Secondary compounds enhance flammability in a Mediterranean plant.

Some plant secondary compounds, such as terpenes, are very flammable; however, their role in enhancing plant flammability is poorly understood and often neglected in reviews on plant chemical ecology. This is relevant as there is growing evidence that flammability-enhancing traits are adaptive in fire-prone ecosystems. We analyzed the content of monoterpenes and sesquiterpenes, performed flammability tests and genotyped microsatellite markers, all in the same individuals of Rosmarinus officinalis, to evaluate the link between the content of terpenes, flammability and the genetic similarity among individuals. The results suggest that terpenes enhance flammability in R. officinalis, and that variability in flammability among individuals is likely to have a genetic basis. Overall our results suggest that the capacity to produce and store terpenes can be considered a flammability-enhancing trait and could have an adaptive value in fire-prone ecosystems.