Community Interactions

1. Community Interactions

2. Forest of New Guinea • Community includes nine species of pigeons that partition the food supply • Pigeons disperse seeds of the trees that provide their food (fruit) • These are just a few of the many interactions that shape this community

3. New Guinea Crowned Pigeon www.worldwildlife.org/newguinea/spec_pigeons.cfm

4. Map of New Guinea • New Guinea is an Island north of Australia www.worldwildlife.org

5. Community • All the populations that live together in a habitat • Habitat is the type of place where individuals of a species typically live • Type of habitat shapes a community’s structure

6. Communities • Don’t confuse meanings of “community”

7. Factors Shaping Community Structure • Climate and topography • Available foods and resources • Adaptations of species in community • Species interactions • Arrival and disappearance of species • Physical disturbances

8. Niche Sum of activities and relationships in which a species engages to secure and use resources necessary for survival and reproduction

9. Realized & Fundamental Niches • Fundamental niche • Theoretical niche occupied in the absence of any competing species • Realized niche • Niche a species actually occupies • Realized niche is some fraction of the fundamental niche

10. Species Interactions • Most interactions are neutral; have no effect on either species • Commensalism helps one species and has no effect on the other • Mutualism helps both species

11. Commensalism The commensal shrimp Periclimenes imperator on Chromodoris tinctoria, Koumac, New Caledonia, Oct, 1993.www.seaslugforum.net Photo: Bill Rudman.

12. Mutualism Clownfish and Sea Anemone From: Essentials of Oceanography, 4th ed. 1993.

13. Species Interactions • Interspecific competition has a negative effect on both species • Predation and parasitism both benefit one species at a cost to another

14. Alligator

15. Parasite “Cattle Tick” www.biosci.ohio-state.edu

16. Symbiosis • Living together for at least some part of the life cycle • Commensalism, mutualism, and parasitism are forms of symbiosis

17. Mutualism • Both species benefit • Many examples in nature • Some mutualisms are obligatory; partners depend upon each other

18. Yucca and Yucca Moth • Example of an obligatory mutualism • Each species of yucca is pollinated only by one species of moth • Moth larvae can grow only in that one species of yucca

19. Yucca Moth Caterpillar www.bobjensenphtography.com

20. Mycorrhizae • Obligatory mutualism between fungus and plant root • Fungus supplies mineral ions to root • Root supplies sugars to fungus

21. Laccaria bicolor basidioma developing on a Pinus strobus seedling under controlled environment. Andre Fortin, author

22. Competition • Interspecific - between species • Intraspecific - between members of the same species • Intraspecific competition is most intense

23. River Otters Avoid Each Other Thus Reducing Intraspecific Competition www.sms.si.edu

24. Forms of Competition • Competitors may have equal access to a resource; compete to exploit resource more effectively • One competitor may be able to control access to a resource, to exclude others

25. Elephants Exclude Competitors www.save-the-elephants.org

26. Competitive Exclusion Principle When two species compete for identical resources, one will be more successful and will eventually eliminate the other

27. Competitive Exclusion Expt Paramecium caudatum Paramecium aurelia

28. Keystone Species • A species that can dictate community structure • Removal of a keystone species can cause drastic changes in a community; can increase or decrease diversity

29. Lubchenco Experiment Periwinkles promote or limit diversity in different habitats Tidepools Rocks exposed at high tide

30. Resource Partitioning • Apparent competitors may actually have slightly different niches • Species may use resources in a different way or time • Minimizes competition and allows coexistence

31. Predation • Predators are animals that feed on other living organisms • Predators are free-living; they do not take up residence on their prey

32. Coevolution • Natural selection promotes traits that help prey escape predation • It also promotes traits that make predators more successful at capturing prey

33. Predator-Prey Cycles • Predator and prey populations may show an apparent correspondence PREY POPULATION PREDATOR POPULATION

34. Variation in Cycles • An association in predator and prey abundance does not always indicate a cause and effect relationship • Variations in food supply and additional predators may also influence changes in prey abundance

35. Prey Defenses • Camouflage • Warning coloration • Mimicry • Moment-of-truth defenses

36. Predator Responses • Any adaptation that protects prey may select for predators that can overcome that adaptation • Prey adaptations include stealth, camouflage, and ways to avoid chemical repellents

37. Parasitism • Parasites drain nutrients from their hosts and live on or in their bodies • Natural selection favors parasites that do not kill their host too quickly

38. Types of Parasites • Microparasites • Macroparasites • Social parasites • Parasitoids

39. Micro and Macroparasites Trypanosome, malaria Human tapeworm

40. Social Parasites Once limited to grasslands, brown - headed cowbirds have extended their range to all 48 contiguous states and Canada. They are a major threat to songbirds. “Of 220 species known to have been parasitized by Brown-headed Cowbirds, and 144 have raised young Brown-headed Cowbirds successfully.” http://www.birds.cornell.edu/bfl/speciesaccts/parasites.html

41. Parasitoids

42. Chemical communication: Butterfly anti-aphrodisiac lures parasitic wasps Male butterflies of the genus, Pieris, pass an anti-aphrodisiac during mating to females. This chemical, benzyl cyanide, renders the mated females less attractive to other males. This strategy tends to maximize the mating males chances of getting their genes into the next generation. Or so it was thought….

43. The Butterfly and its Parasitoid, Wasp

44. The Wasp highjacks the Sexual Communication Signal of the Butterfly The female wasps are attracted to the anti-aphrodisiac of the mated female butterflies. Often they will hitch a ride on the female butterfly. When butterfly lays her eggs, the wasp inserts her egg into the butterfly egg. The larval wasp eats its host alive.

45. A Serve Limitation on the Butterfly Populations This parasitism constrains the the butterfly populations. “If this fascinating strategy is wide spread in nature, it could severely constrain the evolution of sexual communication between hosts.” The wasp is tiny (.5 mm) It is located below the eye Of the butterfly. NATURE|VOL433|17 FEBRUARY 2005| page 704

46. Bloodsucking leech spends month up Hong Kong hiker's nose HONG KONG (AFP) - A Hong Kong woman hiker who washed her face in a freshwater stream unwittingly returned home with a leech embedded in her left nostril. “Doctors finally managed to remove it using a nasal spray to anaesthetise the five-centimetre-long (two-inch) bloodsucker a month after it had invaded her nostril.” 4/15/05

47. Succession Change in the composition of species over time

48. Types of Succession • Primary succession - new environments • Secondary succession - communities were destroyed or displaced

49. Primary Succession Sterile lava converted to a mature ecosystem overtime….

50. Secondary Succession Over time, old fields are gradually and naturally converted to mature and healthy forests….example: Westminster’s forests.