C4 photosynthesis promoted species diversification during the Miocene grassland expansion

PLoS One. 2014 May 16;9(5):e97722. doi: 10.1371/journal.pone.0097722. eCollection 2014.

Abstract

Identifying how organismal attributes and environmental change affect lineage diversification is essential to our understanding of biodiversity. With the largest phylogeny yet compiled for grasses, we present an example of a key physiological innovation that promoted high diversification rates. C4 photosynthesis, a complex suite of traits that improves photosynthetic efficiency under conditions of drought, high temperatures, and low atmospheric CO2, has evolved repeatedly in one lineage of grasses and was consistently associated with elevated diversification rates. In most cases there was a significant lag time between the origin of the pathway and subsequent radiations, suggesting that the 'C4 effect' is complex and derives from the interplay of the C4 syndrome with other factors. We also identified comparable radiations occurring during the same time period in C3 Pooid grasses, a diverse, cold-adapted grassland lineage that has never evolved C4 photosynthesis. The mid to late Miocene was an especially important period of both C3 and C4 grass diversification, coincident with the global development of extensive, open biomes in both warm and cool climates. As is likely true for most "key innovations", the C4 effect is context dependent and only relevant within a particular organismal background and when particular ecological opportunities became available.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biodiversity*
  • Carbon / metabolism*
  • Evolution, Molecular
  • Grassland
  • Photosynthesis / physiology*
  • Phylogeny
  • Poaceae*

Substances

  • Carbon

Grant support

This work was supported by National Science Foundation grant IOS0843231 to EJE and a Marie Curie IOF 252568 fellowship to PAC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.