Biogeography
Biogeography = the distribution of species
Captain Cook (1728-1779):
o In 1766, Cook takes command of the Endeavour for a series of
voyages of discovery that would take the ship around the
world 3 times.
o In 1770, after circumnavigating New Zealand, Cook reaches
the southeast coast of an unexplored continent – he is the first
European to visit the east coast.
o Australia: along with Cook is a naturalist named Joseph Banks,
who makes observations of the flora and fauna. Banks
describes species like the Acacia and Eucalyptus.
o On July 12 1770, Banks spots a strange animal: the “Kanguru”.
It chews grass like an antelope but bounds on long hind legs,
and gives birth to tiny young that it raises in a pouch. Australia
would seem to provide ideal habitats for animals like deer,
horses and camels – instead, it has the kanguru.
o Australia’s mammal fauna is strange: the kangaroo’s cousins –
the Australodelphian marsupials e.g. marsupial mole,
Tasmanian devil, marsupial mouse, gliding possum, koala &
wombat.
o Monotremes: the duck-billed platypus is a toothless mammal
with an electroreceptive (detects electrical fields) beak, and
venomous spines. The echidna is a burrowing anteater. Both
lay eggs instead of giving birth to live young.
o Other strange animals include giant flightless birds (the emu
and cassowary) found nowhere else, strange reptiles such as
the legless pygopod which looks like a snake but is a legless
gecko, and the Australian lungfish which is unlike anything
alive today.
o In Cook’s day, Creationism was the dominant idea – why would
God need to make a completely different set of animals for
Australia? Why do we not find a single mammal common to
Europe and Australia or South America? The conditions of life
are nearly the same, so that a multitude of European animals
and plants have become naturalised in America and Australia.
1.Darwin, Wallace and the discovery of
biogeography:
, o It was Darwin’s voyage on the HMS Beagle in 1831-1836 that
shed light on why species lived where they did.
o The Galapagos Islands: the Galapagos consist of 21 volcanic
islands and islets spread out along the equator. It was the
Galapagos fauna that got Darwin thinking – not finches, but
mammals.
o Only one species of Galapagos land mammal: the
Galapagos Rice Rat!
o Is it possible the environment isn’t conductive to mammals?
Clearly not – once introduced to the Galapagos, goats thrived,
almost destroying the ecosystem in the process. A similar
argument for Australia and placentals, given the success of
invasive rabbits.
o Turtles: Darwin assumed that there was only one turtle
species, but in fact there were many different species and you
could tell where they came from just by the shape of the shell.
o Endemicity: islands just a few miles away have the same
habitats but completely different turtle species.
o Darwin’s insight: environmental conditions don’t drive
distributions. Instead, geographic barriers – oceans and
mountains – are primarily responsible for the distribution of
different groups.
o Alfred Russell Wallace: unlike Darwin, who was
independently wealthy, Wallace was poor – he had to support
his scientific passion by collecting specimens and then selling
them to collectors. In a fit of malarial fever, he hit upon the
basic idea of natural selection – although Dawrin got there first
and had done far more work. Wallace’s other enduring
contribution is to biogeography – he was the first to map out
the distribution of species. He broke the world into a series of
biogeographic realms: Palearctic, Nearctic, Neotropical,
Ethiopian, Oriental and Australian.
o Darwin and Wallace realised these distributions meant that
species’ ranges were controlled by geography, not habitat
type. The fact that physical barriers to movement (oceans,
rivers, mountains, deserts) controlled species distributions
must mean that groups of animals and plants, at one point in
the past, had moved to occupy their present ranges until they
couldn’t move. Present ranges of animals and plants resulted
from movement of species over time.
Biogeography = the distribution of species
Captain Cook (1728-1779):
o In 1766, Cook takes command of the Endeavour for a series of
voyages of discovery that would take the ship around the
world 3 times.
o In 1770, after circumnavigating New Zealand, Cook reaches
the southeast coast of an unexplored continent – he is the first
European to visit the east coast.
o Australia: along with Cook is a naturalist named Joseph Banks,
who makes observations of the flora and fauna. Banks
describes species like the Acacia and Eucalyptus.
o On July 12 1770, Banks spots a strange animal: the “Kanguru”.
It chews grass like an antelope but bounds on long hind legs,
and gives birth to tiny young that it raises in a pouch. Australia
would seem to provide ideal habitats for animals like deer,
horses and camels – instead, it has the kanguru.
o Australia’s mammal fauna is strange: the kangaroo’s cousins –
the Australodelphian marsupials e.g. marsupial mole,
Tasmanian devil, marsupial mouse, gliding possum, koala &
wombat.
o Monotremes: the duck-billed platypus is a toothless mammal
with an electroreceptive (detects electrical fields) beak, and
venomous spines. The echidna is a burrowing anteater. Both
lay eggs instead of giving birth to live young.
o Other strange animals include giant flightless birds (the emu
and cassowary) found nowhere else, strange reptiles such as
the legless pygopod which looks like a snake but is a legless
gecko, and the Australian lungfish which is unlike anything
alive today.
o In Cook’s day, Creationism was the dominant idea – why would
God need to make a completely different set of animals for
Australia? Why do we not find a single mammal common to
Europe and Australia or South America? The conditions of life
are nearly the same, so that a multitude of European animals
and plants have become naturalised in America and Australia.
1.Darwin, Wallace and the discovery of
biogeography:
, o It was Darwin’s voyage on the HMS Beagle in 1831-1836 that
shed light on why species lived where they did.
o The Galapagos Islands: the Galapagos consist of 21 volcanic
islands and islets spread out along the equator. It was the
Galapagos fauna that got Darwin thinking – not finches, but
mammals.
o Only one species of Galapagos land mammal: the
Galapagos Rice Rat!
o Is it possible the environment isn’t conductive to mammals?
Clearly not – once introduced to the Galapagos, goats thrived,
almost destroying the ecosystem in the process. A similar
argument for Australia and placentals, given the success of
invasive rabbits.
o Turtles: Darwin assumed that there was only one turtle
species, but in fact there were many different species and you
could tell where they came from just by the shape of the shell.
o Endemicity: islands just a few miles away have the same
habitats but completely different turtle species.
o Darwin’s insight: environmental conditions don’t drive
distributions. Instead, geographic barriers – oceans and
mountains – are primarily responsible for the distribution of
different groups.
o Alfred Russell Wallace: unlike Darwin, who was
independently wealthy, Wallace was poor – he had to support
his scientific passion by collecting specimens and then selling
them to collectors. In a fit of malarial fever, he hit upon the
basic idea of natural selection – although Dawrin got there first
and had done far more work. Wallace’s other enduring
contribution is to biogeography – he was the first to map out
the distribution of species. He broke the world into a series of
biogeographic realms: Palearctic, Nearctic, Neotropical,
Ethiopian, Oriental and Australian.
o Darwin and Wallace realised these distributions meant that
species’ ranges were controlled by geography, not habitat
type. The fact that physical barriers to movement (oceans,
rivers, mountains, deserts) controlled species distributions
must mean that groups of animals and plants, at one point in
the past, had moved to occupy their present ranges until they
couldn’t move. Present ranges of animals and plants resulted
from movement of species over time.
