Biodiversity series, Paper no. 2
Department of the Environment, Sport and Territories, 1994
3. Biodiversity on land
Arid and semi-arid ecosystems cover some two-thirds of Australia and much of the vegetation experiences severe water stress, which in turn limits plant biomass. Nevertheless, there is considerable ecosystem diversity, particularly at the microhabitat level. In the northern part of Australia, ecosystems are adapted to distinct wet and dry seasons. Because the eastern seaboard extends over a large range of latitudes, its vegetation ranges from tropical in the north to cool temperate in the south. Inland, there are further marked changes, for example the alpine ecosystems of southeast Australia. At a more local level, a complex range of habitats has evolved, providing for a range of biotic communities within each vegetation type.
Australia has a large and varied flora. In common with other southern hemisphere continents, the dominant flowering trees are evergreen, and conifers are less evident in cooler plant associations than in the northern hemisphere 9. Many floral elements are significant for their richness, endemism, ancient origins or distinctive adaptations. Examples of these follow.
Land flora – summary
A close examination of our native plants reveals great species richness and diversity, much of which is unique to Australia (endemic). Although two-thirds of the continent is dry, a large span of latitude provides a variety of climatic zones from the tropical north to the cool temperate south. This has allowed a rich variety of plant habitats to develop and with them the diverse flora that we enjoy.
Australia has an estimated 21-23 000 native species of vascular plants, some 85 per cent of which are unique to Australia. The more primitive seed-bearing plants (gymnosperms) are represented by a number of cycads (palm-like cone bearing trees) and conifers some of which are known from the fossil record. There are 14 endemic families of flowering plants (angiosperms) – the most for any country in the world.
Acacias (Mimosaceae; 950 species) and eucalypts (Myrtaceae; 800 species) dominate the landscape and are adapted to almost every habitat. Australia has the greatest diversity of the family Proteaceae in the world with 42 genera (860 species) from a world total of 72. Thirty-five genera are endemic to Australia (including banksias, grevilleas, hakeas, macadamias and waratahs).
Australia also has a large number of orchids with 1500 known orchid species mostly in the southeast and southwest. Lichens, which are associations of algae and fungi, are also very richly represented in Australia with about 2275 species.
Australian plants have undergone some remarkable adaptations. Sclerophylly is an adaptation to arid conditions in which the leaves are rigid and have a thick waxy cuticle. It is found in many plant groups such as some acacias, eucalypts and banksias. Many Australian plants are adapted to fire and some require fire for regeneration. Adaptations to fire include shedding large quantities of seed, a thick insulating bark, dormant buds, and woody rootstocks.
The origins of some of Australia's plants can be traced to before 160 million years ago when all the continents were joined. Fossils of the kauri pine and a cycad species have been found in 175 million-year-old fossil fish beds in New South Wales. Whereas the cycad is endemic to Australia, kauri pines also occur in Southeast Asia and the western Pacific. The origin of other species can be traced to a time when the southern landmass of Gondwana had split from Pangaea, for example the family Proteaceae, southern beeches and acacias. The rainforests of Australia, especially northern Queensland, harbour some of the world's most important links in plant evolution.
3.1.1 Australia's plants - a rich and highly endemic flora
Australia is home to several endemic genera of gymnosperms. Some, including Athrotaxis (for example the King Billy pine, A. selaginoides), Actinostrobos, Microcachrys, Lagarostrobos (L. franklinii is the huon pine), Microstrobos and Diselma, are associated with formerly widespread rainforests. The primitive cycad genera Lepidozamia, Macrozamia and Bowenia are also endemic (Clifford and Constantine 1980). Many of these primitive plants, including the huon pine and the genus Athrotaxis, are known from the fossil record in Australia. Other more widespread genera found as fossils include kauri pines (Agathis species), plum pines (Podocarpus species), and celery-top pines, Phyllocladus 171.
Australia has 14 families of endemic flowering plants (Table 1), a greater number than is found in any other country 11 190, and of an estimated 18 000 to 20 000 native Australian vascular plant species 92, approximately 85 per cent are endemic 50. Other common families such as Mimosaceae (acacias), Myrtaceae (eucalypts and allied genera) and Proteaceae (banksias, grevilleas etc.) have mainly endemic genera and species.
Mimosaceae and Myrtaceae
The acacias and eucalypts are the dominant flora of the Australian landscape. A high proportion of the species in these groups are endemic and they have diversified into almost every habitat on the continent. This is a manifestation of the much greater genetic diversity contained within these genera than in other Australian groups. The genus Acacia (family Mimosaceae) has about 950 known Australian species, comprising some 1070 taxa 207, and is the largest genus of plants in Australia. Most acacias found in Australia are endemic 9 63 and they span a greater variety of habitats than any other Australian genus. They are found in temperate and tropical rainforest, eucalypt forests, coastal heaths and arid habitats, and several species are dominant on coastal sand dunes. Acacias are the dominant canopy species in the woody flora of arid and semi-arid areas. There are fewer species in colder areas and only one is found in the mainland alpine region – Acacia alpina 11.
The genus Eucalyptus and allied genera (family Myrtaceae) include more than 800 species and 900 taxa 199, of which all but 13 species are endemic to Australia 199. These include: 12 species of the endemic Angophora; more than 100 species of bloodwoods, or Corymbia (which have been recently renamed from Eucalyptus); and at least 700 species of the genus Eucalyptus 199. The eucalypts include gums, stringybarks, peppermints, boxes, mallees, ironbarks and ashes and range in form from giant forest trees to mallee shrubs. The mountain ash, E. regnans, at more than 100 metres, equals the giant redwoods of California (Sequoia and Sequoiadendron) as the tallest trees in the world 3, while some species of mallee growing in low heaths and shrublands are only half a metre tall 75. Eucalypts are mainly open-forest and woodland species 9, but they nevertheless occupy a range of habitats, especially in regions that are subject to frequent water stress during droughts, or low soil moisture levels. A few species are found on rainforest margins, some occur at the alpine treeline, and many arid places have at least one eucalypt species within sight 121. Eucalypt diversity is most apparent in two main locations – eastern New South Wales and on the poor soils of the subhumid southwest of the continent 199.
Other genera of the Myrtaceae also have a high proportion of endemic species, with some 47 endemic or near endemic to Australia. Endemic genera include Callistemon (bottlebrushes), Calothamnus, Darwinia and Verticordia. Near endemic genera include Baeckea, Kunzea, Leptospermum, and Melaleuca 11 190.
Gondwana was the centre of origin of the family Proteaceae and Australia is the region of this family's greatest diversity 76 40. The Proteaceae includes such well known genera as Banksia, Dryandra, Grevillea, Hakea, Macadamia, and Telopea (waratahs), as well as several more obscure monotypic genera. Of the world's 73 genera of Proteaceae, 42 are found in Australia, comprising a total of some 860 species 182, and some 958 taxa (Australian Plant Name Index April 1994). Most of the species and 35 of the genera found in Australia are endemic 76 182. Australia is the only region in the world in which all five subfamilies of the Proteaceae are found, two of which, Sphalmioideae and Carnarvonioideae, consist of very primitive examples of the family and are restricted to Australia 76.
