Convergent seed germination in South African fynbos and Californian chaparral

Abstract

California chaparral and South African fynbos are fire-prone communities dominated by species exhibiting remarkable similarities in germination response. In both regions there are a substantial number of species with germination stimulated chemically by charred wood and smoke. This type of germination behaviour has arisen independently in distantly related families and is interpreted as convergent evolution. Heat-shock is also an important germination trigger that is widespread, although in both regions it is most common in the same families. Phylogeney may play an important role in the presence of this postfire germination cue in both regions, but a much more rigorous analysis is required to show that this trait represents a single unique event in each lineage. In both regions, germination response is not randomly distributed across growth forms and there are marked regional similiarities in the type of germination behaviour associated with certain growth forms. Geophytes largely lack refractory seeds, which require fire-type cues for germination, but the presence of fire-stimulated flowering of bulbs and corms may time recruitment to subsequent postfire years. Annuals that cue germination to postfire conditions are predominantly triggered by chemicals from smoke and/or charred wood.