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Australia born to burn – phylogenetic evidence

March 18th, 2011 Leave a comment Go to comments

Traditionally wildfires were considered a disturbance linked to the recent history of the Quaternary, and specially linked to the humans. However, evidence are accumulating about the ancient role of wildfires in terrestrial ecosystems [1]. In Australia, the flammable continent, the current believe is that fires started to be important during the onset of seasonal aridity in the Miocene (25 Ma). However, two recent and independent papers demonstrate, using phylogenetic techniques, that fire-dependent traits appeared about 60 Ma ago (early Paleocene), implying that fire was already an effective agent of selection by then. Crisp et al [2] studied the Myrtaceae family and showed that post-fire epicormic resprouting (typical of many eucalypts) is an ancient trait linked to the flammable sclerophyll biomes originated about 60-62 Ma. He et al. [3] studied the Banksia genus (Proteaceae) and showed that serotiny (fire dependent dispersal; figure below) and dead floret retention around the cones (enhanced flammability around serotinous cones) co-originate with the first appearance of Banksia 60.8 Ma ago. The coincidence of the two independent papers, using two different taxa (Myrtaceae and Banksia) is amazing, and clearly suggests that fire was a selective force in Australia during the Paleocene.  These papers are part of the accumulating research on the prominent and ancient role of fire in shaping plant species and biodiversity [1, 4 ].

References
[1] Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience 59: 593-601. [doipdfpost slides]

[2] Crisp MD, Burrows GE, Cook LG, Thornhill AH, Bowman DMJS. 2011. Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary. Nature Communications 2: 193. [doi]

[3] He T, Lamont BB, Downes KS. 2011. Banksia born to burn. New Phytol. [doi]

[4] Bond, W. J. and Scott, A. C. 2010. Fire and the spread of flowering plants in the Cretaceous. New Phytol. 188: 1137–1150 [post]

Figure: Banksia cone opened by the fire to release seeds (serotiny).

  1. June 10th, 2011 at 08:34 | #1

    This suggests an explanation for the fact that adaptation to fire in Gondwanan mediterranean shrublands is more widespread than in the Mediterranean Basin. The Paleocene age inferred here is interesting since it is against the hypothesis that angiosperms were initially favoured by fire in the Cretaceous (my previous comment).


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