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Crassulacean acid metabolism (CAM) photosynthesis is an adaptation to water and atmospheric CO2 deficits that has been linked to diversification in dry-adapted plants. We investigated whether CAM evolution can be associated with the availability of new or alternative niches, using Eulophiinae orchids as a case study. Carbon isotope ratios, geographical and climate data, fossil records and DNA sequences were used to: assess the prevalence of CAM in Eulophiinae orchids; characterize the ecological niche of extant taxa; infer divergence times; and estimate whether CAM is associated with niche shifts. CAM evolved in four terrestrial lineages during the late Miocene/Pliocene, which have uneven diversification patterns. These lineages originated in humid habitats and colonized dry/seasonally dry environments in Africa and Madagascar. Additional key features (variegation, heterophylly) evolved in the most species-rich CAM lineages. Dry habitats were also colonized by a lineage that includes putative mycoheterotrophic taxa. These findings indicate that the switch to CAM is associated with environmental change. With its suite of adaptive traits, this group of orchids represents a unique opportunity to study the adaptations to dry environments, especially in the face of projected global aridification.

Original publication

DOI

10.1111/nph.13572

Type

Journal article

Journal

New Phytol

Publication Date

10/2015

Volume

208

Pages

469 - 481

Keywords

Africa, Eulophiinae, Madagascar, Orchidaceae, climate change, crassulacean acid metabolism (CAM) photosynthesis, shift of niche, Biodiversity, Biological Evolution, Carbon Isotopes, Carboxylic Acids, Ecosystem, Madagascar, Orchidaceae, Photosynthesis, Phylogeny, Principal Component Analysis, Time Factors