Population genetics of Ryparosa kurrangii (Achariaceae), a rare lowland rainforest tree

Ryparosa kurrangii B.L. Webber (Achariaceae) is a rare lowland rainforest tree found in dense, discrete populations between the Daintree River and Cape Tribulation in Far North Queensland, Australia. It is one of many Australian rainforest trees thought to rely on the Southern Cassowary (Casuarius casuarius johnsonii) for long-distance seed dispersal. A survey of chloroplast non-coding DNA found no genetic variation at any of four non-coding chloroplast loci. Seedlings of three populations separated by a mountain range were then examined for amplified fragment length polymorphisms. High levels of genetic diversity were found within each population. Only two percent of the variation in this study was explained by separation due to the mountain range. This finding of high genetic diversity but minimal distinction between populations accords with general expectations for outcrossing, large-fruited, animal-dispersed trees. Either continuing or historical long-distance gene flow (mediated by cassowaries) could explain these results.