In a 12-year-long study of 284 of the world’s 338 known hummingbird species, an international team of ornithologists has mapped the 22-million-year-old family tree of these tiny birds.
Hummingbirds are very small, colorful birds with iridescent feathers and a high metabolism. Their name comes from the fact that they flap their wings so fast that they make a humming noise.
These birds are found only in the Western Hemisphere, from southeastern Alaska to southern Chile.
There are about 338 hummingbird species, 16 of which live in the United States and Canada.
The secret to their remarkable success lies in the formation of 9 principal clades: the emeralds; the bees; the mountain-gems; the coquettes; the brilliants; the mangoes; the hermits; the topazes and jacobins; and the giant hummingbird Patagona gigas; hummingbirds’ unique relationship to flowering plants, and the birds’ continued spread into new geographic areas.
While all hummingbirds depend on flower nectar to fuel their high metabolisms and hovering flight, coordinated changes in flower and bill shape have helped to drive the formation of new species of both hummingbirds and plants.
Remarkably, as many as 25 hummingbird species are able to coexist in some places.
“Hummingbirds have essentially been reinventing themselves throughout their 22-million-year history,” said Dr Jim McGuire from the University of California, Berkeley, the lead author of the paper published in the journal Current Biology.
“One of the really cool features of hummingbird evolution is that they all eat the same thing yet have diversified dramatically.”
“It really is a big surprise that hummingbirds have divided the nectarivore niche so extensively.”
The new family tree shows that ancestral hummingbirds split from the swifts and treeswifts about 42 million years ago, probably in Eurasia.
By about 22 million years ago, the ancestral species of all modern hummingbirds had made its way to South America, and that’s when things really took off.
The Andes Mountains are a particular hotspot for hummingbird evolution, because diversification occurred along with the uplift of those peaks over the past 10 million years. About 140 hummingbird species live in the Andes today.
The availability of new land areas in North America and the Caribbean has also played an important role in the evolution of new hummingbird species.
For example, the bee hummingbirds colonized North America about 5 million years ago and consequently experienced rates of speciation that rival textbook examples of adaptive radiation.
The new picture of the birds’ past is an important step toward understanding how they have adapted to novel environments, like those found at low-oxygen, high-altitude mountain peaks. It also points to an exciting future.
“Our findings strongly indicate that hummingbirds remain engaged in a dynamic diversification process, filling available ecological and spatial niches across North America, South America, and the Caribbean. Thus, the dramatic radiation of this unique avian lineage is far from complete,” Dr McGuire and his colleagues concluded.
Jimmy A. McGuire et al. Molecular Phylogenetics and the Diversification of Hummingbirds. Current Biology, published online April 03, 2014; doi: 10.1016/j.cub.2014.03.016