Community Ecology

1. Community Ecology Campbell & Reece Chapter 54

2. Community • a group of populations of different species living close enough to interact

3. Interspecific Interactions • interactions with individuals of other species • includes: • Competition • Predation • Herbivory • Symbiosis • Facilitation

5. Competition • interspecific competition is a +/- interaction that occurs when individuals of different species compete for a resource that limits their growth & survival

6. Competitive Exclusion • grown separately, both show logistic growth • when compete Paramecium caudatum became extinct in the culture • 2 species competing for same limiting resource: 1 will have advantage in either using resources or in reproduction

7. Ecological Niche • is the sum of a species’ use of the biotic & abiotic resources in its environment • Eugene Odem: “If an organism’s habitat is its “address”, then niche is the organism’s “profession,”

8. Niche • not just where an organism lives but also what it eats, when it eats, who eats it, how many resources it uses, how much & what type of wastes it produces, what its parasites are, etc

9. Niches: Resource Partitioning • 3 birds live in spruce tree: each lives in different level so there is no competition even though all live in same trees

10. Character Displacement • closely related species may have populations that are sometimes allopatric (geographically separate) & sometimes sympatric (geographically overlapping)

11. Character Displacement • allopatric populations will be morphologically more similar & use similar resources • sympatric populations more likely to show differences in body structures & in the resources they use

13. Predation • refers to the +/- interaction between species in which 1 species, the predator, kills & eats the other, the prey

14. Feeding Adaptations of Predators • acute senses • claws, teeth, fangs, stingers, or poison • those that have to chase their prey have adaptations that make them fast & agile • those that lie in ambush have adaptations that disguise their position

15. Adaptations of Prey • hiding, fleeing, forming herds or schools • active self-defense less common except for mothers protecting young (especially in larger, grazing mammals) • alarm calls  mob the predator

16. Defensive Coloration in Animals Cryptic Coloration Camouflage makes prey difficult to see

17. Defensive Coloration in Animals • Aposematic Coloration • warning coloration • often used by animals that have effective chemical defenses

18. Defensive Coloration in Animals • Batesian mimicry: a palatable or harmless species mimics an unpalatable or harmful one

19. Defensive Coloration in Animals • Mullerianmimicry: 2 or more unpalatable species resemble each other; the more unpalatable prey there are the more quickly predators learn to avoid anything that resembles them

20. Herbivory • refers to a +/- interaction in which an organism eats parts of a plant or alga • most herbivores are invertebrates • specialized adaptations: • some insect have sensors on feet to detect toxins, or to detect nutritious & less nutritious plants

21. Plant Adaptations • feature toxins, spines, thorns • some toxins: • Strychnine: produced by tropical vine • Nicotine: tobacco • Tanins: variety of plants • Selenium: found in “locoweeds” because sheep & cattle that eat them found wandering aimlessly, some die

22. Plant Adaptations • produce chemicals their predators find distasteful: • Cinnamon • Cloves • Peppermint

23. Symbiosis • when 2 or more species live in direct & intimate contact w/each other • some: helpful, harmful, or neutral

24. Parasites • Ecologists estimate that 1/3 of all species are parasites • many have complex life cycles requiring multiple hosts • some change behavior of their host to increase probability of it being transferred

25. Parasitic accanthcephalan • leads their crustacean host to leave shelter increasing chances it will be eaten by a bird, its next host

26. Parasitism • a +/- symbiotic interaction in which 1 organism, the parasite, derives its nourishment from another organism, its host, which is harmed in the process • Endoparasites: live w/in body of their host • ex: tapeworm • Ectoparasites: feed on external surface of their host • ex: ticks, lice

27. Parasitoid Insects • small wasps that lay their eggs in living hosts that feed on the body, killing it

28. Mutualism • an interspecific interaction that benefits both species, +/+ • Acacia trees & stinging ants: • ants feed on nectar & protein-rich swellings on tree • tree protected by thorns (ants live inside) & stinging ants that attack any herbivores & ants clip vegetation that grows near the tree

29. Mutualism

30. Commensalism • an interaction between species that benefits one of the species but neither harms nor helps the other +/0 • in reality may have some slight + or - affect

31. Facilitation • species can have +/+ or +/0 effects on the survival or reproduction of other species w/out living in direct, intimate contact with each other • this type of interaction = facilitation • common in plant ecology

32. Black rush increases # of plant species that can live in upper middle zone of salt marshes

34. Species Diversity • variety of different kinds of organisms that make up a community • Species richness: # of different species in community • Relative abundance: proportion each species represents of all individuals in community

35. Which is Which?

36. Shannon Diversity • Ecologists use different tools to compare the diversity of different communities over time & space. • Shannon diversity is an index of diversity based on species richness & abundance

37. Shannon Diversity • Shannon diversity = H • ni = # of 1 species • n = # of all species • In = natural logarithm

38. Which Forest is More Diverse?

39. Diversity & Community Stability • higher diversity communities generally are more productive & better able to withstand & recover from environmental stresses

40. Invasive Species • higher diversity communities more resistant to effects of invasive species

41. Trophic Structure • layers in food chains/ pyramids

42. Food Webs • summary of trophic relationships of a community • tells whom eats whom

43. Limits of Food Chain Length • Why are they short? • Energetic Hypothesis • length limited by inefficiency of nrg transfer • Dynamic Stability Hypothesis • longer food chains less stable • population fluctuations @ lower trophic levels magnified @ higher levels

44. Dominant Species • the more abundant species in a community • are highly competitive

45. Dominant Species • 1 way to measure effect is to study what happens when a dominant species is removed: • ex: tree, American Chestnut was dominant tree in deciduous forests before 1910 • fungal disease chestnut blight introduced: killed almost all of them  didn’t bother maples, beeches, oak, or hickories, or birds, or mammals, but 7 species of moths & butterflies became extinct

48. Keystone Species • not usually abundant in community • exert strong control by their pivotal ecological role or niche

50. Ecosystem Engineers • species that dramatically alter their physical environment • aka: foundation species • effect on other species can be + or – depending on needs of other species