FLORAL BIOLOGY OF HORNSTEDTIA-SCOTTIANA (ZINGIBERACEAE) IN A LOWLAND RAIN-FOREST OF AUSTRALIA

Hornstedtia scottiana (Zingiberacee) is a large, rhizomatous, rain for est herb with vegetative aerial shoots and short, lateral inflorescenc es. The floral characteristics, scarlet corolla, no odor, and copious nectar are typical of ornithophily, but the near ground position of th e 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 paleocropical passerines. The floral biology and pollination of Hornstedtia scottian a 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 beg inning 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 manipulati ons determined that outcrossed flowers set significantly more fruit, w ith significantly heavier seeds, than self-pollinated flowers, suggest ing an inbreeding depression. Mean seed mass data from open-pollinated controls suggested that the fruits produced were from a combination o f self (65%) and outcrossed (35%) pollinations.