The evolution of growth rate, resource allocation and competitive ability in seeder and resprouter tree seedlings

Abstract

Many woody plant species in fire disturbed communities survive disturbance events by resprouting. The resprouting life history is predicted to be costly to plants as resources are diverted into storage for post-fire regrowth rather than allocated to current growth, and resprouting species typically grow more slowly than seeder species (species that do not resprout after disturbance events). Differences in allocation to current growth are also predicted to make resprouter species poorer competitors compared to seeder species. We tested the predictions that the evolution of a resprouter life history is associated with slow growth, increased allocation to storage, and low competitive ability in woody plant seedlings. We grew eight phylogenetically independent pairs of seeder and resprouter species in competition and no competition treatments in a field experiment near Sydney, Australia. The presence of competitors reduced plant growth rates across taxa and fire response life histories. However, relative to seeder species, resprouter species were not slower growing, they did not allocate more resources to storage, and they did not have lower competitive abilities. We propose that differences in resource allocation to storage are not responsible for differences in growth rate and competitive ability. Rather, growth rate and competitive ability in seedlings are associated with key aspects of plant life history such as life-span and body size at maturity. These traits that are sometimes, but not always, related to fire response life histories.