Genome study reveals 'gray zone' of animals transitioning from one species to two

December 27, 2016
DNA
DNA double helix. Credit: public domain

There is usually no ambiguity about species delineation when distant lineages are compared. For instance, there is no doubt that dogs and cats belong to two different species. However, such distinction becomes less clear-cut when comparing recently diverged groups of individuals, between which interbreeding is still to some extent possible. This is the paradox of speciation: a gradual, continuous process that ultimately leads to distinct biological entities.

New research publishing December 27 in the open access journal PLOS Biology from French biologists Camille Roux, Christelle Fraïsse, Jonathan Romiguier, Yoann Anciaux, Nicolas Galtier and Nicolas Bierne (CNRS - University Montpellier) characterizes the ability of populations to interbreed and exchange genes as a function of the level divergence of their genomes. These authors improved existing methods, allowing them to infer the history of by modelling the confounding effect of natural selection, drift and migration rates, thereby accounting for the differing patterns of variation seen in different parts of the genome.

The new method was applied to a large genomic dataset consisting of 61 pairs of populations or species of animals. Their analysis uncovered a zone of intermediate molecular divergence, between 0.5% and 2% of differences between genomes, in which the transition from one to two species proceeds - the "gray zone of speciation." Pairs of populations/species falling in this zone are typically characterized by a semi-permeable genome: some genes are freely exchanged between populations, but some are blocked and contribute to isolation - the so-called species barriers. Among the 61 population pairs in this study, the "gray zone" included types of mussel, gorilla, trumpet worm, earthworm, butterfly and mosquito where the animals are in the process of splitting into two species, but still occasionally exchange genetic material.

The authors found that the limits of the gray zone appear somewhat universal and independent of the life-history traits or ecology of the species. This multi-species analysis sheds light on the process of speciation at genomic level, but further highlights the intrinsic difficulty of delineating in the "gray zone," with important implications for conservation and the management of animal biodiversity.

Explore further: Evolution of new species requires few genetic changes

More information: Roux C, Fraïsse C, Romiguier J, Anciaux Y, Galtier N, Bierne N (2016) Shedding Light on the Grey Zone of Speciation along a Continuum of Genomic Divergence. PLoS Biol 14(12): e2000234. DOI: 10.1371/journal.pbio.2000234

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julianpenrod
1 / 5 (3) Dec 28, 2016
Problems still remain for "evolution", even with this attempt at "explanation", and, to an extent, because of it. The process essentially describes "evolution" as proceeding determinedly, with a will of its own. No considerations of a change being lost, not exerting itself so much that it causes a new type of animal to come about. But, Darwin described it as acting only to provide survival advantage. But, if a precursor species can last long enough for "evolution" to take place, that means the precursors already are well adapted to the environment, and so have no impetus to change. And, again, consider the first creature to arrive that cannot even mate successfully with siblings or parents. Who does it mate with to produce a new line?
Sigh
5 / 5 (4) Dec 28, 2016
But, if a precursor species can last long enough for "evolution" to take place, that means the precursors already are well adapted to the environment, and so have no impetus to change.

If you can't be bothered to read text books, you can find answers to that question in more entertaining form in "The Beak of the Finch".

consider the first creature to arrive that cannot even mate successfully with siblings or parents. Who does it mate with to produce a new line?

Did you even bother to read the article? The topic is speciation not being an all-or-nothing process, contrary to the assumption you need for your objection to be valid. From the article:
Pairs of populations/species falling in this zone are typically characterized by a semi-permeable genome: some genes are freely exchanged between populations, but some are blocked and contribute to isolation - the so-called species barriers.

TheGhostofOtto1923
5 / 5 (3) Dec 28, 2016
that means the precursors already are well adapted to the environment, and so have no impetus to change
The godder expects that we live in the perfect world that god hath created and so cant acknowledge that it changes. He cant acknowledge that species create more offspring than can be expected to survive to maturity because that implies nstability. And he cant accept that population pressure compels life to seek out new niches to inhabit because that would imply that gods plan was incomplete.

So of course he is blind to the need for new species.
julianpenrod
1 / 5 (4) Dec 28, 2016
Sigh seems under the impression that just quoting a section of the article "refutes" flaws in the claims of the article. The fact is, in "speciation", at some point, by definition, a creature is born that cannot mater with its own siblings. Random mutations make it completely incapable of producing offspring with them. Where, then, does it find a mate? Will random mutations produce a member of the same group to be such that they can mate with the creature?
In their wholesale hatred of God and me, TheGhostofOtto1923 has declared that the purpose of "evolution" is filling all niches, not helping progeny survive in their own niche as conditions change.
TheGhostofOtto1923
5 / 5 (3) Dec 29, 2016
not helping progeny survive in their own niche as conditions change
-This doesn't mean anything. You want to change definitions to suit your argument. And you bet I hate that.

"In ecology, a niche is a term with a variety of meanings related to the behavior of a species living under specific environmental conditions..."

-Note 'specific'. A changed condition indicates a new niche. And of course a group of animals which have expended a lot of 'effort' over the course of many gens adapting to this new niche, will resist contamination from the old gene pool which would compromise those adaptations.

This is the reason why at some point diverging groups can no longer mate. It is also BTW the source of prejudice and bigotry in the human animal. The 'urge to diverge'.

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