Conservation genetics and ecology of the endangered rainforest shrub, Triunia robusta, from the Sunshine Coast, Australia

Abstract

Triunia robusta, which until recently was thought to be extinct, is now classified nationally as endangered. It is an understorey species restricted to the subcoastal rainforests in a small region of the Sunshine Coast, Queensland. The project involved sampling the genetic variation and measuring the population size and size distribution of T. robusta and its geographically closest congener T. youngiana, which occurs further south and has a wider geographic distribution. A total of 877 T. robusta plants were recorded across the 11 populations, approximately half (56.8%) of these were juveniles less than 1 m tall, whereas in T. youngiana only about 36.4% of a population was composed of juveniles. Genetic diversity was similar but significantly higher for T. robusta than T. youngiana if the very small T. robusta populations (2 or 3 plants) were excluded from analysis (P < 0.05). The mean percentage of polymorphic loci among populations was high for both species. Triunia robusta is not, on average, more inbred than the more common T. youngiana. There was more differentiation between the T. robusta populations, which were in close proximity, than between the more geographically separated T. youngiana populations. Thus, there is evidence of more gene flow between populations of T. youngiana than between those of T. robusta. However, there was no geographic relationship between genetic similarity and geographic proximity in T. robusta