Organic Evolution - Lecture 8/april 18 - Biogeography I

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Biogeography is…

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…the study of the distribution of organisms in space through time
Addresses the distributional patterns of species and processes that produce those distributions
…an endeavor that predates ideas of natural selection and plate tectonics.
For example, ancient cultures may have wanted to know where to reliably find certain sources of food or medicine.

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“Kinds” of biogeography (2)

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Descriptive biogeography - Concerned with finding the ranges of species, genera, families, etc.

Interpretive biogeography - Concerned with taking the data gathered in descriptive biogeography and developing hypotheses, predictions and explanations about organisms.

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Two types of interpretive biogeography

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1. Ecological biogeography - The study of mechanisms which govern the distribution of organisms. Explains why organisms live where they do with reference to physical factors of the environment such as temperature, elevation, and latitude.

2. Historical biogeography - The study of the spatial and temporal distributions of organisms which attempts to provide explanations for these distributions based on past historical events.

These two areas are not mutually exclusive. After all, many historical patterns have, ultimately, ecological bases, and distribution has a historical as well as ecological component. However, the goals and interests of the ecological biogeographer lie more with ecology than with evolution.

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More on descriptive biogeography

Back 4

Determining the ranges of organisms and what taxa are present within a certain geographic area.
In the 1700's & 1800's, the main interest naturalists had in biogeography was to describe where plants and animals lived and the physical factors of the environment.

It was Alfred R. Wallace who first noticed that the distribution of plants and animals revealed the existence of six major biogeographical realms, each characterized by the presence of unique taxa:

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Major Biogeographical Provinces/realms (6)

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1. Paleartic
2. Neartic
3. Neotropical
4. Ethiopian
5. Oriental
6. Australian

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1. Paleartic

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Europe, Africa north of the Sahara, and Asia north of the Himalayas and Nan-ling mountains. The typical animals: oxen, sheep, goats, magpies.

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2. Neartic

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Greenland and North America north of the Northern Plateau in Mexico. The typical animals: prairie dogs, raccoons, turkeys, mountain goats, pronghorn antelope.

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3. Neotropical

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South and Central America, southern Mexico, and the West Indies. The typical animals: alpacas, llamas, prehensile-tailed monkeys, tapirs, sloths.

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4. Ethiopian

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Africa south of the Sahara and Madagascar. The typical animals: gorilla, zebra, hippopotamus, giraffe.

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5. Oriental

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India, Sri Lanka, southeast Asia, southern China, the Malay Peninsula, and some islands of the East Indies (Philippines, Java, Borneo, Bali). The typical animals: orangutan, Indian elephant, black panther.

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6. Australian

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Australia, New Zealand, and New Guinea. The typical animals: kangaroos, wombats, koala, duck-billed platypus, echidna.

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Species distributions

Back 12

Fundamental to biogeography
Observations: no species is found everywhere and individuals of a species are not randomly distributed across the globe
A species range is more difficult to construct than you might initially think

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Special kinds of distributions (are not antonyms) (2)

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Disjunct distribution: range of a particular taxon (species or genus or family…) that is not contiguous

Endemic distribution: range of a particular taxon is confined to a particular area
“Some species of giant tortoise are endemic to the Galapagos Islands.”
“Mesodon normalis is a ubiquitous snail at lower elevations. It is endemic to the Appalachian Mountains .”

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Historical biogeog. - Organisms live where they do for one of two reasons:

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(1) their ancestors originally occurred somewhere else, and later they, or their descendants, dispersed into new areas where their descendants survive today, or
(2) their ancestors originated there and their descendants survive there today.

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Historical biogeog. - Two reasons characterize two types of historical explanation:

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1. Dispersal - the organism moved to the area by some mechanism such as motility, rafting, etc.
2. Vicariance event - geological events, such as continental drift, cause organisms to be where they are.

Front 16

Biogeography is…

Back 16

…the study of the distribution of organisms in space through time
Addresses the distributional patterns of species and processes that produce those distributions
…an endeavor that predates ideas of natural selection and plate tectonics.
For example, ancient cultures may have wanted to know where to reliably find certain sources of food or medicine.

Front 17

“Kinds” of biogeography (2)

Back 17

Descriptive biogeography - Concerned with finding the ranges of species, genera, families, etc.

Interpretive biogeography - Concerned with taking the data gathered in descriptive biogeography and developing hypotheses, predictions and explanations about organisms.