A number of genera (including those of the two subfamilies mentioned) have few species and are restricted to rainforests. There is evidence that the early proteaceous species were rainforest plants, and that the now more common sclerophyllic genera evolved from them. Most genera have developed proteoid roots, which are very efficient at absorbing water and nutrients, and are often found on plants growing in infertile soils, deficient in nitrogen and phosphorus.
ustralia's orchid flora is globally outstanding with the second largest ground orchid flora in the world, exceeded only by South Africa. While 799 taxa are presently described from Australia (APNI May 1994), it is estimated that a total of about 1500 Australian orchid species is known, of which about two-thirds are terrestrial 200. Southeastern and southwestern Australia harbour, by far, the largest number of species. The extraordinary diversity of the Australian orchid flora can be demonstrated by comparing that of Victoria, which has about 260 species of orchids (of which some 254 are terrestrial) 192, with that of the North American continent (a total of about 164 species) and that of Europe (116 species) 144 159.
Other examples of plant families with significant proportions of endemic genera in Australia include Epacridaceae (28 of the world's 30 genera are found in Australia and 21 of these are endemic), Goodeniaceae (including Goodenia and Lechenaultia), Pittosporaceae (including Sollya and the native frangipani, Hymenosporum flavum), the sedge-like Restionaceae, Sterculiaceae (kurrajongs and relatives), Chenopodiaceae (saltbushes and relatives) 11, and the lily families of the orders Liliales and Asparagales 190.
Lichens are associations of at least one species of alga or cyanobacterium with one species of fungus. Australia has a rich lichen assemblage of about 2275 species from a global total of 20 000 currently recognised species 138 51. The Australian species are organised into three divisions of which the major one, Ascomycotina, includes 18 orders and about 100 families 138. Lichens occur on many different substrates in almost every natural environment, and in some arid and semi-arid areas cover the soil surface 137 and may be important in soil stability.
The richness of Australia's lichen flora is further indicated by the 310 genera recognised in Australia compared with 290 from Europe, 291 from North America and 210 from New Zealand. Although recent taxonomic work has rendered direct comparisons difficult, the Australian flora is less well known than the floras of these other regions and additional species may well be revealed with further research 137.
3.1.2 Ancient and relict components of Pangaean and Gondwanan origin
The origin of a number of higher plants can be traced back to Pangaean times. For example, the fossil kauri pine Agathis jurassica is known from the Talbragar Fish Beds in New South Wales, as are fossils of the cycad, Lepidozamia hopei. These beds have been dated as 175 million years old 171. The genus Lepidozamia is endemic to Australia and L. hopei is still found in north Queensland. Agathis is more widespread, and occurs in Australia, Southeast Asia and the western Pacific, with three extant species found in rainforests or rainforest margins of southern Queensland 24.
A later Gondwanan origin is indicated for plants found mainly in the southern hemisphere. Examples of angiosperm families that are confined to, or have their maximum development in the southern hemisphere include: the Byblidaceae, Epacridaceae, Goodeniaceae, Pittosporaceae, Proteaceae, Restionaceae, Stylidiaceae (trigger plants) and Winteraceae (including pepper trees). Within these families, the genera that are shared between continents reflect the early stage at which India separated from Gondwana and the stronger links between Australia and South America 11. As stated earlier, this Gondwanan distribution pattern is shared by many other genera such as the southern beeches (Nothofagus) and Acacia. Nothofagus (which is related to the northern hemisphere beeches or Fagus) is thought to have originated in Gondwana at least 80 million years ago, and is found in South America, Australia, New Zealand, New Guinea and New Caledonia. This genus is of especial interest because of other organisms generally associated with it. The parasitic fungus Cyttaria is found with Nothofagus in South America, New Zealand and Australia and the moss family Dicnemonaceae is associated with Nothofagus throughout its range, with bugs of the family Peloridiidae dependent on the moss 11. It is interesting to note that these bugs possess a mix of primitive and specialised features of both major subgroups of the Hemiptera 20.
Australia's best known Gondwanan inheritance, however, can be seen in the localised areas of relict rainforest scattered close to the eastern coast from southern Victoria to Cape York and across Tasmania. These rainforests include a wealth of primitive flowering plants as well as several gymnosperm genera. The rainforests of northeast Queensland provide some of the world's most important ancestral links in the history of plant evolution. They are the centre of diversity of the cycads, which form an evolutionary link between flowering plants and ferns, and contain concentrations of the most ancient and primitive of the world's surviving conifers. Furthermore, nowhere else in the world is there such a concentration of primitive flowering plant families. Of the 19 known families of primitive flowering plants, 13 are found in northeast Australia and two of these are found nowhere else 123. The species in these two endemic families, Austrobaileya scandens, A. maculata and Idiospermum australiense, are notable primitive and relict species.
The family Proteaceae, in common with the southern beeches, is believed to have originated in the rainforests of Gondwana. Three genera of the Proteaceae, Placospermum, Sphalmium and Carnarvonia, which are restricted to north Queensland tropical rainforests, are regarded as primitive with Placospermum coriaceum perhaps the most primitive extant member of the family 123 182. The Proteaceae diversified mainly in the Australian-Antarctic rift valley as Gondwana was fragmenting during the late Cretaceous. This rift valley region was probably also the centre of origin for ancestors of the present southern heath family, Epacridaceae, and for ancestors of sclerophyllous genera within the Proteaceae 40.
The hollies (Aquifoliaceae), one species of which, Ilex arnhemensis, occurs in Australia, are also ancient and Ilex-type pollen found in southeastern Australia dates from the late Cretaceous. Lagarostrobos-type pollen is dated from the middle or late Cretaceous 39. Similarly, pollen probably of the gymnosperm genera Podocarpus and Microcachrys, which are also currently represented in the Australian flora, dates from the early Cretaceous 11.
3.1.3 Distinctive adaptations
The leaves of sclerophyllous plants are characteristically rigid and usually have a very thick cuticle. Silica is present in the epidermal walls of some species (mostly monocotyledonous groups) for example, species of Gahnia or sword grass. Many sclerophylls also have sunken stomata 11.
Sclerophylly is found in some 20 plant families, mainly the Epacridaceae, the Proteaceae and the Myrtaceae, but is common in several other families, for example the Mimosaceae (in acacias with phyllodes rather than leaves), and peas and beans (family Fabaceae or Papilionaceae). Casuarinas (family Casuarinaceae) and some genera of several other families (for example Exocarpos of the sandalwood family Santalaceae) have leaves that are reduced to scales, with photosynthetic stems. Many monocotyledons are also sclerophyllous, including almost all grasstrees (Xanthorrhoea, family Xanthorrhoeaceae), as well as some sedges (Cyperaceae), kangaroo paws and relatives (Haemodoraceae), the iris family (Iridaceae) and the sedge-like Xyridaceae 11.
According to Beadle11 'sclerophylls are most numerous on sandy soils of low fertility in the higher rainfall areas', and there are two main centres of sclerophyllous species, the Sydney-Blue Mountains region, and southwestern Australia.
Adaptations to nutrient deficiency and aridity may have pre-adapted plants to fire. As outlined in Section 2, many Australian plants are well adapted to particular fire regimes, and some have an obligate association with fire. Banksia coccinea, for example, begins to senesce after 15 years and requires relatively frequent fires to regenerate 91. Several other plants, including grasstrees (Xanthorrhoea) and some species of orchids are known to flower abundantly only after fire 55.
