Granite Outcrop Plants: Biogeography, Evolution and Conservation
This project focuses on granite outcrops in the southwest Western Australian and Greater Cape biodiversity hotspots, using them as a system to investigate biogeographical and evolutionary questions.
North Hill from Mt Arid in the Southwest Australian Floristic Region. Photo: © S.D. Hopper
About 15% of the earth's continents consists of granite, which may outcrop in the form of inselbergs - ranges, ridges and isolated hills - that stand abruptly from surrounding terrain, like islands in a sea. Most commonly, granite outcrops appear as dome-shaped hills with bare rock exposed over much of their surfaces. The water catchment so formed, combined with a diversity of microhabitats, make granite outcrops havens for biodiversity world-wide.
Granite outcrops are of special interest:
- geologically, being among the world's oldest rocks
- hydrologically, providing a source of water in dry landscapes
- biologically, as refuges rich in endemic plants and animals
- culturally, being vital for aboriginal, colonial and contemporary peoples alike.
Despite their intrinsic interest, world-wide occurrence, and special values in places like Western Australia, granite outcrop plants are poorly studied. Potentially, research might highlight ideas of general importance concerning the geology, landforms, biodiversity and human use of granite outcrops. Special research opportunities arise from the insularity and geographically compact nature of most outcrops. They offer model systems for exploring evolutionary and ecological processes, and for achieving conservation outcomes through stewardship by informed local communities. They can also provide important insights into potential responses to climate change. Shallow soils make these habitats good early-warning indicator habitats for drying climates, and wetter microhabitats provide refugia on granite outcrops, evidenced geohistorically by local endemism.
Outcrops often constitute a classic archipelago - real terrestrial islands surrounded by terrain and communities that are inhospitable to many species. As a consequence, there are opportunities to explore evolutionary, biogeographic and ecological questions relating to disjunct population systems. In addition, serious conservation problems such as weed invasion, grazing by feral herbivores, inappropriate fire regimes, dieback disease infection, excessive recreational use and mining are impacting granite outcrops.
This project aims to achieve a cross-disciplinary synthesis of current knowledge on granite outcrops, and to distil effective guidelines for conservation managers. Special focus is on Australian and South African outcrops, but global syntheses are being prepared in collaboration with researchers from around the world. A book entitled Life on the Rocks. The Art of Survival was co-authored by Philippa Nikulinsky and Professor Steve Hopper and published as a second edition in 2008 and a further title Plants of Granite Rock Outcrops is in preparation as a joint publication of Professor Hopper and Professor Dr Stefan Porembski of the University of Rostock.
Key publications 2006-2011
- Tuckett, R.E., Merritt, D.J., Hay, F.R., Hopper, S.D. and Dixon, K.W. (2010). Dormancy, germination and seed bank storage: a study in support of ex situ conservation of macrophytes of southwest Australian temporary pools. Freshwater Biology 55: 1118-1129.
- Tuckett, R.E., Merritt, D.J, Rudall, P.J., Hay, F., Hopper, S.D., Baskin, C., Baskin, J.M., Tratt, J. and Dixon, K.W. (2010). A new type of specialized morphophysiological dormancy and seed storage behaviour in Hydatellaceae, an early-divergent angiosperm family. Annals of Botany 105: 1053-1061.
- Tuckett, R.E., Merritt, D.J., Hay, F.R., Hopper, S.D. and Dixon, K.W. (2010). Comparative longevity and low-temperature storage of seeds of Hydatellaceae and temporary pool species of south-west Australia. Australian Journal of Botany 58: 327-334.
- Roux, J.P., Hopper, S.D. and Smith, R.J. (2009). Isoetes eludens (Isoetaceae), a new endemic species from the Kamiesberg, Northern Cape, South Africa. Kew Bulletin 64: 123-128.
- Byrne, M., and Hopper, S.D. (2008). Granite outcrops as ancient islands in old landscapes: evidence from the phylogeography and population genetics of Eucalyptus caesia (Myrtaceae) in Western Australia. Biological Journal of the Linnean Society 93: 177-188.
Project partners and collaborators
University of Rostock
South African National Botanical Institute