8Species Woodland habitat Hedgerow Habitat Open field habitat A B C D E xBCDEFGHIJKLMNAlpha DiversityBeta DiversityGamma Diversity
910 7 3 Species Woodland habitat Hedgerow Habitat Open field habitat A xBCDEFGHIJKLMNAlpha Diversity1073Beta DiversityGamma Diversity
1010 7 3 (W vs. H) = 7 Species Woodland habitat Hedgerow Habitat Open field habitatAxBCDEFGHIJKLMNAlpha Diversity1073Beta Diversity(W vs. H) = 7Gamma Diversity
1110 7 3 (W vs. H) = 7 (H vs. F) = 8 Species Woodland habitat Hedgerow HabitatOpen field habitatAxBCDEFGHIJKLMNAlpha Diversity1073Beta Diversity(W vs. H) = 7(H vs. F) = 8Gamma Diversity
1210 7 3 (W vs. H) = 7 (H vs. F) = 8 (F vs. W) = 13 SpeciesWoodland habitatHedgerow HabitatOpen field habitatAxBCDEFGHIJKLMNAlpha Diversity1073Beta Diversity(W vs. H) = 7(H vs. F) = 8(F vs. W) = 13Gamma Diversity
1310 7 3 (W vs. H) = 7 (H vs. F) = 8 (F vs. W) = 13 14 SpeciesWoodland habitatHedgerow HabitatOpen field habitatAxBCDEFGHIJKLMNAlpha Diversity1073Beta Diversity(W vs. H) = 7(H vs. F) = 8(F vs. W) = 13Gamma Diversity14
14Sampling area and species richness Relationship b/w sampling area and bird species richness in North America (Fig MacDonald)
15Measuring Diversity Species Richness Species Diversity Species Eveness Total number of species in an areacan also be measured as biomass, basal area, % coverSpecies DiversityConsiders eveness and richnessSpecies EvenessConsiders how abundance data are distributed among the species96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1 chuckwalla20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20 lizards
16Measuring Species Diversity Species RichnessThe number of species in a given area (N0)Sample Size Issue!Margalef Index Mehinick IndexR1 = S-1/ln(n) R2 = S/√nWhere S = total number of species in area sampledn = total number of individuals observedInterpretation:The higher the index the greater the richnessR1 = 1.28R1 = 1.66Example: S = 6 and n = 50S = 6 and n = 20
19Measuring Species Diversity Diversity Indices - Simpson’s Index = probability that 2 individuals selectedat random will belong to the same species= i(ni(ni-1))/N(N-1)Where:ni= total number of individuals in each speciesN = Total number of individuals in all speciesInterpretation:If probability is high, the diversity of sample is low
20Measuring Species Diversity Diversity Indices - Shannon’s Index H’H’= -i ((ni/N) ln (ni/N))Where:ni= total number of individuals in each speciesN = Total number of individuals in all speciesInterpretation:1.5 (low richness/eveness) to 3.5 (high richness and eveness)
21Hill’s Family of Diversity Numbers Units are given in numbers of speciesNO = total number of species in the sampleN1 = the number of abundant speciesN2 = the number of very abundant speciesN1 = eH’ (H’=Shannon’s index)N2 = 1/ (=Simpson’s index)
25Desert Lizard Diversity Number of individuals for each of 6 speciesof lizards counted in a 1 hectare plotLizard SpeciesNumber of IndividualsCnemidophorus tesselatus3Cnemidophorus tigris15Crotophytus wislizenii1Holbrookia maculataPhrynosoma cornutum10Scleoporus magister2TOTAL Individuals32
37Processes Explaining Diversity Gradients • Historical Disturbance Hypothesis- landscape reflects historical events, not currentenvironmental conditions (not in equilibrium)Habitats catastrophically disturbed are “undersaturated” in terms of species because there hasn’t been adequate time for adaptation and speciationProblems: evidence from tropics
39Processes Explaining Diversity Gradients Equilibrium TheoriesLandscape is a reflection of current environmental conditions (in equilibrium)ProductivityClimate stability-Harsh habitatHabitat heterogeneityBiotic interactionsLarge Area
40Processes Explaining Diversity Gradients ProductivityWhat is the link b/w productivity and biodiversity?Tropics 2200 g/m2/yrTemperate 1200 g/m2/yrBoreal 800 g/m2/yrScaleEstuaries, marshes are most productive ecosystems on earth, with lowest diversity
41Processes Explaining Diversity Gradients Climate Stability (Harsh Habitat)Environments with low stability are harsher and are less diverseWhy?ExceptionsAreas with stable climate but low diversity
42Processes Explaining Diversity Gradients Habitat Diversity (Heterogeneity)What is the link?Is it a direct relationship?
43Processes Explaining Diversity Gradients Biotic InteractionsIs speciation driven by competition in low lats and adaptation to physical stress in high lats?Exceptions: trees/plantsWhat about predation as a mechanism?Circularity
44Processes Explaining Diversity Gradients Large Land AreaSupports more individsSupports more speciesTropics? Boreal?.
45Diversity in TRF and Coral Reefs Equilibrium ViewpointStability is the major characteristic of a community. Following disturbance, it recovers and high diversity is maintained by a variety of mechanisms. Community reflects current conditions.Non-Equilibrium ViewpointCommunities rarely reach an equilibrium state and high diversity results from changing environmental conditions.
46Diversity in TRF • Janzen’s Hypothesis (1970): Biotic interactions - host-specific herbivores- seed predation- canopy foliovores• Hubbell’s research (1979, 1980) to support Janzen• Non-equilbrium explanation (Connell 1978)- coral reefs
51The Non-Equilibrium Hypothesis (Connell 1978) Connell’s ConclusionsTRF and Coral Reefs demonstrate Non-Equilibrium HypothesisEquilibrium and Non-Equilibrium are not mutually exclusiveBottom line is:Role of human disturbances
52More Intermediate Disturbance Hypothesis (Denslow 1980) Intermediate levels of disturbance vary by ecosystemEcosystemHistoric Rate ofDisturbance (years)Prairie2Chaparral30Pine50Oak-HW50-100Spruce-Fir1000