Plant species in fire-prone habitats (which includes many Australian landscapes) survive fire by employing two broad strategies either alone, or in combination. Some fire-tolerant species produce large quantities of seed that accumulate in the soil or in woody fruit and germinate after fire. In these species, the entire population of growing plants may be killed by the fire and survival is solely from seeds. The mountain ash (Eucalyptus regnans) is an example of such a species 55. Similarly, Banksia ericifolia individuals are killed by fire, but release large quantities of seed (one study counted a mean of more than 1300 seeds per plant) 126. A considerable advantage for seedling growth is obtained because of the nutrient-enriched substrate and lower canopy cover resulting from fire. Such species are unable to regenerate if the time between successive fires is shorter than the time required to reach maturity and produce seed.
A second strategy employed by other species is to have fire-tolerant individuals that are able to display remarkable powers of survival and regeneration. A variety of mechanisms is used, such as thick insulating bark, numerous buds to allow resprouting, and subterranean buds, including lignotubers (large woody rootstocks), which are also resistant to dry conditions 126 55. The largely intact rootsystems and/or trunks of fire-resistant plants allow quick recovery from fire events. Species such as Eucalyptus paniculata and Banksia aemula (= serratifolia) have thick bark which enables the trunk and main branches to survive fire and send forth new shoots from dormant buds.
B. aspleniifolia, in contrast, regenerates mostly from rootstocks, but also partly from seed (averaging only 15 seeds per plant) and the above-ground parts of the plant generally do not survive fire 108 126.
Some genera, notably Eucalyptus and Banksia, have species employing both strategies 126. Most eucalypts possess lignotubers, but these tend to be more highly developed in those species occurring where fire is naturally frequent. Those species growing where fire is naturally infrequent tend to have less well developed lignotubers, thinner bark, and to regenerate primarily from seed.
Australia's fauna is distinctive and scientifically of great interest. Its unique composition, with many groups of animals absent and others diverse and rich, reflects Australia's long isolation from other continents. Australia's long history as an island also accounts for the high levels of endemism in many faunal groups. Examples of some faunal groups significant for their richness, endemism, ancient origins or distinctive adaptations follow.
Land fauna - summary
Because of its long geological isolation Australia's wildlife is rich and unique with 283 species of mammals; over 770 species of birds; approximately 750 species of reptiles; about 200 species of frogs and an estimated 225 000 species of invertebrates.
All three major groups of modern mammals (monotremes, marsupials and placentals) co-exist in Australia and, of the three species of monotremes (egg-laying mammals) known worldwide, two occur here (the platypus and echidna). The marsupials are the most common mammals in Australia with about 142 species, the majority of which are endemic. They occupy many habitats relating to their preferred foods, which include plants (for example possums, kangaroos and the koala); nectar (for example the pygmy possum); meat and invertebrates (for example planigales and quolls); and carrion (for example the Tasmanian devil). Some marsupials, such as bandicoots, are omnivorous, eating both plant and animal food.
Many of Australia's birds, and most reptiles and amphibians, are also endemic and Australia's fauna is highly diverse compared to that of other continents. For example parrots are more varied in Australia than elsewhere; and the Australian arid zone houses 2-3 times as many lizard species in a given area as desert regions in either Africa or North America.
Australia has a large invertebrate fauna; and about one-third of the estimated total species awaits discovery. The insects are extremely diverse, with perhaps 140 000 species alone, and some families and most species occur only in Australia. Ants are so abundant that there are at least as many genera of ants in part of a Canberra nature reserve as there are species in the whole of Britain. Other terrestrial invertebrate groups such as worms earn distinction with endemic examples such as the giant Gippsland earthworm.
Australia's animals possess a wide range of adaptations to help them cope with arid conditions. About one-third of Australian frogs can burrow and sometimes also form cocoons. Many marsupials produce concentrated urine and some are able to survive without drinking.
As with plants the fossil record shows that some modern species, such as velvet worms (onychophorans) and several insects, have remained relatively unchanged for hundreds of millions of years. Several other invertebrate groups (for example some spiders, centipedes and mites) probably have Pangaean origins. Other faunal groups have fossil records extending back to Gondwanan times, including the emu and cassowary, parrots, and some turtles, geckos, frogs and invertebrates.
3.2.1 Australia's very rich and highly endemic fauna
The nature of Australia's mammalian fauna is partly illustrated by the presence only in Australia and the smaller island of New Guinea, of representatives of all three major extant groups of mammals (monotremes, marsupials and placentals). Of the world's three extant species of monotremes two are found in Australia: the echidna and platypus. Australia also has an abundance of bats and rodents. However, at about 23 per cent of our total mammal fauna of some 282 species (including marine mammals other than whales), there are fewer varieties of rodents in Australia than on other continents and these are restricted to only one family and two subfamilies 149. The number of mammal species recognised is constantly changing as new species are recognised through increased surveying and the application of more sophisticated genetic tools.
The Australian mammal fauna is further distinguished by the preponderance and diversity of marsupials compared with other groups. Some 141 marsupial species, of which over 90 per cent are endemic, occur on the Australian continent 149 48 215. Marsupials in Australia have radiated into a wide range of habitats and now fill many niches. Australian marsupials include insectivores (e.g. planigales); carnivores (e.g. quolls); saprophages (e.g. the Tasmanian devil, Sarcophilus harrisii; nectivores (e.g. pygmy-possums) and herbivores (e.g. possums and kangaroos, and the koala), in a variety of sizes and types 94). This diversification has also led to the development of some interesting examples of convergent evolution – such as gliders, the marsupial moles, and the thylacine or Tasmanian wolf (Thylacinus cynocephalus), which are extraordinarily similar to their placental mammalian counterparts (flying squirrels, moles, and the wolf, Canis lupus) that evolved independently in other parts of the world. Of the six endemic mammalian families, five are marsupials and include the numbat (Myrmecobius fasciatus: Myrmecobiidae), the marsupial moles (Notoryctidae), the koala (Phascolarctos cinereus: Phascolarctidae), wombats (Vombatidae), and the honey-possum (Tarsipes rostratus: Tarsipedidae) 149.
High percentages of species unique to Australia are also found in other mammal groups (see Table 2). Some 88 per cent of native rodents are endemic 215, as are about 58 per cent of described bat species 212. However, in contrast to the marsupials and rodents which have significant endemism at the genus level, only two of 22 bat genera are restricted to Australia and no bat or rodent family is endemic 149.
Australia has a large number of birds. Of the nearly 720 native species listed by Schodde and Tidemann 140 as occurring on the mainland and islands of Australia (excluding Australian external territories), some 320, or more than 40 per cent, are endemic. A more recent checklist includes 777 native birds, with 357 endemic species forming more than 45 per cent of the total 23, although this number includes species found in Australian external territories.
|Total no. species||% of mammal fauna||Endemic species||Non-endemic species||% endemism|
1 Strahan 1988
2 R. Strahan 1993, pers comm
3 G. Richards 1993, 1994, pers comm. This figure includes only described species; a further 18 nominal species await description, and 16 of these are thought to be endemic.
4 R. Strahan 1994, pers comm
5 Strahan 1988. This figure includes only those species which breed or used to breed on the Australian mainland or Tasmania (including King Island). A further four species are casual or accidental visitors.
Several groups of birds have evolved into many species and occupied many ecological niches. For instance, the honeyeaters (Meliphagidae), with about 66 species, are the largest Australian family and have colonised all areas of the continent. Over 80 per cent of Australia's 51 species of parrots are restricted to Australia and its islands. Australian parrots display a greater variety of form than parrots elsewhere, and comprise about 15 per cent of the world's fauna 140.
