Trinity College Dublin zoologists, in collaboration with an Indonesian research team, discovered several new species of colorful tropical sunbirds. The Wakatobi sunbird (Cinnyris infrenatus), which lives on the tiny Wakatobi Islands in central Indonesia, was discovered by zoologists. They also looked at the more common olive-backed and black sunbirds and discovered that individuals labeled as such belonged to multiple unidentified species.
These exciting findings, taken together, have significant implications for our understanding of evolution in this biodiverse region. Sunbirds, which live in the tropics from Africa to Australia, resemble American hummingbirds and occupy a similar ecological niche. Male sunbirds have iridescent or “metallic” feathers that sparkle in the sunlight.
For hundreds of years, zoologists have examined the plumage of sunbirds to identify species, with over 140 currently recognized. However, zoologists discovered that this family is even more diverse than previously thought by using new forms of evidence such as DNA, song recordings, and statistical analyses of body measurements.
The discovery of the Wakatobi sunbird serves as a reminder that biodiversity can be found anywhere. This bird was discovered not in a remote rainforest, but on the scrubby outskirts of busy towns and villages. Let us hope that future generations of Wakatobi children will be able to enjoy these unique birds.”
Dr. David Kelly
Researchers from Trinity’s School of Natural Sciences and Universitas Halu Oleo in Sulawesi, Indonesia, collaborated on this study, which was recently published in the Zoological Journal of the Linnean Society. This journal was the first to publish Charles Darwin and Alfred Russel Wallace’s evolutionary theories in 1858.
The international research team retraced Wallace’s steps in more ways than one, as he based his theories on his studies of animals across the islands of present-day Indonesia.
Fionn Ó Marcaigh, first author on the paper and a Ph.D. Candidate in Trinity’s School of Natural Sciences, said, “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.
“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.”
Despite this split, the olive-backed sunbird covers quite a wide range for such a small bird. The newly discovered Wakatobi sunbird, on the other hand, is restricted to the tiny Wakatobi Islands, off the coast of the larger Sulawesi. Small, isolated islands like these have their own evolutionary processes, and these often produce unique species, as in the famous case of the Galápagos.
Previous work from the Trinity School of Natural Sciences identified two species of white-eye birds from the same area, which has been recognized by international conservation organizations as a Key Biodiversity Area.
The Wakatobi sunbird, in addition to being genetically distinct, has darker plumage, a higher-pitched song, and shorter wings than the olive-backed sunbird. Its short wings most likely contributed to its isolation on the Wakatobi Islands while the olive-backed sunbird was attempting long-distance colonization over the sea.
Fionn Ó Marcaigh added, “It’s amazing that there are still species waiting to be found in this region, which has been important to evolutionary biology since the time of Wallace. I’m thrilled that we’ve added to the list of known species from this wonderful part of the world, it’s the kind of thing I dreamed of when I first got interested in zoology as a child. As well as that, this study has been a brilliant opportunity to build on classic work with new techniques. It’s especially fascinating when we find new discoveries that support Wallace’s original predictions.”
Dr. David Kelly of Trinity University is the paper’s second author. He continued, “The discovery of the Wakatobi sunbird serves as a reminder that biodiversity can be found anywhere. This bird was discovered not in a remote rainforest, but on the scrubby outskirts of busy towns and villages. Let us hope that future generations of Wakatobi children will be able to enjoy these unique birds.”
