Species Diversity Biogeography November 7-14, 2007.

Species DiversitySpecies Diversity

BiogeographyBiogeography

November 7-14, 2007November 7-14, 2007

Geographical EcologyGeographical Ecology

Ecological PatternsEcological Patterns Species diversitySpecies diversity Species Species

distributionsdistributions Island patternsIsland patterns Community Community

distributionsdistributions

Ecological Ecological ProcessesProcesses CompetitionCompetition CoexistenceCoexistence SuccessionSuccession disturbancedisturbance

Species DiversitySpecies Diversity Measuring DiversityMeasuring Diversity

Scales Scales RichnessRichness DiversityDiversity EvenessEveness

Patterns of DiversityPatterns of Diversity Latitudinal gradientsLatitudinal gradients Elevational gradientsElevational gradients Precipitation Precipitation

gradientsgradients PeninsulasPeninsulas Aquatic environmentsAquatic environments

Processes Explaining Processes Explaining Diversity GradientsDiversity Gradients Historical Disturbance Historical Disturbance

HypothesisHypothesis Equilibrium TheoriesEquilibrium Theories

• Productivity Productivity • Climate stabilityClimate stability• HeterogeneityHeterogeneity• Biotic interactionBiotic interaction• Area/distanceArea/distance

Diversity in TRFDiversity in TRF• Equilibrium theoryEquilibrium theory• Janzen’s hypothesisJanzen’s hypothesis• Non-Equilibrium theoryNon-Equilibrium theory

Species Diversity: A Non-Species Diversity: A Non-Concept?Concept?

What determines the number and What determines the number and kinds of species that occur in a kinds of species that occur in a particular place?particular place?

Why do number and kinds of species Why do number and kinds of species vary from place to place?vary from place to place?

How many species are How many species are there?there?

How many species are How many species are there?there?

Scales of DiversityScales of Diversity

Alpha DiversityAlpha Diversity w/in habitatw/in habitat

Beta DiversityBeta Diversity b/w habitatb/w habitat

Gamma Gamma DiversityDiversity Total diversityTotal diversity

SpeciesSpecies Woodland habitatWoodland habitat Hedgerow HabitatHedgerow Habitat Open field habitatOpen field habitat

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Alpha DiversityAlpha Diversity

Beta DiversityBeta Diversity

Gamma DiversityGamma Diversity


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Alpha DiversityAlpha Diversity 1010 77 33

Beta DiversityBeta Diversity



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Beta DiversityBeta Diversity (W vs. H) = 7(W vs. H) = 7



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Beta DiversityBeta Diversity (W vs. H) = 7(W vs. H) = 7 (H vs. F) = 8(H vs. F) = 8



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Beta DiversityBeta Diversity (W vs. H) = 7(W vs. H) = 7 (H vs. F) = 8(H vs. F) = 8 (F vs. W) = 13(F vs. W) = 13



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Beta DiversityBeta Diversity (W vs. H) = 7(W vs. H) = 7 (H vs. F) = 8(H vs. F) = 8 (F vs. W) = 13(F vs. W) = 13

Gamma DiversityGamma Diversity 1414

Sampling area and species Sampling area and species richnessrichness

Relationship b/w sampling area and bird species richness in North America (Fig. 14.1 MacDonald)

Measuring DiversityMeasuring Diversity Species RichnessSpecies Richness

Total number of species in an areaTotal number of species in an area can also be measured as biomass, basal area, % can also be measured as biomass, basal area, %

covercover

Species DiversitySpecies Diversity Considers eveness and richnessConsiders eveness and richness

Species EvenessSpecies Eveness Considers how abundance data are distributed Considers how abundance data are distributed

among the speciesamong the species 96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1 96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1

chuckwallachuckwalla 20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20 20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20

lizardslizards

Measuring Species DiversityMeasuring Species Diversity Species RichnessSpecies Richness

The number of species in a given area (N0)The number of species in a given area (N0) Sample Size Issue!Sample Size Issue! Margalef Index Mehinick IndexMargalef Index Mehinick Index R1 = S-1/ln(n)R1 = S-1/ln(n) R2 = S/√n R2 = S/√n

Where S = total number of species in area sampledWhere S = total number of species in area sampled n = total number of individuals observedn = total number of individuals observed

