1. OUR Ecological Footprint - 5 1. Recycle; pay tax for it. 2. Live near work; Ride bike; minimize car use. 3. Buy energy-efficient furnace. 4. Programmable thermostat: winter/summer 5. Turn in notes from movie for EC

3. Opportunities IB 390 Introductory Research IB 490 Independent Study See Website for IB Majors www.life.uiuc.edu/sib/390_490.htm

4. Next week: Lab Homework 10 ANOVA 5 Abstracts for SDP2 Group Proposal WS - 3 days before lab Exam 2 Formulae will be provided. BRING calculator. Practice ?s: on web on Exam 2 date

5. Ch 21: Community Structure

6. Ch 21 +23 Community Ecology Species Abundance and Biodiversity

7. Objectives Species at regional vs. local scale Species sorting ---> local composition Species richness (# species) Local + regional components Species relative abundance Patterns Controls Species-area relationship Species diversity Hypotheses to explain variation in SD Measures to quantify and compare SD

8. Sample Exam ? A 100-yr experiment tested the effect of fertilizer on species diversity (H’) in a grassland. RESULTS: H’ of unfertilized remained steady. H’ of fertilized decreases through time. 1)Summarize the major result of the study. 2)What 2 components of a community does the Shannon-Wiener Index (H’) incorporate? 3)What combination of these components yields the greatest value of H’? 4)Explain the results in terms of competition and niche theory. 5)Do the results support the hypothesis that the superior competitor can exist at lower resource levels than its competitors? Explain.

9. Local communities are assembled from the regional species pool. Species sorting = processes that determine local community composition.

10. Experimentally-composed communities show species sorting. What caused the sorting? Fertility: low high

11. Environmental filters eliminate species that can’t tolerate conditions---> species sorting

12. Many factors influence regional and local species richness.

13. Local communities contain a subset of the regional species pool. ***What determines whether a species can be a member of a given community? 1 Adaptations of species to environmental conditions (habitat selection) 2 Persistence in face of competitors, predators, and parasites

14. H 1 :Species sorting (and beta diversity) should be greatest where regional species pool is largest. When species pool is smaller, competition should be relaxed---> ecological release = species expand into habitats normally filled by other species and increase in population density Ecological release provides evidence for hypothesis of local interactions controlling species diversity. (e.g. competition for resources structures communities and limits # species)

15. Species richness (# species) has both local and regional components.  (alpha) = local # species in small area of homogeneous habitat  (beta) = # species turnover between habitats  (gamma) = (landscape) regional: total # species in all habitats within a barrier-free geographic area

16. Above species richness measures determined by ecology and regional pool  (delta) = available pool of species within dispersal distance (up to continental scale) determined evolutionarily

17. Species in communities vary in relative abundance. Most species are rare; few are common.

18. What is the likelihood of sampling a rare species? A common species? How accurate are the data for rare species?

19. Species abundance (dominance diversity) curves…Which community has greatest evenness in abundance? Log scales… Rank order of abundance MostLeast

20. Number of species increases with area sampled. log

21. Species - area relationship: S = c A z S = # of species A = area c and z = fitted constants log S = log c + z log A = linear z (slope) = usually 0.2 to 0.35 z = less for continental areas, greater for islands Rapid dispersal within continental areas prevents local extinction within small areas

22. *** Why do larger areas have more species? in part because… larger areas give larger samples but also… greater habitat heterogeneity (sample more types of habitats) larger islands---> bigger target for immigrants larger populations ---> –greater genetic diversity –broader distributions over habitats –numbers large enough to prevent stochastic extinction

23. Area and habitat diversity both contribute to the species-area relationship.

24. Spatial variation in woody species richness

25. Hypotheses to explain variation in species richness 1 Heterogeneity in space and time 2 (Vegetation and food complexity) 3 Predation 4 Competition/niches 5 Disturbance 6 Equilibrium models

26. 1 Heterogeneity in space and time hypothesis Interacts with production hypothesis Relates to niche arguments (see below)

27. 2 Vegetation (structural complexity) overrides primary production in determining local richness.

28. Communities with simple vegetation structure have lower richness, yet can have very different levels of productivity.

