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Lecture 23

BSC 385 Lecture 23: Chapter 15

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Biological Sciences
BSC 385
Carla Atkinson

1. Chapter 15: Species Diversity Rank-Abundance Curve  A plot of the log proportional abundance of each species as a function of its abundance  The slope of this curve is a measure of community evenness- higher slope, less even Spatial Variation of Measures of Diversity  Difficult measures of species diversity: o Total species richness o Threatened species richness o Endemic species richness Five Mass-Extinction Events in Earth’s History 1. End Ordovician 2. Late Devonian 3. End Permian 4. End Triassic 5. End Cretaceous Sixth Mass Extinction  Anthropogenic extinction  Changes in biodiversity over time for several groups of organisms and habitats o WBI = wild bird species index o WPSI = waterbird population status index o LPI = a measure of vertebrate diversity o FLI = red list index, a measure of extinctions Species-Area Effect  Species diversity and area are related: S = cA Z  Where S is the number of species, A is the area, z is the slope of the line and c is a constant Ecological Consequences of Differences in Species Diversity  Ecological stability (Charles Elton): o Dynamic stability: stable communities are those in which the variation in community function is small and centered on an equilibrium value o Reaction to perturbation:  Resistance, the tendency of a system not to change when disturbed  Resilience, the ability of the system to recover from disturbance Testing the Relationship Between Species Diversity and Stability  Hypothesis: high species diversity increases the stability of the community  Measured stability, S, as the constancy of the biomass relative to its mean: o S = / where  is the mean biomass and  is its standard deviation  Prediction: S increases as a function of the number of species in the community  The long-term study carried out at the Cedar Creek Ecosystem Science Reserve in Minnesota, a National Science Foundati
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