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Fire increases species relatedness in plant communities

Mediterranean communities living under high fire recurrence are composed by plant species that are more closely related than what would be expected from the regional species pool (i.e., phylogenetic clustering; Verdú & Pausas 2007). This is because high fire recurrence favors seeder species, and the traits that confer the seeder character (e.g., heat and smoke stimulated germination, Moreira et al. 2010) are evolutionary conserved, that is, closely related species tend to be similar (Pausas & Verdú 2008). In fact, the abundance of seeders species is negatively related to phylogenetic diversity (Coca & Pausas 2009; see Figure 2 below).

The Figure 1 below shows the Net Relatedness Index (NRI, i.e, standardized form of the community mean phylogenetic distance) of woody species coexisting in for communities in contrasted crown-fire regimes (LowFire vs HighFire) at different spatial scales (regional and local). Note that high net relatedness = low mean phylogenetic distance. At regional scale, “LowFire” corresponds to mountain communities living in zones that rarely burnt, and “HighFire” are warm and dry coastal communities subject to a high frequency of crown fires. At local scale (under the same climate), “LowFire” corresponds to communities growing in fertile soils while “HighFire” are communities growing on poor soils where flammability is higher. When comparing from community null models, HighFire communities show higher NRI than expected by chance (phylogenetic clustering), which indicates the importance of habitat filtering in shaping fire-prone communities (Verdú & Pausas 2007, Ojeda et al. 2010).

Fig9.7_phylostruct-NRI

Fig. 1. Elaborated from Verdú & Pausas (2007) and Ojeda et al. (2010).

PD-seeders_Coca-Pausas Fig. 2. From Coca & Pausas (2009).

References

  • Coca M. & Pausas J.G. 2009. Regeneration traits are structuring phylogenetic diversity in cork oak (Quercus suber) woodlands. J. Veget. Sci. 20: 1009-1015. [doi | pdf | post]
  • Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann. Bot. 105:627-635 [doi | pdf | post]
  • Ojeda, F., Pausas, J.G., Verdú, M. 2010. Soil shapes community structure through fire. Oecologia 163:729-735. [doi | pdf | post]
  • Pausas J.G. & Verdú M. 2008. Fire reduces morphospace occupation in plant communities. Ecology 89: 2181-2186. [doi | pdf]
  • Verdú M. & Pausas J.G. 2007. Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities J. Ecol. 95: 1316-323. [doi | pdf]

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