Hummingbirds are diminutive flyers that beat their tiny wings at breakneck speeds. However, new research shows that these little fliers may have also evolved at an extremely rapid pace after reaching South America millions of years ago.
Hummingbirds descended from a group of birds that originated in Europe. The precursors to the hummingbird gradually moved to Asia and ended up in North America. 22 million years ago, the ancestors of modern hummingbirds finally arrived in South America were they flourished and rapidly evolved.
The team of researchers who conducted a study on the diversification of the hummingbird tackled the mystery of how an organism with a very limited food source was able to diversify to the degree seen today. The researchers published their findings at the online journal Current Biology. The research team that conducted the study included researchers from UC Berkeley, the Louisiana State University and other universities located in Michigan, New Mexico and British Columbia.
"Our study provides a much clearer picture regarding how and when hummingbirds came to be distributed where they are today," said University of California Berkeley (UC Berkeley) researcher Jimmy McGuire. McGuire is also an associate professor of integrative biology and curator of herpetology at the university's Museum of Vertebrate Zoology as well as the lead author of the study.
In South America, early hummingbirds quickly adapted to their new environment and underwent a process of rapid diversification. These early hummingbirds quickly spread throughout the entire South America evolving the distinctly colorful and iridescent plumages seen in many modern hummingbirds.
"We are not close to being at the maximum number of hummingbird species," McGuire said. "If humans weren't around, they would just continue on their merry way, evolving new species over time."
While the diversification of such an odd group of birds may be impressive, scientists have been wondering how the early hummingbirds were able to evolve into such a large number of species. Modern hummingbirds are dependent on food sources that co-evolved with them in a mutualistic relationship. The plants provide nectar for the hummingbirds while the hummingbirds help pollinate the plants. If the main food sources co-evolved with the hummingbirds, how did the early hummingbirds survive in a continent that did not yet have the very same plants that modern hummingbirds feed on today?
"It is really difficult to imagine how it started, since hummingbirds are involved in this coevolutionary process with plants that has led to specializations we typically associate with hummingbird plants, such as tubular, often red flowers, with dilute nectar," said McGuire. "They drive the evolution of their own ecosystem. The evolution of hummingbirds has profoundly affected the evolution of the New World flora via codiversification."
When talking about vertebrate organisms, hummingbirds are among the most diverse groups. Today, the scientific community recognizes a total of 338 species. Given the speed at which hummingbirds evolve however, the researchers say that this number could double a few million years into the future.
"Everything about hummingbirds is extreme," said McGuire. "It is amazing that evolution can take an animal to such extremes."