Biodiversity …refers to the variety of living organisms, genetic diversity, and the types of ecological communities into which they are assembled.
What is biodiversity? species richness (N) species diversity (H’)- weighted measure Shannon-Wiener Index Simpson Index intraspecific diversity- within and between populations ecosystem/biome diversity- vegetative patterns
Patterns of Species Richness • The earth is not uniform. • climate • topography, geology, & soil fertility • structural complexity of habitats
Patterns of Richness • alpha richness- number of species in a relatively small homogeneous area • beta richness- rate of species change across habitats • gamma richness- rate of species change across landscapes
Patterns of Species Richness • species richness is greatest in tropical regions • islands tend to be relatively species poor. • species-area relationship • endemism & vicariance • ecological release
Immediate causes effecting current levels of species diversity. (after McNeely et al. 1995) • exploitation of natural resources • expansion of agriculture • habitat loss and fragmentation • species introductions • pollution • global climate change
Underlying causes effecting current levels of species diversity. (after McNeely et al. 1995) • human social organization • human population growth • patterns of natural resource consumption • global trade • economic systems and policies • inequity of ownership and distribution of wealth
Species Density total number of species occurring anywhere within a given quadrate.
Kiester, A.R. 1971. Species density of North American amphibians and reptiles. Syst. Zool.20:127-137. • density increases toward the equator • mammal density is higher in the west while reptiles and amphibians have higher densities in the east. • mammal density is positively correlated with topographic relief • amphibians are positively correlated with topographic relief and annual rainfall • reptiles are negatively correlated with topographic relief
Extinction • mass extinction- a rapid and substantial global decline in species affecting a broad range of taxonomic groups.
Patterns of Species Vulnerability • rare species- human caused rarity may be more devastating because the species are not adapted to low numbers • long lived species- delayed sexual maturity, low fecundity, high juvenile survivorship • keystone species associations-
Endangered Biological Phenomena • Fire • floods • migrating herds
Loss of Ecosystem Function and Disruption of the Evolutionary Process