Twelfth lecture. Biodiversity Population level Genetic diversity Hierarchy of Biodiversity Community...
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Transcript of Twelfth lecture. Biodiversity Population level Genetic diversity Hierarchy of Biodiversity Community...
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