Community and Population Ecology

1. Community and Population Ecology Chapter 6

2. American Alligator

3. American Alligator: community structure • Highly adaptable – around for nearly 200 million years • Keystone species - A species whose loss from an ecosystem would cause a greater than average change in diversity or abundance of other species, community structure or ecosystem process. • Gator holes – fresh water/food supplies, refuges • Nest mounds – nesting/feeding sites for herons & egrets • Balance predator populations • Only natural predator is humans • 1967 – endangered species list – 90% decimated • Successful environmental comeback

4. Affect of Species Diversity on the Sustainability of a Community Species diversity increases the sustainability of communities and ecosystems.

5. Species Diversity • Species richness combined with species evenness • Niche structure • Varies with geographic location • Species richness declines towards poles

6. Species Diversity • Species richness combined with species evenness determines diversity of an ecosystem • Tropical Rainforest vs. Coniferous Forest

7. Species Diversity: communities • Niche structure determines diversity • The number and types of similar and different niches along with how the organisms within them interact • For example – stream macroinvertebrates

8. Species Diversity: communities • Niche structure determines diversity • The number and types of similar and different niches along with how the organisms within them interact • For example – stream macroinvertebrates

9. Species Diversity: communities • Diversity varies with geographic location (richness declines towards poles) Bird species richness in the Western Hemisphere (Hawkins et al. 2006).

10. Sustainability and Environmental Change • Certain factors allow living systems to maintain stability/sustainability (equilibrium) • Inertiaor persistence – ability to resist disturbance • Tropical rainforests (high), grasslands (low) • Constancy- ability to maintain population size within limits • Endemic species vs. invasive • Resilience – ability to recover • Tropical rainforests (low), grasslands (high)

11. Equilibrium: Area and Distance Effects Animations/species_equilibrium.html

12. Richness and Sustainability • Richness tends towards sustainability, productivity and better recovery • Not all of the ‘eggs are in one basket’ • NPP seems to peak with at least 10-40 producers (difficult to distinguish ‘most important’)

13. Roles of Species in a Community Based on ecological roles, species are described as: native endemic nonnative indicator keystone or foundation species

14. Ecological Niche • Niche = unique role • Native/endemic species = normal • Nonnative species =invasives, aliens • Spread in new, suitable niches • Also – most crops and feedstocks • Can reduce native populations (Africanized honeybees) • Lack predators, disease and competition

15. Indicator Species • Early warning system for the health of an ecosystem • Trout - absence means low DO

16. Vanishing Amphibians: indicator species • 33% threatened, 43% declining with no clear-cut reason • Habitat loss and fragmentation (drain/fill) • Prolonged drought (breeding sites) • Pollution (pesticides) • Ultraviolet radiation (ozone loss/egg damage) • Parasites (increased susceptibility) • Viral and fungal diseases (skin) • Climate change • Overhunting • Nonnative predators and competition

17. Vanishing Amphibians • Why we should care • Indicates there is something wrong • Skin – pharmaceuticals – painkillers, antibiotics • Phantasmal poison frog – painkiller , Epibatidine, that doesn’t have the side effects of morphine, but 200x stronger

18. Life Cycle of Typical Frog

19. Frogs Galore Videos/Frogs_Galore.mov

20. Keystone Species • Significant role in their food web • Elimination may alter structure, function of community • Pollinators • Top predators – Grey Wolf in Yellowstone

21. Keystone Species: Dung Beetle Remove dung Aerate soil Nutrient recycling Fig. 6-3, p. 110

22. Sharks – garbage men of the sea • Keystone species • Remove injured, sick animals • Many are non-threatening • Provide potential insight into cures for human diseases(immune system function)

23. Foundation Species • Create habitats and ecosystems • Beavers • Create wetlands • Elephants • Push over trees, allow grasses & nutrient cycling • Seed dispersers • Bats’ & birds’ droppings

24. Species Interaction Competition, predation, parasitism, mutualism, and commensalism – affect resource use and population sizes of the species in a community. Adaptations allow some species to reduce or avoid competition.

25. Interspecific Competition • No two species can share vital limited resources for long • Resolved by: • Migration • Shift in feeding habits or behavior • Population drop (Gause’s Paramecium Experiment) • Extinction • Intense competition leads to resource partitioning Animations/gause_v2.html

26. Resource Partitioning in Warblers

27. Species Interaction • Predator-prey relationships– food webs • Predators and prey both benefit – individual vs. population (weak, sick, aged, least fit) • Predator strategies • Herbivoressimply walk, fly or swim • carnivores (pursuit/ambush – camouflage, poison)

28. Predator Avoidance: camouflage • Prey strategies - Hard shell, speed, smell, spines, etc.

29. Predator Avoidance: chemical warfare, warning coloration Fig. 6-5cd, p. 113

30. Predator Avoidance: chemical warfare, warning coloration, mimicry Fig. 6-5ef, p. 113

31. Predator Avoidance: deceptive looks, deceptive behavior Fig. 6-5gh, p. 113

32. Species Interaction: Symbiosis

33. Symbiosis: Parasitism Tomato horn worm and Braconid Wasp • Live in or on the host • Parasite benefits, host harmed • Parasites promote biodiversity – pick off weak, aged, sick, keep population size low and allows other species to move in. Cowbird

34. Symbiosis: Mutualism • Everybody benefits • Nutrition and protection • Gut inhabitant mutualism • Humans and termites (enzymes for biofuels)

35. Symbiosis: Commensalism • Benefits one with little impact on other • Epiphytes • Bird nests

36. Review: How Species Interact Animations/species_interactions.html

37. Communities Respond to Changing Environmental Conditions Ecological succession – The change in community structure and composition due to changing environmental conditions. Precautionary principle – Measures taken to prevent or reduce harm even if cause-and-effect relationships have not been fully established scientifically.

38. Primary succession • gradual establishment of community in lifeless areas • “Bare” – no soil • 100s to 1,000s of years to establish fertile soil • Secondary succession • More common • Not “bare” • Has soil

39. Succession Animations/succession.html

40. Disturbances create new conditions Eliminates species Opens new niches, increases richness Intermediate disturbance hypothesis frequent/moderate disturbances results in increased species richness Ecological Succession

41. Succession’s Unpredictable Path – Intermediate Disturbance Hypothesis • Doesn’t always arrive at a climax community • Ever-changing mosaics of different stages • Continual change, not permanent equilibrium • Results in highest level of diversity

42. Precautionary Principle • Lack of predictable outcome should not prevent conservation • Consider health of ecosystem & humans

43. Population Growth • Populations differ • Number • Distribution • Age structure • No population can continue to grow indefinitely • Limiting factors • Competition

44. Population Dispersion/Distribution

45. Clumping • Clumped Resources • Protection • Hunting success • Mating or young-rearing

46. Populations Sizes Are Dynamic • Vary over time population = (births + immigration) - (deaths + emigration)

47. Populations Sizes Are Dynamic Changes in Age structure Pre-reproductive stage Reproductive stage Post-reproductive stage

48. Video: Bonus for a Baby Videos/Bonus_for_a_Baby.mov

49. Limits to Population Growth • Biotic potential is idealized capacity for growth • Intrinsic rate of increase (r) • Nature limits population growth with resource limits and competition • Environmental resistance = limiting factors

50. Limits to Population Growth • Carrying capacity – biotic potential and environmental resistance • Exponential growth – unrestricted • Logistic growth – restricted