Flammability as a biological concept.

Studies examining plant flammability descriptors as fire-adaptive traits (e.g., Schwilk, 2003; Scarff & Westoby, 2006; Cowan & Ackerly, 2010; Saura-Mas et al., 2010; Pausas et al., 2012) are normally formulated within the framework of inclusive fitness theory. In such framework, flammabilityenhancing traits are considered to favour individuals if the elevated flammability confers fitness benefits. In post-fire seeder species (i.e., those with fire-stimulated germination from a persistent seed bank), higher flammability could increase the recruitment opportunities for the offspring of the individual with enhanced flammability by increasing the chance of opening spaces and by producing the necessary cues for triggering germination from the seedbank (‘kill thy neighbour’ hypothesis; Bond & Midgley, 1995). This might be specially relevant in non-resprouting (obligate) seeders with strong spatial population structure (e.g., with short-distance dispersal). Because there is some evidence of heritability for both seed dormancy (e.g., Baskin et al., 2000; Huang et al., 2010) and flammability-enhancing traits (e.g. Sampedro et al., 2010), we would expect a selection for higher flammability with repeated fires.