Geographic Distribution of Living Species

Contributed by:
Sharp Tutor
1. What organisms are found where?
2. How are these organisms adapted to the local environment?
3. How have their distributions changed through time?
1. GEOG 215
Introduction to biogeography
Ian Hutchinson (RCB 7226)
Office phone: 778.782.3232 (campus: 23232)
email: [email protected]
TA: Julie Sabau ([email protected])
2. GEOG 215 - Housekeeping
• Course email: [email protected]
• Lecture slides and all handouts are posted
on the course web site:
• “Thumbnail” booklets available from Student
Copy Centre [Maggie Benson Bldg.] (~$12).
• All readings are from the text (MacDonald,
3. GEOG 215 - Grades, etc.
• Laboratory assignments: 25%
• Poster project: 25%
includes research journal: 5%
• Midterm exam: 20%
• Final exam: 30%
4. What is 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.
5. 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
6. 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?
7. “There’s nothing as
as biogeography”
Edward Wilson,
Emeritus Professor of Comparative Zoology, Harvard.
(quoted by David Quammen: “The Song of the Dodo” [1996])
8. Climatology Pedology
Biogeography Ecology
Is multi-
disciplinarity Palaeontology Evolution
9. Is multi-dimensionality romantic?
Evolving and mobile pieces
Time: past future
Why are the pieces laid
out as they are, and how are
their distributions changing?
Changing table-top
10. Or field work in
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11. Biogeography
Present = ecological biogeography
(climate, soil, . . .) experiment
(climate, soil, . . .) inference
Past = historical biogeography
12. GEOG 215: Course themes
Geological history Recent and future
and evolution environmental change
Life forms
The physical template Ecological communities
(climate, soils, landforms) and their dynamics
13. Given the
dazzling array
of life forms
on the planet,
how do we
proceed to
answer the
14. 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
Wilson, E.O. 1992. The Diversity of Life, Penguin. p. 35
15. Biological hierarchies
Taxonomic Ecological Trophic
order (etc.) biome top carnivores
family community carnivores
genus association herbivores
species species primary producers
subspecies Only in trophic hierarchies
where the focus is energy
population flow are species not an
essential unit
16. 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
17. 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.
Irving, L. 1953. The naming of birds by Nunamiut Eskimo. Arctic, 6, 35-43.
Berlin, B. 1966. Folk taxonomies and Biological Classification. Science, 154,
18. 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.
19. 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).
20. Linnean taxonomy
Formalized species descriptions based
on diagnostic traits
Hierarchy based on groupings of
species and genera, not splitting of
larger classes
Carl Linnaeus
Latin binomials (Genus, species)
(1707-1778) [following the Swiss botanist Bauhin {1560-1634}]
(aka Carl von Linné replace long Latin descriptions
and Carolus Linnaeus) (e.g. Sturnella magna = ‘big lark’)
21. Linnean taxonomy:
Eng: eastern meadowlark
Sp: pradero tortilla-con-chile,
Fr: sturnelle des prés
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata QuickTime™ and a
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Class: Aves (birds)
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Order: Passeriformes (perching birds)
Family: Fringillidae (finches)
Genus: Sturnella Image: Delbert Rust
Species: Sturnella magna
(Linnaeus, 1758)
Subspecies: Up to 17 subspecies recognized (indicates local
22. Linnean taxonomy: diagnostic
morphologies of related species
Sturnella magna S. neglecta
Eastern meadowlarks
(Sturnella magna) can
be distinguished
from western
(S. neglecta) by the
white (as opposed to
yellow) feathers
behind the lower
Or can they?
23. 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.
24. 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
25. “Species” in folk vs. scientific
under- 1:1 over-
differentiated differentiated
Birds (Inuit) 4
(2 names)
98 0
102 birds
Plants (Tzeltal) 82 68 50
sample of 200 plants
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)
26. Intra-specific variation in
domesticated plants and animals
Brassica oleracea
Canis familiaris
27. Intra-specific variation in snow geese
Eng: “greater” Eng: blue goose
Inuit: k(h)anguk Inuit: khavik
separate species? or
just morpho-colour phases of the same species?
29. 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)
30. Images:
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• 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.
31. 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?
32. 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
behaviour of only a tiny proportion of the
living species on Earth.
• Impossible to apply to extinct species;
interbreeding cannot be directly
33. Does DNA “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.
34. How much variation in
mtDNA is there in a taxon?
Cytochrome c
oxidase Within Within
subunit I species genus
(COI) gene
moths 0.25% 6.5%
birds 0.4% 7.9%
35. Images:
DNA 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
36. DNA barcodes: skippers
• Neotropical skipper
butterfly (Astraptes
• First described in 1775
• Ranges from south
Texas-northern Mexico
to Argentina
• Is it one species or are
there many “cryptic”
Hebert et al., 2004, Proc. Nat. Acad. Sci., 101, 14812-14817
37. DNA barcodes: skippers
• Single gene tested
from adults reared
from caterpillars in
• 10 species identified
based on significant
differences in COI
gene. Matched to
caterpillar colour
patterns and food
Hebert et al., 2004, Proc. Nat. Acad. Sci., 101, 14812-14817.
38. 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 )
39. Naming fossils:
South African hominids
Australopithecus Australopithecus
robustus? africanus? Paranthropus crassidens?
or are they all
Paranthropus robustus?
40. The Homo
A new human species
or just a local
(individual?) of Homo
How much morpho-
variation should a
paleontologist allow?
See: Hopkin, M. 2006;
Will the hobbit argument ever be resolved?
Nature, 25 August; doi:10.1038/news060821
41. “Mr T”: a composite specimen of
Triceratops in AMNH
Constructed from 14 dinosaur skeletons;
undoubtedly derived from several different species
42. 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.
43. 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
44. 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”
45. 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 sub-
46. Protecting sub-species: island populations
Q: What is the most
endangered mammal in
A: M. vancouverensis?,
M. caligata
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
47. 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.
48. Protecting sub-species: hybrids
 Restricted to Everglades of
southern Florida
 The subspecies is now a
hybrid of a population of
native North American
“cougars” and South
Florida panther American “panthers”
[Puma (Felis) concolor coryi] released into the wild