Schueller 509: Lecture 12 Community ecology 1. The birds of Guam – e.g. of community interactions 2. What is a community? 3. What can we measure about whole communities? An ecology mystery story If birds on Guam are declining due to… • hunting, then bird populations will be larger on military land where hunting is strictly prohibited. • habitat loss, then the amount of land cleared should be negatively correlated with bird numbers. • competition with introduced black drongo birds, then….prediction? • ……. come up with a different hypothesis and matching prediction! $3 million/yr Why not profitable hunting instead? (Worked for the passenger pigeon: “It was the demographic nightmare of overkill and impaired reproduction. If you’re killing a species far faster than they can reproduce, the end is a mathematical certainty.” http://www.audubon.org/magazine/may-june- 2014/why-passenger-pigeon-went-extinct) Community-wide effects of loss of birds Schueller 509: Lecture 12 Community ecology 1. The birds of Guam – e.g. of community interactions 2. What is a community? 3. What can we measure about whole communities? What is an ecological community? Community Ecology • Collection of populations of different species that occupy a given area. What is a community? e.g. Microbial community of one human “YOUR SKIN HARBORS whole swarming civilizations. Your lips are a zoo teeming with well- fed creatures. In your mouth lives a microbiome so dense —that if you decided to name one organism every second (You’re Barbara, You’re Bob, You’re Brenda), you’d likely need fifty lifetimes to name them all. When you climb out of bed in the morning, ten times more bacterial cells climb out of bed than do human cells. In your gut, coalitions of hundreds of different species compete for food in a dark, simmering biome alive with as many as 100 trillion microbes.…Ultimately, we aren’t individuals; we are big permeable societies.” From The New You, BY ANTHONY DOERR, Orion Magazine Display at the American Museum of Natural History (NYC) e.g. Plant microbial community Application: Invasive plant microbiome manipulation What is an ecological community? Community Ecology • Collection of populations of different species that occupy a given area. • Species may interact directly, indirectly Direct Interactions Schueller 509: Lecture 12 Community ecology 1. The birds of Guam – e.g. of community interactions 2. What is a community? 3. What can we measure about whole communities? What can we measure about a community? • Composition • Structure • Function Characteristics of a community • Composition = which organisms are there COMPOSITION Species list and counts of each: • Are certain species or groups (guilds, taxa) present or absent? • What is the relative abundance (proportion of total # individuals, biomass, or cover) of certain species? • Are certain species dominant/rare? • What is the diversity? COMPOSITION: Species diversity Which of these is the most diverse? COMPOSITION: Species diversity • Richness: How many species are present? • Evenness: Are they equally abundant? RICHNESS (S) A Diversity Index considers both! EVENNESS • Which spp. are dominant? • rare? • What is the richness? • Is evenness high or low? COMPOSITION: Species diversity Diversity Index • Shannon (or Shannon-Weiner) index • H = (pi)(log pi) • Where pi = ni / N = proportion of species • Also “Simpson's diversity index" (and many others) A Diversity Index considers both richness & evenness! Examples of communities. Why is Shannon- Wiener diversity index (H) so much lower in the second example? When would H=0? Upstream: Dexter Huron Downstream: Island Park Stream Quality Score (based on composition) Main Branch Tributary 36.2 60.3 Tu AM 38.9 57.2 Tu PM 54.5 Th AM 38.7 Th PM Stream Quality Score (based on composition) Upstream Downstream 68 58.5 58.4 58 55.1 46 How do we know if we have sampled all the species that are there? What can we measure about a community? • Composition – Presence of certain spp. – Relative abundance & dominance – Diversity (at different scales) • Species Richness (S) • Evenness – Similarity • Structure STRUCTURE Depends on how defined – may include: • Number of trophic levels • Layers or patchiness of vegetation • Physical structure created by living things STRUCTURE: Layers and Zones © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. •Effect of sea urchins on structure of kelp forest community https://www.youtube.com/watch?v=D3W4OCnHyCs •Effect of agriculture on structure and composition Monoculture •Effect of agriculture on below ground structure • Relationship between structure (grass height) and composition (birds) Michigan State Extension publication Yvette et al. 2015. Response of avian diversity to habitat modification can be predicted from life-history traits and ecological attributes. Landscape Ecology; 30 (7): 1225 - Compared bird populations in cultivated mango orchards vs. natural habitats in South Africa. - 35 % fewer bird species in agriculture - "Mango orchards are missing the low level woody scrub found in natural vegetation and the birds missing from the orchards are exactly those that depend on this layer of vegetation.” - USE vegetation structure to improve biodiversity in agriculture! Permaculture structure? From: Gaia's Garden: A Guide to Home-Scale Permaculture / by Toby Hemenway Should dead wood be removed from forests? Snags, logs, and Coarse Woody Debris (CWD) What can we measure about a community? • Composition – Presence of certain spp. – Relative abundance & dominance – Diversity… – Similarity • Structure – Height, growth forms, layers, zones, arrangement, etc. • Function – Interactions & processes – more later Which community has greater species richness? Which community has greater species evenness? Which community has greater species diversity? What is an ecological community? Community Ecology • Collection of populations of different species that occupy a given area. • Species may interact directly, indirectly • Has measurable composition, structure & function Direct Interactions 3 1 2 http://www.haehnlesanctuary.org/cranecountfive.html Self assess • What could you measure (make a list) about any two communities we have been to in lab? How would they compare (be specific)? • What community-levels measures could you use to assess the difference between a tall grass prairie and an agricultural field of soybeans? • Name 3 examples fo what we might call an ecological “community” • How is dead wood a part of a community? • What can you measure about a community that you cannot about a population? • How can a community have high richness but low diversity? • What information do you need to obtain a diversity index? • Give 3 examples of community structure measures. • What are the main types of species interactions we might see between species?.