Scientists have shown that a bird found in Pennsylvania is the offspring of a hybrid warbler mother and a warbler father from an entirely different genus — a combination never recorded before now and which resulted in a three-species hybrid bird. This finding has just been published in the journal Biology Letters.
“It’s extremely rare,” explains lead author and Cornell Lab of Ornithology postdoctoral associate David Toews. “The female is a Golden-winged/Blue-winged Warbler hybrid — also called a Brewster’s Warbler. She then mated with a Chestnut-sided Warbler and successfully reproduced.”
Well, if all we’ve heard about “species” and “speciation” is true, it shouldn’t just be extremely rare; it should be impossible.
Hybridization is common among Golden-winged and Blue-winged Warblers, and this has been of particular concern for Golden-winged Warblers which have declined dramatically in some populations. But hybridization has never been recorded between these species and Chestnut-sided Warblers. This kind of rare hybridization event may also occur more often in the declining warbler populations of Appalachia, because there is a smaller pool of mates from which to choose.
“That this hybridization occurred within a population of Golden-winged Warblers in significant decline suggests that females may be making the best of a bad situation,” says Toews. “It also tells us that wood-warblers in general have remained genetically compatible long after they evolved major differences in appearance.” Paper. (open access) – David P. L. Toews, Henry M. Streby, Lowell Burket, Scott A. Taylor. A wood-warbler produced through both interspecific and intergeneric hybridization. Biology Letters, 2018; 14 (11): 20180557 DOI: 10.1098/rsbl.2018.0557 More.
If so, do the genetics of the group permit significant differences in appearance while retaining “insurance against extinction,” in that members remain compatible for mating purposes?
The researchers, having captured and released the bird, are planning to keep an eye on him to see if he finds a mate.
“It tells us that warblers in general appear to be reproductively compatible over millions of years of independent evolution,” Dave Toews, postdoctoral associate at the Cornell Lab of Ornithology, told Gizmodo. “The things that really define them, their distinct colors and their songs, are likely mating barriers, and that they don’t interbreed because they can’t, but because they choose not to.”Ryan F. Mandelbaum, “DNA Testing Reveals Baffling Bird Is Three Species in One” at Gizmodo
As Ryan Mandelbaum philosophizes at Gizmodo, “Birds are just looking for love. Sometimes, if they can’t find the right mate, they’ve got to settle.”
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See also: It’s likely impossible to find out how many species there are
Addressing the speciation mess: View species as models?
A physicist looks at biology’s problem of “speciation” in humans
Cornell lab on warblers, generally: