this group of "Pacific Coastal slope
populations" connected to "northern Rocky Mountain populations" and not
occurring elsewhere. To qualify for this list, it should be a species that
occurs in wet western WA, and this distribution is best known for some of
our characteristic trees such as western hemlock and western red cedar,
which are widely distributed in the "Columbia forest" of southern BC,
northeastern WA, northern ID, and northwestern MT, as well as in the wet
west side.

But how many vertebrate species share this? The Varied Thrush and
Chestnut-backed Chickadee are fine examples, but both birds are of course
widespread throughout wet forests to the north and basically inhabit all
the areas they would be expected to if limited to wet conifer forest. I'm
more inclined to think that both occur as relict populations in isolated
ranges such as the Blue Mountains. but no one has suggested that the CBCH,
for example, are taxonomically distinct from the more widespread
populations (maybe no one has looked?). The Pacific-slope Flycatcher seems
a good example, although we obviously need a lot more information on how
and where it meets the Cordilleran. The Nashville Warbler isn't a good
example, as it isn't a Pacific Coastal slope species in Washington and is
in fact widespread in *dry* environments all the way down through the
Sierras.

Among nonbird vertebrates, there are also few examples. The northern
alligator lizard is one, but no other reptiles are restricted to the
Pacific coast and northern Rockies, nor any amphibians. Among the
amphibians, both the giant salamander and Van Dyke's salamander of western
WA are represented in northern ID by other populations, but they are
*different species*, certainly indicating relict distribution in wet
forests rather than the recent invasion Gene posulates. The spotted frog,
which might have been an example, is to be divided into (I think) 3
species. The tailed frog is on the west side and in the Blue Mountains, an
interesting and surely relict distribution.

I can't think of a single species of mammal that shows the western hemlock
distribution pattern; in group after group, there's a turnover in species
as you move east across WA/ID/MT (examples: red squirrels, jumping mice,
pocket gophers, redback voles, voles), except, of course, for the many
northern species that occur widely across the continent. The yellow-pine
chipmunk comes close, but it's a difficult one to analyze, as it occurs in
so many climatic and environmental zones.

And it further depends whether you're speaking in terms of species or
subspecies. Gray Jays occur in western WA, northeastern WA, and the Blue
Mountains, but the subspecies east of the Cascades range is quite distinct
and of Rocky Mountain affinities. Same is true with Swainson's Thrush, as
well as the two warblers, Hairy and Downy woodpeckers, crow, Black-capped
Chickadee, and really quite a few other bird (check Jewett et al.) and
mammal species. There are of course many other species, typically
wide-ranging ones, in which only a single subspecies occurs throughout the
state, west and east.

Gene is certainly correct on a broad scale. Many northern birds and
mammals occur not only in the mountains of Cascadia and the northern
Rockies, but also along the wet NW coast, and there is indeed a continuity
among these populations, some of which reach their southern limits
somewhere in the northern or central Rockies. All are species
characteristic of cooler and wetter climates.

Well, I always start with the good intention of writing just a few
sentences, but then the Topsy syndrome asserts itself.

Dennis Paulson, Director phone 206-756-3798
Slater Museum of Natural History fax 206-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416