Twelfth lecture

Biodiversity

• Population levelGenetic diversity

Hierarchy of Biodiversity

• Community levelSpecies diversity• Ecosystem levelFunctional group

diversity• Landscape levelSpatial 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 4 H’ = 0.662

• #2: 5 of each species H’ = 1.610

H’ = - Pi loge Pii = 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 types1. 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