Long-held assumption about emergence of new species questioned
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Article by Jim Erickson
UM News Service
Darwin referred to the origin of species as "that mystery of mysteries," and even today, more than150 years later, evolutionary biologists cannot fully explain how new animals and plants arise.
For decades, nearly all research in the field has been based on the assumption that the main cause of the emergence of new species, a process called speciation, is the formation of barriers to reproduction between populations.
Those barriers can be geographic—such as a new mountain, river or glacier that physically separates two populations of animals or plants—or they can be genetic differences that prevent incompatible individuals from producing fertile offspring. A textbook example of the latter is the mule; horses and donkeys can mate, but their offspring are sterile.
But now a University of Michigan biologist and a colleague are questioning the long-held assumption that genetic reproductive barriers, also known as reproductive isolation, are a driving force behind speciation. Their study was published online publication in the Proceedings of the National Academy of Sciences on Sept. 2.
"Most research on the formation of species has assumed that these types of reproductive barriers are a major cause of speciation. But our results provide no support for this, and our study is actually the first direct test of how these barriers affect the rate at which species form," said Daniel Rabosky, assistant professor in the U-M Department of Ecology and Evolutionary Biology and a curator of herpetology at the Museum of Zoology.
Rabosky and Daniel Matute of the University of Chicago reasoned that if genetic barriers to reproduction are a leading cause of new species, then groups of organisms that quickly accumulate those genes should also show high rates of species formation.