Plant diversity on the edge: floristics, phytogeography, fire responses, and plant conservation of Two Peoples Bay Nature Reserve in the context of OCBIL theory

Abstract

Context There have been few long-term studies of the flora, phenology, and ecology of specific reserves in the species-rich flora of the Southwest Australian Floristic Region. Aims This project, extending over five decades, aimed to develop an authoritative flora list and acquire data on phenology, threatened species, endemism, old and young landscapes, phytogeography, old lineages, and fire responses at Two Peoples Bay Nature Reserve. Methods The study used botanical collection on repeat surveys, herbarium studies, granite outcrop surveys and comparative phytogeographic analyses from maps on the Western Australian Herbarium’s Florabase. Key results Floristic survey recovered 853 taxa, 26% of those known in the Albany local government area. Possibly as many as 950–1000 taxa will be found in the future. The herbarium collections are the second largest of any conservation reserve in the Albany area. Flowering was most evident in spring and least in autumn. Three declared rare species and 20 conservation priority species were identified, as were short-range endemics, old clades, and natural hybrids. Conclusions The flora is dominated by species predominantly from wetter forest regions. Consequently, Two Peoples Bay Nature Reserve is correctly placed within the Bibbulmun Botanical Province. Several hypotheses of OCBIL theory (which addresses old, climatically-buffered, infertile landscapes) were supported, with increased local endemism, ancient clades, and reduced rates of natural hybridisation identified for the granite inselberg OCBIL Maardjitup Gurlin/Mt Gardner. Implications Long term studies are invaluable for plant inventory. Continuing the minimal use of prescribed burning is advocated from plant data, in support of approaches to help conserve threatened animals.