The gold-throated hybrid, center, with its parent species H. branickii (left) and H. gularis (right), in the Field Museum’s collections. Credit: Kate Golembiewski, Field Museum
Key points:
- Researchers thought they discovered a new hummingbird species with a gold throat.
- DNA analysis revealed, however, that it was a hybrid.
- While the new study explains the strange coloration of one unusual bird, it opens the door to more questions about hybridization.
The pink-throated brilliant hummingbird, Heliodoxa gularis, sports a luminous pink throat. So does its cousin, the rufous-webbed Brilliant hummingbird, Heliodoxa branickii. That's why when scientists stumped when they came upon a Heliodoxa hummingbird with a glittering gold throat, they thought they discovered a new species.
However, DNA has revealed the gold hummingbird is not a new species, but rather a hybrid of the two pink-throated species.
John Bates, the senior author of a new study in the journal Royal Society Open Science reporting on the hybrid, first encountered the unusual bird while doing fieldwork in Peru’s Cordillera Azul National Park.
According to the study, the initial analysis of mitochondrial DNA gave a clear result matching H. branickii. But when the researchers analyzed the bird’s nuclear DNA, which includes contributions from both parents, results indicated similarities to both H. branickii and its cousin H. gularis. It wasn’t half branickii and half gularis, though—one of its ancestors must have been half-and-half, and then later generations mated with more branickii birds.
The researchers then used electron microscopy and spectroscopy to examine the throat feather structure on a subcellular level. They discovered subtle differences in the origin of the parents’ colors, which explain why their hybrid offspring produced a totally different color.
“There's more than one way to make magenta with iridescence,” said first author Chad Eliason, a Field Museum senior research scientist. “The parent species each have their own way of making magenta, which is, I think, why you can have this nonlinear or surprising outcome when you mix together those two recipes for producing a feather color.”
While this study helps explain the strange coloration of one unusual bird, the researchers say that it opens the door to more questions about hybridization. Separate species are defined as lineages that are genetically distinct and don’t interbreed with each other; hybrids break that rule. It’s not clear how common hummingbird hybrids like the one in this study are, but the researchers speculate that hybrids like this one might contribute to the diversity of structural colors found across the hummingbird family tree.
“Based on the speed of color evolution seen in hummingbirds, we calculated it would take 6 to10 million years for this drastic pink-gold color shift to evolve in a single species,” said Eliason.