a. Isolation correlates with uniqueness

1
Island Biogeography I. Their Historical
Relevance A. Darwin - Galapagos - Sept-Oct,
1835
a. Isolation correlates with uniqueness b.
islands are dominated by dispersive forms
2
Island Biogeography I. Their Historical
Relevance A. Darwin - Galapagos - Sept-Oct,
1835
a. Isolation correlates with uniqueness b.
islands are dominated by dispersive forms c.
there are even different species/varieties on
different islands
3
Tortoises
 Genus species race Island   Geochelone
elephantopus elephantopus Floreana (extinct) "
" not described Santa Fe (extinct) " "
phantastica Fernandina (extinct) " "
wallacei Rabida (extinct) " "
hoodensis Espanola " " abingdoni Pinta "
" ephippium Pinzon " " chatamensis San
Cristobal " " darwini Santiago " "
vicina Volcan Cerro Azul Isabela " "
guntheri Volcan Sierra Negra, Isabela " "
vandenburghi Volcan Alcedo, Isabela " "
microphyes Volcan Darwin, Isabela " "
becki Volcan Wolf, Isabela " "
porteri Santa Cruz
4
Tortoises
5
- Finches
6
"Seeing this gradation and diversity of structure
in one small, intimately related group of birds,
one might really fancy that from an original
paucity of birds in this archipelago, one species
had been taken and modified for different ends."
7
- Mockingbirds
8
- Mockingbirds Darwin classified four varieties
of one species
One species
9
- Mockingbirds John Gould, the premiere
ornithologist of the day, classified these as
four species
10
- Mockingbirds Darwin began to think could the
variation WITHIN species eventually lead to
variation BETWEEN species?
Could organisms in a species become so different
that they become different species?
11
Island Biogeography I. Their Historical
Relevance A. Darwin - Galapagos - Sept-Oct,
1835
- How did these animals get here?
Everything points to migration from Americas -
But if ancestors migrated from Americas, then
the species must have changed over time into
the species we observe there today. Because
they are not the same.
12
Island Biogeography I. Their Historical
Relevance A. Darwin - Galapagos - Sept-Oct,
1835
- How did these animals get here?
Everything points to migration from Americas -
But if ancestors migrated from Americas, then
the species must have changed over time into
the species we observe there today. Because
they are not the same. HOW do they come to
be different?? Of course, although Darwin was
thinking these thoughts in 1838-1844, he did not
publish his ideas until 1859. And in between,
another naturalist was making significant
contributions...
13
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel Wallace
14
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History.
15
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth...
Class Aves
16
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth, while smaller ones, such as families
and genera, are frequently confined to one
portion, often to a very limited district.
Class Aves
Family Trochilidae (Hummingbirds)
17
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth, while smaller ones, such as families
and genera, are frequently confined to one
portion, often to a very limited district.
Class Aves
Family Trochilidae (Hummingbirds)
Archilochus spp.
Selasphorus spp.
18
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth, while smaller ones, such as families
and genera, are frequently confined to one
portion, often to a very limited district. 2. In
widely distributed families the genera are often
limited in range in widely distributed genera,
well-marked groups of species are peculiar to
each geographical district.
19
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth, while smaller ones, such as families
and genera, are frequently confined to one
portion, often to a very limited district. 2. In
widely distributed families the genera are often
limited in range in widely distributed genera,
well-marked groups of species are peculiar to
each geographical district. 3. When a group is
confined to one district, and is rich in species,
it is almost invariably the case that the most
closely allied species are found in the same
locality or in closely adjoining localities, and
that therefore the natural sequence of the
species by affinity is also geographical.
20
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History. 1. Large groups, such as
classes and orders, are generally spread over the
whole earth, while smaller ones, such as families
and genera, are frequently confined to one
portion, often to a very limited district. 2. In
widely distributed families the genera are often
limited in range in widely distributed genera,
well-marked groups of species are peculiar to
each geographical district. 3. When a group is
confined to one district, and is rich in species,
it is almost invariably the case that the most
closely allied species are found in the same
locality or in closely adjoining localities, and
that therefore the natural sequence of the
species by affinity is also geographical. 4. In
countries of a similar climate, but separated by
a wide sea or lofty mountains, the families,
genera and species of the one are often
represented by closely allied families, genera
and species peculiar to the other. (different
from)
21
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1855. On the law that has regulated the
introduction of new species. Annals and Magazine
of Natural History.
Wallace wrote "Every species has come into
existence coincident both in space and time with
a pre-existing closely allied species."
22
Wallace wrote "Every species has come into
existence coincident both in space and time with
a pre-existing closely allied species."
38 Birds of Paradise - Indonesia
23
Wallace wrote "Every species has come into
existence coincident both in space and time with
a pre-existing closely allied species."
