The impact of seed predation by mammals on post-fire seed accumulation in the endangered shrub Grevillea caleyi (Proteaceae)

Over several fruiting seasons, the fates of seeds placed in recently burnt habitats, and one habitat unburnt for more than 10 years, were used to examine the impact of fire on seed predation levels in the endangered species Grevillea caleyi from southeastern Australia. Native rodents. Rattus fuscipes, and macropods. Wallabia bicolor, were responsible for seed losses after seeds fell below parent plants. Virtually all seeds (99-100%) were lost to these mammals for the first two fruiting seasons after a wildfire. Such losses usually exceeded pre-fire loss estimates or estimates from a site unburnt for more than 10 years. There was no significant difference in seed losses to mammals in three recently burnt sites over four fruiting seasons. However, there was a slight trend for some seed escape (seed losses 91-97%) acid a slowing of the rate of seed loss in the fourth fruiting season after fire. Time since the last fire accounted for some 60% of the estimated variation in magnitude of seed losses to mammals. These results suggest that in the endangered, fire-sensitive G. caleyi, replenishment of the soil seed bank after fire is severely retarded by mammal seed predation. The implications are that after a fire, G. caleyi should be protected from the risk of a future fire well beyond three times the primary juvenile period in the species or local extinction will occur. (C) 2001 Elsevier Science Ltd. All rights reserved.