1. Levels of Ecological Organization in Freshwater Systems Population Community Ecosystem

2. Community Ecology in Freshwater Systems What controls species composition (aka, diversity)? What causes species composition to change over space and time? What are the consequences of variation in species composition? Why does “biodiversity” matter in freshwater systems?

3. What is a community? A group of interacting species occurring in a particular place, at a particular time.

4. How do we describe freshwater communities? Species richness Relative abundance Diversity indices (e.g., Shannon, Simpson’s)

5. How do you describe a community? Species richness: 4

6. How do you describe a community? Diversity indices: richness weighted by relative abundance >

7. Food Webs, Functional Groups, and Trophic Levels Sp. 1Sp. 2Sp. 3Sp. 4 Sp. 5 Sp. 6 Sp. 7 Sp. 8 Sp. 9 Sp. 10 Levels ~ Diversity

8. Assumptions: Individual species occupy one level Sp. 1Sp. 2Sp. 3Sp. 4 Sp. 5 Sp. 6 Sp. 7

9. Assumptions: Individual species occupy one level These systems are rare: Sp. 1 Sp. 2 Sp. 3 Sp. 1 Sp. 2 Sp. 4 Sp. 3 Sp. 5

10. Variation in community composition over space

11. SpringFall Variation in community composition over time

12. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment > Limiting resources > Limiting conditions

13. Limiting Resources: Some thing a species or group of species uses to survive.

14. Limiting Condition: Some attribute of the environment that a species or group of species must tolerate to survive in a particular place.

15. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species > Predation (+ / -) > Competition (- / -) > Mutualism (+ / +)

16. Predation and Community Composition Trophic cascades (Flecker and Townsend 1994) …and galaxiid hell.

17. Predation and Community Composition Trophic cascades No Fish (Flecker and Townsend 1994)

18. Predation and Community Composition Trophic cascades Significant effect of “fish species” on total invertebrate density. Significant negative effect of “fish” on species richness, no effect of “fish species”.

19. What isn’t insect richness telling us about the effect of trout on community composition? (Flecker and Townsend 1994)

20. Predation and Community Composition Super predators!! No Fish Fish

21. Competition and Community Composition The ghost of competition past Diet breadth Disruptive selection Proportion of Population

22. Competition and Community Composition The ghost of competition past

23. Competition and Community Composition The ghost of competition past

24. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment AND Interactions among species

25. Abiotic  Biotic effects on community composition Dicosmoecus (Wootton et al. 1996) “Resistant Grazer”

26. Abiotic  Biotic effects (Wootton et al. 1996)

27. Unregulated Regulated =

28. Abiotic  Biotic effects (Wootton et al. 1996)

29. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Ecosystem age

30. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Ecosystem age - Successional ponds - Ephemeral streams and ponds

31. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Ecosystem age Disturbance

32. Disturbance and community composition (Connell 1978) Good Competitors Good Colonizers Good Colonizers + Good Competitors Minimally Disturbed Extensively Disturbed

33. Disturbance and community composition

34. (Pollock et al. 1998) Kadashan River Basin, SE Alaska Response of riparian plant communities to flood frequency. Frequency = number of times per year that the mean elevation of a site was inundated.

35. Disturbance and community composition (Pollock et al. 1998)

36. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Ecosystem age Disturbance Productivity

37. Productivity and community composition VS.

38. Productivity and community composition

39. The paradox of enrichment (Rosenzweig 1971) Time Population Size

40. The paradox of enrichment (Rosenzweig 1971) Time Population Size Low and Moderate Productivity Time Population Size High Productivity

41. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Age Disturbance Productivity Size and Complexity

42. Size and community composition Hypothesis: As size increases, so does habitat heterogeneity, resulting in more “niches” that can be filled by more species.

43. Size and community composition

44. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Age Disturbance Productivity Size and Complexity ?

45. Size versus Productivity (Post et al. 2000) Sampled 25 lakes in North America that varied in size AND productivity. Used N isotopes in top-predators fish to determine food-chain length leading to that predator.  15 N <  15 N Maximum Trophic Position <

46. (Post et al. 2000) Size versus Productivity

47. (Post et al. 2000) Size versus Productivity

48. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Age Disturbance Productivity Size and Complexity ?

49. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Age Disturbance Productivity Size and Complexity Colonization and Extinction

50. Colonization, extinction, and community composition Island Biogeography Theory (MacArthur and Wilson 1987)

51. Colonization, extinction, and community composition Island Biogeography Theory Effect of increased isolation

52. Colonization, extinction, and community composition Electric Fishes (Fernandes et al. 2004)

53. Colonization, extinction, and community composition (Fernandes et al. 2004) “Isolated” “Connected” Amazon Mainstem Tributary

54. Colonization, extinction, and community composition (Fernandes et al. 2004)

55. What controls community composition (i.e., species diversity)? Interactions with the abiotic environment Interactions among species Age Disturbance Productivity Size and Complexity Colonization and Extinction