island biogeography 2
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Island Biogeography
IslandsDiscrete boundaries, and easy to compare & contrast
"Oceanic" vs. Continental & "Landbridge"Oceanic Islands:
diversity lower but area-effect strongerextinction higher (no rescue-effect)immigration lower (distance to mainland)
Examples:Sky IslandsWoodlot "Islands"Prairie Potholes
Historical Background
Static Assumption: Island composition fixed
Pattern recognized by Forster & de Candolle
Lack, Mayer 1940's; Hutchinson 1950's (islands, diversity)
Equilibrium Theory of Island Biogeography
Munroe, E.G. (1948) dissertationR. McArthur and E. Wilson (1963, 1967)Paradigm: central idea, organizing concept
Dynamic Equilibrium (not historic)Diversity Constantbut with Turnover (species list)
Munroe, E. G. 1948. "The geographical distribution of butterflies in the West Indies." Ph. D. Diss ertation, Cornell University, Ithaca.
Island Patterns - Species-Area Relationship
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Power Model S = cAz
Semi-logarithmic S = d + k log(A)
On oceanic islands diversity less but area-effect stronger (curvesteeper)
Area and Abundance
Oceanic islands are a special case of species-abundancerelationship (Preston, 1962)
Most Species are rare and only a few species are dominantLognormal Distribution
Oceanic islands = smaller populations = fewer populous species
Preston 1962. The canonical distribution of commonness and rarity. Part 1 Ecology 43: 185-215. Part 2 Ecology 43: 410-432.
Species-Isolation Relationship
Less "general" than the Species-Area relationshipWhat arethe routes of immigration?
Exponential S = k1
e-k2(I)
Normal S = k1 e-k2(II)
k1 & k2 = constants; S = Species Richness; I = isolation (km)
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Krakatau Islands (1883 eruption):
documentation of species turnover
RakataExtinction
RakataImmigration
SertungExtinction
SertungImmigration
1908-1920
2 20 0 28
1920-1933
5 4 2 7
Is the number of species decreasing, increasing, or stable?
Equilibrium Theory of Island Biogeography
Immigration Rates = DistanceExtincton Rates = Area
Equilibrium Theory of Island Biogeography
Strengths and Weaknesses
Slopes of Extincton and Immigration rate curves not knownSlopes vary from island to islandIslands may not be in equilibriumExtincton and Immigration vary among species(continued)
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Equilibrium Theory of Island Biogeography
Strengths and Weaknesses
(continued)Extincton and Immigration not independent(high immigration rates save species from extinction)
"Rescue Effect"Multiple mainlands = multiple immigration routes, ratesAssumes no speciations on island (strict sense)2 islands - area correlated with habitat diversity
Isolation and Speciation
Low Immigration Rates Permit Speciation (vacant niches)Speciation increases diversity
Equilbrium Island Biogeography & Turnover
Turnover on "Landbridge" islands (California Channel Islands)
IslandArea
km2
Distance
km
Bird Spp.
1917
Bird Spp.
1968Extinctions
Human
Introd.Immigrations
Turnover
%
LosCoronados
2.6 13 11 11 4 0 4 36
San Nicholas 57 98 11 11 6 2 4 50
San
Clemente145 79 28 24 9 1 4 25
SantaCatalina
194 32 30 34 6 1 9 24
Santa
Barbara2.6 61 10 6 7 0 3 62
San Miguel 36 42 11 15 4 0 8 46
Santa Rosa 218 44 14 25 1 1 11 32
Santa Cruz 249 31 36 37 6 1 5 17
Anacapa 2.9 21 15 14 5 0 4 31Diamond, J.M. 1969. Avifaunal equilibria and species turnover rates on the Channel Islands of California. Proc. Natl. Acad. Sci 64: 57-63. Jones,H.L. and Diamond, J.M. 1976. Short-time-base studies of turnover in breeding bird populations on the Channel Islands of California. Condore 73:
526-549. [+]
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California Channel Islands
Porcasi, P., Porcasi, J.F., O'Neill C. Early Holocene coastlines of the California Bight: The Channel Islands first visited by humans. PacificCoast Archaeological Society Quarterly 35 (2&3): 1-24. http://www.pcas.org/Vol35N23/3523Porcasi.pdf
Effect of Island Size on Turnover rates
Turnover rates lower in larger islands:
Wright, S.J. 1980. Density compensation in island avifaunas. Oecologia 45: 385-389. Wright, S. J. 1985. How isolation affects ratesof turnover of species on is lands. Oikos 44:331-340.
