This discussion has come up regularly on Obol and hopefully will continue
to do so. The "biological definition of a species" (BDS) is closely
associated with an Austrian academic named Ernst Mayr . It dominated
biological education in mid-twentieth century America. I got it more from
my parents, who went to college in the fifties, than from textbooks or in
the classroom. According to the BDS if the offspring of two species is
fertile, the two parents must be con-specific. I presume this is why the
AOU recognized only two species of sapsuckers back in the sixties when I
started birding. When I saw my first Red-breasted Sapsucker on Country Club
Hill in Corvallis back in 1968 I opened the Golden Field Guide to discover
it was "only" a subspecies, and promptly lost interest. I had already seen
a Yellow-bellied Sapsucker in my own yard, also in Corvallis.
A few years later the AOU lumped a bunch of common species, resulting
in "Northern Flicker", "Yellow-rumped Warbler", and "Northern Oriole". This
was all due to field studies that had documented hybrid zones of
Yellow-shafted/Red-shafted Flickers,etc and the offspring were fertile.
From what I have read, Ernst Mayr would not have been welcome on Obol. He
had no use for common courtesy and viciously defended his BDS throughout
his life. All too often the history of science is strongly affected by
personality. One of my sons told me that science advances one obituary at a
time . I failed to closely scrutinize the "Yellow-bellied" Sapsucker that
overwintered at my house for three years and will never know if it was a
Red-naped or Yellow-bellied, Both were considered subspecies so the lister
in me didn't care.
As mentioned earlier in this thread, the AOU did split the
sapsuckers. They resplit the Northern Oriole and elevated Sooty and Dusky
Grouse to full species. The AOU will probably resplit the Gray Jay.
"Oregon" Jay was a full species back in the thirties. Ironically, another
concept of Ernst Mayr, the "Rasenkreits", was based on his armchair study
of large, white-headed gulls. The advent of DNA testing revealed a messier
relationship among the Herring Gull complex than Mayr would have liked. The
pink-footed Glaucous-winged Gull is more closely related to the
yellow-footed California Gull than to the pink-footed Western Gull. Despite
genetic distance, the Western and Glaucous-winged Gulls readily hybridize.
On Destruction Island, Washington, 60% of breeding gull pairs are
ascribable to neither species. This "Olympic Gull" poses the question of
definition of a hybrid.
I guess a true hybrid is when a "pure" Western Gull mates with a
"pure"Glaucous-winged Gull. As I recall, such pairings were only documented
7% of the time when someone took the trouble to go into the field. Olympic
Gulls are certainly fertile and generally mate with other Olympic Gulls.
On Wed, Mar 9, 2016 at 11:11 PM, Andrew Thomas <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Thanks, Dave Lauten, for your thorough response. Point taken. (Maybe we
need canofworms@xxxxxxxxxxxxx.) I am not a scientist, but I understand
from your post, as well as from my desultory reading over the years, that
evolution theory presents life as a continuum. So, back to birds; no more
worms.
sent from iPad
On Mar 9, 2016, at 7:06 PM, DJ Lauten and KACastelein <deweysage@xxxxxxxxxxxx> wrote:
POST: Send your post to obol@xxxxxxxxxxxxx
Well this opens a can of worms....
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