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Project: 325/2018
Title: Australasian orchid diversification in space and time: elucidating the floristic interchange between Australia and New Caledonia in a phylogenomic framework
Applicant: Dr. Katharina Nargar and Dr. Mark Clements
Institution: Australian Tropical Herbarium and Centre for Australian National Biodiversity Research
The orchid floras of Australia and New Caledonia are characterised by high levels of endemicity, and a large proportion of species that are threatened. The two orchid floras, nonetheless have strong floristic links, evident through a high proportion of shared and closely related orchid taxa. However, the evolutionary history of the Australian and New Caledonian Orchidaceae, in particular the relative importance of diversification within each landmass and floristic interchange between them is still poorly understood.
This project aims to reconstruct the evolutionary relationships of Australasian orchid lineages based on genomic data and to infer their spatio-temporal evolution in a phylogenomic framework. We will investigate the directionality and timing of floristic interchanges between the two orchid floras and examine to what extend today’s species distributions are the result of more recent long-distance dispersals between the two countries or of biogeographic events in the deeper evolutionary history of the respective orchid lineages. The results of the phylogenomic study will be critical to re-assess the taxonomic and conservation status of rare New Caledonian species. Further, this project aims to establish and strengthen collaborations between Australian and New Caledonian orchid taxonomists through joint fieldwork, workshops and research projects.
Research Outcomes
This project facilitated new insights into evolutionary relationships and the spatio-temporal evolution of major Australasian orchid lineages, as well as the floristic interchange between Australia and New Caledonia.
Ancestral range analyses for the two largest terrestrial Australasian orchid lineages (Diurideae and Pterostylidinae) inferred an Australian origin for both lineages. Ancestral range analyses in these groups revealed multiple independent range expansions and range shifts between Australia and New Caledonia. These occurred long after New Caledonia separated from the Australian continent, implying that these range evolutionary events are the result of long-distance dispersal between the two regions. Our phylogenomic analyses in terrestrial Australasian orchid lineages provided evidence that the Australian continent was the key source area for today’s distribution of these lineages in New Caledonia.
For epiphytic orchid lineages such as the Dendrobiinae and Bulbophyllinae, our studies also inferred long-distance dispersals as most likely mechanism for floristic exchange between New Caledonia and Australia. However, ancestral range reconstructions revealed more complex biogeographic scenarios which included other neighbouring regions, such as Asian and Malesian regions to a greater extent.
The project facilitated taxonomic reassessments for Australasian orchids including New Caldedonian endemics, e.g., through research presentations to the Orchid Taxonomy Advisory Group Australasia (OTAGA).
The findings of this projects are important for our understanding past impacts of climatic and environmental changes on Australasian plant diversity to inform conservation management in a changing world.
Publications
Nargar K and Clements M (2022). The evolutionary journey of the greenhood orchids. https://www.csiro.au/en/news/all/articles/2022/september/orchid-evolution
Nargar K, O’Hara K, Mertin A, Bent S, Nauheimer L, Simpson S, Zimmer H, Molloy BPJ, Clements MA (2022). Evolutionary relationships and range evolution of greenhood orchids (subtribe Pterostylidinae): insights from plastid phylogenomics. Frontiers in Plant Science 13: 912089. doi: 10.3389/fpls.2022.912089.
Perez-Escobar OA, Bogarín D, Przelomska NAS, Ackerman JD, Balbuena JA, Bellot S, Bühlmann RP, Cabrera B, Cano JA, Charitonidou M, Chomicki G, Clements MA, Cribb P, Fernández M, Flanagan NS, Gravendeel B, Hágsater E, Halley JM, Hu A-Q, Jaramillo C, Mauad AV, Maurin O, Müntz R, Leitch IJ, Li L, Negrao R, Oses L, Phillips C, Rincon M, Salazar-Chavez G, Simpson L, Smidt E, Solano-Gomez R, Parra-Sánchez E, Tremblay RL, van den Berg C, Villanueva BS, Zuluaga A, Chase MW, Fay MF, Condamine FL, Forest F, Nargar K, Renner SS, Baker WJ, Antonelli A (2023): The origin and speciation of orchids. New Phytologist, accepted manuscript. biorxiv preprint: https://doi.org/10.1101/2023.09.10.556973
Simpson S, Clements MA, Orel HK, Crayn DM, Nargar K (2023). Plastid phylogenomics clarifies broad-level relationships in Bulbophyllum (Orchidaceae) and provides insights into range evolution of Australasian section Adelopetalum. Frontiers in Plant Science 14: 1219354. doi: 10.3389/fpls.2023.1219354. Accepted manuscript. bioRxiv preprint: https://doi.org/10.1101/2022.07.24.500920