Twenty of the world's 26 species of fairy-wrens and allies (Maluridae) occur in Australia and all are endemic, as are more than 80 per cent of the approximately 45 scrubwrens, thornbills, pardalotes and allies (Acanthizidae) 140. At the family taxonomic level, some four small families of birds are endemic to Australia: the plains wanderer (Pedionomidae), lyrebirds (Menuridae), scrub-birds (Atrichornithidae) and Australian chats (Epthianuridae). A further nine Australian-centred families of birds extend no further than New Guinea 214. Examples include the Australian treecreepers (Climacteridae) and Australian babblers (Pomatostomatidae) 140.
The reptile fauna of Australia is also highly distinct. A remarkable 89 per cent of the more than 750 reptile species found in Australia and its external territories occur nowhere else 25. Furthermore new species (generally endemic ones) are being described every year. Australia has an exceptional lizard fauna in the arid zone, showing a high level of local species richness 107. As indicated in Table 3, 30 or 40 species of lizards can, for example, be found in a typical ten hectare patch of spinifex grassland, which is two to three times the numbers found in patches of similar size in southern African and North American deserts 116 117. Several factors appear to cause this diversity. These may include the wide range of suitable habitats provided by tussock grasses and an abundance and diversity of termites, a primary food source for lizards. Australian lizards have evolved many hunting modes to exploit the number and range of termites, and this has given to Australia an abundant and diverse fauna of legless and reduced-limb lizards as well as many nocturnal and subterranean species 170.
|Lizard family||North America||Africa (Kalahari)||Australia|
Source: adapted from Pianka 1986
A number of Australian lizard taxa are comprised of species found almost exclusively in Australia and are also notable for their diversity. These taxa include the dragons (family Agamidae) with 63 species, of which about 94 per cent are endemic. At the level of genera, some six dragon genera, including the members of Tympanocryptis and the thorny devil, Moloch horridus 25, are endemic. Some ten genera of geckos are also endemic, including all those of the tribe Dyplodactylini, and the distinctive members of Nephrurus, which all possess short fat tails terminating in a small knob. The legless lizards of the family Pygopodidae are confined to Australia and New Guinea, with all but two species endemic to Australia 25. Australia has a notable fauna of monitors or goannas (family Varanidae), with at least 25 of the world's approximately 40 species 80. One quarter of the world's skinks are also found here 72. The skinks can be regarded as reaching their greatest taxonomic and morphological diversity in Australia 73.
Australia is noted for its varied fauna of terrestrial proteroglyphous (fixed, front-fanged) snakes. These are more diverse in Australia than anywhere else in the world and there is usually at least one species present in all parts of mainland Australia and Tasmania 25. Some 92 per cent of the 77 species listed by Cogger
Australian frogs are very diverse, particularly within the families Hylidae (tree frogs) and Myobatrachidae (southern frogs), with some 93 per cent of about 200 species being endemic 25. Southern frogs, including Rheobatrachus (gastric brooding frogs, the only frogs known to incubate young in the stomach) and Pseudophryne (toadlets, including the corroboree frog), are confined to the Australian region. However, these are closely related to the South American family Leptodactylidae, and this reflects their Gondwanan origin. The family Myobatrachidae contains many monotypic genera, and an example is provided by the pouched frog, Assa darlingtoni, which earns its name through the existence of pouches on the males. The larvae of this species, once hatched, complete their development in these pouches.
Overall, one of the most striking features of the Australian frog fauna is the lack of dependence upon permanent bodies of water. The general trend is to breed in ephemeral pools, and accordingly, the period of larval development is relatively short.
A wide diversity of invertebrates is also supported by Australian ecosystems, with a total invertebrate fauna estimated at perhaps 225 000 species. A significant proportion of this number is restricted to Australia and possibly one-third of Australian terrestrial invertebrates is confined to the tropical forests of northern Queensland. More than half the invertebrate fauna remains to be described, and an estimated third awaits discovery 208.
Some families of insects are endemic and examples include three families each of beetles, Coleoptera 90 and wasps, Hymenoptera 109, three of bugs and cicadas, Hemiptera 20, and the monotypic termite family Mastotermitidae 166. Endemism at genus and species levels is frequently very high: 75 per cent of beetle genera are endemic 64, as are 21 of 37 genera of praying mantids 8. More than half of stick insect (Phasmatodea) genera are endemic, as are over 90 per cent of grasshopper genera belonging to the superfamily Acridoidea 132. Endemism at the species level is even higher than that for genera and approaches 100 per cent for some groups.
Australian ants are widely distributed, diverse and abundant compared with elsewhere. With at least 4000 different species, of which only a quarter or less have been formally named 216 109, there are more subfamilies and genera of ants in Australia than in any other continent. An indication of this diversity is given by comparing the ant fauna of Britain with that of Black Mountain Nature Reserve in Canberra (covering 519 hectares). Whereas all of Britain has fifty species of ants, there are at least as many genera in the Canberra reserve 12.
Other invertebrate groups also exhibit high rates of endemism and species richness, although in many cases, the faunal composition is not well known. Springtails (Collembola), with perhaps 2000 species, have 90 per cent endemism at species level and 21 per cent at the genus level 63. Four families of land snails are endemic to Australia, while earthworms of the tribe Megascolecini (including some of the world's largest worms) have 71 per cent endemism at the genus level. Twenty-six per cent of spider genera are also endemic 64, as is the Tasmanian spider family Hickmaniidae 96. Australia is home to the only continental ribbon worms (Nemertina) and the three species of the endemic genus Argonomertes form a quarter of the world's known nemertine species. These worms may have an ancient lineage of Cretaceous origins 94.
3.2.2 Ancient and relict components of Pangaean and Gondwanan origin
Rare fossils of onychophorans or velvet worms indicate that the surviving group of these animals has persisted and remained relatively morphologically static for hundreds of millions of years 56 150 151 194 and it is possible that Australia is the ancient centre of the onychophoran world 150. Molecular biology techniques have recently established that onychophorans in Australia are extremely diverse, with more than 50 distinct species 151.
Several invertebrate groups present in Australia most likely have Pangaean origins. The spider superfamily Hypochiloidea is an ancient basal group which was certainly present in Pangaean times and elements belonging to it, such as the family Hypochilidae, still survive in Australia. The centipede genus Craterostigmus occurs in Tasmania and possibly New Zealand and is very similar to fossils found in the Gilboa deposits in New York 194. Very recently, a family of mites basal to the whole mite subclass, has been found in the Kimberleys, Western Australia. These mites, of the family Opilioacharidae, were previously only known from southwestern United States, central Asia, and the Mediterranean 196. A rare and disjunct distribution is also exhibited by the ancient monotypic earthworm family Haplotaxidae (Oligochaeta), of which one species is found in Tasmania. Other species are known from Spain, and several northern Balkan countries 194.
