INTERSPECIFIC POLLEN PISTIL INTERACTION IN EUCALYPTUS LHER (MYRTACEAE) - THE EFFECT OF TAXONOMIC DISTANCE

The pollen-pistil interaction was investigated in three intraspecific, 57 interspecific and six intergeneric crosses using three species of Eucalyptus (Myrtaceae) subgenus Symphyomyrtus, section Bisectaria as female parents Interspecific prefertilization isolation occurs in the pistil and manifests as a number of pollen-tube abnormalities in the style and ovary associated with a lowered probability of ovule penetration The major selection points in the pistil are the upper style and the ovary The seventy of abnormalities and the probability of pollen-tube arrest in the pistil was proportional to the taxonomic distance between parent species Ovule penetrations were seen mainly in crosses within the section Bisectaria or between the sections Bisectaria and AdnatariaPollen storage, style length and mean maximum temperature during the flowering period of the male parent had no significant effect on pollen-tube growth in the crosses used Mechanisms of reproductive isolation are discussed in relation to evolutionary relationships and the implications for taxonomic groupings. © 1991 Annals of Botany Company.