Subject: Allen's Hummingbird
Date: Jun 3 10:10:44 2004
From: Guttman, Burt - GuttmanB at evergreen.edu


Jim Rosso writes:

This all reminds me of the whole SuperSpecies concept,
which I will be the first to admit I do not understand very well.
Is it possible that there is a wide variance in the Selasphorus genus?
Should the Rufous and Allen's Hummingbird be combined into one
species named Selasphorus selasphorus, with a common name
of Allen's rufous Hummingbird?

A superspecies is a group of populations caught in the midst of speciation.
The general picture of speciation through geographic separation is that a
species with a relatively wide range is broken up into two or more
populations by some geographic barrier, so they can no longer interbreed
across the barrier. The test of whether two populations belong to the same
species is whether they interbreed where they are in contact; they must be
sympatric, having at least overlapping ranges. If they are allopatric,
having distinct ranges, there is no way to tell their species status. So
allopatric but closely related populations are called semispecies, or
allospecies, and the group of semispecies constitutes a superspecies. Now,
the 5th edition of the AOU Checklist notes that S. rufus (Rufous) and S.
sasin (Allen's) constitute a superspecies, but the range maps I have
available to me show that the ranges of the two overlap in northern
California and southern Oregon. So the critical question is, What happens
in that range? The only difference between the two seems to be in the color
of the back--green or brown. Are there apparent hybrids in that range, with
plumages of some mixed color? But if the color were determined by some gene
with one allele completely dominant and the other recessive, it would really
be hard to tell from casual observation whether hybridization occurs. And
the females of the two types are supposed to be impossible to distinguish in
the field. Anyone have useful information to contribute?

Burt Guttman guttmanb at evergreen.edu
The Evergreen State College
Olympia, WA 98505 360-456-8447
Home: 7334 Holmes Island Road S.E., Olympia 98503



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