Disturbance and Succession

Henry C. Cowles (center)

about 1920

Successional Species Types

Early successional, pioneer,

opportunist

Late successional

seed dispersal distance

long, good short, poor

growth rate fast slow

reach maturity early late

number of offspring

high low

competitive ability low high

The Kabetogama Peninsula

Kabetogama Peninsula

Beaver – Castor Canadensis

BeaverDam

Pond and Bog Succession

Climax Community

Many Communities Experience Constant Disturbance or Change

Fir Wave on Mt. Coe,Baxter State Park, Maine

Fir Wave Up Close

Global Patterns of Species Richness

Global Amphibian Diversity

Measures of Biodiversity

• Species richness – the number of species in an area – the simplest measure of biodiversity

• Species evenness or equitability – the relative proportion of number of individuals of each species in an area

• Often richness and evenness are combined into a Species Diversity Index

A comparison of species diversity in two communities

Community 1A: 25% B: 25% C: 25% D: 25%

Community 2A: 80% B: 5% C: 5% D: 10%

D

C

BA

Animated Life of A.R. Wallace

• http://www.nytimes.com/video/opinion/100000002534565/the-animated-life-of-a-r-wallace.html

Explanations for Global Patterns of Species Richness

1) Morphological diversity, spatial heterogeneity2) High average rarity - no monocultures – in tropics3) Climatic constancy of tropics4) Geological age5) Special adaptations in extreme (harsh) environments6) Competitive "balance"7) Alternating competitive advantages8) "All niches filled theory" - saturation of community9) Productivity

from A.R. Wallace - 1878

Richness andProductivity

Richness andStructural Diversity

Environmental harshness

Richness and Climatic Variability

South American Rain Forest – Today and Past Refuges

Richness and Environmental Age

Richness and High Average Rarity

Global PlantRichness

Local CentersOf Diversity

Quality ofData

Richness and High Average Rarity

Endemic Plant Species Globally

Richness and High Average Rarity

Endemic Plants in Africa