Multiple paternity in Eucalyptus rameliana (Myrtaceae)

Abstract

Estimates of the level of multiple paternity/correlated outcrossing within and between fruits in a predominantly outbreeding population of the bird-pollinated mallee, Eucalyptus rameliana, were made using six allozyme loci. The correlation of outcrossed paternity (rp) was positive and significant within fruits (0.26) and the effective number of mates for a single fruit was estimated to be 3.85. This correlation was attributed to the low number of potential male parents and pollen-bearing flowers available at any one time in the population. Although consistent with suggestions that correlation of paternity may be a general feature of animal-pollinated plants, the level in E. rameliana was remarkably low considering its population size and phenology. There was no significant correlation of paternity between fruits, probably because flowers were pollinated at different times during the long season. Individual plants differed greatly in both male and female contributions to the next generation, with a small proportion of genotypes located in a small area contributing at least half of the gene pool of the seeds stored in the canopy. In contrast, the male contribution is probably from a wider area. The specialization of floral structure and phenology in E. rameliana for bird-pollination has probably contributed to correlation of paternity within fruits because there are fewer male parents available at any one time than in mass-flowering species. However, the behaviour of the bird pollinators also promotes pollen dispersal and multiplicity of paternity, factors which would be particularly significant when the female contribution to the gene pool is concentrated in a few plants.