1. Competition

2. Competitive Release
Competitive Release is a prediction from examining the competitive exclusion principle that in the absence of competition a species should expand its niche

4. Chalcophaps indica – Emerald Dove

5. Chalcophaps
stephani –
Stephen’s
Dove

6. Gallicolumba rufigula

8. Character Displacement
Character displacement is a measurable physical difference between two species which has arisen by natural selection as a result of the selection pressure on one or both to avoid competition with each other - here we assume that environment is the same at all locations

9. Hydrobia ulvae
Hydrobia ventrosa

11. Hydrobia ulvae – note size

13. Patterns like character displacement or competitive release can be caused by several things:
the pressure of current competition causes the pattern
competition which occurred in the past may have driven natural selection to cause the pattern we see today - "the ghost of competition past"
competition in the past eliminated a number of other species, leaving behind only those that were different in the use of habitat
the species may have evolved independently and in different ways and have never competed with each other
the species may differ in their niches, but not enough to coexist in a stable environment, however the environment varies and thus prevents competition from reaching its predicted end result

14. The Ghost of Competition Past
Joe Connell

15. Blackburnian warbler
Cape May warbler
Black-throated green
warbler
Bay-breasted warbler
Yellow-rumped

16. Ghost of Competition Past in Israeli Rodents
Gerbillus allenbyi
Meriones tristami

17. Mt. Carmel, Isreal

19. Competition

20. California Coastal sage scrub – note bare spots near shrubs

21. Rabbit grazing – source of apparent competition

22. Species Coexistence
Serengeti National Park

23. Species Coexistence
Competition is a common feature of species interactions, yet often we find very similar species coexisting in nature, species that seem to need the same resources. How do they coexist?
Refuge from competition
Predation and disease keep populations of each species low enough that they do not compete
Resources may be variable in space and time, so that the species coexist because both do not find resource at same time

24. Dung – a valuable, variable resource
Dung Beetles
Dung Fly

25. Predation
Great White Shark and Fur Seal

27. Lions hunting – True Predator

28. Red squirrel – true predator

29. Moose Browsing – Partial Predator

30. Parasitoid Wasp

31. Specialists and Generalist Predators
Advantages to being a specialist
1. Avoid interspecific competition
2. Allows evolution to overcome chemical defense
3. Allows evolution of cryptic coloration that matches prey - mostly for insects on plants
4. Increases chance of mate encounter
Advantages of being a generalist 1. Flexibility in face of environmental uncertainty 2. Broad diet needed to get all necessary nutrients and vitamins 3. Avoid overdosing on any one toxin - mostly for animals grazing on chemically defended plants

32. Factors affecting predator behavior
1. Search time - the amount of time spent looking for food items
2. Handling time - the amount of time spent capturing prey once it is found, also includes time for consuming prey and time to digest before a predator can search for food again

33. Predator response to prey

35. Pied Wagtail

37. Caribou feeding in winter

38. Edible mussel – Mytilus edulis

39. Shore crab and edible mussels

42. Black oystercatcher

43. Bluegill sunfish

45. Mink
Muskrat

47. Red grouse in heather

48. Bank vole
Tawny Owl

50. Cinnabar Moth and Caterpillar on Ragwort Tansy