Experimental Biogeography
Defaunation of Florida Mangrove Islandsrapid increase, overshooting, stabilization"E1" is small isolated island
Simberlof & Wils on 1970. Experimental zoogeography of islands: a two-year record of colonization. Ecology 51: 934-937.
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Continental Islands
Rescue Effect: reduced turnover due to replacement
Wright, S.J. 1980. Density compensation in island avifaunas. Oecologia 45: 385-389. Wright, S. J. 1985. How isolation affects ratesof turnover of species on is lands. Oikos 44:331-340.
Target Area Effect:
greater immigration rate on larger islands
Buckley, R.C. and S.B. Knedlhans (1986). Beachcomber biogeography: interception of dispersing propagules by islands. Journal ofBiogeography, 13: 69-70.
Small Island Effect:
no area-diversity effect on small islands too few habitats
Niering, W.A. 1963. Terrestrial ecology of Kapingamarangi Atoll, Caroline Islands. Ecological Monographs 33:131-160.
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Sky Islands
Nonequilibrium: no isolation effect, slow extinction, no dispersal
S = cAz
Smammal = 1.188 A0.326 Sbird = 2.526 A
0.165
Brown, 1978. The theory of insular biogeography and the distribution of boreal birds and mammals. Great Basin Nat. Mem. 2:209-277.
Great Basin Sky Islands - RELAXATION
Pleistocene Species Supersaturation
Brown, 1978. The theory of insular biogeography and the distribution of boreal birds and mammals. Great Basin Nat. Mem. 2: 209-277.
Sky Island Biogeography
Southwestern Sky Islands In Equilibrium: frequent dispersal
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Lomolino, Brown, Davis, 1989. Island biogeography of montane forest mammals in the American Southwest. Ecology 70:18-194.
Sky Island Biogeography
Southwestern Sky Islands In Equilibrium
Lomolino, Brown, Davis, 1989. Island biogeography of montane forest mammals in the American Southwest. Ecology 70:18-194.
Sky Island Biogeography
Andean Birds: Holocene colonization
(Nores, 1995)
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Freshwater Lakes Biogeography
Speciation vs. Immigration
Effect of Antiquity (!) and Speciation on Diversity
Barbour & Brown, 1974. Fish diversity in lakes American Nat. 108: 473-489
Krakatau Islands Biogeography
Immigration RatesTurnover and Equilibrium
Krakatau Islands Biogeography
Speciation vs. ImmigrationVolcanicvs.Mature Islands
Thornton 1996. Krakatau: The destruction and reassembly of an island ecosystem. MA, Harvard.
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Krakatau Islands Biogeography
Differential Immigration Rates for Plants
Bush Whittaker 1991. Krakatau: Colonization patterns and hierarchies. Journal Biogeography 18: 341-356.
Extinction on Sky Islands
Small generalist herbivores have lower extinction rates.
low energy requirements (smaller size, larger popn.)more available energy (lower trophic level)
Brown, J.H. 1971. Mammals on mountaintops: Non-equilibrium insular biogeography American Naturalist 105: 467-478. Brown, J.H.1978. The theory of insular biogeography and the distribution of boreal birds and mammals . Great Basin Nat. Memoirs 2: 209-277.Patterson, B.D. 1984. Mammalian extinction and biogeography in the southern ROc ky MOuntians. p. 247-294 in M.H. Nitecki (ed.)Extinctions Univ. Chicago.
Relaxation and Nested Island Biotas
immigrant pattern: dominated by "best migrators"relict pattern: random extinctions of original biotarelaxation model: patterned extinction of original biota
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Darlington, 1957. Zoogeography: The Geographical Distriburion of Animals. John Wiley & Sons, NY.
Nested Island DistributionsMalaysian Archipelago ants
Wilson, E.O . 1959. Adaptiave shift and dispersal in a tropical ant fauna. Evolution 13: 122-144.
Single-species Distributions
Metapopulation analysis: minimum area needed to escapeextinction
Insular Distribution Function: tradeoff of immigration & extinctonsmall islands OK if they're close to the mainland
Lomolino, M.V. 1986. Mammalian comm unity structure on islands: Immigration, extinction and interactive effects. Biol. Journal LinneanSoc. 28: 1-21. Lomolino, M.V. 1998. A species-based, hierarchical model of island biogeography. In E. Wiher and P.A. Keddy (eds.) The
search for assembly rules in ecological communities. Cambridge Univ. Press.
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Variable Immigration Abilities
Channel Island Distances (& Rates)
Wenner, A.M. and Johnson, D.L. 1980. Land vertebrates on the California Channel Islands: Sweepstakes or bridges? p. 497-530 In: D.M.Power (ed.) The California Islands: Proceedings of a multi-disciplinary symposium Santa Barbara Museum Nat. Hist.
