From Holy Smokes News! Simons Foundation’s magazine, Quanta 
In Darwinian evolution, organisms compete for resources, and the winners get to pass their genome to future generations. According to these rules, two similar species using the same resources in the same environment will be forced to compete with each other. If both are to survive, they will need to become more distinct from each other over time. The famous naturalist E. O. Wilson, along with collaborator William Brown, dubbed this pattern character displacement in the 1950s and proposed that it explains much of the diversity among the world’s organisms.
“It’s one of the main Darwinian ideas for explaining why species are different,” said Joseph Tobias, an evolutionary biologist at Oxford University. But some scientists, including Tobias, are now questioning the data supporting character displacement as a driving force in the evolution of diversity. A report published last year examining 144 studies found that few met the strongest criteria for character displacement. Scientists often failed to rule out other possible explanations, for example, or to show that the change resulted from a heritable trait. And in February, Tobias and collaborators published a large-scale study in Nature that questions how widespread character displacement is in nature. Focusing on ovenbirds, a family of birds that, like Darwin’s finches, have evolved different beak sizes, they found little evidence that character displacement was responsible for differences in the species if the ages of the species are taken into account. That is, given enough time, species tend to diverge, or become more different from each other, even without interspecies competition. More.
See also: Science news release admits evidence for speciation “implicit in Charles Darwin’s work” is scarce
Has anyone ever made a list of all the ways we thought Darwinian evolution could happen, but it turned out it can’t?
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