Disturbance and Succession

Henry C. Cowles (center) about 1920

Successional Species Types Early successional, pioneer, opportunist Late successional seed dispersal distance long, goodshort, poor growth ratefastslow reach maturityearlylate number of offspring highlow competitive abilitylowhigh

The Kabetogama Peninsula

Kabetogama Peninsula

Beaver – Castor Canadensis

Beaver Dam

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 1 A: 25%B: 25%C: 25%D: 25% Community 2 A: 80%B: 5%C: 5%D: 10% D C B A

Animated Life of A.R. Wallace /the-animated-life-of-a-r- wallace.htmlhttp:// /the-animated-life-of-a-r- wallace.html

Explanations for Global Patterns of Species Richness 1) Morphological diversity, spatial heterogeneity 2) High average rarity - no monocultures – in tropics 3) Climatic constancy of tropics 4) Geological age 5) Special adaptations in extreme (harsh) environments 6) Competitive "balance" 7) Alternating competitive advantages 8) "All niches filled theory" - saturation of community 9) Productivity from A.R. Wallace

Richness and Productivity

Richness and Structural 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 Plant Richness Local Centers Of Diversity Quality of Data

Richness and High Average Rarity Endemic Plant Species Globally

Richness and High Average Rarity Endemic Plants in Africa