Pollen can protect mahogany from extinction

New research from the University of Adelaide could help protect one of the world's most globally threatened tree species - the big leaf mahogany - from extinction.

Big leaf mahogany (Swietenia macrophylla) is the most prized mahogany timber around the world. It is at risk of extinction in its native habitats because of the timber trade, particularly in Central and South America.

To better understand how such a threatened species can be brought back from the brink of extinction, scientists from the University of Adelaide's Environment Institute have studied the important role played by the trees' pollen in the health and re-growth of mahogany forests.

The results of this study have been published online in Ecology Letters.

The researchers found that the extensive exploitation of mahogany forests has had a major impact on the diversity and availability of the trees' pollen. This in turn limits the ability of individual trees to grow and provide cross-fertilization for other mahogany trees.

"We collected data across seven Central American countries (Mexico, Guatemala, Belize, Honduras, Nicaragua, Costa Rica and Panama) which shows that trees remaining in cleared forest areas suffer from too much self-fertilization and low pollen diversity," says lead author Martin Breed, a PhD student with the University of Adelaide's Environment Institute and the School of Earth & Environmental Sciences.

"This results in less competitive seedlings and affects the rate of re-growth of the species."

Mr Breed says to restore forests would require replanting key species and finding good-quality seeds from healthy trees. "Growing new mahogany trees has proven a major challenge in the past. By better understanding the importance of pollen diversity, we hope this research provides the key to restoring forests at a much higher rate.

"Ensuring seed is collected from healthy populations will improve our chances of protecting not only mahogany, but the hundreds of other species - and human communities - that rely on it," he says.

Senior co-author Professor Andrew Lowe, Director of the Australian Centre for Evolutionary Biology and Biodiversity at the University of Adelaide, says: "Aside from being one of the world's most prized timbers, every mahogany tree provides habitat for hundreds of animals and plants, so they're ecologically very important."

He says this discovery has the potential to impact the way we think about restoring forests and shows us why it is vital to protect areas of high conservation value.

"Preserving areas where large populations of species have existed for the longest time not only assures the future of these iconic sites, but also provides insurance for entire species beyond the sites themselves," Professor Lowe says.

The project was largely funded from the European Union through the project SEEDSOURCE, with a portion of the funding coming from a grant awarded by the Australian Research Council.

Dr Carlos Navarro, who was employed by CATIE (the Tropical Agricultural Research and Higher Education Center) in Costa Rica at the time, was primarily responsible for directing the fieldwork and the collection of leaf and seed material used in the analysis and was the researcher who did the growth assessments.