Welcome to Ohio-birds.
Genetics isn't my field of exper
Hi Chuck,
Welcome to Ohio-birds.
Genetics isn't my field of expertise, but I believe your notions about hybridization are correct. Apparently many of hybrids are fertile, and like you suggested, they would be more likely to mate with a "pure-blooded" bird than another hybrid, since there are so many more "pure-blooded" birds. Since each parent provides one-half of the genes of its offspring, if the descendants of a hybrid always mate with the same species, then the genetic contribution of the aberrant ancestor is reduced by 50% each generation. Presumably at some point, the expression of these genes in the population would no longer scream out "hybridization", but rather would be seen as part of the normal variation of species.
On the Frontiers in Identification web site
<http://www.birdingonthe.net/mailinglists/FRID.html#1323233292>
there is some discussion of a recent paper in The Auk that deals with this phenomenon. Apparently the authors give it the seasonally apt name of "the ghost of introgression past".
As I understand it, if we observe, say, a small Snow Goose, we can't really know if its small because
(1). it has all Snow Goose genes which happened to sort out it a way that creates small size,
(2). it has all Snow Goose genes that should have been expressed as normal size, but bad nutrition or other environmental factors limited the bird's growth, or
(3). one or more ancestors was a Ross's Goose and those genes are being expressed as small size.
All we can do as birders is rely on a combination of field marks, then make a personal decision as to whether the bird "looks good enough" to be added to our list.
Happy birding,
Paul
Paul Gardner
Columbus, OH
--- On Mon, 12/12/11, Chuck Slusarczyk Jr. <[log in to unmask]> wrote:
> From: Chuck Slusarczyk Jr. <[log in to unmask]>
> Subject: Re: [Ohio-birds] Ashtabula Goose ID Debate
> To: [log in to unmask]
> Date: Monday, December 12, 2011, 11:15 PM
> Hi All, I'm a new poster, but have
> been lurking for a while and find this
> site very informative, thank you all.
>
> I too found this conversation very interesting, and agree
> that sometimes you
> just may never know for certain.
>
> In reference to this discussion, I have a few questions
> that have been
> running through my mind, and please forgive me if it's
> already been
> discussed because I haven't seen it.
>
> Are these hybrids mules or can they reproduce? If so,
> could some of this
> variation be attributed to hybrids mating with other
> hybrids or even pure
> members of the two species?
>
> A hybrid x hybrid match seems unlikely to me, but not
> impossible. A hybrid
> x pure pairing seems probable as long as these birds are
> viably
> reproductive. I may be wrong in my thinking, but
> would the progeny of a
> Snoss x Snow pairing be 75% Snow, and conversely, a Snoss x
> Ross pairing be
> 75% Ross's?
>
> Just throwing that out there.
>
> -Chuck
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