Lecture 3 and the biogeography activity

Biogeography

The study of where organisms and ecosystems are distributed across geographic space and through geologic time.

Historical biogeography

Study of how species distributions and ranges have changed through evolutionary history.

Ecological biogeography

Study of how current environmental conditions, habitats, and species interactions explain where organisms live.

Phylogeography

Study of how genetic relationships and geographic history help explain the distribution of populations or lineages.

Easy way to remember historical vs ecological vs phylogeography

Historical = past ranges; Ecological = current environment/habitat; Phylogeography = DNA + family relationships + geography.

Species range

The geographic area where a species is found.

Endemism

A species being naturally found only in one particular geographic area.

Endemic

Describes a species naturally found only in one geographic area.

Example of endemism

Lemurs are endemic to Madagascar.

Disjunct distribution

A distribution split into separate areas with large gaps in between.

Example of disjunct distribution

Marsupials in South America and Australia.

Species richness

The number of different species in an area.

Vicariance

When a physical barrier splits one population apart and can lead to divergence or speciation.

vicariance

A mountain range forms and separates one mammal population into two groups.

Dispersal

The movement of organisms from one area to another.

Active dispersal

An animal moves itself by walking, flying, swimming, or other movement.

Passive dispersal

An organism is moved by an outside force, such as water, wind, or land movement.

Corridor

A pathway that allows many different species to move between areas with little resistance.

Filter

A route or barrier that only allows species with certain adaptations to cross.

Example of a filter

The Bering land bridge allowed mainly cold-adapted species to cross.

Great American Biotic Interchange

The movement of animals between North and South America after the land bridge formed.

Background extinction

The normal, gradual loss of species over time.

Mass extinction

A relatively rapid global event in which a very large number of species go extinct.

Diversification

The formation of new species that become genetically and/or physically different over time.

Adaptive radiation

Rapid formation of many new species from one ancestral group as they adapt to different ecological niches.

Example of adaptive radiation

Lemurs diversifying into many species on Madagascar.

Convergent evolution

Unrelated species independently evolving similar traits because they face similar environmental pressures or lifestyles.

Example of convergent evolution

Echidnas, pangolins, anteaters, numbats, aardwolves, and aardvarks evolving similar ant- and termite-eating adaptations.

Myrmecophagy

Eating mainly ants and termites.

Myrmecophagous

Describes an animal that eats mainly ants and termites.

Difference between convergent evolution and adaptive radiation

Convergent evolution = unrelated species become similar; adaptive radiation = one ancestral group splits into many different species.

Refugium

A protected area where organisms survive environmental changes, such as an ice age.

Refugia

Plural of refugium.

Nunatak

An ice-free area surrounded by continental ice sheets; a specific type of refugium.

Why refugia can lead to new species

Isolated populations can become genetically different over time and eventually speciate.

Effect of ice ages on mammals

Ice ages can shift ranges, isolate populations, create refugia, and affect modern distributions.

Rain shadow

When moist air rises over mountains, cools and drops rain on one side, then descends dry on the other side.

Windward side of a mountain

The wetter side where rising air cools and releases precipitation.

Leeward side of a mountain

The drier side where descending air warms and loses moisture.

Where are many major deserts located

Around 30° north and south latitude.

Island Rule

Large mammals tend to become smaller on islands, while small mammals tend to become larger.

Bergmann’s Rule

Mammals and birds tend to be larger at higher latitudes.

Why do larger mammals lose heat more slowly

Larger bodies have less surface area relative to volume, so less heat escapes.

Nearctic biogeographic region

North America.

Palearctic biogeographic region

Europe, northern Asia, and northern Africa.

Neotropical biogeographic region

Central America, South America, and the Caribbean.

Afrotropical biogeographic region

Sub-Saharan Africa and nearby areas.

Indomalayan biogeographic region

South and Southeast Asia.

Australian biogeographic region

Australia, New Guinea, and nearby islands.

Marine biogeographic region

Oceans and marine ecosystems.

Pika activity example

Pikas in cool, high-elevation rocky habitats are an example of ecological biogeography because present climate and habitat explain their distribution.

Polar bear and brown bear activity example

Using DNA and ice-age history to study their relationship is phylogeography.

Camelid activity example

Camel movement from North America into South America and Eurasia is an example of historical biogeography and dispersal.

What makes a location good for pika habitat

Cool temperatures, high elevation, rocky talus habitat, and nearby meadow food sources.

Why are warm valleys barriers for pikas

Warm low-elevation habitats are unsuitable and can isolate cooler mountain populations.

Why is connectivity important for pika populations

It allows gene flow between populations and lowers isolation risk.