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Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway
Author(s) -
Horn James W.,
Xi Zhenxiang,
Riina Ricarda,
Peirson Jess A.,
Yang Ya,
Dorsey Brian L.,
Berry Paul E.,
Davis Charles C.,
Wurdack Kenneth J.
Publication year - 2014
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12534
Subject(s) - biology , aridification , lineage (genetic) , crassulacean acid metabolism , arid , ecology , clade , phylogenetics , botany , evolutionary biology , photosynthesis , biochemistry , gene
The mid‐Cenozoic decline of atmospheric CO 2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO 2 ‐concentrating mechanisms (CCMs)—crassulacean acid metabolism (CAM) and C 4 —evolved from the C 3 photosynthetic pathway, enabling more efficient whole‐plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates ( r ) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM‐using stem succulents, plus a single species‐rich C 4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17–22 times in Euphorbia , principally from the Miocene onwards. Analyses assessing among‐lineage variation in r identified eight Euphorbia subclades with significantly increased r , six of which have a close temporal relationship with a lineage‐corresponding CCM origin. Our trait‐dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C 3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia .