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WHAT IS BIOGEOGRAPHY?
WHAT IS BIOGEOGRAPHY?
•Hybrid discipline between biology and geography
•Examines spatial distribution of organisms
•Sample Questions
•Why did tuataras survive in New Zealand?
•Why are salamanders so abundant in North America?
•How did Plenthodontidae get to South America?
•Why are there so many species in the tropics >
•Many Scales
•Individual animals
•Patterns of genetic diversity
•Species Ranges
•Global diversity patterns
•Major Subdisciplines
•Zoogeography--Mainly studied by biologists
•Phytogeography--Mainly studied by geographers
Let’s Start Small Scale--Individual Animals
•Why do individuals live where they do?
•Interactions with conspecifics
•Territoriality
•Defense of Mates
•Defense of Resources
•Both
•Saved for “Exclusive” Use
•When Are Resources Worth Defending
•Home Range
•Nonexclusive
•Area of “Normal Use”
•Methods of Analysis
•Dispersal
•Individual Permanently Changes Home Ranges
•High Costs--So Why Do It?
•Inbreeding Avoidance
•Resident Fitness
Let’s Start Small Scale--Individual Animals
•Why do individuals live where they do?
•Individual Behaviors
•Migration
•Need Not Be 2 Directional
•Relatively Rapid
Fig 12-10
•Predictable
•Not Easily Interrupted
•Usually Seasonal Change in Home Range
•Examples
•Sea Turtles
•Trips To and From Hibernacula
•Trips To and From Breeding Sites
•All of These Behaviors Can Lead to Population Mixing
Now For Moderate Scale--Community Level
•Latitudinal Species Gradient:
Bill Mitchell
•Northern Hemisphere Bias
•Reverse Trend in # Individuals
•Hypotheses
•Intermediate Disturbance
•Available Energy
•Energy by Moisture
16-1
Now For Moderate Scale--Community Level
•Are Communities The Result of Internal or External Factors
•Community Composition Driven By Species/Species Interactions
•Positive Interaction
•F. C. Clements
•Holistic Model
•Species Have Evolved Together
•True for Parasites and Hosts, Specialized “Predators” and Prey
•Negative Interactions
•Competition
•Niche Theory
•Communities are Random Associations of Species
•H. A. Gleason
•Individualistic Model
•Little Association Between Species
•Species Individual Characteristics Control Presence?Absence
•Which is True?
Now For Moderate Scale--Community Level
•Both Are True
•Communities are Mostly Random Associations
•Individuals Species Respond Independently
•Apparent Competition is not Necessarily Competition.
•True for Parasites and Hosts, Specialized “Predators” and Prey
•Negative Interactions
•Competition
•Niche Theory
•Communities are Random Associations of Species
•Regional Species Pool
•Little Association Between Species
•Species Individual Characteristics Control Presence?Absence
•Which is True?
Figures from Ricklefs Ecology
MOST ECOLOGISTS AGREE THAT COMMUNITIES
ARE PRIMARILY ASSEMBLED INDIVIDUALLY.
SEVERAL FEATURES OF THE HOLISTIC MODEL
DO ROUTINELY OCCUR.
EXAMPLES OF HOLISTIC PATTERNS
Intraspecific Competition
Can have a major impact on Community Structure
Coevolution of Pollinators and Plants
Some of these relationships are species specific
Parasites and Hosts
These are typically host- or group-specific
Other Close Associations
Specialist Predators and Prey: Ex Lynx/Hare
Plant Specialists
Organism-like structuring--Ecological Roles
Hard Ecological Edges (Forest/Lake)
Most of this community ecology is based either on
plants, birds, or insects. Do these interactions occur
between local herp populations?
Differential Predation Can Shift Competitive Relationships
Example: Has the Community Changed
Since Newts Were Extirpated From Sandcut?
Toad=Tasty
We love
newts
No Newts is
good newts
Say no to
newts
Without newts, tree frog tadpoles are outcompeted by toads
(In Cattle Tanks)
WHY DO WE RECORD WHETHER PONDS HAVE FISH IN
THEM OR NOT?
Photo from www.cabelas.com
In fact, loss of the newts at Dave’s Pond occurred simultaneously with
introduction of catfish. If so, what changes would you predict?
Great, Now
I’m Tasty
What other than habitat is different between these ponds?
Pond
Pond
Parking Lot
Woods
Why is this Difference Important?
Is there a relationship between the size of a habitat and
Note this is a log the number of species present?
Scale—what does
This relationship
Really look like?
Figures from Ricklef’s Ecology
WHY DOES THIS SPECIES
AREA RELATIONSHIP EXIST
2 Conflicting Ideas
Balance Between Extinction and Colonization
Larger “Islands” have slower rate of extinction
These Issues are the Classic Problems of Island Biogeography
BACK TO THE BIG QUESTION:
WHAT FACTORS CONTROL THE
SPECIES PRESENT AT ANY ONE SITE?
WHAT FACTORS CONTROL THE
SPECIES PRESENT AT ANY ONE SITE?
•Is the habitat appropriate?
•Specialists need particular habitat
•Even habitat generalists have needs
•Includes physical conditions (i.e. rainfall, temperature extremes)
•What limits the northern end of the range of Alligator mississippiensis
•Why are tail-water pits allowing aquatic species to invade dry areas
•If the habitat is appropriate is it occupied
•Niche theory
•Principle of competitive exclusion
•Fox assembly rules
•Can also be restricted by presence of predators/parasites
WHAT FACTORS CONTROL THE
SPECIES PRESENT AT ANY ONE SITE?
•Can enough individuals get there?
•Within dispersal range
•How do species invade “new” habitat patches
•Any barriers?
•Vicariant Biogeography
•Oceans
•Roadways
•Lead to view of habitat islands
•Will someone take me?
•Intentional and Unintentional Introductions
•Interactions between the history of the species and the Earth
•Historical Biogeography
•Paleobiogeography
•“Anthrobiogeography”
WORLD HISTORY 101
•Pay Attention To Pattern—Dates are Important, but Too Detailed
•When vertebrates evolved in the late Paleozoic….
•All major landmasses were united in Pangea
Fig 5-3a
WORLD HISTORY 101
•Midway through the age of Dinosaurs (i.e. early Jurassic) Pangea starts
to spit into 2 continents (Laurasia and Gondwanaland)
Fig 5-3b
WORLD HISTORY 101
•Late in the age of Dinosaurs (i.e. late K) Laurasia and Gondwanaland
are separate, and Gondwanaland itself starts to split
Fig 5-3d
WORLD HISTORY 101
•Mid Miocene Most Continents close to current positions—Note
Shallow seas separating Asia and India, N+S America, Middle East,
Australia and Antarctica. Also note the relationship of NA and Europe
via Greenland.
Fig 5-4a
WORLD HISTORY 101
•Modern World—Note you only sea NA and SA joined VERY recently.
Fig 5-4c
WORLD HISTORY 101
•Why do we see Boidae mostly in Africa, Australia, and South America?
•Why are the fauna’s of Holoarctic so different from those of the
Neotropics
•Why are the Faunas of Madagascar and Australia so different?
Fig 5-6
Interpreting Distributions
•Modern distributions are the result of both dispersal and vicariant
events.
•Remember that taxa differ wildly in their abilities to move across
different types of barriers.
Fig 5-4a
•Keep in mind weather
patterns and vegetation play a critical role.
•Dispersal can happen via unusual events.
•Rain of frog eggs in New England following hurricanes in summer
2003.
•Rafting of green Iguanas to Angualla Island in 1995
•Movement of brown snakes to Guam in Aircraft
•Snakes in Bananas—see text