Life history and morphological variation in intraspecific seeder and resprouter populations of two species from rock outcrop vegetation in north-east New South Wales

Abstract

The processes underlying differentiation of seeder and resprouter life histories were explored by studying changes in life history and morphological traits in intraspecific seeder and resprouter populations of the grass Entolasia stricta and shrub Keraudrenia hillii var. hillii from adjoining rock pavement and fringing woodland habitats. Population traits were sampled in the field and studied under controlled conditions in a randomised experimental design with two levels of population/habitat (seeder/rock outcrop and resprouter/woodland) and two levels of fertiliser (low and high). Life history traits reflecting rate of growth, relative allocation of resources to reproductive and vegetative growth and timing of events, as well as a selection of simple morphological traits were recorded. Generalised linear model analysis showed that population had a strong, significant effect on the majority of traits examined, particularly those relating to reproductive output. Many traits were also significantly responsive to nutrient, or induced plasticity, and significant interaction terms were very few. The two species exhibited parallel intraspecific changes in life history between habitats and traits recorded under experimental conditions were similar to those observed in the field. The populations from pavement shrubland produced a more compact shoot system, faster early shoot growth (E. stricta), more numerous flowers and more numerous and lighter seeds. In fringing woodland, both species produced a larger shoot system, slower early shoot growth and fewer and larger seeds. Significant intraspecific differences in population traits and correlation of population with habitat type indicated that the intraspecific seeder-resprouter populations of both species were ecotypes selected by habitat factors, most likely associated with the edaphic environment rather than fire regime variables.