41-1 Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox,...
-
Upload
sharleen-pope -
Category
Documents
-
view
232 -
download
4
Transcript of 41-1 Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox,...
41-1Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Part 6: Ecology
Chapter 41: Australian biota
41-2Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-3Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.4: Sea-floor spreading
41-4Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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)
41-5Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Ancient forests: the Triassic, Jurassic and Cretaceous
• By the Triassic (230 mya) Glossopteris forests disappeared from fossil record
• Forked-frond seed ferns (Dicroidium), early conifers and cycad fossils appear 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
41-6Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Forests at the end of the CretaceousClimate 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
41-7Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The Cenozoic era: climate change• 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
41-8Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The Cenozoic era: land and 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
41-9Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.6: Laterite
Copyright © Professor Pauline Ladiges, University of Melbourne
41-10Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The Cenozoic era: 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
41-11Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-12Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Arrival of humans—when?
• 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
41-13Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.10: Vegetation changes associated with increased burning
41-14Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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)
41-15Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.12: Australian climatic regions
41-16Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Modern Australian environments—marine• Australia is an island continent surrounded by the
Pacific, Southern and Indian Oceans• Continental shelf is 15–400 km wide• Outer edge of slope is about 150 m deep• Coastlines consist of rocky shore (in South and
East), sandy shores, muddy shores with seagrass meadows and mangroves, and coral reefs
41-17Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Marine biodiversity—flora
• Rhodophyta (red algae) – includes many endemic species– growing 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)
41-18Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Marine biodiversity—fauna
• Fish: 3 500 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
41-19Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-20Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-21Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Proteaceae: the banksia family
• Includes Grevillea, Telopea, Macadamia, Banksia• Proteacaea are a Gondwanan group, i.e. occur 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
41-22Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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. 41.25)
• Root symbionts increase nitrogen availability
41-23Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.25a: Phyllodinous acacia
41-24Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.25b: Acacia longifolia
41-25Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Fig. 41.25c: Acacia mearnsii
41-26Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-27Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Biogeographic patterns—frogs
• Frogs (order Anura) (and mammals, class Mammalia) have poor powers of dispersal over seawater, so provide 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
41-28Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
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
41-29Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
Adaptive radiation in mammals
• Australia is only continent where monotremes (Prototheria), marsupials (Metatheria) and placental mammals (Eutheria) are represented
• Terrestrial and marine mammals are very diverse• First introduced species was the dingo, 7000 years
ago• Introduced species (incl. humans) have had
profound effect on Australian ecosystems extinctions of native species
41-30Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The Prototheria: platypus and echidna
• Endemic to the Australian plate• 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
41-31Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The Metatheria: marsupials
• Present marsupial fauna of Australia includes 4 orders
– Dasyuromorphia and Pelamelemorphia have more than 1 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
41-32Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint
The 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 yrs)
after dispersal from the north