Transcript Australian biota - McGraw Hill Higher Education

Part 6: Ecology
Chapter 41: Australian biota
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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
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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)
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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
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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
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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
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Fig. 41.6: Laterite
Copyright © Professor Pauline Ladiges, University of Melbourne
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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
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Slides prepared by Karen Burke da Silva, Flinders University
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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
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41-11
Fig. 41.8: Glacial period sea level
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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
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Slides prepared by Karen Burke da Silva, Flinders University
41-13
Fig. 41.10: Vegetation changes associated
with increased burning
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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
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41-15
Fig. 41.12: Australian climatic regions
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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
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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
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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
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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
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PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint
Slides prepared by Karen Burke da Silva, Flinders University
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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
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41-22
Fig. 41.24a: Phyllodinous acacia
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41-23
Fig. 41.24b: Acacia longifolia
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41-24
Fig. 41.24c: Acacia mearnsii
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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
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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
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41-27
Fig. 41.30: Myobatrachid frog
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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
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41-29
Fig. 41.32b: Australian bearded
dragon
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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
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Discussion question 1:
What are the current hypotheses for the loss of
Australian megafauna?
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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
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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
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Discussion question 2:
What proportion of Australian mammals are
marsupials?
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41-35
Fig. 41.36: In the pouch of an echidna
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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
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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