Poster Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Genetic consequences of wildfire in an insular stand of the bird-pollinated, granite-outcrop endemic tree Eucalyptus caesia (659)

Nicole Bezemer 1 2
  1. Centre of Excellence in Natural Resource Management, University of Western Australia, Albany, Western Australia, Australia
  2. Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, Perth, Western Australia, Australia

In south-west Australia, granite outcrops support hyper-diverse plant communities and provide a refuge for fire-sensitive biota in an otherwise seasonally dry and fire-prone landscape. However, some granite plants require disturbances such as fire to trigger recruitment. Wildfires occur infrequently on granite outcrops, and the conservation status of many granite endemics makes experimental burns inappropriate. As such, opportunities to study the impact of fire on population genetics seldom arise. Following a wildfire in a small, isolated stand of the lignotuberous Eucalyptus caesia at Boyagin Reserve, I surveyed genetic diversity, recruitment and survival. The entire adult stand (n = 188) plus all seedlings located (n = 115) were mapped using a differential GPS and genotyped with 15 microsatellite loci. Despite temporary reduction of adults to 60 plants, there were no significant differences in adult heterozygosity pre- and post-fire. Conversely, there were marked differences in genetic variation between adults and seedlings, with reduced heterozygosity and increased fixation in the seedlings. Preliminary analyses do not support expectations of post-germination selection against homozygous progeny. Based on height measurements and survivorship, seedlings resulting from self-pollination could not be distinguished from outcrossed seedlings. Parentage analysis using CERVUS revealed mostly limited seed dispersal. By comparison, pollen movement was more extensive, yet restricted within the stand. Genetic mixing through wide pollen dispersal and occasional short-distance seed dispersal may buffer genetic decline in the study population. Alternatively, purging of deleterious alleles may preclude inbreeding depression. However, rare recruitment and high seedling mortality may diminish the genetic benefits of outcrossing or purging.