revised evolutionary history of Poales: origins and diversification

• Published in: Botanical journal of the Linnean Society Vol. 175; no. 1; pp. 4 - 16
• Main Authors: Bouchenak‐Khelladi, Yanis, Muasya, A. Muthama, Linder, H. Peter
• Format: Journal Article
• Language: English
• Published: Oxford Published for the Linnean Society of London by Academic Press 01.05.2014; Blackwell Publishing Ltd; Oxford University Press
• Subjects: ancestral reconstructions; Bromeliaceae; Carbon dioxide; Cenozoic; CO2-concentrating mechanisms; Crassulacean acid metabolism; Cretaceous; Cyperaceae; habitats; interspecific variation; molecular dating; open and dry habitats; parallel evolution; Photosynthesis; phylogeny; Poaceae; radiation; rain; species differences; species diversity; Species richness
• ISSN: 0024-4074; 1095-8339
• DOI: 10.1111/boj.12160

Poales represents more than one‐third of all monocotyledons (c. 20 000 species in 16 families) and constitutes a microcosm of the angiosperms. The extreme variation in species richness among the families of Poales is still not understood: Poaceae includes ∼10 000 species, whereas six families have fewer than ten species. Here, using the largest phylogenetic analysis of Poales to date, molecular dating, ancestral reconstructions and diversification analyses, we develop a macro‐evolutionary and macro‐ecological approach to seek correlates for changing diversification patterns. We show that the poalean families diverged in the Late Cretaceous, a time of high levels of CO₂ and high rainfall. Our habitat reconstructions indicate that Poales inhabited open and dry habitats in this environment. We also demonstrate that lineages with CO₂‐concentrating mechanisms inhabiting dry and open environments exhibited higher diversification rates than C₃, shade and wet lineages. CO₂‐concentrating mechanisms counteract the effects of low atmospheric CO₂ and reduce phototranspiration. It is believed that the parallel evolution of C₄ and CAM (Crassulacean acid metabolism) photosynthesis in Poaceae, Cyperaceae and Bromeliaceae is an adaptation to changes in atmospheric CO₂ concentrations. Combinations of extrinsic and intrinsic factors might have played a role in shifts in diversification rates and may explain the variation in species richness in Poales. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 4–16.