Weird warbler reveals genetics of its mismatched colours

An extremely uncommon hybrid warbler with mismatched shade patterns has allowed researchers to disentangle the genetic drivers of two traits that normally come as a package deal deal—the black face masks and the black throat patch in blue-winged and golden-winged warblers. A brand new examine describing the peculiar hen and pinpointing the situation within the genome that controls the face masks and throat patch seems on-line within the journal Ecology.

“Golden-winged warblers have both a black face mask and a black throat patch, while blue-winged warblers have neither,” stated Marcella Baiz, postdoctoral researcher at Penn State and first writer of the examine. “When individuals of each species mate with each other, almost all of their hybrid offspring have matched traits, so both black plumage traits are present or both are absent. But we captured this very weird bird that looks almost entirely like a golden-winged warbler but is missing the black throat patch.”

The researchers consider this distinctive mixture happens in lower than 0.5% of the hybrid warblers. To their information, this kind of hybrid had been beforehand documented solely as soon as in a hen that was collected in 1934 and described in 1951 from a museum assortment.

“We originally found this bird thanks to a tip from a local birder who works at Shaver’s Creek Environmental Center,” stated David Toews, professor of biology at Penn State and an writer of the examine. “He suggested that a nearby area seemed like good warbler habitat and also uploaded observations of warblers onto the app eBird, which scientists can use in their research. We went to scout the location when we spotted this unique and exciting bird. We carefully captured the bird so we could document its plumage, took a blood sample so we could sequence its genome, and then released it.”

In a earlier examine, the researchers sequenced the genomes of blue- and golden-winged warblers and their hybrids and recognized a small area that drives the black coloration in these birds upstream of the Agouti-signaling protein (ASIP) gene. But as a result of the 2 traits are virtually all the time inherited collectively, it was unclear if ASIP regulated the traits collectively or individually.

“Because we already had genome sequencing data from the parent species and hybrids with the matched face and throat color, sequencing the genome of the mismatched bird allowed us to separate out the genetic regions underlying the face mask versus the throat patch,” stated Baiz.

The crew confirmed that the beforehand recognized area is linked to the black throat patch, and in addition recognized a brand new location—close by, however additional upstream within the genome—that they consider is linked to the black face masks. For black pigment to happen in these birds, the 2 copies (one on every chromosome) should have initially come from the golden-winged warbler, suggesting that these are “recessive” traits. Having one or each copies from the blue-winged warbler in these spots leads to no face masks or throat patch.

“More than a hundred years ago, a biologist named John Treadwell Nichols hypothesized that the black throat coloration was a recessive trait,” stated Toews. “Later, when Kenneth Parkes described the rare hybrid in 1951, he suggested that if throat and mask color were controlled separately, they would need to be linked in some way or located very close together on the genome. Parkes described his theory as a ‘genetic problem for future study,’ and we were able to confirm both theories using modern genetic tools.”

The researchers counsel that the places they recognized may be situated inside two separate promoter areas for the ASIP gene, which flip the gene on or off in numerous contexts. Because they’re situated so shut to one another on the chromosome, the promoters would normally be inherited collectively—even when genetic materials is shuffled between chromosomes throughout copy—which might clarify why most hybrids carry each or neither of those black plumage traits. The mismatched hen, nonetheless, was probably a results of a particularly uncommon occasion the place this was not the case, adopted by a number of generations of backcrossing with golden-winged warblers.

“If coloration genes in warblers have a similar genetic architecture, with multiple promoters controlling where pigment is deposited, it’s easy to see how just a few mutations could produce a variety of different color patterns among these songbird species,” stated Baiz. “This may help explain why there are so many different species of warblers with such a diversity of colors.”

Because a warbler‘s coloration is a vital cue for behaviors like mating, it’s doable there are implications of the mismatched hybrid bearing solely one of many traits. For instance, it could be engaging to females of each species as a result of it has qualities of each, or to neither. The researchers hope to look at this hen sooner or later and decide if it has a mate, and future analysis linking plumage traits to reproductive success would make clear these implications.

“We have now observed this bird two years in a row, so it has survived at least two migration events,” stated Toews. “This study and the story of how we found this bird is an excellent example of how birders and citizen scientists can make a real difference in research.”