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Phylogenetic analyses reveal the shady history of C 4 grasses

Edwards, Erika J. ; Smith, Stephen A.

Proceedings of the National Academy of Sciences - PNAS, 2010-02, Vol.107 (6), p.2532-2537 [Periódico revisado por pares]

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  • Título:
    Phylogenetic analyses reveal the shady history of C 4 grasses
  • Autor: Edwards, Erika J. ; Smith, Stephen A.
  • É parte de: Proceedings of the National Academy of Sciences - PNAS, 2010-02, Vol.107 (6), p.2532-2537
  • Descrição: Grasslands cover more than 20% of the Earth's terrestrial surface, and their rise to dominance is one of the most dramatic events of biome evolution in Earth history. Grasses possess two main photosynthetic pathways: the C 3 pathway that is typical of most plants and a specialized C 4 pathway that minimizes photorespiration and thus increases photosynthetic performance in high-temperature and/or low-CO 2 environments. C 4 grasses dominate tropical and subtropical grasslands and savannas, and C 3 grasses dominate the world's cooler temperate grassland regions. This striking pattern has been attributed to C 4 physiology, with the implication that the evolution of the pathway enabled C 4 grasses to persist in warmer climates than their C 3 relatives. We combined geospatial and molecular sequence data from two public archives to produce a 1,230-taxon phylogeny of the grasses with accompanying climate data for all species, extracted from more than 1.1 million herbarium specimens. Here we show that grasses are ancestrally a warm-adapted clade and that C 4 evolution was not correlated with shifts between temperate and tropical biomes. Instead, 18 of 20 inferred C 4 origins were correlated with marked reductions in mean annual precipitation. These changes are consistent with a shift out of tropical forest environments and into tropical woodland/savanna systems. We conclude that C 4 evolution in grasses coincided largely with migration out of the understory and into open-canopy environments. Furthermore, we argue that the evolution of cold tolerance in certain C 3 lineages is an overlooked innovation that has profoundly influenced the patterning of grassland communities across the globe.
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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