The helmet orchid genus Corybas contains about 140 species with exquisitely complex flowers, distributed from Asia to Australia and other parts of the southwest Pacific basin. Corybas has been poorly studied due to their small size and the large number of species in tropical montane forests. The goals of this project are to use DNA variation from a broad sample of species to examine relationships within Corybas; to reconstruct the historical timing and geographic patterns of distributional changes and species diversification; and to examine the frequency and ecological context for changes in flower structure. One group of closely related species in Australia will be studied in detail to investigate these questions on a finer scale.

This research will result in the discovery and description of new species, in development of a revised classification, and in helping set conservation priorities by quantifying patterns of genetic uniqueness and diversity. The results will provide an important context for future studies on the ecology of individual species, and will further our understanding of historical biogeography and speciation. This project involves substantial collaboration with foreign researchers, including several in developing countries, and will contribute to the professional development of scientists in these regions.

Project Report

The orchid subtribe Acianthinae, containing roughly 170 species in five genera, consists of almost exclusively terrestrial, diminutive species, most of which seem to be pollinated by small flies. The group is poorly studied, and presents unique opportunities for evolutionary studies. While the vegetative features are fairly uniform within the group, floral diversity is quite substantial, especially in the large genus Corybas. Though part of the primarily Australian Diurideae, this particular subtribe has a remarkably wide range spanning much of Australasia and the Malay Archipelago, into mainland Asia and the Pacific. This is the first study to extensively sample the Acianthinae outside of Australia, New Zealand, and New Caledonia. During extensive collecting efforts, we worked extensively with both young researchers and members of the public in a number of developing countries, exchanging taxonomic and technical knowledge, and providing resources and networking opportunities. Our research in Papua New Guinea uncovered about 10 new species of Corybas, suggesting a large amount of undiscovered botanical diversity in the New Guinea highlands. By sequencing multiple genes, we were able to reconstruct the evolutionary history of this group with high confidence, allowing us to propose a revised classification system than would both minimize taxonomic changes yet incorporate our new understanding of evolutionary relationships in the group. Some distinctive floral traits appear to have arisen multiple times in the group, pointing to an important role for pollinators in generating diversity. Biogeographical studies indicate a mid-Oligocene origin in Australia with extensive dispersal to New Zealand and New Caledonia. In the tropical parts of its range, dispersal appears more limited, mostly occurring on a smaller scale—with some dramatic exceptions. Much diversification appears to occur locally, especially within the rapid uplifting island of New Guinea. We also employ new techniques (Genotyping-by-Sequencing) to address relationships within one very recently evolved clade restricted to Australia, the genus Corysanthes Jones et al., resulting in unprecedented resolution within and among species, allowing us to evaluate the history of dispersal in Australia and make recommendations on species delimitation. This information will be shared with the Australian botanical community to promote more accurate communication about species and the conservation of biological diversity. We are one of the first projects to assess species-level relationships using this new technique, which we expect will have broad applicability within the field of evolutionary biology.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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David Mindell
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University of Wisconsin Madison
United States
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