29. Bird richness increases with greater structural complexity.

30. Species richness increases as a stream becomes larger and has more habitat and food diversity.

31. 3 Predation hypothesis High productivity---> high predator populations ---> reduce competition among prey and permit more to coexist (starfish experiment) More predation---> more selection for escape adaptations by prey Crypsis to avoid predation

32. Pest pressure hypothesis for maintaining tree species richness

33. Distance-dependent mortality is consistent with the pest pressure hypothesis.

34. Soil pathogens kill seedlings near parent trees ---> maintain species richness?

35. 4 Competition hypothesis: High richness --> less competitive exclusion? Why? By what means?

36. Niche metrics

37. How can more species be added to a community? Increase total niche space Increase niche overlap Decrease niche breadth

38. Does increase in niche diversity --> increase in species richness? As s.r. increases, so does morphological diversity.

39. 4 Competition hypothesis, cont.: High richness --> less competitive exclusion? Why? By what means? greater specialization (narrower niche) greater resource availability (greater niche space) reduced resource demand (smaller populations) intensified predation (populations below K) Are there more ecological roles in tropics? Greater niche space from greater number of niche axes and length of each axis? relates to heterogeneity in space/time hypothesis

40. Populations in regions with few species show ecological release (and larger realized niches). Less regional species ---> 1) less local sp. rich 2) each species more abundant greater habitat breadth 3) beta diversity (turnover of species) decreased.

41. Realized niche is always smaller than fundamental niche, but with ecological release ---> larger realized niches

42. 5 Intermediate Disturbance Hypothesis Richness peaks at intermediate levels Too low disturbance --> competitive exclusion Too high disturbance --> limited number of species adapted

43. 6 Equilibrium hypothesis Richness reaches an equilibrium when factors removing species = factors adding species.  more additions (e.g. speciation) or and/or fewer deletions (e.g. extinctions) = greater species richness.

44. Nile perch vs. cichlid fish in Lake Victoria

45. Scientific Process Observation: Cichlid fish populations declined after the introduction of Nile perch. Question: Did the introduction of the perch cause the decline in cichlid populations? ***Generate an ‘if…then’ hypothesis/prediction

46. Hypothesis 1: If introduction of Nile perch caused the decline of cichlid populations, then 1) lower cichlid populations in areas with high than low perch populations. 2) then higher cichlid populations in areas with perch removed than in control areas. ***What are independent and dependent variables? Plot each prediction. Which provides a stronger test of the hypothesis? If get no support, what do next?

47. ***Are there alternative hypotheses? H1: original hypothesis H2: A newly introduced cichlid parasite caused the decline. H3: A marked decline in aquatic vegetation on which cichlids feed caused the decline. H4: Dramatic changes in water chemistry caused by agricultural runoff caused the decline. H5….

49. How can community structure be quantified and compared?

50. *** Which variables can be used to describe the species diversity of a community? Which community is more diverse? Species richness Species relative abundance

51. Species richness (# of species) = S S varies with sample size so… Compare S by rarefaction: equal-sized subsamples randomly drawn.

52. Species richness: # of species BUT species differ in abundance and thus in role Species diversity: weight species by their relative abundance Simpson’s index: D = 1 /  p i 2 p = proportion of each species in total sample Shannon-Wiener index: H' = -  p i ln p i Evenness = ratio observed/maximum diversity E D = D/D max, where D max = S or E H’ = H'/H max, where H max = ln S Measures of community structure

53. Calculate Species Diversity: Species No. Ind. p i p i 2 ln p i p i ln p i 1 5.25.0625 -1.386 -.3465 2 4.20.0400 -1.609 -.3218 3 3.15.0225 -1.897 -.2846 4 4.20.0400 -1.609 -.3218 54.20.0400 -1.609 -.3218 Total (N) 20 1.00 ∑=.205 ∑= -1.5965 D = 1/ ∑p i 2 = 1/.205 = 4.878 H' = -∑ p i ln p i = 1.5965 Calculate Evenness: E D = D/D max 4.878/5 =.9756(D max = S) H' = H'/H max = 1.5965/1.609 =.9922 (H max = ln S)

54. Comparisons of diversity indices among communities. ***What factors increase species diversity? more species. less difference in relative abundance among species. C1 C2 C3 C4 C5

55. Objectives Species at regional vs. local scale Species sorting ---> local composition Species richness (# species) Local + regional components Species relative abundance Patterns Controls Species-area relationship Species diversity Hypotheses to explain variation in SD Measures to quantify and compare SD