Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 9, Issue 1 (2005)
Refine
Year of publication
- 2005 (3)
Document Type
- Article (3)
Language
- English (3)
Has Fulltext
- yes (3)
Is part of the Bibliography
- no (3)
Sclerolaena napiformis is found on fertile plains in northern Victoria and southern New South Wales and is endangered Australia-wide. Introductory work on its germination shows that seeds cannot germinate until the woody fruit has broken down. The seeds tolerate a wide range of temperatures for germination, suggesting that germination occurs regardless of season if sufficient rain falls. Seed ageing effects reduce seed viability, but some seed is still viable after two years storage. Flower buds first appear 21 weeks from germination and some fruits have matured by week 29. In the field, plants die back to their taproots in late autumn and resprout in spring. Ninety percent of tagged plants were still alive two years later. The physiological seed dormancy imposed by an intact fruit wall provides a mechanism for the development of persistent soil seed banks. Work on the ecological significance of such banks is needed. The literature on interactions between Sclerolaena fruit and seed biology and ants is briefly reviewed.
Ecological data in tabular form are provided on 668 plant species of the families Lemnaceae to Zosteraceae, 505 native and 163 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, Canada Bay, Canterbury, Cessnock, Crookwell, 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: Lemnaceae, Liliaceae, Lomandraceae, Luzuriagaceae, Najadaceae, Orchidaceae, Philydraceae, Phormiaceae, Poaceae, Pontederiaceae, Posidoniaceae, Potamogetonaceae, Restionaceae, Ripogonaceae, Smilacaceae, Sparganiaceae, Thismiaceae, Typhaceae, Uvulariaceae, Xanthorrhoeaceae, Xyridaceae, Zingiberaceae, Zosteraceae.
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.
The Orchidaceae are one of the largest and most diverse families of flowering plants. Orchids grow as terrestrial, lithophytic, epiphytic or climbing herbs but most orchids native to the Sydney Region can be placed in one of two categories. The first consists of terrestrial, deciduous plants that live in fire-prone environments, die back seasonally to dormant underground root tubers, possess exclusively subterranean roots, which die off as the plants become dormant, and belong to the subfamily Orchidoideae. The second consists of epiphytic or lithophytic, evergreen plants that live in fire-free environments, either lack specialised storage structures or possess succulent stems or leaves that are unprotected from fire, possess aerial roots that grow over the surface of, or free of, the substrate, and which do not die off seasonally, and belong to the subfamily Epidendroideae.
Orchid seeds are numerous and tiny, lacking cotyledons and endosperm and containing minimal nutrient reserves. Although the seeds of some species can commence germination on their own, all rely on infection by mycorrhizal fungi, which may be species-specific, to grow beyond the earliest stages of development. Many epidendroid orchids are viable from an early stage without their mycorrhizal fungi but most orchidoid orchids rely, at least to some extent, on their mycorrhizal fungi throughout their lives. Some are completely parasitic on their fungi and have lost the ability to photosynthesize. Some orchids parasitize highly pathogenic mycorrhizal fungi and are thus indirectly parasitic on other plants.
Most orchids have specialised relationships with pollinating animals, with many species each pollinated by only one species of insect. Deceptive pollination systems, in which the plants provide no tangible reward to their pollinators, are common in the Orchidaceae. The most common form of deceit is food mimicry, while at least a few taxa mimic insect brood sites. At least six lineages of Australian orchids have independently evolved sexual deception. In this syndrome, a flower mimics the female of the pollinating insect species. Male insects are attracted to the flower and attempt to mate with it, and pollinate it in the process.
Little is known of most aspects of the population ecology of orchids native to the Sydney Region, especially their responses to fire. Such knowledge would be very useful in informing decisions in wildlife management.