Transcript PowerPoint Presentation - GEOG 215 Introduction to biogeography

GEOG 215
Introduction to biogeography
Instructor
Ian Hutchinson (RCB 7226)
Office phone: 778.782.3232 (campus: 23232)
email: [email protected]
TA: Julie Sabau ([email protected])
GEOG 215 - Housekeeping
• Course email: [email protected]
• Lecture slides and all handouts are posted
on the course web site:
www.sfu.ca/~ianh/geog215/
• “Thumbnail” booklets available from Student
Copy Centre [Maggie Benson Bldg.] (~$12).
• All readings are from the text (MacDonald,
2003).
GEOG 215 - Grades, etc.
• Laboratory assignments: 25%
• Poster project: 25%
includes research journal: 5%
• Midterm exam: 20%
• Final exam: 30%
What is biogeography?
Biogeography:
the study of the geographical distribution
of organisms, their habitats (ecological
biogeography), and the historical and
biological factors which produced them
(historical biogeography).
Lincoln , R.J., Boxshall, G.A., and Clark, P.F. 1982.
Dictionary of Ecology, Evolution and Systematics.
Cambridge University Press.
Goals of biogeography
1. To develop natural laws and concepts that
explain biogeographic processes and account
for the development of biotic distributions.
2. To provide baseline information on the
spatial and temporal distribution of
organisms that can be used to conserve and
manage Earth’s biotic resources and
heritage.
Central questions of biogeography
• What organisms are found where?
• How are these organisms adapted
to the local environment?
• How have their distributions
changed through time?
“There’s nothing as
ROMANTIC
as biogeography”
Edward Wilson,
Emeritus Professor of Comparative Zoology, Harvard.
(quoted by David Quammen: “The Song of the Dodo” [1996])
Climatology
Geology
Is multidisciplinarity
romantic?
Pedology
Biogeography Ecology
Palaeontology Evolution
Is multi-dimensionality romantic?
Evolving and mobile pieces
(life-forms)
Time: past
Why are the pieces laid
out as they are, and how are
their distributions changing?
global
future
Changing table-top
(environment)
local
SPACE
Or field work in
exotic
locations?
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Rupununi
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Biogeography
Present = ecological biogeography
observation
ENVIRONMENT
BIOTA
(climate, soil, . . .) experiment
Time
ENVIRONMENT
(climate, soil, . . .) inference
Past = historical biogeography
BIOTA
GEOG 215: Course themes
Geological history
and evolution
Recent and future
environmental change
Life forms
The physical template
(climate, soils, landforms)
Ecological communities
and their dynamics
Given the
dazzling array
of life forms
on the planet,
how do we
proceed to
answer the
“central
questions”
Search for an “atomic” unit
“Of what then is biodiversity composed? Since antiquity
biologists have felt a need to posit an atomic unit by which
diversity can be broken apart, then described, measured,
and reassembled… Western science is built on the
obsessive … search for atomic units with which abstract
laws and principles can be derived. Scientific knowledge is
written in the vocabulary of atoms, subatomic particles,
molecules, organisms, ecosystems, and many other units,
including species. The metaconcept holding all the units
together is hierarchy, which presupposes levels of
organization.”
Wilson, E.O. 1992. The Diversity of Life, Penguin. p. 35
Biological hierarchies
Taxonomic
order (etc.)
Ecological
biome
family
community
genus
association
species
subspecies
population
individual
species
Trophic
top carnivores
carnivores
herbivores
primary producers
Only in trophic hierarchies
where the focus is energy
flow are species not an
essential unit
Some basic terminology
• Taxonomy: classification & naming of
organisms [taxis (Gr.) = “order”]
• Systematics includes evolutionary
relationships of organisms
• Ecology: how organisms interact and are
affected by their environment
• Trophic: how energy flows in an ecological
community
Towards a scientific taxonomy
Folk taxonomy:
1. Inuit in one district of Arctic Canada
have 100 names for local birds.
2. Tzeltal-language speakers in Chiapas
have 1100 names for local plants.
Sources:
Irving, L. 1953. The naming of birds by Nunamiut Eskimo. Arctic, 6, 35-43.
Berlin, B. 1966. Folk taxonomies and Biological Classification. Science, 154,
273-275.
Taxonomy in the
“Classical World”
Aristotle (384–322 BC ). formulated two
classifications, genos and eidos. Genos
referred to broad categories of animals, (e.g.
reptiles), while eidos were animals in a genos.
