Within population variation in germination response to smoke cues: convergent recruitment strategies and different dormancy types
Aims: Maintaining variation in germination response provides a selective advantage, by spreading risk during recruitment. In fire-prone regions, physically dormant (PY) species vary their response to dormancy-breaking fire-related heat cues at the intra-population level. However little is known about physiologically dormant (PD) species, which respond to smoke cues. These contrasting dormancy types reflect different evolutionary developmental pathways and we considered whether intra-population variation in germination of Boronia floribunda (PD) occurs in response to smoke. Methods: Seeds were collected from individual plants. We assessed germination magnitude and rate of seeds from each individual in response to a single aerosol smoke treatment, and three concentrations of smoke water, using replicate seed lots in temperature-controlled incubators. Results: The magnitude and onset of germination differed significantly among individuals in response to the same smoke treatment. Seeds from different individuals varied in their sensitivity to smoke water concentration, with some responding to very low doses, and others obligated to high doses. Conclusions: Variation in germination response to smoke highlights a mechanism by which PD species spread risk, by allowing some seeds to emerge quickly, while others remain dormant in the soil seed bank. The similarity to heat-cued variation displayed by PY species suggests that this could represent a convergent functional response.