Lecture 18 Biogeography

Plate tectonics with continental drift ‘______’ the continents

reorganized

The movement of tectonic plates on the surface of the earth reconfigured the

landmasses throughout geological history

Name the 6 biogeographic regions

Nearctic, Palearctic, Neotropical, Ethiopian, Oriental, Australian

What is Biogeography?

The study of patterns of species composition and richness across geographic locations

Species richness and composition vary with

latitude

Is there more diversity closer to the arctics or equator?

Equator

Global Biogeography

Global patterns of species richness and composition are influenced by geographic area and isolation, evolutionary history, and global climate

Latitude is important, but are there other clear global patterns in species richness?

Area effect, isolation, energy/productivity, and environmental stability

Where is the most species richness of vascular plants?

Closer to the equator mainly south America and Asia

Where is the most species richness of freshwater fish?

In Americas closer to the equator and Asia

Where is the most species richness for terrestrial vertebrates?

South America and Africa

Auks occur in the

Northern Hemisphere

Pelicans occur in the

tropics

Penguins occur at the

South Pole

Species diversification rate:

Speciation rate - Extinction rate

Species diversification rate is higher in the

tropics

Diversification rates are similar, but

evolutionary time is greater in the tropics

Higher productivity results in more

abundant resources in the tropics

Species diversification rate

Large, thermally stable areas → Lower extinction rates + larger population sizes and geographic ranges → Speciation is more likely to occur

Terrestrial Productivity

is highest in the tropics

High Productivity → Larger carrying capacities → Larger population sizes

→ Lower extinction rates

Species diversity at different scales

Alpha diversity

Species richness:

Number of species in a community or in a defined area

gamma diversity

richness over a larger geographic area

gamma diversity example

Number of fish species in all lakes in california

Beta diversity

Relates alpha to gamma diversity. Represents the rate of change of species composition among an environment of geographic gradient

When all local communities are identical

alpha diversity equals gamma diversity & beta diversity equals 1

When local communities are completely different,

gamma diversity equals the multiplication of alpha diversity and the number of sites

High isolation/small area =

Lower immigration/high extinction

Low isolation/large area =

Higher immigration/less extinction