Aristotle's system was intentionally
hierarchical with mammals placed at the top of
the hierarchy. Aristotle’s ideas held sway (in
Europe) until the 17th century.
Early modern taxonomy
John Ray (1627–1705) introduced the term
species, which he defined (following plant
and animal breeders) as a group of
organisms capable of interbreeding and
producing fertile offspring. His taxonomy
used multiple morphological characters to
classify species (e.g. flowers, seeds, fruits
and roots for plants).
Linnean taxonomy
Formalized species descriptions based
on diagnostic traits
Hierarchy based on groupings of
species and genera, not splitting of
larger classes
Carl Linnaeus
(1707-1778)
(aka Carl von Linné
and Carolus Linnaeus)
Latin binomials (Genus, species)
[following the Swiss botanist Bauhin {1560-1634}]
replace long Latin descriptions
(e.g. Sturnella magna = ‘big lark’)
Linnean taxonomy:
Eng: eastern meadowlark
Sp: pradero tortilla-con-chile,
Fr: sturnelle des prés
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Aves (birds)
Order: Passeriformes (perching birds)
Family: Fringillidae (finches)
Genus: Sturnella
Species: Sturnella magna
(Linnaeus, 1758)
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Image: Delbert Rust
Subspecies: Up to 17 subspecies recognized (indicates local variation)
Linnean taxonomy: diagnostic
morphologies of related species
Eastern meadowlarks
(Sturnella magna)
can be distinguished
from western
meadowlarks
(S. neglecta) by the
white (as opposed to
yellow) feathers
behind the lower
mandible.
Or can they?
Sturnella magna
S. neglecta
Images: http://birds.cornell.edu/crows/mlarkdiff.htm
Why did Linnaeus base his
classification on species?
Are species real?
1. There is general agreement amongst disparate
human groups as to what constitutes separate
“sorts” of organisms, based on differential
morphology, and
2. “Like begets like” - intermediate forms are
rare.
The importance of the
species concept
“The species concept is crucial to the study of
biodiversity. It is the grail of systematic biology.
Not to have a natural unit such as the species
would be to abandon a large part of biology into
free fall. ….. Without natural species, ecosystems
could be analyzed only in the broadest terms, using
crude and shifting descriptions of the organisms
that compose them.”
Wilson, E.O. 1992. The Diversity of Life. Penguin. p. 36
“Species” in folk vs. scientific
taxonomies
underdifferentiated
Birds (Inuit)
102 birds
Plants (Tzeltal)
sample of 200 plants
1:1
overdifferentiated
4
98
0
82
68
50
(2 names)
under-differentiated = fewer names for organisms than species recognized
by science; 1:1 = correspondence; over-differentiated = more names, etc.
(mainly cultivated plants; e.g. four varieties of beans)
Intra-specific variation in
domesticated plants and animals
Brassica oleracea
Canis familiaris
Intra-specific variation in snow geese
Eng: “greater”
Inuit: k(h)anguk
“lesser”
Eng: blue goose
Inuit: khavik
separate species? or
just morpho-colour phases of the same species?
http:// www.qc.ec.gc.ca/faune/guide/html/oie_neiges_e.html
Difficulties in defining species strictly on
morphological traits led to the adoption
of the
biological species concept.
“Species are groups of actually (or
potentially) interbreeding natural
populations which are reproductively
isolated from other such groups.”
Ernst Mayr (1953)
(apply this to previous examples)
Images: http://evolution.berkeley.edu/evosite/evo101/
Meadowlarks
western
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eastern
• Western and eastern meadowlarks are almost
identical in appearance.
• Their geographical ranges overlap, but their distinct
songs prevent inter-breeding.
• The species are maintained by sexual signaling.
Merits of the biological
species concept
• Emphasises the critical importance of
evolutionary descent,
• Emphasises that species act as
discrete breeding groups - they breed
“true to type”.
• Provides a testable hypothesis - can
they produce viable offspring?
Drawbacks of the biological
species concept
• Some organisms that are morphologically
± distinct can interbreed (=“bad species”;
e.g. pines)
• We have knowledge of the breeding
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DoesDN A “barcoding”
solve the problem?
• Mitochondrial DNA indicates the genetic similarity
between organisms and can be used to establish
an evolutionary time frame;
• mtDNA is passed on from mother to offspring. If
the mutation rate is known, the ancestry of the
lineage can be estimated (e.g. “Mitochondrial Eve”
lived about
~140 000 years ago])
• Many copies per cell; a single gene is all that is
required for “barcoding” plants or animals.
