Floral biology of dry rainforest in north Queensland and a comparison with adjacent savanna woodland

Abstract

In north Queensland, Australia, dry rainforest (deciduous and semi-evergreen vine thicket) occurs as patches within a matrix of savanna woodland. With floral morphology and pollen–ovule ratios as indicators of pollination syndrome and breeding system, the floral biology of dry rainforest was compared with that of adjacent savanna woodland and with rainforest elsewhere. Contingency tables and analysis of variance were used to examine and compare breeding system, flower diameter, floral display and putative pollination syndrome for 156 dry rainforest and 33 savanna woodland taxa. Most (91 of 97) dry rainforest species had pollen–ovule ratios indicating obligate outbreeding. Similar levels of dioecy (21%) and patterns of flowering phenology were observed to those reported for rainforests elsewhere. For dry rainforest canopy trees, flower diameter and morphology indicated pollination by small, generalist insects. Canopy trees tended to flower in the wet season and have low ovule numbers. Taxa assigned to the wind-pollination syndrome had the highest pollen–ovule ratios, suggesting less efficient pollen transfer. Sclerophyll savanna taxa (and some emergent dry rainforest trees) tended to flower in the dry season, have large flowers, high ovule numbers and a high level of floral display.