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Nick Barton and Jerry Coyne Don’t Like Your Sympatric Speciation

Posted by RPM on September 22, 2006
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The Scientist (we’re not sure which one) reviews the palm tree sympatric speciation paper from February (doi here). Here’s what Jerry Coyne has to say:

“Both these cases are most parsimoniously interpreted as sympatric speciation,” said Jerry Coyne at the University of Chicago. Still, he questioned whether the species are truly sister taxa, and didn’t reach the island or crater lake from separate invasions from a source population. “If there’s a little bit of hybridization between the species, they’re going to become genetically more similar to each other than either is to a mainland species,” Coyne told The Scientist. “They’d look like sister species when they’re not.” He noted that the two palm species do indeed form hybrids, albeit infrequently.

Nick Barton is equally pessimistic, saying that “it’s so hard to even demonstrate one example” of sympatric speciation. Maybe if some of the examples involved chromosomal inversions, Barton would be more willing to accept them as evidence of sympatric speciation. However, one of our best examples of sympatric speciation via chromosomal inversions is actually allopatric speciation with reinforcement. Allopatry with reinforcement — it’s the new sympatric speciation people.

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Comments

  1. #1 Russell Johnston
    September 23, 2006

    Which conclusion does Occam’s Razor favor? Careful – don’t be too quick to answer. In this case is it simpler to believe that the isolation of populations can only happen in one way, geographically: or is it simpler to believe that isolation by micro-environment (the plant fed on, etc) could function in just the same way as geographical isolation, rather than be a different case, which introduces the complexity of special cases? My answer at http://logictutorial.com/occam.html is that we should (and do) seek “downstream” complexity and “upstream” (theoretical) simplicity. Which suggests, contra the skeptics, that Occam’s rule would favor (but not necessitate) sympatric speciation.

  2. #2 Matt Dunn
    September 25, 2006

    I think you’re right about reinforcement being the new sympatric speciation. And I’m ok with that and actually kind of excited about it. The two aren’t really that different. There has to be gene flow for reinforcement to work…so allopatric speciation didn’t actually occur if reinforcement is operating. There has to be hybrids produced in order for selection to stop them being produced! Also, the other explanation used to explain away sympatric speciation is sequential invasions and ecological character displacement. This is a lot like sympatric speciation too and often leads to reproductive isolation that didn’t exist BEFORE, of course reproductive isolation is not directly selected for here as it is with reinforcement. It’s funny that Coyne et al. don’t see the striking similarities between sympatric speciation on the one hand and reinforcement and ecological character displacement on the other.

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