Global Patterns of Species Richness

Global Amphibian Diversity

Wallace’s hypotheses for higher species diversity in the tropics:

1. Productivity

2. Spatial heterogeneity; morphological diversity

3. High average rarity – no monocultures

4. Climatic constancy – little seasonal variation

5. Geological age

6. Special adaptations required for “harsh” environments

7. Greater competitive “balance” in tropics

8. Alternating competitive advantages

9. All niches filled – saturation of community

Early Island Biogeography

IslandHabitats inBaltic Sea

Reptile and Amphibian Species Area Curve for Caribbean Islands

Habitat IslandsIn the Great BasinTop – Birds,Bottom - Mammals

Species Richness related to Island Size and Island Isolation

Species-Area Curves for Islands

S = cAz where:

S = number of species

A = area of island

c = constant for habitat type - forest, desert, grassland

z = slope of the curve - predicted to be 0.263, but actually varies with dispersal ability

Ant speciesOn NewGuinea andNearbyIslands

An area of island will have fewer species than equal sized area of continent

The slope of the line plotted for species-area curve is

larger for species with poor dispersal abilities Oceanic islands

birds - New Guinea islands z=0.22beetles - West Indies z=0.34land plants - Channel islands z=0.37

Habitat islandsbirds - Andes paramo z=0.29birds - mtns of Great Basin z=0.165mammals - mtns of Great Basin z=0.326inverts -caves in West Virginia z=0.72

Island Biogeography

Species Dispersal to Islands

Cape May Warbler on a Ship

Krakatoa pre-eruption

Looking at Volcano Rakata

Krakatoa mid-eruption

Map of Krakatoa pre-eruption

Landsat Image of Anak Krakatau and Krakatau

Dan Simberloff and Mangrove Islands

Simberloff’s defaunation experiment on Mangroves

Simberloff’s defaunation experiment on Mangroves

Results from Simberloff’s Experiment

Islands recovered to pre-defaunation number of species, but only 30%of original species resident on each island returned after defaunation.

BrackenFern

Bracken fern stand Australia

Number of species found on Bracken Fern

Professor Axel Meyer – Cichlid Man

Lake Malawi Cichlids

Adaptive radiation within cichlid lineages