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Niches
- 1. Ecological niches Niches:fundamental and realized Principle of competitive exclusion Realized niche as competitive refuge Niche crossovers Character displacement Adaptive radiation
- 2. Ecological niche concept Habitatoccupance = “Where are you from?” “What’s your address?” Ecological niche = “What do you do?” “Do you eat meat?”
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- 5. Categorizing niches Junco Chickadee Douglas squirrel Deermouse Deer Coyote Cougar Main food generalist/ source specialist seeds ? specialist seeds & insects ? generalist seeds ? specialist seeds ? specialist Niche overlap?
- 6. The principle ofcompetitive exclusion “Two species requiring approximately the same resources are not likely to remain long evenly balanced in numbers in the same habitat.” J. Grinnell (1915) Also known as “Gause’s principle” after mathematical formulation by Gause in 1930. In consequence, the loser is excluded, at least locally, unless…
- 7. 1. There arerefuges from competition; the potential loser hangs on in marginal habitats; or 2. The loser can re-immigrate from elsewhere; or 3. Disturbances in the environment prevent the winner from gaining a complete monopoly.
- 8. Categorizing niches: dietary segregationamongst local granivores Species Habitat Other foods? junco floor berries, insects (esp. ants and beetles) chickadee canopy insects Douglas squirrel canopy insects, mushrooms, flowers, birds’ eggs deer mouse floor insect larvae (esp. moths)
- 9. Reducing niche overlapthrough habitat segregation upper canopy lower canopy shrub floor resource overlap?
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- 11. Niche compression Realizedniches are narrower than fundamental niches, therefore the species occupies a narrower range of habitats than it would in the absence of competition. The realized niche can be regarded as a ‘competitive refuge’.
- 12. Determining niche compression Naturalexperiments compression
- 13. Niche compression: barnacles onScotland’s rocky shores
- 14. QuickTime™ and a TIFF(Uncompressed) decompressor are needed to see this picture. Connell, J. 1961. Ecology 42, 710-72
- 15. Sedge niches: Fraserdelta low tide high tide Inundation Daily Rare Inundation Daily Rare H1: realized = fundamental H2: Scirpus occupies refuge
- 16. Determining niche compression A.Field experiments: reciprocal transplants low tide high tide Two-year transplant experiment was inconclusive. Both species grew well in other species zone. (Mike Pidwirny)
- 17. Dominance hierarchy A B C dominantsp. subdominant sp. resource gradient in the absence of competition with competition refuge exclusion refuge zone resource gradient
- 18. Dominance hierarchies are environmentallycontingent dominant sp. subdominant sp. B A C resource gradient in the absence of competition with competition exclusion refuges zone resource gradient
- 19. Flexible dominance hierarchies resource gradient resourcegradient inundation/ waterlogging salinity B A C
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- 23. Competitive ‘release’ orare niches and habitat occupance more-or-less fixed? NB: hypothetical !
- 24. Can niches bevacant? mainland vs. island absent new invader? evolution of new species? competitive release OR
- 25. Does evolution fill afinite number of jobs? (e.g. community wants burrower?) Is there a restricted “guild”? Burrower Placental mammals Australian marsupi
- 26. Hawaiian honeycreepers: seed-eating finchevolves into vacant niches? http://biology.swau.edu/faculty/petr/ftphotos/hawaii/postcards/birds/ “woodpecker”“nectar-feeder”
- 27. Galapagos finches: opportunistic evolution Source:Lack, D. 1966. Darwin’s Finches. Harper, N.Y.
- 28. Parallel (or convergent) evolution of animals inhabiting African(right) and S. American (left) tropical forest
- 29. Stickleback niches incoastal lakes of SW British Columbia Texada Is. (4 lakes) Van. Is. (1 lake) Lasqueti Is. (extinct, 1996) Pairs of stickleback species occur in these lakes
- 30. Stickleback pairs incoastal lakes of SW British Columbia Source: BC Min. Environment Land and Parks, 1999. “Wildlife in BC: At Risk” brochure benthics feed on lake bed, limnetics in water column
- 31. Stickleback pairs • Asingle episode of colonization of coastal lakes by a marine stickleback about 11 000 to 13 000 years ago (when sea level was higher than at present. • Lakes colonized independently • Divergence into benthic and limnetic niches in each lake • Indicates “vacant niches” in each lake?
