Making a dent in cataloguing Earth’s biodiversity
The number of species on our planet is estimated at ten million; in 250 years of biodiversity research, two million have been described. At this speed, we need another thousand years to catalogue the remaining species. However, Earth’s biomes are threatened by the Sixth Mass Extincion, the loss of biodiversity due to poaching, habitat destruction, and global climate change. Many species become extinct before they are discovered. Therefore, efforts are made to accelerate biodiversity research through international collaborations, combining modern methods of DNA sequencing with the tedious work of revising thousands of historic natural history collections.
Fungi play important roles in ecosystems as decomposers, parasites, and symbionts, unlocking nutrients, controlling populations of other species, fostering plant growth, and exploring new environments in mutualistic associations. The most successful fungal symbioses are lichens: the 20,000 known species are important pioneer organisms and take part in the nutrient cycle, providing nitrogen to ecosystems; they draw pharmaceutical interest due to their chemical compounds, and they are widely used as bioindicators of environmental health. Lichens are better studied than other fungi; yet, 10,000 species remain to be discovered, particularly in tropical regions.
Trypetheliaceae is the second most important family of tropical lichens. Its members often form colourful mosaics on the bark of trees and produce peculiar spores with diamond-shaped cells. The first species were described and beautifully illustrated two centuries ago, often collected from exotic timber brought to Europe from South America, Africa and Asia. Many species reproduce with large spores presumably dispersed by ants; others form galls on tree bark. Trypetheliaceae are especially dominant in the Amazon, Astrothelium being the most speciose lichen genus there, and in the savannah-like Cerrado and the thorn-bush like Caatinga in Brazil, with Polymeridium particularly species-rich in the latter.
To date, the diversity in this family was not properly documented and many species remained undescribed. To remedy this situation, we joined forces with 44 colleagues and students from 25 countries, as far away as Brazil, Sri Lanka, and Australia. With financial support from the National Science Foundation and relentless effort by our colleague Matt Nelsen from the Field Museum in Chicago, hundreds of specimens were analyzed through DNA sequencing, which for the first time allowed us to understand the evolution of this family into so many species. Besides visiting important collections ourselves, the Global Plants Initiative, an international effort joining natural history collections in 57 countries, spearheaded by the Andrew W. Mellon Foundation, helped us to study over 400 digitized type specimens. Many colleagues provided material and we participated in numerous expeditions in the tropics to study and collect the species in the field.
The Thematic Issue Trypetheliaceae is the largest monographic treatment published to date in The Lichenologist, with 406 pages. The number of known species has doubled to more than 400, and 800 are predicted in an innovative outlook, which means that still another 400 await discovery in hotspots such as the Amazon and the Congo Basin.
Complimentary access has been provided to the full issue until February 13th 2017.
Written by Robert Lücking and André Aptroot