34 species - Tenrecs (Tenrecidae) - Madagascar
24
Wallace wrote "Every species has come into
existence coincident both in space and time with
a pre-existing closely allied species." "Saint
Helena is a very ancient island having obtained
an entirely peculiar, though limited, flora. On
the other hand, no example is known of an island
which can be proved geologically to be of very
recent origin and yet possesses generic or family
groups, or even many species peculiar to
itself."
70 species of native flora 60 species are
endemic, and there are 10 endemic genera.
Dicksonia arborescens
25
Wallace wrote "Every species has come into
existence coincident both in space and time with
a pre-existing closely allied species." "Saint
Helena is a very ancient island having obtained
an entirely peculiar, though limited, flora. On
the other hand, no example is known of an island
which can be proved geologically to be of very
recent origin and yet possesses generic or family
groups, or even many species peculiar to
itself." "In all those cases in which an island
has been separated from a continent, or raised by
volcanic or coralline action from the sea... in a
recent geological epoch, the phænomena of
peculiar groups or even of single representative
species will not exist."
26
Wallace wrote "Why are the genera of Palms and
of Orchids in almost every case confined to one
hemisphere? Why are the closely allied species of
brown-backed Trogons all found in the East, and
the green-backed in the West? Why are the Macaws
and the Cockatoos similarly restricted? Insects
furnish a countless number of analogous
examples--the Goliathi of Africa, the
Ornithopteræ of the Indian islands, the
Heliconidæ of South America, the Danaidæ of the
East, and in all, the most closely allied species
found in geographical proximity. The question
forces itself upon every thinking mind,--why are
these things so? They could not be as they are,
had no law regulated their creation and
dispersion."
27
Wallace wrote "Why are the genera of Palms and
of Orchids in almost every case confined to one
hemisphere? Why are the closely allied species of
brown-backed Trogons all found in the East, and
the green-backed in the West? Why are the Macaws
and the Cockatoos similarly restricted? Insects
p. 190 furnish a countless number of
analogous examples--the Goliathi of Africa, the
Ornithopteræ of the Indian islands, the
Heliconidæ of South America, the Danaidæ of the
East, and in all, the most closely allied species
found in geographical proximity. The question
forces itself upon every thinking mind,--why are
these things so? They could not be as they are,
had no law regulated their creation and
dispersion." - More endemics on isolated
islands - More endemics on old islands -
Migration and speciation in geographic isolation
explains why allied species have restricted
distributions
28
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural History.
29
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural
History. "This view of the origin of the Aru
fauna is further confirmed by considering what it
is not, as well as what it is its deficiencies
teach as much as what it possesses. There are
certain families of birds highly characteristic
of the Indian Archipelago in its western and
better-known portion. In the Peninsula of
Malacca, Sumatra, Java, Borneo and the Philippine
Islands, the following families are abundant in
species and in individuals. They are everywhere
common birds. They are the Buceridæ, Picidæ,
Bucconidæ, Trogonidæ, Meropidæ, and Eurylaimidæ
but not one species of all these families is
found in Aru, nor, with two doubtful exceptions,
in New Guinea. The whole are also absent from
Australia."
30
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural
History. "To complete our view of the subject, it
is necessary also to consider the Mammalia, which
present peculiarities and deficiencies even yet
more striking. Not one species found in the great
islands westward inhabits Aru or New Guinea. With
the exception only of pigs and bats, not a genus,
not a family, not even an order of mammals is
found in common. No Quadrumana, no Sciuridæ, no
Carnivora, Rodentia, or Ungulata inhabit these
depopulated forests. With the two exceptions
above mentioned, all the mammalia are Marsupials
in the great western islands there is not a
single marsupial! A kangaroo inhabits Aru (and
several New Guinea), and this, with three or four
species of Cuscus, two or three little rat-like
marsupials, a wild pig and several bats, are all
the mammalia I have been able either to obtain or
hear of. "
31
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural
History. "Physics is the only real science. The
rest are just stamp collecting."-- Ernest
Rutherford "if this highest branch of our
science were more frequently alluded to by
writers on natural history ...the too prevalent
idea--that Natural History is at best but an
amusement, a trivial and aimless pursuit, a
useless accumulating of barren facts,--would give
place to more correct views of a study, which
presents problems as vast, as intricate, and as
interesting as any to which the human mind can be
directed, whose objects are as infinite as the
stars of heaven and infinitely diversified, and
whose field of research extends over the whole
earth, not only as it now exists, but also during
the countless changes it has undergone from the
earliest geological epochs."
32
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural History.
33
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1857. On the Natural History of the Aru
Islands. Annals and Magazine of Natural History.
