Canadian ornithologists accidentally discovered that the yellow-capped pipras, a rare Amazonian tropical bird, are the first "natural" hybrid birds in America and probably the Earth as a whole, according to an article published in the journal PNAS.
"There are a huge number of hybrid plant varieties, but hybrids are extremely rare among vertebrates. If both ancestors of these birds did not live in conditions of geographical isolation, then the yellow-capped pipras would not exist - in any other parts of the Earth where closely related species live, hybrids will never don't become a separate species, "said Jason Weir of the University of Toronto, Canada.
In most cases, scientists call the descendants of two different types of related living creatures, which somehow exchanged genetic material, as hybrids. As a rule, hybrids are often found among plants, while among animals they are very rare, and among birds, scientists did not know about the existence of a single "natural" hybrid, whose hybrid essence was not disputed by half of the scientific community.
Their rarity is explained by one simple thing - the overwhelming number of hybrids are sterile, which does not allow them to continue the genus and isolate into a separate species, even if they have a number of obvious advantages over both the parental species. There are small exceptions to this rule - tropical dolphins Stenella clymene, bison, hybrids of steppe bison and ancestors of modern cows, American red wolves, descendants of coyotes and wolves, and several species of flies and fish.
Weir and his colleagues discovered the first, according to most scientists, feathered hybrid, studying the relationship between the so-called pipras - small tropical birds of the family of passerines. They live in the forests of the Amazon and are variegated in color.
To do this, scientists made several expeditions to the tropical forests of Brazil and collected feathers and other traces of these birds containing DNA, extracted genetic material from them, deciphered it and compared it with each other. This comparison revealed the unusual origin of one of the rarest subspecies of these birds, the yellow-capped piper (Lepidothrix vilasboasi).
It turned out that the genome of these small birds consisted of two dissimilar parts - they inherited about 20% of their DNA from white-capped pipers (Lepidothrix nattereri), and the remaining 80% from opal-headed pipers (Lepidothrix iris). This hybrid species of birds, as shown by further analysis of their DNA, appeared quite recently by evolutionary standards, about 180 thousand years ago.
This became possible due to two things - the large degree of isolation of the ancestors of these pipers at that time, associated with the advances and retreats of glaciers and climate changes in the tropics, and also by the fact that the ancestors of the white-capped and opal-headed pipras also separated not so long ago, about 300 thousand years ago ...
This unique example of natural hybridization has led to unusual changes in the structure of the feathers that cover the cap of these birds. According to scientists, this decoration of males has become unusually dull due to the fact that its feathers have a completely different structure in white-capped and opal-headed pipers.
This negative consequence of crossing, according to Weir, forced the ancestors of yellow-capped pipers to acquire bright yellow plumage, attracting the attention of females no less than the shiny white or blue cap of their progenitors. This change, in fact, was the reason why these pipras became a separate species of birds, and not just one of the varieties of their progenitors, the geneticist concludes.