Abstract Detail

Development and Structure

Zhou, Haoran [1], Earles, Mason [2], Théroux-Rancourt, Guillaume [3], Broderson, Craig [4], Edwards, Erika [5].

Dissecting an evolutionary syndrome: ecophysiological modeling points to a mechanistic link between succulence and CAM photosynthesis.

The repeated evolution of adaptive syndromes in organisms is a common and significant phenomenon and is often used as evidence of strong selection. Strongly correlated sets of traits can be mechanistically linked, genetically correlated, or co-selected and both genetically and mechanistically independent. In plants, succulence is a prominent adaptive syndrome that often co-occurs with the CAM photosynthetic pathway. Both succulence and CAM can contribute to survival under drought independently, so are they simply co-selected, or is a succulent anatomy required for CAM? We present the first anatomically explicit physiological model of CAM photosynthesis that identifies the anatomical thresholds that govern the relative advantages of C3 and CAM under a set of environmental conditions. In our model, cell size emerged as the primary driver of the evolution of a strong CAM metabolism. Theoretical modeling predictions were validated with a diverse set of C3, C3+CAM, and strong CAM species of bromeliads, and our predicted anatomical thresholds corresponded with measured parameters. We conclude that strong CAM metabolism is mechanistically linked to succulence via the need for large cells for malate storage, as well as compensating the side effect on leaf water potential of malate storage. Arid environments provide strong selection for both increased water storage and increased water use efficiency, and selection for increased cell size will simultaneously advantage CAM metabolism as well as tissue capacitance. This positive “anatomical pleiotropy” likely drives the repeated evolution of this adaptive syndrome across the tree of life.

1 - 470 Prospect St, APT 2, New Haven, CT, 06511, United States
2 - University of California, Davis, Viniculture and Enology
3 - University of Natural Resources and Life Sciences, Vienna, Institute of Botany
4 - Yale University, Yale School of the Environment
5 - Yale University, Department Of Ecology And Evolutionary Biology, 165 Prospect St, New Haven, CT, 06511, United States

convergent evolution
form and function

Presentation Type: Oral Paper
Number: DS6002
Abstract ID:660
Candidate for Awards:None

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