Introduction to Biogeography

• Almost all places on Earth have some kind of organism living there
• No single species lives in all of those places
• Species are restricted to a small area with a narrow range of conditions
• Global biodiversity is a consequence of millions of limited species ranges overlapping and replacing each other

Introduction to Biogeography

• Biogeography is Geography (GEOG 2437)

Biogeographical Truths

• Life is found nearly everywhere
• But no species is found everywhere
• Life varies from place to place and is non-random and predictable
• Early hominins and ancient civilizations recognized patterns of life
• The recognition was essential to survival

What is Biogeography?

• The science of documenting and understanding the spatial patterns of biological diversity
• The study of the distribution of organisms in the past and present
• The study of all the patterns of geographic variation in nature
• The study of genes, communities, and ecosystems
• The study of the elements of biological diversity that vary across geographic gradients
• Gradients of area, isolation, latitude, depth, and elevation

Why Study Biogeography?

• It helps to make sense of the forces structuring the natural world
• It is a holistic discipline in the natural sciences
• It combines and synthesizes inputs from genetics, geology, paleontology, anthropology, meteorology, oceanography, and ecology
• Supports conservation
• Assesses changes in biodiversity due to habitat fragmentation or climate change
• Assesses spread and establishment of invasive species

Fundamental Terms & Concepts

• Historical Biogeography*
• Focuses on long term processes over evolutionary or geological time periods
• Larger scale geographic areas
• Higher taxonomic levels and taxa that are extinct
• Includes the history of a group and where earlier members lived
• Ecological Biogeography*
• Generally deals with shorter time periods and smaller geographic scales
• Includes extant taxa
• For example, the relationship between mountain elevation and species diversity of butterflies
• Phytogeography*
• The study of plant distributions
• Includes flora
• Zoogeography*
• The study of animal distributions
• Includes Fauna
• Highly intertwined in reality

Biogeography: Integrations

• A synthesis of biology (life science) and geography (earth science)
• Evolutionary Biology*
• Role of geographic isolation in evolution and maintaining of genetic differentiation
• Ecology, Climatology, and Physiology*
• Distributions are constrained by predators, parasites, competition for food/resources
• Distributions are constrained by physiological abilities to survive/reproduce in certain climatic conditions
• Geology*
• Geology, the study of plates tectonics, is also related to biology

Penguins and Polar Bears

• One of the central questions is why geographic ranges differ among species
• Polar bears (Ursus maritimus) range is shown in green
• Penguins (17 species in the family Spheniscidae) range is shown in red
• Polar bears and penguins ranges are restricted to the Northern and Southern Hemispheres respectively

Exploration and Biogeography

• 18th Century was the “Age of Exploration"
• Explorers encountered numerous plant and animal specimens
• This created a need for standard, systematic schemes to classify new specimens
• Carolus Linnaeus (1707-1778)*
• Created Binomial nomenclature
• Thought about the origin and spread of life
• Post creation and post-biblical flood
• Thought Animals and plants colonized down exposed slopes of Paradisical Mountain or Mt Ararat before becoming worldwide
• Georges Buffon (1707-1788)*
• Came up with Buffon's Law
• Different parts of the globe contain different species, even in similar climatic and environmental conditions
• Postulated the northern origin of all life forms and a southward spread changing climate
• Theorized organisms become improved or degenerated as they become isolated and the survival of improved forms
• Believed that the earth and its species were dynamic
• Voyages of James Cook*
• Included naturalists and explorers of the world by Europeans
• Provided information on the distributions of plants and animals during the 18th century
• Included Sir Joseph Banks
• Johann Forster Sr*
• Made important contributions to plant biogeography
• Applied Buffon’s Law applied to plants
• Found Plant diversity increases toward equator Larger islands, with more varied habitats, have more plant species than smaller islands
• Alexander Von Humboldt (1769-1859)*
• The Founder of plant geography (phytogeography)
• Recognized the world is divided into natural biogeographical regions with distinct assemblages of plants/animals
• Adopted a holistic approach
• Augustin de Candolle (1778-1841)*
• Contributed to knowledge of plant dispersal and barriers to dispersal
• Studied plant adaptations to heat and moisture
• Stressed importance of competition for resources
• Coined the word “endemic”
• Darwin used the ideas of Augustin de Candolle

How Old is The Earth?

• End of the 18th Century had biogeographic knowledge growing
• It was primarily descriptive
• There was a lack of "how" and "why” for explaining patterns
• Distribution maps were based on ecological biogeography
• A historical biogeographical approach was needed to explain distribution
• There was a Lack of understanding and acceptance of the ancient age of the earth
• The Biblical interpretation said the earth only a few thousand years old
• James Hutton (1726-1797)*
• Recognized Earth's history as immense
• Uniformitarianism: the present is the key to the past
• Charles Lyell (1797-1875)*
• He wrote "Principles of Geology"
• He Popularized uniformitarianism and the ancient age for Earth

Darwin, Wallace, and Evolution

• Charles Darwin (1809-1882)*
• A naturalist aboard the HMS Beagle
• Ancestral South American finches had colonized Galapagos Islands
• They then radiated and became adapted to different lifeways
• Postulated evolution by natural selection
• Life on Earth is NOT fixed and unchanging
• Alfred Russel Wallace (1823-1913)*
• Made voyages of exploration
• Jointly postulated evolution by natural selection with Darwin
• Noted biogeographic divisions of animal populations

Dispersal vs Vicariance

• Vicariance and dispersal are historical explanations for the disjunct distribution of two taxa (A, B)

Explaining Disjunctions

• Disjunct distributions presented a problem
• One example is Glossopteris fossils (300-250 mya)
• It raised the question of how this distribution arose
• Some common explanations included wind, land bridges and continental movement

Explaining Disjunctions

• Extensionists proposed hypothetical land bridges in the late 19th and early 20th Centuries
• The bridges would account for major disjunctions in the distributions of terrestrial organisms

Continental Drift

• Concluded that Solid Earth is NOT fixed and unchanging
• An example is German geophysicist and meteorologist Alfred Wegener

Late 20th Century Progress

• Cladistics*
• Organisms categorized into groups (“clades”) based on the hypothesis of most recent common ancestry
• Based on shared derived characteristics
• Molecular genetics*
• Uses fundamental characteristics of organisms (in DNA) to determine evolutionary relationships
• Maturation of ecology as a science*
• Integration with biogeography
• Ecological biogeography focuses on biotic and abiotic factors that influence distribution
• Seminal work on island biogeography (MacArthur & Wilson, 1967)
• Marine biogeography as the “final frontier”*
• There is growth in knowledge of marine realms
• There are ongoing Technological innovations like deep sea exploration and satellites

Review the Readings

• Cox et al, Biogeography: an ecological and evolutionary approach
• 10th edition (2020): pages 1-19
• 9th edition (2016): pages 1-16

Next Time

• Patterns of Distribution
• Biology and taxonomy basics
• How we describe distributions of biota
• Limits on distributions

Readings for next unit:

• Cox et al, Biogeography: an ecological and evolutionary approach
• 10th edition (2020): pages 39-92
• 9th edition (2016): pages 33-85

Explore the distribution of life on Earth and the factors influencing it, with a focus on biogeographic gradients and the contributions of key figures like Forster, Humboldt, and Candolle. The quiz covers the history, scope, and fundamental concepts of biogeography.