Subject: splits
Date: Apr 14 16:51:26 1994
From: Dennis Paulson - dpaulson at ups.edu


In response to Gene Hunn's posting:
"Re, "Timberline Sparrow." I suspect this "new species concept" is
a make work program for biotaxonomists. In any case, what about the
seeming
parallel with White-crowned Sparrows where we have the race gambeli
nesting in the sub-alpine from near the Canadian border north in Cascades
& Rockies with pugetensis nesting in brushy cleared areas below -- but
note that clearcutting has allowed pugetensis to expand its breeding
range in the Washington Cascades up to at least 4500 feet (eg., near
Potato Hill on the Yakima Res for example, also at Stevens & SNoqualmie
Passes... Also I believe the Sierra Nevadea White-crown race oriantha is
isolated at higher elevations from the lowland nuttallii. Where will it
end? Is it not now a game of geographic cookie cutting... looking for
allopatric subspecific populations, then calling them species?"

There's no doubt that this new splitting trend has aroused a
tremendous amount of excitement among birders--I wonder why? I guess the
splitting trend is a manifestation of the new attitude toward the
phylogenetic species concept (PSC), in which populations that are
distinctive (genetically as well as morphologically) are recognized as
distinct species. These changes are not being udnertaken lightly, as the
burden of proof is on anyone who proposes a population for species status.
In most cases, molecular analysis has been undertaken to distinguish such
populations from their closest relatives, and "genetic distance" has to be
of the magnitude typically used to separate species.
The genetic distance between Canyon and California towhees is of a
level high enough to warrant species status, in addition to their looking
different from one another and not interbreeding. If the same is true of
Brewer's and Timberline sparrows, why not separate them as species? These
two would be very difficult to separate in the field. Then what happens
when we find two populations that look alike and sound alike but are
abundantly different genetically? Time will sort this out, I suppose, but
it's clear that at present systematic ornithologists are not letting
themselves be limited by "can birders tell these birds apart?" or even "can
ornithologists studying them tell them apart?"
PSC is considered a worthy alternative to the long-held biological
species concept (BSC), in which reproductive isolation (the potential for
interbreeding) was considered the primary criterion to determine whether
two populations were actually different species. "Potential" is the key
word here, because many populations (for example, scattered across the
Hawaiian Islands or West Indies) couldn't possibly interbreed with one
another.
If recognizable and non-interbreeding populations can be considered
separate species, Gene is right, that at least some of the races of
White-crowned Sparrow have to be looked at in the same way as the Brewer's
Sparrows. White-crowned subspecies leucophrys and gambelii intergrade,
nuttallii and pugetensis intergrade, but neither of these pairs of
subspecies intergrades with the other pair. I'm not sure which if any of
the others oriantha (the race that breeds in the far northeastern and
southeastern WA mountains) intergrades with, obviously a relevant question.
If pugetensis does come into contact with gambelii in the North Cascades
(probably not any time soon), this could be a very interesting situation to
watch. It would be interesting from a regional standpoint to see if we can
think of other populations that might be comparable (Gray Jays come to mind
immediately).
David Wright at UW has mentioned writing something in WOSNEWS about
PSC vs. BSC, which will add edification to this discussion.