Birds do it (was: Cats pump rabbits/Soon we will all be Yoda)

Cameron Laird claird at
Thu Jun 17 10:17:45 EST 1993

In article <1993Jun16.000525.13805 at> klier at writes:
>In article <1vl086$3je at>, Bill Williams <bwilliam at> writes,
>referring to ring species and species definitions:
>> "As long as gene flow occurs between two populations, they belong to
>> the same species even if their members cannot breed together.  For
>By this definition, most of the Orchidaceae, the largest family of 
>flowering plants, becomes a single species... 
>In truth, there doesn't seem to be a simple definition of species
>appropriate to all groups of organisms -- the best I'm able
>to come up with, is "A species is a group delineated a competent taxonomist
>familiar with the organisms in question."  (yes, tongue in cheek).
Kay is, of course, quite right in pointing out to what extent
some of the other kingdoms mock our zoo-centric "definitions".

My proposal is that we give up on (well, at least postpone for
a bit) definition-hunting, and pursue the study of particular
cases.  One that caught my eye recently is

	Parsons, Thomas J., Storrs L. Olson, and
	Michael J. Braun
	1993	"Unidirectional Spread of Secondary
		Plumage Traits Across an Avian Hy-
		brid Zone", Science, volume 260,
		pages 1643-1646 (11 June 1993)

As the abstract summarizes, "Theory predicts that traits under
positive selection can rapidly cross a hybrid zone in spite of
a substantial barrier to neutral gene flow between hybridizing
taxa.  An avian hybrid zone ... is reported here that displays
an unusual patter of noncoincident clines.  ... [S]exual sel-
ection is driving male sexual traits across the zone."  I wish
I could come up with something novel, but sexual selection 
continues to be, as a number of senior biologists have publicly
opined, the big story we need to understand.

I've adjusted follow-ups a bit.

Cameron Laird
claird at ( at	+1 713 267 7966
claird at ( at  	+1 713 996 8546

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