Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 6, Issue 4 (2000)
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In Australia, the Proteaceae are a diverse group of plants. They inhabit a wide range of environments, many of which are low in plant resources. They support a wide range of animals and other organisms, and show distinctive patterns of distribution in relation to soils, climate and geological history. These patterns of distribution, relationships with nutrients and other resources, interactions with animals and other organisms and dynamics of populations in Proteaceae are addressed in this review, particularly for the Sydney region.
The Sydney region, with its wide range of environments, offers great opportunities for testing general questions in the ecology of the Proteaceae. For instance, its climate is not mediterranean, unlike the Cape region of South Africa, south-western and southern Australia, where much of the research on plants of Proteaceae growing in infertile habitats has been done.
The diversity and abundance of Proteaceae vary in the Sydney region inversely with fertility of habitats. In the region’s rainforest there are few Proteaceae and their populations are sparse, whereas in heaths in the region, Proteaceae are often diverse and may dominate the canopy. Research in the region has led to an understanding of their various responses to fire, dynamics of their populations in fire-prone landscapes, interactions with animals in pollination and dispersal, and of their breeding systems. This review examines results of this research and shows that ecological research has been uneven in Australian Proteaceae, with little work done on rainforest and alpine Proteaceae.
The review reveals an enormous range of interesting features of the Proteaceae of the Sydney region. It also identifies a large number of questions about ecological and evolutionary processes that are at the cutting edge of our current knowledge. The diversity of taxa of Proteaceae, the range of habitat, soil and climatic zones they occupy, the variety of life-histories (even among populations within species), fire responses, floral morphologies, pollinator types and breeding systems combine to make this family in the region a rich ‘test bed’ for many of these questions.
The geographic distribution, community distribution, taxonomy, and growth form of the flora listed as threatened under Schedules 1 and 2 of the New South Wales Threatened Species Conservation Act 1995 were examined. The North Coast and Central Coast Botanical Divisions have the highest number of threatened plant species, with both these divisions having significantly more threatened plant species than expected. A large disparity between the east and the west of the state was found, with the eastern divisions generally containing larger numbers and higher proportions of threatened plant species than the western divisions. Rainforest, sclerophyll forest and sclerophyll woodland communities were all found to contain large numbers of threatened plant species, with woodland containing more threatened plant species than expected. Some large families and genera contain significantly more threatened plant species than expected (e.g. Myrtaceae, Proteaceae, Grevillea and Zieria), while others contain significantly fewer (e.g. Asteraceae, Poaceae and Cyperaceae). The analysis of habit showed that fewer than expected threatened plant species were herbs. Possible explanations for the apparent distribution of threatened flora are discussed.
Vegetation in the Holsworthy Military Area located 35 km south-west of Sydney (33°59'S 150°57'E) in the Campbelltown and Liverpool local government areas was surveyed and mapped. The data were analysed using multivariate techniques to identify significantly different floristic groups that identified distinct communities. Eight vegetation communities were identified, four on infertile sandstones and four on more fertile shales and alluviums. On more fertile soils, Melaleuca Thickets, Plateau Forest on Shale, Shale/Sandstone Transition Forests and Riparian Scrub were distinguished. On infertile soils, Gully Forest, Sandstone Woodland, Woodland/Heath Complex and Sedgelands were distinguished. We identified sets of species that characterise each community either because they are unique or because they contribute significantly to the separation of the vegetation community from other similar communities.
The Holsworthy Military Area contains relatively undisturbed vegetation with low weed invasion. It is a good representation of continuous vegetation that occurs on the transition between the Woronora Plateau and the Cumberland Plain. The Plateau Forest on Shale is considered to be Cumberland Plains Woodland and together with the Shale/Sandstone Transition Forest, are endangered ecological communities under the NSW Threatened Species Conservation Act 1995. The Melaleuca Thickets may also be considered part of the endangered ecological community, Sydney Coastal River-flat Forest. As such the area has high conservation significance.
Experimental hand pollinations were used to examine factors that influence fruit production in Persoonia juniperina (Proteaceae). Assessment of the breeding system indicated no clear pre-zygotic barriers to self-fertilisation. Rates of pollen tube growth and numbers of pollen tubes were similar after selfing and outcrossing. Plants also clearly had the capacity to produce fruit from selfing, although there was some evidence of inhibition in the development of selfed zygotes. More fruit were initiated after cross-pollination, and rates of abortion were greater after selfing, resulting in lower final fruit set. Inhibition of selfed fruit is most probably exhibited post-zygotically since the percentage of ovules penetrated did not differ between treatments. However, at this stage it is difficult to differentiate between late-acting self-incompatibility and genetic load. Supplementary hand pollinations did not increase numbers of pollen tubes or percentage fruit set above natural levels, indicating that plants in the population were not pollen limited. These results contrast with those found in most other species of Proteaceae.
Ecological data in tabular form are provided on 246 plant species of the families Proteaceae to Rubiaceae, 216 native and 30 exotics, occurring in the Sydney region, defined by the Central Coast and Central Tablelands botanical subdivisions of New South Wales (approximately bounded by Lake Macquarie, Orange, Crookwell and Nowra). Relevant Local Government Areas are Auburn, Ashfield, Bankstown, Bathurst, Baulkham Hills, Blacktown, Blayney, Blue Mountains, Botany, Burwood, Cabonne, Camden, Campbelltown, Canterbury, Cessnock, Concord, Crookwell, Drummoyne, Evans, Fairfield, Greater Lithgow, Gosford, Hawkesbury, Holroyd, Hornsby, Hunters Hill, Hurstville, Kiama, Kogarah, Ku-Ring-Gai, Lake Macquarie, Lane Cove, Leichhardt, Liverpool, Manly, Marrickville, Mosman, Mulwaree, North Sydney, Oberon, Orange, Parramatta, Penrith, Pittwater, Randwick, Rockdale, Ryde, Rylstone, Shellharbour, Shoalhaven, Singleton, South Sydney, Strathfield, Sutherland, Sydney City, Warringah, Waverley, Willoughby, Wingecarribee, Wollondilly, Wollongong, Woollahra and Wyong. The study area falls within the Sydney Basin IBRA Bioregion.
Families are: Proteaceae, Ranunculaceae, Resedaceae, Rhamnaceae, Rosaceae, Rubiaceae.
Data are derived from herbarium collections, literature and field observations. It is hoped that the many, often alarming gaps in the information available will stimulate much-needed research into the ecology of more of the species. Information is provided so far as available to us for each plant species in the following categories:
Life History: Growth form, vegetative spread, longevity, primary juvenile period (time from germination to fruiting), reproduction, flowering and fruiting times, fruit/seed type, dispersal, establishment and growth, fire response, interaction with other organisms.
Distribution: Status/origin (native/naturalised), botanical subregions, distribution in Sydney area, selected locations.
Habitat: Habitat, altitude, annual rainfall, typical local abundance, vegetation, substrate, exposure.
Conservation: Conservation status.