The evolution of CAM photosynthesis in Australian Calandrinia reveals lability in C₃+CAM phenotypes and a possible constraint to the evolution of strong CAM

Hancock, Lillian P., Holtum, Joseph A.M., and Edwards, Erika J. (2019) The evolution of CAM photosynthesis in Australian Calandrinia reveals lability in C₃+CAM phenotypes and a possible constraint to the evolution of strong CAM. Integrative and Comparative Biology, 59 (3). pp. 517-534.

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Abstract

Australian Calandrinia has radiated across the Australian continent during the last 30 Ma, and today inhabits most Australian ecosystems. Given its biogeographic range and reports of facultative Crassulacean acid metabolism (CAM) photosynthesis in multiple species, we hypothesized (1) that CAM would be widespread across Australian Calandrinia and that species, especially those that live in arid regions, would engage in strong CAM, and (2) that Australian Calandrinia would be an important lineage for informing on the CAM evolutionary trajectory. We cultivated 22 Australian Calandrinia species for a drought experiment. Using physiological measurements and δ¹³C values we characterized photosynthetic mode across these species, mapped the resulting character states onto a phylogeny, and characterized the climatic envelopes of species in their native ranges. Most species primarily utilize C₃ photosynthesis, with CAM operating secondarily, often upregulated following drought. Several phylogenetically nested species are C₃, indicating evolutionary losses of CAM. No strong CAM was detected in any of the species. Results highlight the limitations of δ¹³C surveys in detecting C₃+CAM phenotypes, and the evolutionary lability of C₃+CAM phenotypes. We propose a model of CAM evolution that allows for lability and reversibility among C₃+CAM phenotypes and C₃ and suggest that an annual life-cycle may preclude the evolution of strong CAM.

Item ID: 61732
Item Type: Article (Research - C1)
ISSN: 1557-7023
Copyright Information: © The Author(s) 2019. All rights reserved.
Funders: National Science Foundation (NSF), Australian Research Council (ARC), NSF IGERT, NSF EAPSI
Projects and Grants: NSF DEB-1252901, ARC DP160100098, NSF IGERT grant DGE-110966060, NSF EAPSI Australia (2015) award
Date Deposited: 12 May 2020 19:04
FoR Codes: 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060705 Plant Physiology @ 100%
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