Mast Flowering and Semelparity in Bamboos: The Bamboo Fire Cycle Hypothesis

Mast flowering is the phenomenon of massive flowering and fruiting at intermittent intervals that is synchronized within a species across large areas. Most masting species are iteroparous, flowering and fruiting multiple times during their life span (Silvertown 1980). Bamboos are an exception as mast flowering is largely restricted to semelparous species that flower once and die (Janzen 1976). Additionally, whereas most mast-flowering species produce seed crops on a cycle of 3–7 yr (Silvertown 1980), bamboos have intermast intervals that are typically an order of magnitude longer. The earliest explanation for mast flowering in bamboo was that of external controls on physiological processes by available resources such as rainfall (Brandis 1899), the resource-matching hypothesis. Today, this bottom-up hypothesis largely has been replaced by top-down explanations involving pollinators and predators (Kelly 1994). It is widely accepted that the selective force driving the evolution of masting in bamboos is “predator satiation” (Janzen 1976; Gadgil and Prasad 1984; Kelly 1994). This hypothesis proposes that irregular fruiting cycles are sufficient disequilibrium to inhibit seed predators from main-