Someone tweeted earlier this evening to advise that there is indeed evidence for Darwinian speciation. Presumably responding to “Has there really just not been enough time to observe Darwinian evolution at work?
In which we pointed out that we are turning up a number of instances of evolution by horizontal gene transfer but explicitly Darwinian evolution is woefully short of evidence (as opposed to biologists’, Darwin lobbyists, or judges’ statements of faith—a wholly different category of information).
Perhaps the tweeter saw this piece from ScienceDaily:
Size differences among fish and competition for breeding space lead to the formation of new species, according to a new study, but empirical evidence for this is scarce, despite being implicit in Charles Darwin’s work and support from theoretical studies. Speciation occurs when genetic differences between groups of individuals accumulate over time. In the case of Telmatochromis fish in Africa, subject of a new study, there are no obvious obstacles to the movement and interaction of individuals. But, the non-random mating between large- and small-bodied fish sets the stage for the evolutionary play.
Note that, despite all the trumpeting in textbooks, the ScienceDaily release simply admits that evidence for Darwinian evolution is rare.
In the study described,
They found that the cichlid fish Telmatochromis temporalis shows two genetically distinct ecomorphs (local varieties of a species whose appearance is determined by its ecological environment), that strongly differ in body size and the habitat in which they live.
Dr Genner said: “We found large-sized individuals living along the rocky shoreline of Lake Tanganyika and, in the vicinity of these shores, we found small-sized individuals, roughly half the size of the large ones, that live and breed in accumulations of empty snail shells found on sand.”
The authors think that the bigger fish drive the smaller ones from the rock to the sand and that both groups mate with others of the same size, so there is “virtually no genetic exchange.”
We are then told,
Speciation occurs when genetic differences between groups of individuals accumulate over time. In the case of Telmatochromis there are no obvious obstacles to the movement and interaction of individuals. But, the non-random mating between large- and small-bodied fish sets the stage for the evolutionary play. (Kai Winkelmann, Martin J. Genner, Tetsumi Takahashi, Lukas Rüber. Competition-driven speciation in cichlid fish. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4412)
In short, it is unclear, even in this fairly straightforward case, that Darwinian speciation has actually occurred. Circumstances have been spotted under which it might be occurring. Of course, some perturbation in the landscape might blow it all away. The overblown claims for “Darwin’s finches” come to mind.
Hey, that guy was following UD News at Twitter. Why not u?
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