Interpretation: Interpretation: The higher the index the greater the richnessThe higher the index the greater the richness

Example: S = 6 and n = 50 S = 6 and n = 20

R1 = 1.28

R1 = 1.66

Measuring Species Measuring Species DiversityDiversity

Diversity Indices - Simpson’s Index Diversity Indices - Simpson’s Index = probability that 2 individuals selected = probability that 2 individuals selected

at random will belong to the same speciesat random will belong to the same species

= = ii(n(nii(n(nii-1))/N(N-1)-1))/N(N-1)Where: Where:

nnii= total number of individuals in each species= total number of individuals in each species

N = Total number of individuals in all speciesN = Total number of individuals in all species

Interpretation:Interpretation:

If probability is high, the diversity of sample is lowIf probability is high, the diversity of sample is low

Measuring Species Measuring Species DiversityDiversity

Diversity Indices - Shannon’s Index Diversity Indices - Shannon’s Index H’H’

H’= -H’= -i i ((n((nii/N)/N) ln (nln (nii/N))/N))

Where: Where:

nnii= total number of individuals in each species= total number of individuals in each species

N = Total number of individuals in all speciesN = Total number of individuals in all species

Interpretation: Interpretation: 1.5 (low richness/eveness) to 3.5 (high richness and 1.5 (low richness/eveness) to 3.5 (high richness and

eveness)eveness)

Hill’s Family of Diversity Hill’s Family of Diversity NumbersNumbers

Units are given in numbers of speciesUnits are given in numbers of speciesNO = total number of species in the sampleNO = total number of species in the sample

N1 = the number of abundant speciesN1 = the number of abundant species

N2 = the number of N2 = the number of veryvery abundant species abundant species

N1 = eN1 = eH’H’ (H’=Shannon’s index) (H’=Shannon’s index)

N2 = 1/N2 = 1/ ( (=Simpson’s index)=Simpson’s index)

Measuring Species DiversityMeasuring Species Diversity Species EvenessSpecies Eveness

How abundance data are distributed among speciesHow abundance data are distributed among species 96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1 96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1

chuckwallachuckwalla 20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20 20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20

lizardslizards

Modified Hill’s Ratio Modified Hill’s Ratio E5 = N2-1/N1-1E5 = N2-1/N1-1

Where: N1 = eWhere: N1 = eH’H’ N2 = 1/ N2 = 1/

Interpretation: Interpretation: 0 = less even, 1 = more even0 = less even, 1 = more even

Desert Lizard DiversityDesert Lizard Diversity

Lizard Species Number of Individuals

Cnemidophorus tesselatus

3

Cnemidophorus tigris 15

Crotophytus wislizenii 1

Holbrookia maculata 1

Phrynosoma cornutum 10

Scleoporus magister 2

TOTAL Individuals 32

Number of individuals for each of 6 species of lizards counted in a 1 hectare plot


N2 =

N1 = R2 =

H’ = R1 =

E5 = =NO =

EvenessDiversityRichness


N2 = 3

N1 = 4R2 = 1.06

H’ = 1.33R1 = 1.44

E5 = 0.80 = 0.31NO = 6

EvenessDiversityRichness

Patterns of DiversityPatterns of Diversity

Latitudinal GradientsLatitudinal Gradients Elevation GradientsElevation Gradients Precipitation GradientsPrecipitation Gradients PeninsulasPeninsulas Aquatic EnvironmentsAquatic Environments

Mammals Birds

Processes Explaining Diversity Processes Explaining Diversity GradientsGradients

• • Historical Disturbance Hypothesis Historical Disturbance Hypothesis - - landscape reflects historical events, not landscape reflects historical events, not current current

environmental conditions (not in equilibrium)environmental conditions (not in equilibrium)

Habitats catastrophically disturbed are “undersaturated” in terms Habitats catastrophically disturbed are “undersaturated” in terms of species because there hasn’t been adequate time for adaptation of species because there hasn’t been adequate time for adaptation and speciationand speciation

Problems: evidence from tropicsProblems: evidence from tropics

Extent of tropics during last glacial Extent of tropics during last glacial maximummaximum

