A team of zoologists from Trinity College Dublin (TCD) in Ireland and the Halo Oleo University in Indonesia has recently found several new species of colorful, tropical sunbirds, including the “Wakatobi Sunbird” (Cinnyris infrenatus), which lives only on the tiny Wakatobi Islands in Central Indonesia. Moreover, by examining the more widespread Olive-backed Sunbirds and Black Sunbirds, the scientists found that individuals named as such actually belong to multiple unrecognized species. These findings have important implications for our understanding of evolution in this highly biodiverse region.
Living in the tropics from Africa to Australia, sunbirds resemble the American hummingbirds and fill similar ecological niches. Male sunbirds frequently have bright plumage, with iridescent feathers that shine in the sunlight. For centuries, zoologists have examined sunbirds’ plumage to identify different species, over 140 of which are currently recognized. However, with the help of new forms of evidence, such as DNA, song recordings, and statistical analyses of body measurements, the scientists have now found that this family is even more diverse than previously thought. To discover these new species, the researchers re-traced famous biologist Alfred Russel Wallace’s steps, as he based his theories on his investigations of animals across the islands of present-day Indonesia.
“One of Wallace’s major findings is referred to as ‘Wallace’s Line’ – a boundary between deep and shallow seas that many animals have been unable to cross, leading to marked differences in the species found on either side. The widespread Olive-backed Sunbird appeared to be an exception, being found all the way from China to Australia with Wallace’s Line right in the middle of its range,” said study lead author Fionn Ó Marcaigh, a PhD student in Zoology at TCD.
“The new study, however, has shown that the populations on either side actually represent two different species, in keeping with Wallace’s original predictions. The Black Sunbird was already known to be subject to Wallace’s Line, but the new research has shown that the population around Sulawesi is a separate species from the one in New Guinea.”
While the Olive-backed Sunbird covers quite a wide range for such a small bird, the newly discovered Wakatobi Sunbird is restricted to the tiny Wakatobi Islands off the coast of Sulawesi. Besides being genetically unique, this species also has darker plumage, a higher-pitched song, and shorter wings than the Olive-backed Sunbird. According to the scientists, its short wings have likely contributed to its remaining isolated on these islands.
“The identification of the Wakatobi Sunbird serves to remind us that biodiversity is everywhere. This bird wasn’t found in a remote rainforest, but along the scrubby margins of busy towns and villages. Let us hope the children of the Wakatobi will be able to enjoy these special birds for generations to come,” concluded co-author David Kelly, a behavioral ecologist at TCD.
The study is published in the Zoological Journal of the Linnean Society.
Image Credit: Nicola Marples and David Kelly, Trinity College Dublin
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