Scientists from the Smithsonian using DNA data sets to outline the evolutionary family tree of the Hawaiian honeycreeper have determined that the 56 species of the native bird evolved from the Eurasian rosefinch.
In another important finding, the researchers linked the timing of the evolution of the honeycreeper to the formation of the four main Hawaiian Islands.
“It was fascinating to be able to tie a biological system to geological formation and allowed us to become the first to offer a full picture of these birds’ adaptive history,” said Helen James, a research zoologist at the Smithsonian’s National Museum of Natural History and an author of a paper on the study.
Fern Duvall, state Forestry and Wildlife Division wildlife biologist, who was not involved with this study but is working with two of the authors of the paper, James and Rob Fleischer, on a similar project with shorebirds, called the findings “dynamic” and “unique.”
Putting the research in context, Duvall noted that many bird experts believed the honeycreepers to be descendants of the house finch of North America. Instead, the researchers say the Eurasian rosefinch from Asia is the mother bird of the species.
As for the evolutionary discoveries, Duvall said it had been theorized that there was a link between the biologic and geologic development of the birds to the islands. The scientific connection made in the study is new, he said.
“For them to show that that is the case is dynamic,” he said Wednesday. “I think it’s an excellent example that birds’ forms are tied to diverse habitat types.”
The findings will be published in hard copy in Current Biology on Nov. 8, with Heather Lerner, an assistant professor of biology at Earlham College, as lead author. A pdf version of the paper is available online today on Current Biology’s media pages.
“There were once more than 55 species of these colorful songbirds, and they are so diverse that historically it wasn’t even entirely clear that they were all part of the same group,” said Lerner, who was a postdoctoral researcher at the Smithsonian Conservation Biology Institute’s Center for Conservation and Evolutionary Genetics when she conducted this research.
She noted that the species that includes the akepa, poouli, alauahio and akiapolaau have diverse diets and physiques. Different species of birds eat seeds, fruit, snails or nectar. Some birds have parrotlike bills and others have straight, thin bills.
“So the question that we started with was how did this incredible diversity evolve over time,” Lerner said in the news release.
The answer has a uniqueness tied to the development of the Hawaiian Islands.
The largest development of new species occurred between 2.5 million and 4 million years ago, after Kauai-Niihau and Oahu were formed but before Maui Nui and the Big Island. Six of 10 distinctive groups of species developed with different sizes, shapes and colors during that time.
“Each island that forms represents a blank slate for evolution, so as one honeycreeper species moves from one island to a new island, those birds encounter new habitat and ecological niches that may force them to adapt and branch off into distinct species,” a news release about the paper said.
Duvall said Hawaii is such a prolific spot for evolution that scholars say that if Charles Darwin, the father of evolutionary theory, had visited the Hawaiian Islands before going to the Galapagos, where he did his research, “the Galapagos would have been fairly uninteresting in comparison.”
James’ previous work on Hawaiian birds’ morphology, the branch of biology that deals with form and structure of organisms, played a pivotal role in determining which avian species to survey to determine the closest living relatives of the Hawaiian honeycreepers. Using genetic data from 28 bird species that seemed similar to the honeycreepers morphologically, genetically or that shared geographic proximity, the paper’s authors determined that the various honeycreeper species evolved from Eurasian rosefinches.
Unlike most other ancestral bird species that came from North America and colonized the Hawaiian Islands, the rosefinch likely came from Asia, the scientists found. Duvall said it is likely that the birds got blown in on a storm.
“These are truly native birds that are scientifically valuable and play an important and unique ecological function,” said Rob Fleischer, head of the Smithsonian Conservation Biology Institute’s Center for Conservation and Evolutionary Genetics and an author of the paper.
Fleischer has been studying the genetics, evolution and conservation of these birds for more than 25 years.
“I’m thrilled that we finally had enough DNA sequence and the necessary technology to become the first to produce this accurate and reliable evolutionary tree,” he said.
The diversity of Hawaiian honeycreepers has taken a huge hit, with more than half of the known 56 species already extinct. The paper’s researchers focused on the 18 species that have not gone extinct, but of those, six are considered critically endangered by the International Union for Conservation of Nature, four are considered endangered and five are vulnerable.
In order to analyze the DNA for the study, researchers used specialized and advanced sequencing protocols developed at the Max Planck Institute for Evolutionary Anthropology. To look at ancient DNA that is by nature damaged or degraded, scientists needed to use innovative techniques to capture and analyze DNA, the news release said.
Besides Lerner, Fleischer and James, other authors of the study included Michi Hofreiter from the University of York and Matthias Meyer from the Max Planck Institute for Evolutionary Anthropology. The work was funded by the National Science Foundation.