Equilibrium TheoriesEquilibrium Theories Landscape is a reflection of current Landscape is a reflection of current

environmental conditions (in environmental conditions (in equilibrium)equilibrium)• Productivity Productivity • Climate stability-Harsh habitatClimate stability-Harsh habitat• Habitat heterogeneityHabitat heterogeneity• Biotic interactionsBiotic interactions• Large AreaLarge Area


ProductivityProductivity What is the link b/w productivity and What is the link b/w productivity and

biodiversity?biodiversity?• Tropics 2200 g/m2/yrTropics 2200 g/m2/yr• Temperate 1200 g/m2/yrTemperate 1200 g/m2/yr• Boreal 800 g/m2/yrBoreal 800 g/m2/yr

ScaleScale• Estuaries, marshes are most productive Estuaries, marshes are most productive

ecosystems on earth, with lowest diversityecosystems on earth, with lowest diversity


Climate Stability (Harsh Habitat)Climate Stability (Harsh Habitat) Environments with low stability are Environments with low stability are

harsher and are less diverseharsher and are less diverse Why?Why? ExceptionsExceptions

• Areas with stable climate but low diversityAreas with stable climate but low diversity


Habitat Diversity (Heterogeneity)Habitat Diversity (Heterogeneity) What is the link?What is the link? Is it a direct relationship?Is it a direct relationship?


Biotic InteractionsBiotic Interactions Is speciation driven by competition in Is speciation driven by competition in

low lats and adaptation to physical low lats and adaptation to physical stress in high lats?stress in high lats?• Exceptions: trees/plantsExceptions: trees/plants

What about predation as a mechanism?What about predation as a mechanism? CircularityCircularity


Large Land AreaLarge Land Area Supports more individsSupports more individs Supports more speciesSupports more species Tropics? Boreal?Tropics? Boreal?


Diversity in TRF and Coral Diversity in TRF and Coral ReefsReefs

Equilibrium ViewpointEquilibrium Viewpoint Stability is the major characteristic of a Stability is the major characteristic of a

community. Following disturbance, it community. Following disturbance, it recovers and high diversity is maintained recovers and high diversity is maintained by a variety of mechanisms. Community by a variety of mechanisms. Community reflects current conditions.reflects current conditions.

Non-Equilibrium ViewpointNon-Equilibrium Viewpoint Communities rarely reach an equilibrium Communities rarely reach an equilibrium

state and high diversity results from state and high diversity results from changing environmental conditions. changing environmental conditions.

Diversity in TRFDiversity in TRF• • Janzen’s Hypothesis (1970): Biotic interactionsJanzen’s Hypothesis (1970): Biotic interactions

- host-specific herbivores- host-specific herbivores- seed predation- seed predation- canopy foliovores- canopy foliovores

• • Hubbell’s research (1979, 1980) to support Hubbell’s research (1979, 1980) to support JanzenJanzen

• • Non-equilbrium explanation (Connell 1978)Non-equilbrium explanation (Connell 1978)- coral reefs- coral reefs

The Non-Equilibrium Hypothesis The Non-Equilibrium Hypothesis (Connell 1978)(Connell 1978)

Intermediate Disturbance HypothesisIntermediate Disturbance Hypothesis

The Non-Equilibrium Hypothesis The Non-Equilibrium Hypothesis (Connell 1978)(Connell 1978)

Connell’s ConclusionsConnell’s Conclusions TRF and Coral Reefs demonstrate Non-TRF and Coral Reefs demonstrate Non-

Equilibrium HypothesisEquilibrium Hypothesis Equilibrium and Non-Equilibrium are not Equilibrium and Non-Equilibrium are not

mutually exclusivemutually exclusive Bottom line is:Bottom line is: Role of human disturbancesRole of human disturbances

More Intermediate Disturbance More Intermediate Disturbance Hypothesis (Denslow 1980)Hypothesis (Denslow 1980)

Intermediate levels of disturbance vary by Intermediate levels of disturbance vary by ecosystemecosystem

Ecosystem

Historic Rate of Disturbance (years)

Prairie 2

Chaparral 30

Pine 50

Oak-HW 50-100

Spruce-Fir

1000

Species Diversity Biogeography November 7-14, 2007.

Documents

cover species diversity

species diversity biogeography

beta diversity w

kinds of species

richness species eveness

bird species richness

area total number of

macdonald slide