Ch. 47 – Community Ecology

1. Ch. 47 – Community Ecology

2. Concept of Community • Acommunityis an assemblage of populations interacting with one another within the same environment • Composition is a thorough listing of various species in the community • Species Diversity includes: 1. Species Richness – total number of different species in the community 2. Relative Abundance – proportion of the total population represented by each species

3. Figure 53.1 • The various animals and plants surrounding this watering hole are all members of a savanna community in southern Africa

4. Community Structure Rain Forest Coniferous Forest

5. Two different communities can have the same species richness, but a different relative abundance A B C D Community 1 A: 25% B: 25% C: 25% D: 25% Community 2 Figure 53.11 A: 80% B: 5% C: 5% D: 10% • A community with an even species abundance • is more diverse than one in which one or two species are abundant and the remainder rare

6. Structure of the Community • Competition • When two species compete, the abundance of both species is negatively impacted Predation (Herbivory – plant predation) ● One organism, the predator, eats another called the prey. Parasitism ● One organism, the parasite, feeds ON another called the host. These tend to increase the abundance of the predator (or parasite) and reduce the abundance of the prey (or host)

7. Table 53.1

8. Habitat and Ecological Niche • Habitat • The area an organism lives and reproduces in • Ecological niche • The role a species plays in its community • Includes its habitat, and • Its interactions with other organisms • Fundamental niche - All conditions under which the organism can survive & reproduce • Realized niche – part of the fundamental niche that the species actually occupies

9. Feeding niches for Wading Birds

10. Competition Between Populations • Interspecific competition • When members of different species try to use a resource that is in limited supply (food, light, etc.) • Competitive Exclusion Principle • No two species can indefinitely occupy the same niche at the same time • Resource Partitioning decreases competition • Can lead to character displacement. This is the tendency of a characteristic to become more divergent when species are together.

11. Competition betweentwo laboratory populations of ParameciumBoth grow fine separately but only P. aurelia survives when they are grown together

12. Character Displacement in Fincheson the Galápagos Islands

13. Niche Specialization AmongFive Species of Coexisting Warblers

14. Competition BetweenTwo Species of Barnacles Connell removed the larger Balanus individuals. The smaller Chthamalus barnacles moved down & survived equally well in both places

15. Competition BetweenTwo Species of Barnacles EXPERIMENT RESULTS When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area. Ecologist Joseph Connell studied two barnacle speciesBalanus balanoides and Chthamalus stellatus that have a stratified distribution on rocks along the coast of Scotland. High tide High tide Chthamalus Chthamalusrealized niche Balanus Chthamalusfundamental niche Balanusrealized niche Ocean Ocean Low tide Low tide In nature, Balanus fails to survive high on the rocks because it isunable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata. CONCLUSION The spread of Chthamalus when Balanus wasremoved indicates that competitive exclusion makes the realizedniche of Chthamalus much smaller than its fundamental niche. Figure 53.2

16. Predator-Prey Interactions • Predation • One living organism, the predator, feeds on another, the prey • Predator is frequently larger • Predator population is usually smaller than the prey population • Predator has lower reproductive rate • Prey is usually consumed in its entirety • Presence of predators can decrease prey densities, and vice-versa

17. Predators

18. Predator-prey Interaction BetweenParamecium caudatum and Didinium nasutum Paramecium & Didinium placed in same culture. Didinium ate all the Paramecium and then died of starvation

19. Predator-prey InteractionBetween a Lynx and a Snowshoe Hare When hares have adequate food & there are no predators, the cycling stops. Hares given adequate food but with predators; they still cycle Predators excluded but no food was given to hares; cycling stopped

20. Boom-and-bust cyclesare influenced by complexinteractions between biotic and abiotic factors. Predator populations may be influenced by availability of prey - as more prey is available, they reproduce more and their population increases. When the predator population gets too high and they eat all the prey, their population falls.

21. Prey populations may be influenced by 1.Predation 2. Fluctuations in the availability of the plants they feed on Prey may not be regulated by predators. Their population may increase until they run out of resources, then their population crashes. As a result the predator population soon declines because of lack of food availability.

22. Feeding adaptations of predators include: claws, teeth, fangs, stingers, and poison Some predator-prey interactions lead to coevolution: a series of reciprocal adaptations in two species

23. Predator Adaptations

24. Prey Defenses • Mechanisms that thwart the possibility of being eaten by a predator. Some examples: • - Spines • - Tough Epidermis • - Poisonous Chemicals • - Camouflage – ability to blend into the background. Have cryptic coloration. • - Bright Coloration • - Flocking Behavior

25. Spines as protection for plants against herbivory

26. Chemical Defenses in Plants Poison Oak and its rash

27. Camouflage in the Anglerfish

28. Cryptic Coloration Figure 53.5

29. Cryptic Coloration

30. Cryptic Coloration

31. Anti-predator Defenses False eyespots Poisonous skin + Warning coloration Large false head

32. Aposematic (warning) coloration All these snakes are poisonous

33. Mimicry • One species (mimic) resembles another species (model) that possesses an overt anti-predator defense. • Two main types: • 1. Batesian Mimicry - Mimic lacks defense of the organism it resembles • 2. Müllerian Mimicry - Mimic shares same protective defense as its model

34. Mimicry Among Insects withYellow and Black Stripes a, b, & c are examples of Batesian mimicry because they do not have the capability to sting. Beetle Fly Moth Yellow jacket d & e are Mullerian mimics since they both use stinging as a defense Bumblebee

35. In Batesian mimicry A palatable or harmless species mimics an unpalatable or harmful model (b) Green parrot snake (a) Hawkmoth larva Figure 53.7a, b

36. Batesian Mimicry (flies, beetles & ants mimic wasp) Wasp

37. Batesian Mimicry Poisonous models on left Harmless mimics on right

38. In Müllerian mimicry Two or more unpalatable species resemble each other (a) Cuckoo bee (b) Yellow jacket Figure 53.8a, b

39. Symbiotic Relationships • Interactions in which there is a close relationship between members of two species. Frequently one species lives in or on another. • Three main types of symbiosis are: • - Parasitism • - Commensalism • - Mutualism

40. Symbiotic Relationships • Parasitism • - Parasite derives nourishment from a host, and may use host as habitat and mode of transmission • - Endoparasites - live inside host • - Ectoparasites - live on outside of host • Natural selection favors parasites that infect but don’t kill their hosts.

41. Parasites Leech Flea Mosquito Ringworm

42. The Life Cycle of a Deer Tick Human may end up with Lyme Disease

43. Mutualism • A symbiotic relationship in which both members of the association benefit • Need not be equally beneficial to both species • - Cleaning Symbiosis - one animal cleans another • - E. coli in human intestines • - Protozoans in termite intestines • - Mycorrhizae between roots & fungi • - Ants & bullhorn acacia trees • Often help each other obtain food or avoid predation

44. Cleaning Symbiosis

45. More Cleaning Symbiosis

46. Mutualism Betweenthe Bullhorn Acacia Tree and Ants Figure 53.9

47. Pollination of Plants by Animals is an example of Mutualism

48. Commensalism • A symbiotic relationship in which one species benefits and the other is neither benefited or harmed • - Remoras attach to sharks & get a free ride • - Clownfish living inside of sea anemone’s tentacles • - Epiphytes, like Spanish moss, live on trees • Many supposed examples may turn out to be mutualism or parasitism • Inferred amount of harm or benefit that 2 species do to one another is subject to investigator bias

49. Remoras & Sharks Whales & Barnacles Spanish Moss

50. Clownfish AmongSea Anemone’s Tentacles