A number of biotic groups in Australia have fossil records extending back to Gondwanan times. Vertebrate faunal groups include the marsupial mammals, ratite birds (the emu, Dromaius novaehollandiae, and cassowary, Casuarius casuarius), chelid turtles (side-necked or snake-necked turtles) and geckos of the tribe Diplodactylini. Fossil remains from the early Cretaceous indicate that monotremes were in Australia well before it separated from the rest of Gondwana and the possible ancestors of all known extant and extinct Australian marsupials, the microbiotheriids, probably dispersed to Australia in the late Cretaceous to early Tertiary times 64. Parrots too are Gondwanan in origin and are found in Africa and South America. Moreover, recent research points to the possibility that Australian songbirds as a whole (order Passeriformes) may have Gondwanan origins 22. There is some evidence that the families Hylidae and Myobatrachidae, which comprise more than 90 per cent of the Australian frog fauna, are also of Gondwanan origin 134.
The insects are an ancient group, with some primitive taxa having links to Jurassic, Cretaceous and Tertiary times. The primitive cicada family Tettigarctidae, for example, is known from two extant Australian species and from northern hemisphere fossil genera dating from the Mesozoic 20. Many more extant taxa can be traced to Gondwanan radiations. The endemic termite Mastotermes darwiniensis is the only surviving member of the family Mastotermitidae, members of which were widespread in the Tertiary. It possesses some primitive morphological features and may be the most primitive living termite 84 166. Other termites of ancient origin include Australian representatives of the genera Stolotermes and Parotermes 166.
Many orders of insects also have Gondwanan links, such as the primitive aphid genera Neophyllaphis and Taiwanaphis, and numerous tribes and genera of beetles, such as the stag beetles of the subfamily Lampriminae (family Lucanidae) 167 20 90. Many Gondwanan-derived insect taxa have evolved with Australian eucalypts, acacias and casuarinas. These include lerp and scale insects (superfamilies Psylloidea and Coccoidea), and dry temperate bees - notably native bees of the family Colletidae, which are highly dependent on Eucalyptus species 20 109.
Examples of other ancient species abound and include flies of the genus Exeretonevra (Xylophagidae), and primitive midges (Chironomidae) of the genus Archaeochlus 26. Archaic families of moths, such as ghost moths (Hepialidae) and wood moths (Cossidae) are also well represented in Australia 111).
With the exception of one species in New Caledonia, the two subfamilies of ants thought to be the most primitive in the world are endemic to Australia. One of these, the subfamily Myrmeciinae, contains the highly distinctive bullants (or bulldog ants). These have a very generalised structure and are thus considered to be amongst the most primitive of ants. Even more primitive is Nothomyrmecia macrops of the subfamily Nothomyrmeciinae, which is known only from a very small area on the Eyre Peninsula in South Australia 12. It has the most generalised morphology of all, and is considered to be the world's most archaic extant ant. This species is similar to one that existed approximately 60 million years ago 151 12.
Unique groups of ancient lineage
The Cooloola monster (Cooloola propator) is a cricket-like insect that has been found in Cooloola National Park and Fraser Island in Queensland. The unusual combination of characteristics of the Cooloola monster prevented its inclusion in any recognisable family or in either of the two traditional orthopteran suborders 131. C. propator is considered to be an aberrant member of the suborder Ensifera and has, with three other more recently discovered species, been assigned to the new family Cooloolidae 130 132 31. Superficially, C. propator resembles the Indian stenopelmatid Oryctopus, and thus represents an extraordinary example of convergent evolution 131. The sperm of C. propator is believed to be the most primitive known of any orthopteran 7.
3.2.3 Distinctive adaptations
Some Australian animals provide outstanding examples of adaptations to geographic features of Australia. Since about 70 per cent of Australia is arid or semi-arid, a number of these adaptations allow inhabitation of dry areas. Some of the most interesting examples of behavioural and physiological peculiarities for coping with arid conditions are displayed by the considerable number of arid-adapted Australian frog species.
One of the commonest strategies, employed by approximately 35 per cent of Australian frogs, is burrowing 160. It should be noted, however, that the burrowing habit is not restricted to frogs of arid regions; it is also found in species inhabiting moderately moist (mesic) environments such as rainforests, where standing water other than streams is scarce 93. Burrowing species have quite a distinctive form with short legs and a generally globose body shape 33. A number of burrowing frogs survive even better in arid zones by producing cocoons that reduce water loss. Several species of Neobatrachus and Cyclorana, in addition to burrowing and forming cocoons, can further minimise water loss by reducing their metabolic rates 133 33. An estimated 10 per cent of dormant C. platycephala were able to live at least five years without emerging from their cocoons 161. Evaporative water loss in cocooned Litoria alboguttata has been found to be reduced by approximately seven-and-a-half times compared with individuals lacking cocoons 160.
Physiological adaptations of Australian marsupials to dry conditions have been mentioned in Section 1 and the dasyurids, including quolls, the Tasmanian devil and antechinuses, provide several examples. The mulgara (Dasycercus cristicauda) produces urine with a high concentration of urea, thus conserving water and permitting it to obtain sufficient water from food. Other examples of small marsupials apparently able to survive without drinking include the fat-tailed dunnart (Sminthopsis crassicaudata) and the narrow-nosed planigale (Planigale tenuirostris) 149. Parallel adaptations have been observed in several endemic rodents, such as several hopping mice (Notomys) and the plains rat (Pseudomys australis). The plains rat is able to obtain water by metabolising food starches and minimises water loss by producing highly concentrated urine and by the absence of sweat glands 149.
Adaptations to aridity are also notable in invertebrates, where, for example, the blackfly Austrosimulium pestilens, lays eggs on the surface beds of intermittent rivers. The eggs sink deeply into the mud and those in permanently damp patches can remain viable for up to two-and-a-half years awaiting fresh flooding 113. All other members of the family Simulidae lay their eggs in water 194. Two subfamilies of land snails of the family Camaenidae have radiated into arid areas of Australia and some 83 per cent of the genera and all the species of the Sinumeloninae and Pleurodontinae are endemic to the red centre. These radiations may have arisen from a preadaptation to inactivity during monsoonal dry periods 147.
While all species interact with others in communities and ecosystems, often in complex ways, there are a number of ecological interactions that are of particular interest in Australia. In some cases, two major groups of organisms have such a close ecological relationship that mutual adaptation during the course of evolution, or 'co-evolution', is implied. Seed dispersal by vertebrates, ant/caterpillar interactions, plant interactions with leaf-eating animals and the interdependence of plant groups and pollinating animals are discussed below.
Associations of certain birds and butterflies with mistletoes (family Loranthaceae) illustrate the complexity of some ecological interactions. The mistletoe bird (Dicaeum hirundinaceum), the main dispersal agent for mistletoes in Australia, is dependent on these plants for the greater part of its diet. The bird is locally nomadic which may enable it to take advantage of the varying fruiting times of mistletoes in different regions 140. Along with other birds in the family Dicaeidae, the mistletoe bird has a digestive system adapted to a diet of mistletoe fruits. Some 25 to 60 minutes after being swallowed, and their fleshy coats digested, the mistletoe seeds are ejected. Being very sticky, they adhere to any surface on which they are deposited.
Other species also depend on mistletoes for food. Almost all of the 12 Australian azure butterflies of the genus Ogyris (Lycaenidae) feed exclusively on mistletoes. In common with other lycaenids, Ogyris caterpillars are tended by ants of several genera, including Camponotus and Crematogaster. It is thought the ants may provide protection against predators in return for sugary secretions used as food, and large numbers of caterpillars are sometimes found in ant nests at the base of the mistletoe host trees 30. Mistletoes themselves may play an important ecological role in Australian forests and ecosystems in reducing host vigour and life expectancy, for example by killing branches, so making light and space available to other plants 95.
