Conservation genetics and ecology of Angiopteris chauliodonta Copel. (Marattiaceae), a critically endangered fern from Pitcairn Island, South Central Pacific Ocean

Angiopteris chauliodonta, endemic to remote Pitcairn Island, was until recently thought to occur in only two small populations. Survey work carried out on the island in 1997 increased the number of populations to six, but as the total number of plants found was 774 (of which only 147 were mature adults) the species should be regarded as critically endangered. The species occurred in native fern-rich Homalium taypau and Metrosideros collina forest that was in many areas heavily invaded by Syzygium jambos and Lantana camara. RAPD analysis identified related populations but there was no correlation between genetic and geographical distance. The highest levels of genetic diversity was partitioned within populations (H_S=0.154; D_ST=0.116), although the larger populations were not necessarily the most diverse. Threats are primarily due to forest clearance, invasive species and erosion. Conservation management for this species will be through reinforcement of existing populations to maximise their genetic diversity and translocation of new populations to suitable habitats.