Joint senior authorship in alphabetical order.
Genetic structure of seedling cohorts following repeated wildfires in the fire-sensitive shrub Persoonia mollis ssp. nectens
Article first published online: 26 MAY 2009
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Journal of Ecology
Volume 97, Issue 4, pages 752–760, July 2009
How to Cite
Ayre, D. J., Ottewell, K. M., Krauss, S. L. and Whelan, R. J. (2009), Genetic structure of seedling cohorts following repeated wildfires in the fire-sensitive shrub Persoonia mollis ssp. nectens. Journal of Ecology, 97: 752–760. doi: 10.1111/j.1365-2745.2009.01516.x
- Issue published online: 16 JUN 2009
- Article first published online: 26 MAY 2009
- Received 16 February 2009; accepted 14 April 2009Handling Editor: John Pannett
- fire ecology;
- genetic diversity;
- pollen dispersal;
- seed banks;
- seed dispersal
- 1Increased fire frequency is seen as a key threat to plant populations in Mediterranean-type ecosystems across the globe. Short inter-fire periods may exhaust soil-stored and fire-stimulated seed banks of fire-sensitive species, reducing actual and effective population sizes and eroding genetic diversity.
- 2Here we used microsatellite genotyping to investigate the genetic impacts of repeated wildfires and, in particular, the contribution of above-ground genetic processes (seed and pollen dispersal) to the genetic structuring and composition of post-fire recruits in an isolated population of the fire-sensitive shrub Persoonia mollis ssp. nectens.
- 3We tested the hypothesis that limited pollen and seed dispersal, in combination with the potentially patchy effects of fire at a fine scale within populations, would generate a highly structured population, a decline in genetic diversity after each fire and genetic heterogeneity between successive cohorts.
- 4Wildfires killed all 25 adult plants in 1997 and, in 2001, killed all of the 476 seedlings remaining from the 1997 seedling cohort. Although there was no possibility of replenishment of the seed bank in the interval between fires, a second cohort of 381 seedlings emerged after the 2001 fire.
- 5We found no evidence that successive fires produced either a decline in genetic diversity, as measured by allelic richness or expected heterozygosity, or the genetic differentiation of adult and successive seedling cohorts (Pairwise FST = −0.0125 to 0.0009). The seedling cohorts displayed less genetic structuring than anticipated. Spatial genetic structure was low, ranging from Sp = 0.02 in the 1997 seedlings to Sp = 0.06 in the 2001 seedlings, and using parentage analysis, we found that seedlings clustered under dead adults rarely reflected simple seed shadows.
- 6Synthesis. Overall, we found that a numerically large seed bank with a bet-hedging strategy of staged seed germination, in combination with genetic mixing achieved by both pollen and seed dispersal, provides a powerful buffer against the negative impacts of frequent fire in P. mollis ssp. nectens.