EAPSI: Phylogenetic Resolution and the Evolution of CAM Photosynthesis within Australian Calandrinia

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This award supports research that aims to resolve the species relationships and the evolution of Crassulacean Acid Metabolism (CAM) photosynthesis within Calandrinia s.l., a genus of plants widely distributed across the Australian continent, typically inhabiting arid to semi-arid environments, although several species have also been collected from temperate Tasmania, and from the monsoon-dominated tropics of coastal Australia. CAM photosynthesis is an adaptation that improves photosynthetic and water use efficiency under hot and dry conditions. In light of climate change and the increasing aridity of the world?s land (~40% of which is already considered arid, semi-arid or sub-humid), it is necessary that we understand the expression and evolution of CAM photosynthesis as it will likely play an important role in the future of carbon sequestration, sustainable biomass production, and food-crop security. This research will be conducted in collaboration with Dr. Joseph Holtum (James Cook University), an expert on the succulent flora of Australia and CAM photosynthesis. In efforts to collect specimens comprehensively across the genus, additional collaborations have also been established with the WA Herbarium, Melbourne Botanic Garden, SA Herbarium, Australian Tropical Herbarium, and NT Herbarium.Since the evolution of C3 photosynthesis - the pathway used by most green plants - only two known alternative pathways have evolved: C4 and CAM photosynthesis. Both of these derived pathways improve photosynthetic efficiency under hot/dry and low CO2 conditions. Much is known about the step-like evolution of C4 photosynthesis but little is known about the evolutionary history of CAM and its phylogenetic distribution. This study will use novel DNA sequencing techniques to generate robust molecular phylogenies of Calandrinia, a genus that represents the C3 to CAM-intermediate (CAM-cycling and facultative CAM) to CAM photosynthetic spectrum. To characterize photosynthesis physiological, isotopic (13C/12C and D/H), and anatomical measurements will be comprehensively made across the genus. These data will be interpreted in light of the molecular phylogenies to generate hypotheses on the historical transformations leading to the assembly of the CAM phenotype from C3 and CAM-intermediate ancestors. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.