How much variation in
mtDNA is there in a taxon?
Cytochrome c
oxidase
subunit I
(COI) gene
Within
species
Within
genus
moths
0.25%
6.5%
birds
0.4%
7.9%
~20x
Images: http://evolution.berkeley.edu/evosite/evo101/
DN A barcodes: meadowlarks
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• mtDNA sequencing indicates that the eastern
meadowlark (remember the 17 subspecies) consists of
two “cryptic” [i.e. difficult to differentiate] species.
COI divergence between the two = 4.8%.
Hebert et al., 2004, Pub. Lib. of Science, Biology, vol 2; issue 9
DNA barcodes: skippers
• Neotropical skipper
butterfly (Astraptes
fulgerator)
• First described in 1775
• Ranges from south
Texas-northern Mexico
to Argentina
• Is it one species or are
there many “cryptic”
species?
Hebert et al., 2004, Proc. Nat. Acad. Sci., 101, 14812-14817
DNA barcodes: skippers
• Single gene tested
from adults reared
from caterpillars in
laboratory.
• 10 species identified
based on significant
differences in COI
gene. Matched to
caterpillar colour
patterns and food
plants.
Hebert et al., 2004, Proc. Nat. Acad. Sci., 101, 14812-14817.
How does a palaeontologist assign a
species name to a fossil?
Evidence: shell or bone beds ……..
tracks or burrows.
Taxon named from:
Morphology -- yes (hominid fossils illustrate difficulties)
Breeding behaviour -- no
mtDNA -- yes (if DNA is preserved in the specimen )
Naming fossils:
South African hominids
Australopithecus
robustus?
Australopithecus
africanus?
Paranthropus crassidens?
or are they all
Paranthropus robustus?
Images: http://www.modernhumanorigins.com/robustus.html
The Homo
floresiensis
controversy:
A new human species or
just a local population
(individual?) of Homo
sapiens?
How much morphovariation should a
paleontologist allow?
See: Hopkin, M. 2006;
Will the hobbit argument ever be resolved?
Nature, 25 August; doi:10.1038/news060821
“Mr T”: a composite specimen of
Triceratops in AMNH
Constructed from 14 dinosaur skeletons;
undoubtedly derived from several different species
Species definition in use today
Organisms that share at least
one diagnostic morphological
trait; that can interbreed freely
under natural conditions, and
whose direct ancestors or
descendants can be traced in
the fossil record.
Naming species in the field
Biogeographers and field biologists recognize
the superiority of the biological species
concept, but base their field identifications
almost entirely on diagnostic morphological
criteria.
The DNA barcode project envisages that by
the end of this century everyone will own a
mini mtDNA analysis kit that will return a
species name for every organism encountered
on a walk in the woods.
Continuing problems:
what is a sub-species?
A sub-species is a geographical race that has
distinctive traits which interbreeds with
other subspecies where their ranges overlap.
“sub-species are recognized according to
whatever traits taxonomists choose to
study”
Designating sub-species
Thousands of geographical races possible
because in most species thousands of genes in
operation, and many segregated populations! The
sub-species (as a formal concept) is therefore
now essentially abandoned, but some organisms
covered by the Species-At-Risk Act (Canada)
and Endangered Species Act (U.S.) are subspecies.
Protecting sub-species: island populations
Q: What is the most
endangered mammal in
Canada?
A: M. vancouverensis?,
or
M. caligata
vancouverensis?*
See also: VI ermine (Mustela erminae anguinae)
VI water shrew (Sorex palustris brooksi)
VI wolverine (Gulo gulo vancouverensis)
*genetic analysis suggests the latter; i.e. that the Vancouver Island marmot
is a darker phase of the relatively common hoary marmot of the mainland
Protecting sub-species: local populations
Cutthroat Trout [Oncorhynchus clarkii]
 The most widespread and diverse trout species in the
western hemisphere
 15 sub-species in North America as a result of genetic
isolation (one recently extinct)
 Many of the subspecies are protected
 Rocky Mountain cutthroat [O.c. virginalis, pictured] is but
one example.
Protecting sub-species: hybrids
Florida panther
[Puma (Felis) concolor coryi]
 Restricted to Everglades of
southern Florida
 The subspecies is now a
hybrid of a population of
native North American
“cougars” and South
American “panthers”
released into the wild