Twelfth lecture

Biodiversity

Population level Genetic diversity Hierarchy of Biodiversity Community level Species diversity Ecosystem level Functional group diversity Landscape level Spatial heterogeneity Biome level Biosphere level

Defining and quantifying species diversity Species diversity: –Species richness: # of different species –Species evenness: relative abundance of species Diversity indices –There are many! –“Shannon-Wiener index” takes into account both richness and evenness H’ = diversity Pi = proportion of the ith species (e.g. 0.5 means that species i represents 50% of total) S = number of species in the community –e.g. two ecosystems, each has 5 species and 25 individuals #1: 21 of one species, 1 each of other 4H’ = #2: 5 of each speciesH’ = H’ = -  Pi log e Pi i = 1 s

Functional group diversity Functional group: –e.g. Coniferous vs. deciduous –e.g. Warm blooded herbivores –e.g. Nitrogen fixers –e.g. Organisms at a given trophic level Two types 1. Within group diversity (# species/group) e.g. “Trophic breadth” Provide “Functional redundancy” 2. Diversity of groups (# groups/ecosystem) e.g. “Trophic depth”

Species vs. functional group diversity Key questions –Which one is important? –How are they important? –(We will come back to these…..)

Anthropogenic loss of biodiversity Land use change (habitat loss & fragmentation) Over-harvesting Introduction of exotic species Eutrophication and other changes in biogeochemical cycles Pollution (water, land, atmospheric) Climate change Synergistic effects –e.g. (Fragmentation + climate change)

Value of biodiversity To humans –Direct market value as genetic repository for crops and pharmaceuticals –Recreation, aesthetics, spirituality –Ecosystem services To biological and ecological systems –Adaptation –Function