It's all very well to rubbish the PSC, but let's recognise the
unsatisfactory nature of the BSC as well. Also, splitting on the basis of
molecular evidence is usually done on the basis of a difference of 3% or
more, which is just the kind of difference found between taxa already
accepted as good species.
Below is a para that I copied from a message that I sent to ornith-l a while
back. Any thoughts?
John Penhallurick
I have been wrestling with the PSC and BSC approaches. I find the BSC, even
Mayr's "multidimensional" version, to be profoundly unsatisfactory, with its
appeal to "inference" in all the difficult cases of allopatry and parapatry.
I can't accept the extreme version of the PSC, either, in that to break an
obvious cline into multiple species seems wrong-headed. For a while, I
thought we should accept diagnosable allopatric taxa as species, but treat
forms with evidence of interbreeding, particularly over a wide area, as one
species. But cases of interbreeding between taxa that genetic analysis
reveals to be not even sister-taxa (the Black-eared Miner Manorina melanotis
and the Yellow-throated Miner M.flavigula in Australia, and the Colaptes
cafer/Colaptes auratus complex in North America come to mind) imply that
even extensive interbreeding between two diagnosably different taxa can be
no more than prima facie evidence that two taxa are conspecific, not
conclusive evidence.
On a related matter, is anyone aware of any genetic studies on the American
and African taxa within the current Sarkidiornis melanotus? The two forms
are quite diagnosably distinct and I suspect that they have been separated
for millions of years (more so than the African and American populations of
Dendrocygna viduata which I would guess to have separated relatively recently).
I'd appreciate any comments or thoughts or information.
Associate Professor John M. Penhallurick<>
Canberra, Australia
Phone BH( 61 2) 6201 2346 AH (61 2) 62585428
FAX (61 2) 6258 0426
Snail Mail Faculty of Communication
University of Canberra,A.C.T.2601, AUSTRALIA
OR PO Box 3469, BMDC, BELCONNEN, ACT 2617, AUSTRALIA
"I'd rather be birding!"
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