Floral Biology of Hornstedtia scottiana (Zingiberaceae) in a Lowland Rain Forest of Australia

Hornstedtia scottiana (Zingiberaceae) is a large, rhizomatous, rain forest herb with vegetative aerial shoots and short, lateral inflorescences. The floral characteristics, scarlet corolla, no odor, and copious nectar are typical of ornithophily, but the near ground position of the flowers seemed inappropriate for bird pollination. Also, the nectar of Hornstedtia scyphifera was reported to be largely sucrose, a sugar composition apparently atypical of plants pollinated by paleotropical passerines. The floral biology and pollination of Hornstedtia scottiana were studied in Queensland, Australia. Three species of honeyeaters (Melphagidae) were observed to be the only floral visitors capable of effecting pollination. Similar to Hornstedtia scyphifera, H. scottiana produced sucrose-rich nectar. Flowering was diurnal with anthesis beginning at dawn. Floral visits were most frequent during mid-mornings. By early afternoon, if flowers were not visitor-pollinated, elongation of the corolla tube effected self-pollination. Pollination manipulations determined that outcrossed flowers set significantly more fruit, with significantly heavier seeds, than self-pollinated flowers, suggesting an inbreeding depression. Mean seed mass data from open-pollinated controls suggested that the fruits produced were from a combination of self (65%) and outcrossed (35%) pollinations.