What is Biological Diversity? Brook Milligan Department of Biology - - PowerPoint PPT Presentation

What is Biological Diversity?

Brook Milligan

Department of Biology New Mexico State University Las Cruces, New Mexico 88003 brook@nmsu.edu

Fall 2009

Brook Milligan What is Biological Diversity?

Biological Diversity in General

Part of the challenge facing conservation biologists is the threat to biodiversity and its impact on human welfare. So . . . How do we know what regions of the Earth are high in biological diversity and which are low? How do we know that biological diversity is changing? What constitutes biodiversity?

Brook Milligan What is Biological Diversity?

Ways of Organizing the Concept of Biodiversity

Taxonomy based upon traditional biological hierarchy: Species Genetics Communities and ecosystems Taxonomy based upon conceptual divisions: Compositional Structural Functional

Brook Milligan What is Biological Diversity?

Species-based Biodiversity Measures

Species richness: S (1) Shannon index: H = −

n

• i=1

pi ln(pi) (2) H′ = eH (3) Evenness: E = H ln(S) (4) Simpson’s Index: D =

n

• i=1

p2

i

(5) Simpson’s Index of Diversity = 1 − D (6) Simpson’s Reciprocal Index = 1 D (7)

Brook Milligan What is Biological Diversity?

Biological Diversity in General

Encompasses all variation in life Encompasses all levels of the biological hierarchy Characterization of biological diversity

species genetics communities and ecosystems

Tradeoffs may exist among different dimensions

Brook Milligan What is Biological Diversity?

Species Diversity

Species richness: number of species occuring in an area Alpha diversity: number of species in a community Gamma diversity: number of species in a large geographic area Beta diversity: change in diversity among communities

Brook Milligan What is Biological Diversity?

Genetic diversity

Genetic structures: genomes, chromosomes, genes (loci), alleles Genetic diversity: differences among genetic structures

percent polymorphic loci P heterozygosity ¯ H: average proportion of heterozygous loci distribution of allele frequencies gene diversity HE = 1 −

n

• i=1

p2

i

(8)

Brook Milligan What is Biological Diversity?

Community and Ecosystem Diversity

Community: species occupying a particular location + interactions Ecosystem: biological community + the associated physical and chemical environment What factors characterize communities and ecosytems?

Brook Milligan What is Biological Diversity?

Community and Ecosystem Diversity

Keystone species: 2 orthogonal dimensions characterizing species’ effects Total Proportional biomass impact Low High Low rare species (wildflowers, butterflies, mosses) common species with low impact (understory trees/shrubs, weedy grasses) High keystone species (wolves, bats, figs, diseases) dominant species (forest trees, deer, kelp, prairie grasses)

Brook Milligan What is Biological Diversity?

Categorizing Biodiversity Conceptually

Brook Milligan What is Biological Diversity?