Re: Article: Speciation's Defining Moment
- From: "g" <gillawton@xxxxxxxxxxxxx>
- Date: Tue, 19 Apr 2005 17:31:51 -0400 (EDT)
"Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx> wrote in message
news:d3um04$1he$1@xxxxxxxxxxxxxxxxxxxxxx
> Speciation's Defining Moment
> Genetics and genomics enliven an old controversy on reinforcement
> By Nick Atkinson
>
> Courtesy of Victoria Braithwaite
>
> Evolutionary biologists, both theoreticians and empiricists, have argued
> for
> decades about the relative merits of two speciation scenarios: allopatry
> and
> sympatry. The multifaceted debate bristles with any number of sharply
> contested points, but one that has provoked the greatest polarization is
> the
> concept of reinforcement. This is the crucial last step in the process,
> when
> behavioral mechanisms finally become established, driving a reproductive
> wedge between incipient species.
>
> Broad consensus has been reached on what constitutes a "good" biological
> species. The late Ernst Mayr defined species as "groups of interbreeding
> natural populations that are reproductively isolated from other such
> groups."1 Nevertheless, at that critical point when one species becomes
> two,
> the distinction often becomes blurred. The whole theory of evolution rests
> on the notion that species can split and diverge, but the precise
> mechanics
> of that process have been difficult to discern. Reinforcement has long
> been
> suspected to be key, but empirical evidence has lagged behind the
> algebraic
> march.
>
> "Selection can act no further on inviable or sterile hybrids," says Nick
> Barton, professor in population genetics at the University of Edinburgh's
> Institute of Cell, Animal, and Population Biology. But the genetic
> underpinnings of mate preferences are a different matter: Reinforcement
> therefore allows speciation to be adaptive, rather than arbitrary. Because
> of this, reinforcement has occupied a "special place amongst theories of
> speciation," says Barton. Now, modern genetic and genomic methods are
> increasingly being brought to bear on this lingering theoretical debate,
> unearthing surprising new findings along the way towards a resolution.
>
> Full Text at TheScientist
> http://www.the-scientist.com/2005/4/11/30/1
>
> Comment:
> Allopatric species are those that are geographically separated. Sympatric
> species share the same geographical area. 'Speciation' indicates that two
> varieties of the same kind of animal no longer interbreed.
>
> Kind Regards
> Robert Karl Stonjek
>
We posted concerning same article on same day, so I'm copying and pasting
from my post to combing and mark to watch this conversation closely.
The concept of reinforcement (whereby, as some believe, the clincher in
speciation comes in the form of behavioral mechanisms that close the door
to further crossbreeding between an evolved new specie and its ancestor
specie).
The article maintains that ecological niche separation leads threespine
stickleback fish populations to develop exclusory mating preferences.
It stands to reason that the mechanics of speciation would not
provide in retrospect a means whereby research could identify the precise
point of no return (i.e., the first individual, or generation, incapable of
breeding successfully with its "other specie" relatives). Pure speculation
would seem to SUGGEST a more fuzzy scenario, in which, say, some
siblings, in a single multiple birth, might be able to breed with either the
old specie and produce a hybrid.
However, hybrids (mules) seem to result uniformly from breeding of
horses with asses (no pun suggested nor intended). Among other species
close enough to produce hybrid offspring, can any of you offer any other
scenarios? (Such as: a.) mostly hybrid offspring, but occasional
exception; b.) mixed results of hybrids and stillborns; c.) other?
Surely some research been done in effort to identify precisely what
gene, or specific antigen, or mechanism... renders the offspring of a
horse and an ass sterile?
According to the article, Nick Barton, professor in population genetics
at the University of Edinburgh's Institute of Cell, Animal, and Population
Biology is one of those bringing modern genetic and genomic methods
to the questions, and progressing towards clearer answers.
Would be grateful to anyone knowing DETAILS to post to this watched
topic.
Also, would be grateful for any advanced discussion as to whether
proteomics is being examined as potentially playing a role in speciation,
along with genetics and genomics.
g
.
- References:
- Article: Speciation's Defining Moment
- From: Robert Karl Stonjek
- Article: Speciation's Defining Moment
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