jeannot
Posts: 1201
Joined: Jan. 2006
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Yes, thank you both for the links.
| Quote | | “Darwin’s famous book was called ‘On the Origin of Species,’ but it was really about natural selection on traits rather than species formation. Since our study suggests that natural selection is a general cause of species formation, it seems that Darwin chose an appropriate title after all.” |
They have to be careful with such a claim. What is “a general cause of species formation”… > 50 % of species formation, > 5% …?
Their published results show an association between ecological divergence and reproductive isolation in all the tested taxa, at the same level of genetic distance (= time of evolution in generations). From this, we can suppose that ecological divergence (= adaptation) accelerate reproductive isolation, hence speciation. This is an important result but it doesn't demonstrate that natural selection is involved in most speciation events.
Example: in angiosperms, they show a high positive correlation between species' habitat and post-mating isolation (r=0.43). Ok, in this phylum, ecological divergence seems to accelerate speciation. However, we can still imagine the possibility that most species pairs (90 %) developed reproductive isolation very slowly through allopatry and genetic drift, and that only a small percentage of angiosperm species diverged rapidly through their adaptation to different habitats. This would produce a highly significant correlation as well.
Nevertheless, their huge dataset should easily provide an answer to my interrogation. Maybe a more complete paper is on its way. 
EDIT: the best evidence of sympatric speciation so far, Sympatric speciation in Nicaraguan crater lake cichlid fish
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