THE INFLUENCE OF POLLINATORS ON FRUIT POSITIONING IN THE AUSTRALIAN SHRUB TELOPEA-SPECIOSISSIMA (PROTEACEAE)

The waratah, Telopea speciosissima (Proteaceae), produces more than 60 % of fruit in the top third of its inflorescences where the flowers ar e the last to complete anthesis. Three hypotheses were examined which may account for this positioning of fruit. First, the flowers at the b ottom of inflorescences have only a male function. Second, fruit abort ion occurs more commonly at the bottom of inflorescences. Third. polli nation is greater in the top third of an inflorescence. Hand-pollinati ons of flowers in the bottom third of inflorescences showed that these flowers had the same capacity to develop into fruits as the flowers i n the top third. Contrary to the prediction of the second hypothesis, fruit abortion was greatest in the top third of inflorescences where m ost fruits were initiated. suggesting that pollination levels were als o greatest there. Exclusion of pollinators from the top third of inflo rescences eliminated fruit-set in that region and resulted in a larger number of inflorescences failing to produce fruit. Plants were unable to compensate by maturing more fruits in the lower portions of inflor escences. Therefore the preponderance of fruits in the top third of wa ratah inflorescences is most likely caused by the behaviour of pollina tors, probably because of a greater number of Visits by pollinators to inflorescences at this stage of opening. Birds were the most abundant floral visitors and their numbers were closely related to the abundan ce of open inflorescences. These results are discussed in relation to the Various proximate and ultimate hypotheses which attempt to account for the low fruit-flower ratios in hermaphroditic plants.