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Banksia ericifolia is killed by fire and so depends upon seeds for persistence. In contrast, B. oblongifolia can persist after fire by resprouting from protected buds, as well as by recruiting seedlings. These serotinous species coexist in the fire-prone scrublands of the Sydney Basin. Here we report experiments that compared seed release from cones retained in the canopy, seed germination, and seedling establishment in these two species. B. oblongifolia seeds were released more quickly than B. ericifolia seeds after a fire, and B. oblongifolia follicles opened and shed seeds after exposure to lower temperatures than those of B. ericifolia. B. oblongifolia seeds germinated more quickly than those of B. ericifolia. The relative growth rates and leaf mass ratios (mean ratio of leaf dry mass to plant dry mass over sequential harvests) of the two species did not differ. Root : shoot ratios were significantly large and biomass allocation to roots was faster in B. oblongifolia seedlings. B. ericifolia seedlings survived low and intermediate levels of droughting better than B. oblongifolia under greenhouse conditions. In a field experiment in which water was not limiting, large B. oblongifolia seedlings had the highest survival rate. These results suggest that selection has acted on B. ericifolia to minimize the chance of zero seedling survival by distributing the risks over more than one germination episode. There was no consistent evidence to support the hypothesis that selection on this species has increased its probability of seedling survival during any one germination opportunity relative to its congener.

Models of the evolution of seed dormancy reveal that dormancy is favoured either when opportunities for establishment vary over time and when there is wide variation in the probability of success, or when the probability of success is limited by frequency dependence. Empirical evidence supporting the temporal heterogeneity hypothesis exists, but there is scant evidence for dormancy being favoured by frequency dependent competition among seedlings. We test the hypothesis that the intensity of between-sib competition should favour a positive relationship between maternal fecundity and seed dormancy. This hypothesis is supported for the rare, vernal pool annual,Pogogyne abramsii: the proportion of dormant offspring was significantly higher among high fecundity mothers than among other mothers. Dormancy inP. abramsii is controlled by the seed coat, a maternal tissue, so delaying germination favours the inclusive fitness of mothers by reducing the potential for competition among siblings. Seed weight and time to first germination varied significantly amongP. abramsii plants and mean seed weight increased linearly with plant biomass. Seed weight and seed number are independently regulated by plant size. Overall, seed weight varied 10-fold and variability in seed weight within mothers was not explained by plant biomass, seed yield or mean seed weight. GerminableP. abramsii seeds were significantly heavier than dormant seeds, and germinable seeds heavier than 0.20 mg germinated more rapidly than those smaller than 0.20 mg.

No abstract

The resprouting response of different sized Banksia oblongifolia lignotubers (genets) was followed in two field experiments. In the first, the density and speed of resprouting. and the growth in length of the leading shoot from each lignotuber in response to fire and to the time elapsed since the last fire was monitored for 18 months after fire and clipping treatments. In the second, sizes of bud banks were estimated by repeatedly clipping new shoots from individual lignotubers.Density of resprouting (shoots dm^-lignotuber) decreased with increasinglignotuber size, and the length of the leading shoot increased. The direct effect of fire was to reduce shoot density by about 75%. The speed of resprouting (time taken by a cohort of shoots to reach 50% of their peak density) was similar after fire and clipping, but leading shoots grew significantly longer after fire. The elapsed time since lignotubers were last burnt did not influence their density of resprouting, but it did influence the speed of resprouting. Shoots from clipped lignotubers that had burnt 3 years earlier took about 90 days to each 50% of their peak density while shoots on lignotubers las! burnt 5 and 17 years earlier took about 40 days. Death of shoots was unrelated to crowding in any stand. More lignolubersfrom the oldest unbitrnt stand were grazed by herbivores.The number of buds converted into shoots after successive clippings was surprisingly small: for most lignotubers this reserve was less than three times the size of their standing crop of •Present address: