Biogeography - Cockrell - Tarleton State University

Michelle Cockrell
 Why is a species or higher taxonomic group confined to
its present range?
What enables a species to live where it does, & what
prevents it from colonizing other areas?
What role does geographic variation in climate,
topography, & interactions with other organisms play in
limiting the distribution of a species?
How do different kinds of organisms replace each other
as we go up a mountain or move from a rocky shore to a
sandy beach nearby?
How does a species come to be confined to its present
What are a species’ closest relatives, & where can they be
found? Where did its ancestors live?
 How have historical events – such as continental drift,
Pleistocene glaciation, & recent climatic change –
shaped a species’ distribution?
Why are animals and plants of large, isolated regions –
such as Australia, New Caledonia, & Madagascar – so
Why are some groups of closely related species confined
to the same region, while others are found on opposite
sides of the world?
Why are there so many more species in the tropics than
at temperate or arctic latitudes?
How are isolated oceanic islands colonized, & why are
there nearly always fewer species on islands than in the
same kinds of habitats on continents?
Biogeography is:
 The study of the distributions of organisms in space
and time.
 How does biological diversity vary over the surface of the
 Attempts to ask and answer: Which? Where? How?
Why? And Why Not?
 Includes plant and animal species; in their past &
present habitat, interim living sites, and/or survival
 Aristotle – climate and geography determined an organism’s form
 George-Louis LeClerk, Compte de Buffon –
 1st to offer a method to explain distribution patterns
 Organisms changed over time to get along with their environment
 1st principle – environmentally similar but isolated regions have distinct
assemblages of mammals & birds (Buffon’s Law)
 Augustin Pyramus de Candolle –
 beginnings of ecological and historical biogeography
 Recognized limiting factor of competition & problem of dispersal
 Phillip Lutley Schlater – each species created within & over the
geographical area which it now occupies
 Charles Darwin –
 suggests that animals change to fill the niche available to them
 Suggests that some of the differences between floras & faunas of the
separate continents might have resulted from their having separate
evolutionary histories.
History cont’d
 Alfred Russel Wallace –
 created 6 biogeographic regions based on the congruent patterns of
endemic species
 Identified & commented on many aspects of biogeography that still occupy
us today:
 Effects of climate, extinctions, dispersal, competition, predation &
adaptive radiation
 Need to be knowledgeable about past & present faunas, fossils &
 Distribution of organisms might indicate land connections
History cont’d
 Alfred Lothar Wegener –
 Proposed continents were once connected = Pangea
History cont’d
 Leon Croizat –
 “Earth and life evolve together.”
Concept of a dynamic Earth evolving along with the
organisms that inhabit it = Panbiogeography
 Rejected concept of origin in a limited area & that of
dispersal. Organisms always occupied the areas where
we see them. Idea of vicariance.
 Used a vast array of distributional data, representing
each biogeographical pattern as a ‘track’, connecting its
known area of distribution. Tracks of similar taxa
combined to form a generalized track that connected
different regions of the world.
 Earth’s geography still assumed
to be stable. Unable to explain
the distribution of the
glossopterus flora.
 60’s – Invention of techniques
that used magnetized particles
in rocks to trace movement of
the rocks & of the land masses
in which they lay
Century cont’d
 If continents never moved, these “fossil compasses” should all point to
present magnetic poles
 Types of rocks laid down in the continents also shows this.
 Also supported and confirmed by study of the ocean floor.
Divisions in Biogeography
 Ecological biogeography – study of distributions &
geographic variation of biotas, with special emphasis
on the influences of interations between organisms
and their abiotic and biotic environments.
 Historical biogeography – study of development of
lineages and biotas including their origin, dispersal
and extinction
 9 basic approaches
Patterns of Interest
 Endemism – How did a taxa come to be endemic in an
Provincialism – If multiple taxa share same endemism, do
they share same historical cause for present distribution?
Disjunction – Taxon on both sides of a barrier, is said to
have disjunct distribution
Phylogeny – Hypothesis about distribution, also implicitly
makes a statement about phylogeny.
Fossil record – Rich source of data on past distributions.
Historical Geology – Geologic action has a profound
evolutionary effect. (continents coming together & moving
apart; sea level rising & falling, glacial ice)
Processes of Biogeography
 Dispersal – movement of
organisms away from their
point of origin. Basis that taxa
are distributed via physiological
adaptation and locomotion on a
static Earth.
 Vicariance – some barrier to
genetic exchange causes the
separation of the related taxa.
Proposed in response to the
discovery of a dynamic Earth.
Organisms are forced to move
(rising sea level) or move
unwittingly (continental drift).
Processes of Biogeography
 Speciation – evolutionary development of a biological
species, as by geographical isolation of a group of
individuals from the main stock. Formation of a new
biological species by the development or branching of
one species into 2 or more genetically distinct ones.
 Extinction – fact of being extinguished; suppressed;
coming to an end or dying out
 Naturally integrative field of study that encompasses a
broad range of methods, data, habitats, and organisms.
 Helps us understand our planet; its geography, geology,
and organisms, where they have interacted through time,
evolving together to form the places we know today.
 Comparative science that interprets the complexity of
relationships and distributions of life on earth with respect
to its geological history.
 Common goal: to understand the relationship between life
and its distribution.
Literature Cited
 Cox, C. B. & Moore, P.D. 2005. 7th ed. Biogeography: An Ecological and
Evolutionary Approach. Blackwell Publishing.
Crisci, J.V., Katinas, L., & Posadas, P. 2003. Historical Biogeography, An
Introduction. Harvard University Press.
Huggett, R. J. 2004. 2nd ed. Fundamentals of Biogeography. Routledge.
Lomolino, M.V., Riddle, B.R. & Brown, J. H. 2006. 3rd ed. Biogeography. Sinauer
Associates, Inc.
Parenti, L, & Ebach, M 2009, Comparative Biogeography : Discovering And
Classifying Biogeographical Patterns Of A Dynamic Earth, University of
California Press, eBook Collection (EBSCOhost).
Williams, D, Ebach, M, & Nelson, G 2008, Foundations Of Systematics And
Biogeography, Springer, eBook Collection (EBSCOhost)

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