34
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1859. On the Zoological Geographyof the
Malay Archipelago. Proceedings of the Linnean
Society "To define exactly the limits of the two
regions where they are (geographically) most
intimately connected, I may mention that during a
few days' stay in the island of Bali I found
birds of the genera Copsychus, Megalaima, Tiga,
Ploceus, and Sturnopastor, all characteristic of
the Indian region and abundant in Malacca, Java,
and Borneo while on crossing over to Lombock,
during three months collecting there, not one of
them was ever seen neither have they occurred in
Celebes nor in any of the more eastern islands I
have visited. Taking this in connexion with the
fact of Cacatua, Tropidorhynchus, and Megapodius
having their western limit in Lombock, we may
consider it established that the Strait of
Lombock (only 15 miles wide) marks the limits and
abruptly separates two of the great Zoological
regions of the globe."
35
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace. 1859. On the Zoological Geographyof the
Malay Archipelago. Proceedings of the Linnean
Society
15 miles
36
Island Biogeography I. Their Historical
Relevance A. Darwin B. Alfred Russel
Wallace C. Summary - Isolated islands have
fewer species/genera than continental islands -
Isolated islands have more endemism than
continental islands - Old islands have more
species and more endemism than new islands -
Large islands have more species than small
islands
37
Diversity Patterns and Processes I. Pattern 1
Diversity is Inversely Correlated
with Latitude II. Pattern 2 Diversity Changes
with Time III. Pattern 3 Diversity Increases
with Area
38
III. Pattern 3 Diversity Increases with
Area "species - area relationship"
39
S CAz log10S log10 C z log10 A where C is
the y intercept and z is the slope of the line.
40
III. Pattern 3 Diversity Increases with
Area "species - area relationship"
Breedings Birds - North Am.
41
III. Pattern 3 Diversity Increases with
Area "species - area relationship"
Number of Bat Species log(N)
Island Area log(square km)
42
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III. Pattern 3 Diversity Increases with Area -
WHY? MacArthur and Wilson (1967) THEORY OF ISLAND
BIOGEOGRAPHY
Edward O. Wilson Prof. Emer., Harvard
Robert MacArthur 1930-1972
45
III. Pattern 3 Diversity Increases with Area -
WHY? MacArthur and Wilson (1967) THEORY OF ISLAND
BIOGEOGRAPHY - Species Richness is a balance
between COLONIZATION (adds species) and EXTI
NCTION (subtracts species)
46
III. Pattern 3 Diversity Increases with Area -
Colonization Increases with Area - larger
target - more habitats
Mainland
47
III. Pattern 3 Diversity Increases with
Area confirmation greater immigration rate on
larger islands
48
III. Pattern 3 Diversity Increases with Area -
Colonization Increases with Area - larger
target - more habitats
49
III. Pattern 3 Diversity Increases with Area -
Colonization Increases with Area - larger
target - more habitats (except very small)
Niering, W.A. 1963. Terrestrial ecology of
Kapingamarangi Atoll, Caroline Islands.
Ecological Monographs 33131-160.
50
III. Pattern 3 Diversity Increases with Area -
Colonization Increases with Area - larger
target - more habitats - Extinction Decreases
with Area - more food means larger populations
that are less likely to bounce to a size of "0"
(extinction)
51
III. Pattern 3 Diversity Increases with Area -
Extinction Decreases with Area
Reduced Turnover on larger islands
Wright, S.J. 1980. Density compensation in island
avifaunas. Oecologia 45 385-389.     Wright,
S. J. 1985. How isolation affects rates of
turnover of species on islands. Oikos 44331-340.
   
52
III. Pattern 3 Diversity Increases with Area
COL - large
RATE
EXT - small
COL - small
EXT - large
SMALL
LARGE
species richness
53
III. Pattern 3 Diversity Increases with Area -
Colonization Decreases with Distance - fewer
species can reach
Mainland
54
III. Pattern 3 Diversity Increases with
Area greater immigration rate on close islands
saturation is the of species found on a patch
of mainland that size
55
III. Pattern 3 Diversity Increases with Area -
Extinction Increases with Distance -
recolonization less likely at distance
Mainland
"Rescue Effect"
56
III. Pattern 3 Diversity Increases with Area -
Extinction Increases with Distance -
recolonization less likely at distance
Wright, S.J. 1980. Density compensation in island
avifaunas. Oecologia 45 385-389.     Wright, S.
J. 1985. How isolation affects rates of turnover
of species on islands. Oikos 44331-340.
57
III. Pattern 3 Diversity Increases with Area
COL - close
RATE
EXT - far
COL - far
EXT - close
far
close
species richness
58
III. Pattern 3 Diversity Increases with Area -
59
equilibria
60
equilibria and turnover
61
III. Pattern 3 Diversity Increases with Area
62
III. Pattern 3 Diversity Increases with Area
Dramatic evidence that, although the communities
had recovered in terms of species richness, the
composition was very different with typically
about 80 of the species turning over.
63
III. Pattern 3 Diversity Increases with Area -
Why is this important?