Fire

Picking up on my elemental theme, fire has long been considered a major influence on evolution of the angiosperms, whether natural or anthropogenic conflagrations. This incendiary interaction has not been helped by plants themselves, which not only generate highly calorific and combustible dry matter but also provide the oxygen needed to permit their combustion. The dramatic effect of fire on vegetation was graphically demonstrated in the Australian wildfires in January. Although fire has been an abiotic factor for hundreds of millions of years, the origins of so-called ‘fire prone’ floras have hitherto been considered to be comparatively recent phenomena. However, using a molecular-dated phylogeny for the Proteaceae, a ‘great Gondwanan family with a 113-million-year evolutionary history’, Byron Lamont and Tianhua He have established that angiosperm fire proneness can now be traced back 83–94 million years into the ‘fiery Cretaceous’. Furthermore, the associated evolution of on-plant (serotiny; in which seed release occurs in response to an environmental trigger, e.g. fire) and soil seed storage, and – evolutionarily – more recent ant-dispersal characteristics, affirms those behaviours as ancient adaptations to fire among flowering plants. Interestingly, and by way of setting up some sort of competition between angio- and gymnosperm, Tianhua He et al. have previously suggested a 126-million-year evolutionary history of fire-adapted traits in the Pinaceae. And if you want more on the evolutionary supremacy tussle between those great seed-bearing phyla, then I can recommend Clément Coiffard et al.’s paper that proposes a window of opportunity of approximately 145–66 million years ago (the Cretaceous Period) during which angiosperms rose to dominance over the gymnosperms – and all other members of the Plant Kingdom.