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Fire as a key driver of Earth’s biodiversity

July 12th, 2019 2 comments

Regions subject to regular fire have exceptionally high levels of species richness and endemism, and fire is likely a major driver of their diversity. In a recent paper [1] we reviewed the mechanisms that enable fire to act as a major ecological and evolutionary force that promotes and maintains biodiversity over different spatiotemporal scales. Specifically, we reviewed the different components of fire regime, the diversity through time (postfire), the intermediate disturbance hypothesis, the pyrodiversity-begets-biodiversity hypothesis, the fire-driven evolution and diversification, and the mutagenic effect of fire.

From an ecological perspective, the vegetation, topography and local weather conditions during a fire generate a landscape with spatial and temporal variation in fire-related patches (pyrodiversity), and these produce the biotic and environmental heterogeneity that drives biodiversity across local, regional and global scales scales [2]. We show that biodiversity should peak at moderately high levels of pyrodiversity. Overall species richness is typically greatest immediately after fire and declines monotonically over time, with postfire successional pathways dictated by animal habitat preferences and varying lifespans among resident plants.

From an evolutionary perspective, fire drives population turnover and diversification by promoting a wide range of adaptive responses to particular fire regimes [3,4]. In addition, fire and its byproducts may have direct mutagenic effects, contributing to the formation of novel genotypes that can lead to trait innovation. As a consequence of all these processes, the number of species in fire-prone lineages is often much higher than that in their non-fire-prone sister lineages.

Figure 1: The six components that define an individual fire event (in red the two core components). The fire regime arises from repeated patterns (means plus variance) over time of the properties of the components for each fire. For more details, see [1].

Figure 2. Relationship between species richness (S) of a reference area (community, landscape, region) and mean fire interval (a fire regime component). For a given fire regime, there is a mosaic of patches defined by different times since the last fire (represented by black circles) about the mean time interval (central circle). For more details, see [1].

 

References

[1] He T., Lamont B.B., Pausas J.G. (2019). Fire as s key driver of Earth’s biodiversity. Biological Reviews [doi | pdf]

[2] Pausas J.G. & Ribeiro E. 2017. Fire and plant diversity at the global scale. Global Ecol. Biogeogr. 26: 889–897. [doi | pdf | data & maps (figshare)]

[3] Keeley J.E., Pausas J.G., Rundel P.W., Bond W.J., Bradstock R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16: 406-411. [doi | pdf]  

[4] Pausas J.G. & Keeley J.E., 2014. Evolutionary ecology of resprouting and seeding in fire-prone ecosystems. New Phytologist 204: 55-65. [doi | pdf]