Macro-Climatic Distribution Limits Show Both Niche Expansion and Niche Specialization among C4 Panicoids

PLoS One. 2016 Mar 7;11(3):e0151075. doi: 10.1371/journal.pone.0151075. eCollection 2016.

Abstract

Grasses are ancestrally tropical understory species whose current dominance in warm open habitats is linked to the evolution of C4 photosynthesis. C4 grasses maintain high rates of photosynthesis in warm and water stressed environments, and the syndrome is considered to induce niche shifts into these habitats while adaptation to cold ones may be compromised. Global biogeographic analyses of C4 grasses have, however, concentrated on diversity patterns, while paying little attention to distributional limits. Using phylogenetic contrast analyses, we compared macro-climatic distribution limits among ~1300 grasses from the subfamily Panicoideae, which includes 4/5 of the known photosynthetic transitions in grasses. We explored whether evolution of C4 photosynthesis correlates with niche expansions, niche changes, or stasis at subfamily level and within the two tribes Paniceae and Paspaleae. We compared the climatic extremes of growing season temperatures, aridity, and mean temperatures of the coldest months. We found support for all the known biogeographic distribution patterns of C4 species, these patterns were, however, formed both by niche expansion and niche changes. The only ubiquitous response to a change in the photosynthetic pathway within Panicoideae was a niche expansion of the C4 species into regions with higher growing season temperatures, but without a withdrawal from the inherited climate niche. Other patterns varied among the tribes, as macro-climatic niche evolution in the American tribe Paspaleae differed from the pattern supported in the globally distributed tribe Paniceae and at family level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Climate*
  • Droughts
  • Evolution, Molecular
  • Photosynthesis*
  • Poaceae / metabolism*
  • Poaceae / physiology
  • Temperature

Grants and funding

This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina (http://www.conicet.gov.ar, research grant - PIP 0207), National Geographic Society (grant nos. 8365-07 and 8862-10 supported Field work), Agencia Nacional de Promoción Científica y Tecnológica, Argentina (http://www.agencia.mincyt.gob.ar/, research grant - PICT 0207), and Myndel Botanical Foundation supported field work.