Ecological interactions - summary
Sometimes in nature groups of organisms interact to gain mutual benefit and it often appears that 'co-evolution' of the organisms has occurred. The complexity of such interactions can be very great and there are numerous interesting examples in Australia. Seed dispersal, pollination and protection from predation are common themes. For example, mistletoe seeds are dispersed by the mistletoe bird while azure butterflies, which feed on mistletoe, have a special relationship with ants, which protect the caterpillars in return for sugary secretions. The seeds of some plants such as the nitre bush germinate more easily after being digested by vertebrates.
Ants also disperse seeds for numerous plants – indeed Australia's 4000 species of ants fulfil many roles and are particularly important in arid areas where they account for a large percentage of the invertebrate fauna and are involved in many interactions with other species.
Both vertebrate and invertebrate pollinators of flowering plants benefit by feeding on the flowers' nectar, for example honeyeaters, the honey-possum and numerous insects. Many flowers have characteristics that attract particular animal species, for example some orchids mimic female flightless wasps in order to attract males.
Many insects have co-evolved with acacias and eucalypts, for example sucking lerp-forming bugs, gall-forming wasps, and seed-eating weevils. Other insects chew foliage, a habit which requires major adaptations because acacia and eucalyptus leaves contain toxic chemicals that deter predation. Vertebrates also have to overcome this problem - koalas select leaves to avoid cyanide precursors. Some insects make use of the native plants' chemical weapons to avoid predation themselves, for example sawfly larvae regurgitate toxic oils to deter bird predators.
3.3.1 Seed dispersal
Vertebrates play an important role in seed dispersal, as illustrated by the mistletoe bird example above. When fleshy fruits are eaten by birds or mammals, the soft parts are digested, and the seeds pass through the gut and are excreted, often some distance from the parent plant. The seeds of some plants actually germinate more readily after being ingested. An example is provided by the seeds of the nitre bush (Nitraria schoberi), a favoured food of the emu. The seeds of this plant have a salt-rich pericarp which inhibits germination but which provides food for emus. The seed passes through the bird's gut and is voided in its own supply of nutrient from the emu 162.
Ants are responsible for seed dispersal of some 1500 species of Australian vascular plants. This phenomenon of ant seed dispersal (or myrmecochory) occurs predominantly in arid areas, in lowland heaths, mallee understorey, dry sclerophyll forests and scrubby woodlands, and is distinct from seed harvesting 113. Myrmecochory has been recorded for only about 300 plant species in the rest of the world 14. Myrmecochory is a clear case of co-evolved mutualism: ants obtain the benefit of special nutritive structures on the seeds (correctly, the disseminules), and the plant benefits by having its seeds taken to the ants' nests, and protected against consumption by other ants.
3.3.2 Other ant interactions
Australia's large ant fauna occupies an important place in many ecosystems and influences the composition of much of the rest of the insect fauna 64. Ants are notably diverse in arid and semi-arid Australia 62 and can, for example, comprise up to 68 per cent of the overstorey invertebrate fauna in mallee ecosystems 185. Ants are not only predators, seed harvesters and scavengers, but are an important food source for other invertebrates, and vertebrates such as the magpie (Gymnorhina tibicen), all members of the subendemic bird family of treecreepers (Climacteridae), the numbat and the thorny devil lizard, which is a specialist predator on small ants of the genus Iridomyrmex 190.
The interdependence of pollinating animals and various groups of plants is another instance of evolved interactions. Vertebrate-pollinated plants probably constitute a greater proportion of the woody flora in Australia than they do on any other continent, with birds and/or mammals pollinating more than 30 genera 125. Many plants that rely wholly or partly on vertebrate pollination produce copious quantities of nectar, and the long curved bills and brush-tipped tongues of honeyeaters are obvious adaptations to nectivory.
Kangaroo paws (Anigozanthos) are adapted to pollination by birds, and Eucalyptus and other myrtaceous genera include many vertebrate-pollinated species. The nine species of megachiropterans (fruit bats and their relatives) found in Australia are known to be important long-distance pollinators of many eucalypts 156. The often spectacularly flowered members of the family Proteaceae also provide numerous examples of vertebrate pollination and small mammals and numerous birds are important pollinating agents. Banksia ericifolia may be principally pollinated by mammals such as the bush rat (Rattus fuscipes) and the brown antechinus (Antechinus stuartii)125 and Banksia prionotes may require bird pollination to set seed 27. Some Dryandra in Western Australia have flowers positioned in a way that encourages non-flying mammal pollination and discourages bird attendance 125.
The vertebrate pollinators can gain substantially from the relationship. The banksias of southwestern Australia, for example, support many pollen and nectar-dependent organisms. These include the unique honey-possum (Tarsipes rostratus), which has evolved morphological features permitting it to feed on nectar. Also Banksia prionotes provides an important source of nectar for honeyeaters in the Western Australian wheat lands from March through to May, when other sources of nectar are scarce 87. Three genera (Phylidonyris, Acanthorhynchus and Myzomela) of the country's 66 species of honeyeaters, which are major pollinating agents for a variety of Australian plants, are nectar dependent 125.
Insect pollination has been an important factor in the evolution of flowering plants for some 130 million years and specific relationships have arisen, particularly with the insect orders Diptera, Lepidoptera and Hymenoptera 113. Australian examples include the seven species of the terrestrial orchid Drakaea, each of which has its own species of wasp pollinator in the subfamily Thynninae (family Tiphiidae). The flowers mimic the flightless females of these wasps, in morphology, colour and pheromone production, and attempts to carry away the mimic by the males result in pollination 148. The orchid Leporella fimbriata is pollinated by the bulldog ant Myrmecia urens and is a rare example of an obligate ant pollination mechanism 115.
Tiny wasps of the subfamily Agaoninae (family Agaonidae) are host-specific pollinators of figs (Ficus), which have internal flowers, and rely on these insects for fertilisation. Forty-two species of figs occur naturally in Australia 21, and Australian agaonine genera include Pleistodontes and Ceratosolen 109. Figure 3 below illustrates the interdependence between figs and fig-wasps.
The life cycles of fig-wasps and figs are bound together inextricably. Each kind of fig has its own species of wasp which it needs for fertilisation, and which in turn relies on fig for its own reproduction.
Source: adapted from Ramirez 1974
3.3.4 Leaf-eating, and plant defences
In Australia many insects have co-evolved a number of trophic interactions with the two large and dominant plant genera Acacia and Eucalyptus. These include sucking insects, such as lerp-forming insects of the family Psyllidae; gall formers such as some wasps of the family Pteromalidae; pollinators of the bee family Colletidae; and seed eaters including many weevils such as species of Melanterius 112 20 109. In addition, a large range of insects chew foliage, including leaf beetles of the subfamily Chrysomelinae (family Chrysomelidae) with more than 600 species, and the Christmas beetles, Anoplognathus 90.
