A Blow Against Hybrid Speciation?

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A recent flurry of papers (reviewed here) have presented evidence for homoploid hybrid speciation in insects -- one in Rhagoletis (a fruit fly) and two in butterflies (one in Heliconius and one in Lycaeides). The Rhagoletis paper showed that a hybrid species formed from two other species -- one that feeds on snowberries and one that feeds on blueberries -- native to North America. The hybrid species feeds on an invasive honeysuckle that was introduced from Asia within the last couple of centuries.

The paper on Heliconius butterflies described a hybrid between H. melpomene and H. cydno which has an intermediate wing pattern. The researchers were able to recreate the hybrid species (H. heurippa) in the lab, which is pretty cool. Finally, the paper on Lycaeides showed that a hybrid species in western North America is adapted to alpine environment in the Sierra Nevadas.

A new study on another potential hybrid between H. melpomene and H. cydno. This species, H. pachinus (shown above), which was suspected to have arisen in a similar manner as H. heurippa, turns out to be a close relative of H. cydno. How boring. That means it arose via the tradition bifurcating process. Is there now a cottage industry made up of people desperately searching for more examples of hybrid speciation?

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Hybrids are sort-of a mystery in evolutionary biology. In the strictest sense, they shouldn't exist because the offspring are often sterile or reproductively impaired.
We usually think of speciation as a bifurcating process -- a single lineage splitting into two. The relationships of those species can often be determined using DNA sequences. But we know that there are exceptions, like horizontal gene transfer in bacteria.
Wild specimen of the butterfly species, Heliconius heurippa.
For some reason, I have been collecting links to articles involving hybridization. That, on its own, would call for a massive link dump, but a recent news item makes for a nice contrast. First, the hybrids:

Thats so lame. Interspecies sex is way more racy than bifurcation.

By Kevin Zelnio (not verified) on 05 Apr 2007 #permalink