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Part 6: Ecology Chapter 41: Australian biota Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-1 The Australian biota: southern connections • Distributions of many plant and animal taxa are best explained by past connections of present southern continents • This supercontinent was called Gondwana • Australia severed its final link with Gondwana about 30 million years ago (mya), when it split from Antarctica (see Fig. 41.4) • Environmental changes and isolation moulded the evolution of the modern Australian biota Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-2 Fig. 41.4: Sea-floor spreading Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-3 Ancient forests: Permian times • Fossils of seed ferns (Glossopteris) from 250 mya occur in India, South America, South Africa and Australia (coal formation) • Similar samples of fossils were found with the perished remains of Capt. Scott’s fatal expedition to Antarctica (to the South Pole) • Amphibians, insects and reptiles inhabited Glossopteris forests • These forests dominated the Permian (246–248 mya) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-4 Ancient forests: the Triassic, Jurassic and Cretaceous • By the Triassic (230 mya) Glossopteris forests disappeared from the fossil record • Forked-frond seed ferns (Dicroidium), early conifers and cycad fossils appeared in the Triassic • From the Jurassic to early Cretaceous (213–100 mya) forests were dominated by conifers, some genera of which survive today (e.g. Gingko) • Dinosaurs lived in Australian forests during the Cretaceous Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-5 Forests at the end of the Cretaceous Climate started to dry out… By 65 mya • Dinosaurs became extinct • Flowering plants replaced coniferous forests – earliest pollen is from Nothofagus and family Proteaceae, up to 80 million years old • Break-up of Gondwana was well underway Evolution of unique Australian biota Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-6 The Cenozoic era: climate change and increased aridity • The circum-Antarctic current began once the Southern Ocean was formed • After 10 million years the sea began to freeze, causing the south polar icecap and arid (dry) conditions in Australia • Gondwanan rainforests contracted to far north Queensland • Rainfall patterns in southern Australia changed Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-7 The Cenozoic era: changing landforms and weathering of soil • Rocks were weathered and worn down to low hills • Nutrients (e.g. phosphorus and nitrogen) were leached out by rainfall over millions of years • Lateritic soils formed, see Fig. 41.6 • Lakes dried out, saline mudflats remain today (Lake Eyre) • Inland seas retreated, leaving limestone deposits from shelled invertebrates • Nullarbor Plain and Murray Basin were exposed as dry land Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-8 Fig. 41.6: Laterite Copyright © Professor Pauline Ladiges, University of Melbourne Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-9 The Cenozoic era: increasing frequency of fire • Preserved charcoal and pollen combinations reveal past history • Rarity of eucalypts and high rainfall fires were not catastrophic but • Fire events increased as climate dried out, towards end of Neogene • Fire-adapted open-forest species began to replace existing rainforest species Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-10 The Cenozoic era: ice • Westerly winds first influenced Australia 2 mya – wet winters – hot, dry summers • Quaternary period (1.8 mya present) is characterised by climatic fluctuations • Glacial periods (Pleistocene ice ages) occurred – lower sea levels land bridges (to Tasmania and New Guinea) – increased aridity • Only minor glaciation occurred in Australia, but many dune systems formed Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-11 Fig. 41.8: Glacial period sea level Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-12 Arrival of humans • Fossils (e.g. Mungo Man) suggest humans colonised Australia > 40 000 years ago • Charcoal remains suggest humans had fires here perhaps 128 000 years ago, see Fig. 41.10 • Species’ extinctions 35 000–15 000 years ago suggest effect of humans using fire, and the associated vegetation changes Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-13 Fig. 41.10: Vegetation changes associated with increased burning Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-14 Modern Australian environments: terrestrial • Continent spans latitude10–40°S, so wide range of climate – – – – – monsoonal, tropical north has summer rainfall subtropical warm temperate cool temperate southern regions have winter rainfall Great Dividing Range separates narrow eastern, wetter side from drier west (see Fig. 41.12) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-15 Fig. 41.12: Australian climatic regions Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-16 Marine biodiversity: flora • Rhodophyta (red algae) – includes many endemic species – grown for pharmaceutical and economic use • Phaeophyta (brown algae, e.g. kelps and fucoids) – abundant on rocky shores – commercially harvested • Chlorophyta (green algae) – also diverse, but most evident in tropical regions • Marine flowering plants include – seagrasses (> 30 species) – mangroves (about 30 species) Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-17 Marine biodiversity: fauna • Fish – 3500 species in Australia – high species diversity but low endemism in north – lower diversity but higher endemism (85 per cent) in south • Molluscs and echinoderms display similar patterns of diversity and endemism as fish • Many exotic marine species have been accidentally introduced in ballast, on hulls etc. • These may become pests if they are successful competitors, e.g. Japanese sea star Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-18 Australian terrestrial flora • Major components of the flora have a Gondwanan origin • Sclerophyll plants, e.g. Eucalyptus and Acacia