A macro-ecological perspective on crassulacean acid metabolism (CAM) photosynthesis evolution in Afro-Madagascan drylands: Eulophiinae orchids as a case study

New Phytol. 2015 Oct;208(2):469-81. doi: 10.1111/nph.13572. Epub 2015 Jul 20.


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.

Keywords: Africa; Eulophiinae; Madagascar; Orchidaceae; climate change; crassulacean acid metabolism (CAM) photosynthesis; shift of niche.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biodiversity
  • Biological Evolution*
  • Carbon Isotopes
  • Carboxylic Acids / metabolism*
  • Ecosystem*
  • Madagascar
  • Orchidaceae / physiology*
  • Photosynthesis*
  • Phylogeny
  • Principal Component Analysis
  • Time Factors


  • Carbon Isotopes
  • Carboxylic Acids