Population structure and breeding biology in relation to conservation in the dioecious Gardenia actinocarpa (Rubiaceae) - a rare shrub of North Queensland rainforest.

摘要

Spatial distribution, flowering and fruiting patterns of Gardenia actinocarpa (Rubiaceae), a rare and endemic dioecious shrub of lowland tropical rain forest of Cape Tribulation, North Queensland, Australia were documented in 4 subpopulations duringOctober 1993 to September 1996. Sex ratio was unity at 2 of the sites, and significantly biased in favour of male plants at the other 2 sites. At most sites, analysis of spatial distribution of individuals indicated aggregated dispersion patterns irrespective of quadrat size and plant size/reproductive status. There was no evidence of niche differentiation nor switching of the sexes. The species exhibited an extended flowering pattern of almost 6 months. However, male trees flowered earlier, longer andproduced more flowers than female trees. Intensity of flowering was significantly correlated with plant size in both sexes. Fruit set was very low in each of the 2 years of observation, but was significantly predicted by female habitat light environment, flower production and plant size. The lack of neighbourhood effects such as male tree density, male tree flower production around a focal female tree and distance from a female tree to the nearest male tree on fruit set is an indication that G. actinocarpa pollinators are capable of carrying pollen over long distances. The implications of these findings to conservation management are discussed.