species, dominate the continent • Sclerophylly arose as an adaptation to low-fertility soils, but also increased survival from drought and fire • Succulent plants, e.g. pigface and saltbush, store water to survive drought Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-19 Myrtaceae: the eucalypt family • Includes eucalypts, tea-trees, paperbarks and lilly pilly • 50 per cent of all genera live in Australia • Leaves: oil glands • Flowers: 4 or 5 perianth parts above the inferior ovary • Eucalypts are fast-growing: planted for timber, paper pulp, firewood and oils Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-20 Proteaceae: the banksia family • Includes Grevillea, Telopea, Macadamia, Banksia • Proteaceae is a Gondwanan group, i.e. it occurs in South Africa, India, South-East Asia, South America; fossils in Antarctica • Flowers have 4-lobed perianth, 4 stamens, 1- or 2- celled ovary • Flowers attract bird-pollinators Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-21 Mimosaceae: the wattle family • Approx. 955 Australian species of wattle, all of which are leguminous • The family also occurs in Africa and tropical America • Foliage: either compound bipinnate leaves or phyllodes • Some wattles retain mature bipinnate leaves throughout life, e.g. Acacia mearnsii • Mature foliage of others is phyllodinous and replaces juvenile bipinnate leaves, e.g. Acacia longifolia (see Fig. 41.24b) • Root symbionts increase nitrogen availability Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-22 Fig. 41.24a: Phyllodinous acacia Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-23 Fig. 41.24b: Acacia longifolia Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-24 Fig. 41.24c: Acacia mearnsii Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-25 A unique southern fauna • Characterised by many unique and endemic groups that evolved during the break-up of Gondwana • Tuatara in NZ has survived 160 million years • Australia drifted north in relative isolation • Insect distributions show primitive Gondwanan groups, but also some modern genera derived from Asia • Old connections between South America and Australia are indicated by preferences of insects for feeding on related plants Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-26 Biogeographic patterns: frogs • Frogs (order Anura) (and mammals, class Mammalia) have poor powers of dispersal over seawater, so they provide a clear evolutionary history • The largest component of Australia’s frog fauna are Gondwanan families that adapted to dry environments • Adaptive radiation is best shown by the myobatrachid frogs • Two other families of native amphibians in northern Australia are of Asian origin Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-27 Fig. 41.30: Myobatrachid frog Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-28 Australian reptiles • There are no derivative modern descendants of the dinosaurs in Australia • The New Zealand tuatara, Sphenodon punctatus, is a survivor from Triassic and Jurassic times • Modern reptilian fauna are probably derived from Asian groups • Bearded dragon (family Agamidae) may have stronger African than Asian affinities Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-29 Fig. 41.32b: Australian bearded dragon Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-30 Adaptive radiation in mammals • Australia is the only continent where monotremes (Prototheria), marsupials (Metatheria) and placental mammals (Eutheria) are all represented • Terrestrial and marine mammals are very diverse • First introduced species was the dingo, 7000 years ago • Introduced species (including humans) have had a profound effect on Australian ecosystems extinctions of native species Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-31 Discussion question 1: What are the current hypotheses for the loss of Australian megafauna? Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-32 Prototheria: the platypus and echidnas • Endemic to Australia • Fossil representatives known from South America • Display many primitive features – – – – egg-laying secrete milk from glands with no nipples cloaca reptilian features • But also display specialisations – sense weak electric fields to locate prey Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-33 Metatheria: marsupials • Present marsupial fauna of Australia includes four orders – Dasyuromorphia and Pelamelemorphia have more than one pair of incisors in lower jaw. Include carnivores and omnivores, e.g. quolls, dunnarts, Antechinus, Tasmanian devil, numbat – Diprotodontia are herbivores with one pair of incisors in lower jaw, e.g. koalas, wombats, possums, gliders, kangaroos, wallabies, bettongs, potoroos – Notoryctemorphia, the marsupial moles Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-34 Discussion question 2: What proportion of Australian mammals are marsupials? Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-35 Fig. 41.36: In the pouch of an echidna Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-36 Eutheria: bats and rats Eutherians comprise a large number of endemic fauna belonging to two orders • Chiroptera (bats) – fruit and blossom bats and flying foxes (suborder Megachiroptera) are large herbivores – small predatory bats (suborder Microchiroptera) hunt using echolocation • Rodentia (rats) – >50 species of native rodents, all family Muridae – diversified over relatively short period (last 15 million years) after dispersal from the north Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-37 Summary • The break-up of Gondwana influenced the evolution of Australia’s biota • The evolution of Australia’s flora and fauna was influenced by increased aridity and isolation • Relic Gondwanan components of Australia’s biota are confined to rainforest habitats • The remaining biota has evolved from Gondwanan ‘stock’ and diversified, filling niches in temperate and more arid environments • Australia’s climate varies with latitude, providing a range of different environments Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 41-38
