The rate at which new species evolve is limited by competition for ecological niches, report scientists from the University of Chicago in Nature on April 30. The study, which analyzes the evolutionary and genetic relationships between all 461 songbird species that live in the Himalayan mountains, suggests that as ecological niches within an environment are filled, the formation of new species slows or even stops.
To study what controls the process of speciation, Trevor Price, PhD, professor of ecology and evolution at the University of Chicago, Dhananjai Mohan of the Indian Forest service and their colleagues looked at songbirds in the eastern Himalayas, a region which contains the greatest diversity of songbirds in the world. Thought to have originated from a single species around 50 million years ago, the songbird suborderwhich includes swallows, warblers, finches and crowscontains more than 5,000 species, occupies a wide range of climates and possesses extreme variations in body mass, shape and feeding adaptations.
The team collected and sequenced DNA from all 461 species of Himalayan songbirdsincluding ultra-rare species such as the Bugun liocichla. Of these species, 358 breed within a 10,000 square kilometer area, offering the ability to compare the difference between species in the area and those elsewhere in the Himalayas. The team then created a molecular-based phylogenetic tree that detailed the evolutionary relationships between all the species.
Based on genetic information, the researchers discovered that eastern Himalayan songbirds are, on average, separated from each other by six to seven million yearsroughly the same amount of time that humans and chimpanzees have been separated.
"Despite the great diversity of environments and ability for species to move between areas, evolution in eastern Himalayas appears to have slowed to a basic halt," Price said. "Other species have formed elsewhere, such as
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University of Chicago Medical Center