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•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

Fig 12-10

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

•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

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 PlantsSome of these relationships are species specific

Parasites and HostsThese are typically host- or group-specific

Other Close AssociationsSpecialist Predators and Prey: Ex Lynx/HarePlant 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?

Without newts, tree frog tadpoles are outcompeted by toads (In Cattle Tanks)

No Newts is good newts

Say no to newts

We love newts

Toad=Tasty

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

WoodsParking Lot

Why is this Difference Important?

Is there a relationship between the size of a habitat andthe number of species present?Note this is a log

Scale—what doesThis relationshipReally look like?

Figures from Ricklef’s Ecology

2 Conflicting IdeasBalance Between Extinction and ColonizationLarger “Islands” have slower rate of extinction

WHY DOES THIS SPECIES AREA RELATIONSHIP EXIST

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

•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”

WHAT FACTORS CONTROL THE SPECIES PRESENT AT ANY ONE SITE?

•Pay Attention To Pattern—Dates are Important, but Too Detailed•When vertebrates evolved in the late Paleozoic….•All major landmasses were united in Pangea

WORLD HISTORY 101

Fig 5-3a

•Midway through the age of Dinosaurs (i.e. early Jurassic) Pangea starts to spit into 2 continents (Laurasia and Gondwanaland)

WORLD HISTORY 101

Fig 5-3b

•Late in the age of Dinosaurs (i.e. late K) Laurasia and Gondwanaland are separate, and Gondwanaland itself starts to split

WORLD HISTORY 101

Fig 5-3d

•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.

WORLD HISTORY 101

Fig 5-4a

•Modern World—Note you only sea NA and SA joined VERY recently.

WORLD HISTORY 101

Fig 5-4c

•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?

WORLD HISTORY 101

Fig 5-6

•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.

•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

Interpreting Distributions

Fig 5-4a