Other insects that associate intimately with acacias and eucalypts are the spitfires (Pergidae) and many moths. The Oecophorinae, or mallee-moths – which comprise perhaps 20 per cent of Australia's moth and butterfly fauna, with an estimated 5500 species known – feed mainly on living and fallen Eucalyptus leaves 28 29. This is a highly significant percentage of the total moth fauna, and species of oecophorids perform a key ecological role by breaking down leaves. Several species of oecophorids have taken the specialisation a step further, and their larvae are found feeding on the remains of myrtaceous leaves in possum and koala faeces 67. The significance of such interactions is further illustrated by a number of eucalypts and acacias, which are known to support at least 100 phytophagous (plant-eating) species each 112. Each group of plant species and phytophagous invertebrates in turn supports a host of microorganisms, predatory and parasitic invertebrates, and associated vertebrate species, in a highly complex community.
Major adaptations are required for eating the leaves of many Australian plants. Eucalypts possess an array of toxic chemicals such as phenolic compounds and cyanide precursors, and animals that feed on them have had to evolve mechanisms to bypass these phytochemical barriers. Koalas, for example, selectively browse to avoid cyanide precursors, and possess a liver capable of detoxifying oils and phenolic compounds. Larvae of the sawfly genus Perga (including spitfires) have not only acquired the ability to ingest such chemicals, but are also able to store a concentrate of toxic plant oils which they can regurgitate to effectively protect themselves against bird predation 113.
Special terrestrial areas
An important aspect of biodiversity is the variety of habitats and biological communities that there are in a region. In this context some areas of Australia warrant special mention. It has already been noted (3.1) that the rainforests of north Queensland have great importance, not only for the species richness and diversity of biotic communities that live there, but as a repository of some of the world's most important links in plant evolution, retaining the very 'stock' of botanical diversity as we know it today.
The South West Botanical Province of Western Australia and the alps of southeast Australia are two other areas with diverse habitat systems. The former area of forest, woodland and scrub has the greatest floral diversity in Australia and is famous for its banksias (75 per cent of Australian species grow here) and carnivorous plants (including over half the world's species of sundews). The alps comprise a variety of herbfield, heath, bog, grassland and rocky scrubland lying above the treeline, providing habitats not found elsewhere and supporting a significant component of Australia's biodiversity.
The gorges and caves of central Australia are also distinctive and important habitats. The gorges provide moisture in an otherwise dry landscape allowing development of diverse and stable communities, and the caves are home to a number of highly adapted species (for example cave-dwelling arthropods and the blind gudgeon) not found elsewhere.
Another distinctive habitat is provided by the mangroves that cover 11 500 square kilometres of Australia's coast and contain various species of mangrove trees from different lineages. These are all superbly adapted to tolerate excess salt and for immersion and waterlogging, particularly by the development of aerial roots. Leaf litter produced by the mangrove trees supports complex food webs including invertebrates, birds and fish, making the mangroves a rich and unique habitat.
3.4.1 Rainforest areas of north Queensland
The wet tropical rainforests of north Queensland occur over an altitude gradient from sea-level to mountains more than 1600 metres high. They include a number of different types of vineforest types and communities, including complex evergreen forests, deciduous and semi-deciduous forests and simple vine-fern forests, and these are interspersed with open forests and woodlands, paperbark (Melaleuca) swamps and mangroves 123. The rainforests are noted for their very high biological diversity, with 516 genera and 1161 species of plants listed, some 710 of which are endemic to Australia, and 435 endemic to the region 123.
Many species are of ancient lineages and are thus of great interest. The significant number of families of primitive flowering plants (angiosperms) found in the region has already been noted in Section 3.1.2 and is illustrated in Table 4 below. Of the 98 rainforest genera of primitive angiosperms and gymnosperms in Australia, at least 73 are found in the north Queensland wet tropics 169. Many rainforest plants are known only from one or a few populations, such as Gymnostoma australianum, which is the oldest living member of the Casuarinaceae and has a fossil record extending back perhaps 65 million years. G. australianum is restricted to a few small populations near Thornton Peak 179.
|Plant family||World species||Australian species||Found in north Qld rainforests||Endemic to north Qld rainforests|
Note: * endemic families
Source: adapted from RCSQ 1986
The region's contribution to floral genetic diversity is also worth noting. This is indicated not only by the number of primitive families found there but also by the number of monotypic genera: 43 monotypic genera of flowering plants have been recorded there, of which 37 are endemic to Australia and 28 to the area. The rainforests of this area can be characterised by proportionately very high diversity at the genus level. A total of 340 angiosperm and 46 gymnosperm genera are represented in the area by only one species 123. The largest genus, Syzygium, has 29 species and only two other genera have more than 20 species. This is in contrast to the rainforests of Indo-Malesia, for example, where Syzygium has over 200 species 123. There is also greater morphological and genetic diversity in the Australian Syzygium species and Australia is regarded as the major centre for diversity and endemism for this and allied genera (Whiffin and Hyland 1984, in RCSQ 1986123).
Floral diversity is paralleled by faunal richness, knowledge of which is still far from complete. These rainforests contain a high proportion of Australia's ancient frog fauna and a very high proportion of the more recently evolved frog species 123. Forty-seven species of frogs, or 23 per cent of the Australian total, are found in this area, with 19 endemic to it. One hundred and twenty-eight species of birds make the wet tropics of north Queensland one of the richest areas in Australia for bird life, with many localised endemics and a particularly rich and diverse avifauna occurring in eucalypt forest adjacent to rainforest 123 214. Some 89 mammal species occur in the wet tropics area, including 60 per cent of the Australian bat species 123 215. The 160 species of reptiles found in the area constitute 23 per cent of the Australian total.
Many invertebrate species remain to be discovered in the area but the diversity will prove immense. At one survey at Bellenden Ker, more than 4385 species of invertebrates were found, including at least 4029 species of insects, or perhaps 7 per cent of the Australian total. Of the 1514 species of beetles identified in this survey, 86.5 per cent were unnamed. Only 45 of the 314 species of spiders found were able to be named 105.
As with other mountain tops, those of north Queensland can be considered as geological islands 64, and as such, may contain species of great antiquity. Examples of such species include the giant stag beetle, Sphaenognathus queenslandicus, of Gondwanan origins, and the blind water beetle, Terradessus caecus, which has adapted to terrestrial life and may have a biological lineage of more than 100 million years 123 168. A number of spiders are similarly restricted to rainforest mountain tops, including species of Otira, Pararchaea and Gradungula. Gradungula may date back well beyond 80 million years 123.
3.4.2 The South West Botanical Province
The South West Botanical Province stretches from Shark Bay on the west coast to Esperance on the south coast of Western Australia and covers an area of 309 840 square kilometres. This region, encompassing eucalypt forest, woodland, mallee and scrub, has the greatest native floral diversity in Australia, with about 9000 species of vascular plants, or well over a third of the Australian total. Some 70 per cent of these plants are endemic to the province 59. Few areas in the world have such diversity, and perhaps only a handful exceed it. The family Proteaceae is most diverse in this area, and the region is famous for its banksias. Of the approximately 75 species of banksias, about 75 per cent are found in the region, with most of these restricted to it and all the 57 or more species of Dryandra are found only in the South West Botanical Province 182. The often impoverished soils are also associated with an abundance of carnivorous plants: some 76 species, or well over half of the world's species, of sundews (Drosera) are found there 206. One of two rainbow plants (Byblis) is endemic, together with bladderworts of the genus Polypompholyx. The Western Australian pitcher plant (Cephalotus follicularis), which is the only species of the family Cephalotaceae, is also endemic to the region 106.