Front 18

Two types of interpretive biogeography

Back 18

1. Ecological biogeography - The study of mechanisms which govern the distribution of organisms. Explains why organisms live where they do with reference to physical factors of the environment such as temperature, elevation, and latitude.

2. Historical biogeography - The study of the spatial and temporal distributions of organisms which attempts to provide explanations for these distributions based on past historical events.

These two areas are not mutually exclusive. After all, many historical patterns have, ultimately, ecological bases, and distribution has a historical as well as ecological component. However, the goals and interests of the ecological biogeographer lie more with ecology than with evolution.

Front 19

More on descriptive biogeography

Back 19

Determining the ranges of organisms and what taxa are present within a certain geographic area.
In the 1700's & 1800's, the main interest naturalists had in biogeography was to describe where plants and animals lived and the physical factors of the environment.

It was Alfred R. Wallace who first noticed that the distribution of plants and animals revealed the existence of six major biogeographical realms, each characterized by the presence of unique taxa:

Front 20

Major Biogeographical Provinces/realms (6)

Back 20

1. Paleartic
2. Neartic
3. Neotropical
4. Ethiopian
5. Oriental
6. Australian

Front 21

1. Paleartic

Back 21

Europe, Africa north of the Sahara, and Asia north of the Himalayas and Nan-ling mountains. The typical animals: oxen, sheep, goats, magpies.

Front 22

2. Neartic

Back 22

Greenland and North America north of the Northern Plateau in Mexico. The typical animals: prairie dogs, raccoons, turkeys, mountain goats, pronghorn antelope.

Front 23

3. Neotropical

Back 23

South and Central America, southern Mexico, and the West Indies. The typical animals: alpacas, llamas, prehensile-tailed monkeys, tapirs, sloths.

Front 24

4. Ethiopian

Back 24

Africa south of the Sahara and Madagascar. The typical animals: gorilla, zebra, hippopotamus, giraffe.

Front 25

5. Oriental

Back 25

India, Sri Lanka, southeast Asia, southern China, the Malay Peninsula, and some islands of the East Indies (Philippines, Java, Borneo, Bali). The typical animals: orangutan, Indian elephant, black panther.

Front 26

6. Australian

Back 26

Australia, New Zealand, and New Guinea. The typical animals: kangaroos, wombats, koala, duck-billed platypus, echidna.

Front 27

Species distributions

Back 27

Fundamental to biogeography
Observations: no species is found everywhere and individuals of a species are not randomly distributed across the globe
A species range is more difficult to construct than you might initially think

Front 28

Special kinds of distributions (are not antonyms) (2)

Back 28

Disjunct distribution: range of a particular taxon (species or genus or family…) that is not contiguous

Endemic distribution: range of a particular taxon is confined to a particular area
“Some species of giant tortoise are endemic to the Galapagos Islands.”
“Mesodon normalis is a ubiquitous snail at lower elevations. It is endemic to the Appalachian Mountains .”

Front 29

Historical biogeog. - Organisms live where they do for one of two reasons:

Back 29

(1) their ancestors originally occurred somewhere else, and later they, or their descendants, dispersed into new areas where their descendants survive today, or
(2) their ancestors originated there and their descendants survive there today.

Front 30

Historical biogeog. - Two reasons characterize two types of historical explanation:

Back 30

1. Dispersal - the organism moved to the area by some mechanism such as motility, rafting, etc.

2. Vicariance event - geological events, such as continental drift, cause organisms to be where they are.

*Both dispersal and vicariance can result in allopatric speciation! MAKE SURE YOU LOOK AT SLIDE 20!

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History of historical biogeography

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After 1859, many biologists thought dispersal was the main process responsible for modern distributions. They believed in different land bridges (LOOK AT SLIDE 23)

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Vicariance

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Rather than organisms actively dispersing themselves across the landscape, vicariance explanations propose that the landscape transforms and moves the organisms.
The most obvious mechanism of vicariance comes from continental drift.
Acceptance of continental drift led biogeographers to realize that vicariance also played a major role in shaping organismal distributions.

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Some biological implications of continental drift - The continents' odyssey across the globe influences evolution in a number of ways (5)

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1. It carries the plants and animals that live on the continents into new climates, thus altering their environment and often requiring new adaptations or causing extinction.
2. It may split a continent, resulting in allopatric speciation
3. When continents collide, organisms once separated come into contact with each other. This sets up new competition and coevolution interactions.
4. The position of the continents affects global climate patterns and is responsible for general warming or cooling trends.
5. Habitats are changed—coastline is formed and lost, plains become flooded with sea water, shallow seas become cut off and evaporate, etc.