- 32. QuickTime™ and a TIFF(Uncompressed) decompressor are needed to see this picture. Tapirus bairdii (Belize) Situations vacant? Large generalist herbivore wanted??
- 33. Niches and diversity 6species ‘community’ 10 species ‘community’ original state more resources 10 species ‘community’ more specialization
- 34. So, are communities‘designed’ by natural selection for maximum efficiency and orderly function?* Does this only happen in stable ‘saturated’ communities? And how do we determine that a community is ‘saturated’? *Source: Eric Pianka.
- 35. “The Panama CanalExperiment: fishes” Fish censused in 1922-2; canal completed in 1914; fish re-censused in 2002 QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Rio Chagres 7 additions 0 extinctions Rio Grande 5 additions 0 extinctions Invaders contradict the “saturation” model Smith et al. ( 2004) Proc. Roy Soc., 271, 1889-189
- 36. Island invasions and community saturation: plants Sax D.F.and Gaines S.D. 2008. PNAS 105 :11490-11497 NY Times, Sept. 09, 2008
- 37. Island invasions andcommunity saturation: plants New Zealand ~2000 native plants ~2000 naturalized aliens 3 natives extinct California ~5000 native plants ~1000 naturalized aliens 30 natives extinct Brown, JH and Sax, DF 2004. Austral Ecology 29, 530-536.
- 38. Island invasions andcommunity saturation: fish Hawaii 5 native freshwater fish species 40 naturalized aliens no extinctions 124 watersheds in temperate North America Fish diversity increased in 100; declined in 20 Brown, JH and Sax, DF 2004. Austral Ecology 29, 530-536.
- 39. The challenge toclassical niche theory: Hubbell’s unified neutral theory Hubbell champions the idea that tree species in the tropical forests of Panama, are competitively equivalent (i.e. “neutral”= red line). Coexistence is not a function of niche segregation across a spatially heterogeneous landscape (blue line). See: Hubbell, S.P. 2001. The Unified Neutral Theory of Biodiversity and Biogeography. Prince Graphic: New Scientist, 9 February 2002.
- 40. What is a“community”?* *or is it a “commutiny”? An ecological (or biological) community refers to a group of interacting organisms living together in a specific geographical area or habitat. An equivalent (and now somewhat anachronistic) term is biocenosis (proposed by Karl Möbius in 1877 to describe the interacting organisms of the oyster- and mussel-bearing tidal flats of the North Sea).
- 41. Community structure Closed vs.open communities Ecotones (community boundaries) The continuum concept Biogeoclimatic zones
- 42. Are communities closed,or open? E = ecotone = a continuum? * * * *community named after dominant(s): e.g. Douglas fir, hemlock- cedar. fidelity?
- 43. Characteristics of openand closed communities OPEN CLOSED Early proponent H.A. Gleason F.E. Clements Organization Individualistic Holistic Boundaries Diffuse Distinct Species ranges Independent Coincident Coevolution Uncommon Prominent
- 44. Testing the community concept in montane forestsof the American West
- 45. Plant associations Environmental gradient 12 3 4 1 2 3 4 5 1 2 3 4 trees shrubs mosses * Ass: 111 122 232 343 345 454 *An association is a local grouping (a sub-community)
- 46. Local plant associationmapping UBC Research Forest, Haney (after Klinka, 1975)
- 47. Map of plant associations inpart of UBC Research Forest, Haney, BC 100 m
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- 49. Biogeoclimatic zones and subzones purple =mountain hemlock; green = coastal western hemlock; yellow = coastal Douglas- fir
- 50. Terrestrial biomes (plants andanimals)
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