Vertebrate endemism is also high in some groups of the region. This is particularly so for frog and reptile genera but three mammals – the quokka (Setonix brachyurus) the banded hare-wallaby (Lagostrophus fasciatus) and the honey-possum (Tarsipes rostratus) – are also restricted to the area 191 215. The South West Botanical Province is moderately rich in honeyeaters, although not in other birds 214. The invertebrate fauna has been comparatively little studied but some elements are likely to be as unique as the flora. The family of mainly seed-feeding bugs Lygaeidae (Hemiptera) exhibits high endemism in the area 20and 79 per cent of the region's caddis flies (Trichoptera) are also endemic 110.
3.4.3 Gorges and caves of central Australia
Gorges in South Australia retain moisture even in dry years and may harbour faunas and floras with lineages of some 12 million years 195, extending back to a time of moister climate. In the Northern Territory, the relict cabbage palm (Livistona mariae) is only one of some 333 plant species found in Palm Valley near the Macdonnell Ranges. Its nearest relative, L. alfredii, occurs on the Fortescue River in the Hamersley Range (Western Australia) in a similar stand to that of Palm Valley 163. The George Gill Range, adjacent to the Macdonnell Ranges, is even more important botanically than Palm Valley, with almost 600 plant species, some 10 per cent of which have rare, relict or otherwise unusual distributions 163.
Caves often possess small but interesting faunas, such as the blind gudgeon of the North West Cape, and the almost 100 species of troglobitic arthropods (i.e. arthropods generally found only in caves) in 47 caves in the Nullarbor Plain 113.
3.4.4 The alps of southeast Australia
The alpine areas of southeast mainland Australia (some 0.15 per cent of the land surface) and Tasmania comprise a variety of herbfield, heath, bog, grassland and rocky scrubland communities. These lie above tree lines that are relatively low – some 700-1350 metres in Tasmania and 2000-2200 metres in Victoria and New South Wales – but nevertheless are true climatically-determined tree lines. As a contrasting habitat of relative complexity in an otherwise generally arid and flat continent, the alpine regions form a significant component of Australia's biodiversity.
There are notable differences between the alpine ecosystems of Tasmania and the mainland. The Tasmanian alpine flora more closely reflects Gondwanan elements with the bulk of Tasmanian endemic species being Gondwanan in origin. In addition, the western Tasmanian alpine flora is predominantly sclerophyllic, a characteristic found, although not so markedly, in the alpine vegetation of Norway and in very small areas of New Zealand, southern South Africa and the subantarctic islands 82.
In contrast, the alpine flora of the mainland exists in some newly created, small 'island' habitats surrounded by an older continental landscape. This alpine flora, of about 700 species, is an unusual assembly of colonists from surrounding, lower subalpine woodlands many of which have opportunistically colonised the young and ephemeral alpine habitat. This infiltration by lowland genera occurs to a greater extent in Australian alps than in alpine regions elsewhere 58 and may reflect the long history of response to increasing aridity. Adaptations to dryness also appear to provide physiological adaptation and tolerance to frosts and alpine climates 10. A smaller proportion of the Australian flora represents highly dispersible cosmopolitan elements. As a result, the treeline of the mainland alpine flora is formed by relatively large-leafed evergreen angiosperm species, the snow gums (Eucalyptus pauciflora alliance). This contrasts with most other alpine tree lines that are formed by coniferous species or deciduous angiosperm taxa. Also of scientific significance are the convergences in growth form developed by unrelated species. For example, the plantains, found in mainland alpine areas, adopt a similar growth form beneath areas of snow to the dwarf willows in the northern hemisphere.
The relationships of the Australian mainland alpine flora, the New Zealand alpine flora and that of Tasmania and the subantarctic islands, is particularly interesting as the affinities and differences evolved in two or three distinct and different time frames of geomorphogenesis and climate change 193. One of the most botanically interesting plant taxa found in Australian alpine areas is the grass genus Poa, which is widely distributed in the northern hemisphere, Australia and New Zealand. Australian alpine species of this genus are notably different to those found in New Zealand, and can be considered to have differentiated in the regions where they now occur 10. Other grass genera of the alpine area, including Chionocloa, Erythranthera and Rytidosperma (Danthonia), are now regarded as living representatives of ancestral grasses that arose in the Tertiary, in the rainforests of Gondwana 32 58.
Lichens of the mainland alpine area are globally significant. The Kosciusko area has representatives of over 50 lichen genera; this being more than 20 per cent of the total number of genera reported for Australia and including nine of the world's ten largest lichen genera 49.
Even though the percentage of animal species endemic to Australian alpine areas is relatively low, the range of environments and climatic regimes of the alps provides feeding, breeding and refuge habitats for a considerable fauna. Some 20 species of mammals and 110 species of birds have been reported from the mainland alpine and subalpine areas, and nine frogs and 27 reptiles have been found in the high country of the Kosciusko National Park alone 58. The invertebrate fauna of the region is poorly documented with only 850 species recorded from the Kosciusko National Park out of probably thousands 58. Several invertebrate species are known to be restricted to the Snowy Mountains, including two wolf spiders (genus Lycosa), the green cockroach (Polyzosteria viridissima), and ten megascolecid species of earthworms. The grasshopper Kosciuscola tristis, confined to the Australian alps, is the only grasshopper known to exhibit a rapid physiological colour change 54. The males in particular respond to temperature and are black at night and blue in sunlight.
Also of conservation significance is the regionally endemic mountain pygmy-possum (Burramys parvus). B. parvus is the only burramyid that occurs in alpine and subalpine areas and does not store fat in its tail. It is unique among the Australian small mammal fauna because it is the only marsupial to store food and it shows physiological adaptations similar to those described for many placental mammals from cold climates. These adaptations include the storage of subdermal fat and the ability to undergo extensive periods of torpor during winter 18.
With some 11 500 square kilometres of mangroves, Australia has the most extensive areas of mangroves of any of the 80 countries with mangroves, other than Brazil and Indonesia. Mangrove species occur in a number of families with various phylogenetic origins, but all have some tolerance for salt and possess characteristics enabling them to survive in the marine intertidal zone. Mangroves have several ways of dealing with excess salt: salt filters in their roots, salt storage in leaves that are later shed, and glands that excrete the salt so that it can be washed away. Salt accumulation and excretion through glands in the surface of the leaves has been reported in Acanthus, Aegialitis, Aegiceras and Avicennia species. 11. Mangroves also have specialised adaptations to immersion and waterlogging, particularly the development of aerial root systems. Some mangroves, notably Rhizophora species, develop stilt roots which first emerge in the air. In many other species, the cable roots produce lateral roots (pneumatophores) which grow vertically above the surface of the mud in a range of shapes: massive cones two metres tall in Sonneratia, and planks or plates in Xylocarpus granatum.
Australian mangrove species span 14 families and 25 genera, and floral diversity in Australian mangroves is greatest in the northeast tropics, where, with the exception of Avicenna integra, all of the approximately 35 Australian species can be found in some estuarine ecosystems 136 42. Mangrove systems are highly productive, with large amounts of leaf litter providing organic matter that supports rich food webs. They support a large microbial and algal flora, many crabs and large bird populations. Mangrove waterways are also of critical importance to many invertebrates such as the copepod genera Oithona, Parvocalanus and Paracalanus, as well as to a number of fish species. Up to 197 species of fish have been recorded from individual mangrove-dominated estuaries in tropical Australia (Robertson and Alongi, in press).