Pollination ecology of Christmas Bells (Blandfordia nobilis): Patterns of standing crop of nectar

Abstract Standing crop of nectar (both volume and sugar concentrations) was measured from flowers in a population of Blandfordia nobilis. Nectar in this honeyeater‐pollinated species was extremely viscous during one flowering season and averaged approximately 95% sugar, while it averaged only 25% sugar two seasons later. Nectar volume was significantly and negatively correlated with sugar concentration on nine often sampling dates. There was no significant relationship between either nectar volume or sugar concentration and a number of measures of plant size (inflorescence height, numbers of open flowers, buds, spent flowers and total flowers). Similarly, no consistent relationship was found between measures of flower size and reward level. There were significant positive correlations between the reward (both volume and sugar concentration) offered by blossoms on the same plant. The nectar volume of flowers from nearest neighbouring inflorescences were significantly and positively correlated with one another on three of six occasions while the sugar concentrations of those blossoms were significantly correlated on just two of six sampling dates. There was no significant difference in reward (both volume and sugar concentration) between open flowers and those bagged to exclude pollinators. There was significant heterogeneity in the nectar volumes offered by plants to pollinators during a single flowering season.