The South Pacific islands are a biodiversity hotspot, but their jagged peaks, hot and humid conditions, and remote locations have limited scientists’ ability to document the region’s many fantastic lifeforms.
In a new study published this week in the Journal of Biogeography, researchers at the University of California, Berkeley, provide the first detailed description of the amazing array of fungi that live on the Polynesian island of Mo’orea. The collection includes more than 200 species of macrofungi, that is, fungi that produce visible fruiting bodies, many of which may be new to science.
“It’s like a treasure trove,” said the study’s lead author, Matteo Garbelotto, a cooperative extension specialist and assistant professor of environmental science, policy and management at UC Berkeley. “This is truly uncharted territory in the evolutionary biology and biodiversity of the fungal kingdom, and this is one of the first attempts to generate baseline information on fungal diversity, not just for Mo’orea, but for the whole vast region of insular Oceania.”
As part of the Mo’orea Biocode project, the study team spent months scouring the island for new species of fungi, eventually collecting a total of 553 fungal specimens and sequencing the DNA of 433 d ‘between them. Since only a handful of sequenced specimens have exact genetic matches to other known species, Mo’orea’s collections are likely to contain completely new species.
By comparing the DNA sequences of these fungi to those of other species around the world, the team was also able to piece together the origin of the remote island’s fungal biodiversity. The results suggest that the majority of species, or their ancestors, were transported by easterly winds from Australia or other South Pacific islands, although small numbers may have been brought to Mo’orea. by humans from distant places like East Asia, Europe and South America.
“We were really interested in the biodiversity of the island,” said the study’s first author, Todd Osmundson, who completed the work as a postdoctoral researcher at UC Berkeley. “Mo’orea is an island in the middle of the ocean, and it is a geologically young volcanic island. It has never touched another piece of land. How did the mushrooms get there and where did they come from- they?”
Understanding both the biodiversity of fungi on the island and how different species have traveled across the world to arrive at this remote location can help scientists combat the ongoing impacts of global travel and trade on biodiversity.
“The Mo’orea BioCode Project was the first survey of all taxa on a tropical island to include DNA vouchers and other associated information. It included all organisms from marine and terrestrial habitats and everything that is bigger than bacteria,” said George Roderick, William Muriece. Hoskins Professor of Environmental Science, Policy and Management at UC Berkeley. “The data has since proven extremely valuable for monitoring the impacts of global change on Mo’orea but also on other tropical islands in the Pacific.”
“Every day we had a different challenge”
The Mo’orea Biocode Project was led by Neil Davies, executive director of UC Berkeley’s Gump South Pacific Research Station, and ran from 2007 to 2010. One of the motivations for the project was to create a model ecosystem that could be used to answer questions about ecosystem functioning.
“Fungi are really important parts of ecosystems,” said Osmundson, who is currently a professor of biology at the University of Wisconsin-La Crosse. “They act as primary decomposers and in some cases (as) pathogens that break down decaying organic matter and recycle nutrients into forms that other organisms can use. They are also very important as symbionts. They live with other organisms and take advantage of that organism in exchange for other things.For example, some fungi attach themselves to the roots of plants and exchange nutrients with them.
To collect the specimens, the research team spent months on Mo’orea, beginning each day before dawn to collect samples of the mushrooms from all corners of the ecosystem, including soil, roots and plant leaves, and even the air.
As the heat and humidity increased throughout the day, the conditions outside often became inhospitable both to the scientists and to the delicate fruiting bodies of the mushrooms they had collected. In the early afternoon, they would bring their samples back to the lab and begin the process of documenting and culturing the specimens they found, often staying up late into the night to complete their work.
“The terrain on the island is incredibly steep, and when it rains it gets incredibly muddy, and many areas are unmanaged. So every day we had a different challenge,” Garbelotto said. “There are slopes that you can only really explore with ropes. I remember being tied to a rope with my hands outstretched over the precipice, trying to pick up a mushroom that was growing on a small outcrop where it was impossible to walk.“
Each of the specimens was photographed and dried for storage in the University Herbarium and compared to databases of known species. As part of the biocode project, the research team also obtained DNA sequences of a specific gene that can be used as a unique “barcode” to differentiate one species from another.
“In many ways Mo’orea is not a virgin island, and that makes it more interesting to me,” Garbelotto said. “The island has completely pristine areas and also has areas that have been inhabited and profoundly modified by man, beginning with the arrival of the Polynesians 3,000 years ago and continuing until relatively recently with the arrival of the French, the English and the Americans. Compared to completely virgin places, Mo’orea is more interesting for me because it is more representative of what the world really is.
Additional co-authors on the paper are Sarah E. Bergemann of Middle Tennessee State University and Rikke Rasmussen, who worked on DNA sequencing as a volunteer at UC Berkeley. The Moorea Biocode project was supported by the Gordon and Betty Moore Foundation.