The evolutionary significance of hybridization in Eucalyptus

Abstract

In a recent article, we presented a novel mechanism of plant migration by long distance interspecific hybridization followed by back selection to the phenotype of the pollen parent and suggested that hybridization may be of evolutionary significance as a means of gene dispersal where the adapuve response is limited by restricted seed dispersal (Potts and Reid, 1988). In our study area the localized Eucalyptus risdonii appeared to be invading the rangeofthe surrounding, more widespread species E, amygduiina by bath pollen and seed dispersal (Potts, 1986) and from estimates of the diatance of pollen- and seed-mediated dispersal of E. nsdonii we sugsestedthat interspecific hybridization may double the rate of Raw of E. risdonii genes into the range of E. amygdaiina (Potts and Reid, 1988). However, Schemskc and Morgan (1990) have questioned this conclusion on the basis of our failure to consider intraspecific pollen dispersal, potential bias in the estimation of interspecific gene Row (e.g., small sample sizes, life history effects, rarity of hybridization) and