BIOL 312 Lecture Slides Topic 11 PDF

BIOL 312, Topic 11 Community ecology: implications for ecosystems License: CC0 Public Domain Associated Readings/Videos Textbook Chapter 11 pg. 322-335 McCann KS (2000) The diversity-stability debate. Nature 405: 228-233. PDF posted on Blackboard Topic 11: Outline Introduction t...

BIOL 312, Topic 11 Community ecology: implications for ecosystems License: CC0 Public Domain Associated Readings/Videos Textbook Chapter 11 pg. 322-335 McCann KS (2000) The diversity-stability debate. Nature 405: 228-233. PDF posted on Blackboard Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate What is a community? Community: group of interacting species in a defined geographic area Community boundaries are blurry Extent of interaction? Extent of geographic area? All species or taxonomic or functional groups? - Boreal community (plants, animals, fungi, etc.) in terrestrial & aquatic habitats - Boreal forest community - Boreal aquatic community - Plant community in boreal forest - Bird community in boreal forest - And many more possibilities How do we measure or describe community attributes? Trophic Structure (last day) Richness, evenness, diversity (today) Species Composition, functional groups (today) What is biodiversity? Merriam-Webster – “biological diversity in an environment as indicated by numbers of different species of plants & animals” Biodiversity – measure of total biological diversity, at all levels of biological organization, including ▪ Species diversity ▪ Diversity of functional groups ▪ Diversity of habitats communities & biomes ▪ Genetic diversity Which habitat has higher species diversity? Habitat 1 Habitat 2 Species richness: Species richness: 4 species present 6 species present Which habitat has higher species diversity? Habitat 1 Habitat 2 6 Species 4 Species 1 with 15 individuals with 5 individuals each 5 with 1 individual Measures or components of diversity Species diversity is best described as a composite measure of: ▪ The number of species in a community (species richness, S) ▪ The relative abundance or evenness of those species Relative abundance: How common or rare a species is relative to other species in a community. Can use various abundance metrics: # individuals, biomass, % cover. # individuals Relative abundance (proportion) yellow poplar 122 122/274 = 0.45 sassafras 107 0.39 black cherry 12 0.044 cucumber magnolia 11 0.04 red maple 10 0.036 red oak 8 0.029 butternut 1 0.004 shagbark hickory 1 0.004 american beech 1 0.004 sugar maple 1 0.004 total # species = 10 274 1 Species diversity: Composite measure of species richness & evenness How can we compare across two sites or points in time? Need to combine parameters into a single measure H’: an integrative index of species diversity Shannon-Wiener Index (H’): s pi = relative abundance of species i sum this product (pi x lnpi ) loge = natural log (ln) across all species (species 1 to s) and multiply by –1 (to get a positive #) S = # species Bounded between 0 & Hmax Hmax = lnS (all species present in equal abundance) e.g., If S = 10, Hmax = ln (10) = 2.3 Calculate H’ for our example habitats 1 & 2 Habitat 1 Species # of Relative Abundance (pi) ln(pi) pi x ln(pi) trees = # of trees in ea species/total number of trees Trembling aspen 5 = 5/20 Balsam poplar 5 White spruce 5 Pine 5 Total # of trees 20 Σ (pi) (loge pi ) = Total # of species 4 H= Habitat 2 Species # of Relative Abundance (pi) ln(pi) pi x ln(pi) trees = # of trees in ea species/total number of trees Trembling aspen 15 =15/20 Balsam poplar 1 White spruce 1 Pine 1 Birch 1 Willow 1 Total # of trees 20 Σ (pi) (loge pi ) = Total # of species 6 H= Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate Species diversity is measured at a range of scales Alpha (α), Beta (β) & Gamma (γ) Diversity Region 1 Region 2 A C D B Species diversity is measured at a range of scales α → diversity within a community or site (local species pool) Region 1 Region 2 A C D B  Species diversity is measured at a range of scales γ → diversity across multiple regions within larger landscape (landscape species pool) Region 1 Region 2 A C D B  Species diversity is measured at a range of scales β→ diversity between communities (within a region); usually a measure of dissimilarity Region 1 Region 2 A C D B  Species diversity is measured at a range of scales γ (landscape species pool) = α (local species diversity) + β (dissimilarity among sites) Region 1 Region 2 A C D B Interpreting measures of species diversity Which community has higher diversity? Trembling Aspen – 4 individuals White birch – 4 individuals White Spruce - 4 individuals Alder - 4 individuals Balsam poplar - 4 individuals Tamarack - 4 individuals Black spruce - 4 individuals Pine - 4 individuals Should we consider these communities equal in terms of function or diversity? Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate Do all species in a community equally contribute to diversity? Issues with diversity measures – what is not accounted for? Genetic diversity Species composition White birch – 4 individuals Functional groups Trembling Aspen – 4 individuals Alder - 4 individuals White Spruce - 4 individuals Balsam poplar - 4 individuals Tamarack - 4 individuals Black spruce - 4 individuals Pine - 4 individuals Species composition Exotic vs. native Invasive or weedy vs. rare vs. Functional types Groups of sp. that are ecologically similar with respect to their effects on ecosystems or their response to environmental change Alder, lupine, vetch Longsepal globemallow & snowbrush N-fixing plants Woody browsers seeds germinate after fire shewhodreams.weebly.com science.halleyhosting.com All species in a community do not equally contribute to diversity Dominant species: most abundant (or largest biomass) in a community. Impact relative to abundance. Keystone species: relative to its biomass or abundance, has a disproportionately large impact on community structure Ecosystem engineers: maintain or create new habitats for themselves &/or other species mcgregors.co.nz/sites/default/files/leaf-roller.jpg Keystone species: Species with disproportionately high influence on community structure, relative to their abundance. – E.g., Predators may keep several prey populations well below carrying capacity – Decreases likelihood of competitive exclusion – Increase species diversity Classic Study Invertebrate sp. richness Sea stars as Keystone Species 20 15 Robert Paine (1966, 1976) 15 10 8 5 0 Pisaster Control Removed Purple starfish as keystone species in the intertidal zone Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate Why do we care about biodiversity (and/or its components)? Because its declining…… Why do we care about biodiversity (and/or its components)? Because its declining…… Why do we care about biodiversity (and/or its components)? Because composition is changing Many ecosystems dominated by invasive species Range limits are moving Why do we care about biodiversity (and/or its components)? Compositional affects on ecosystem processes Isbell, F. (2010) Causes and Consequences of Biodiversity Declines. Nature Education Knowledge 3(10):54 Why do we care about biodiversity (and/or its components)? Compositional effects on ecosystem processes (esp. via interactive controls) How does “who’s there” affect ecosystem processes? Species effects on resource supply (N availability) Introduction of the N-fixing fig, Morella faya, in Hawaii resulted in the displacement on the dominant native tree species and large increases in N availability botany.hawaii.edu Textbook Fig. 11.3: Impact of the N-fixing tree Morella faya on N inputs, litter N concentration, & N mineralization rate in a Hawaiian montane forest. Species effects on disturbance regime Species present can alter fire disturbance regimes ▪ E.g., Foliage of deciduous trees generally less flammable than conifers ▪ See table http://stopthespraybc.com Brooks et al. 2004 Species composition can alter disturbance regimes Fire isn’t the only disturbance regime altered by species composition Invasive Tamarix (salt cedar) alters flooding regimes by desiccating waterways Black wattle (Acacia Invasive European beach grass alters mearnsii) increases dune formation in Australia, New streambank erosion in S. Zealand & N. America Africa by uprooting Hendrik Mentx during high flows  Textbook Fig. 11.6 Species effects on microclimate Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate  Are more diverse communities more stable? Charles Elton (1920’s); Robert MacArthur, Eugene Odum (1950’s) Diversity = Stability Diversity-stability hypothesis: more diverse and complex communities are better buffered from impacts of species loss & environmental fluctuations?  Are more diverse communities more stable? Charles Elton (1920’s); Robert MacArthur, Eugene Odum (1950’s) Diversity = Stability Diversity-stability hypothesis: more diverse and complex communities are better buffered from impacts of species loss & environmental fluctuations? Associated Readings/Videos Textbook Chapter 11 pg. 322-335 McCann KS (2000) The diversity-stability debate. Nature 405: 228-233. PDF posted on Blackboard Topic 11: Outline Introduction to ecological communities Community structure - Species richness, evenness, & diversity - Alpha, beta & gamma diversity - Species composition, functional groups - Keystone species & ecosystem engineers How does community structure affect ecosystems? – Diversity & compositional effects – Diversity-stability debate