Selective Immigration & Extinction
Biased insular community composition
harmonic (balanced)disharmonic (proportions different from mainland)
Establishment of Immigrants
Population-Ecology Life Strategies
r-Selected: disturbed ecosystems, broad ecologicaltolerance, rapid population growth
K-Selected: mature ecosystems, stable population
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Extinction of Birds in the Hawaiian Islands
Selective extinction of ground-dwelling and carnivorous birds
James, H.F. 1995. Prehistoric extinctions and ecological c hanges on oceanic islands. p. 87-102. in P.M. Vitousek, L.L. Loope, and H. Anderson.Islands: Biological Diversity and Ecosystem Function. Springer Verlag, NY.
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Nested Island Distributions
Aleutian Island ArchipelagoLand plant dispersal - "Filter" Dispersal Route
Williamson, M. 1981. Island Populations, Oxford Univ. Press.
Patterns Reflecting Interspecific Interactions
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Checkerboard Distribution: only one or the other of twocompeting species occur on each island.Example: Bismark Archipelago flycatchers Pachycephalapectoralisand P. melanura dahli
Patterns Reflecting Interspecific Interactions
Incidence Function: proportion of islands inhabited vs. numberof species per island (diffuse competition)
Diamond, J.M. 1975. Assembly of s pecies communities. p. 342-444 In. M.L. Cody and J.M. Diamond (eds.) Ecology and evaluation ofCommunities. Belknap Press, Cambridge.
Patterns Reflecting Interspecific Interactions
Effect of close-competitors on an island being invadedsuccess correlated with difference from resident species
Moulton, M.P. and Pimm, S.L. 1986. The introduced Hawaiian avifauna: Biogeographical evidence for c ompetition. American Naturalist121: 669-690.
Patterns Reflecting Interspecific Interactions
Niche shift: atypical habitats occupied on islands where preditor
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absent (shrews are predators on voles)
Lomolino, M.V. 1984. Immigrant selection, predatory exclusion and the distributions of Microtus pennsylvanicusandBlarina brevicaudaon islands. American Naturalist 123: 468-483.
Patterns Reflecting Interspecific Interactions
Niche shift: Anolissize differentiation when more than specieson island
Roughgarden, J. 1974.Niche width: Biogeographic patterns among Anolis lizard populations. American Naturalist 108: 429-442.Roughgarden, J. and Fuentes, E.R . 1977. The environmental determinants of s ize in solitary population of West IndianAnolis lizards.Oikos 29: 44-51. Foughgarden, J. Heckel, S. and Fuentes, E.R. 1983. Coevolutionary thoery and the biogeography and comm unitystructure of Anolis. p. 371-410 IN Huey, R.B. and Pianka, E.R. and Schoener, T.W. (eds.) Lizard Ec ology: Studies of a model organism. HarvardUniv. Press.
Patterns Reflecting Interspecific Interactions
Predator Release: species (example spiders) more aboundantwhere predator absent
Schoener, T.W. and Spiller, D.A. 1987. High population persistence in a system with high turnover. Nature 330: 474-477.
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Patterns Reflecting Interspecific Interactions
Density Overcompensation: combined populations onseveral small islands greater than on a single large island ofequal area.Density Compensation: abundance constant despiteincreasing species (fewer per species)Density Stasis: abundance increases with increasing
species biomass
Wright, S.J. 1980. Density compensation on s mall islands. Oecologia 45: 385-389.
Applications of Island Biogeographic Theory toNature Preserves
SLOSSSingle Large or Several Small
Applications of Island Biogeographic Theory toNature Preserves
Single Large vs. Several Small
Circular vs. "Peninsular"
Clumped vs. Spread out
Connected vs. Unconnected
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Wilson, E.O. & E.O. W illis 1975. Applied biogeography. pp. 522-534 inM.L. COdy & M.M. Diamond (eds.) Ecology and Evolution of Communities.Cambridge, Belknap Press.
Applications of Island Biogeographic Theory toNature Preserves
Reserves should be as large as possibleArea - Diversity
Unique habitats (biotas) should have multiple preserves(nearby)
RedundancyIsolation
Preserves should be round and continuousPeninsula effectIsolation
Priority given to highest endemicity and vulnerabilityCorridores between preserves should be maintained
Evolutionary Trends on Islands
Flightlessness and reduced dispersal ability
Birdsabsence of predators (no need to fly)
limited resources (expensive to fly)InsectsExpansion into vacant niches
(Orthopteran "wettas" of New Zealand)Precintiveness: dispersal away from hatching area isfatal
Evolutionary Trends on Islands
Land Snails (smaller)Wind-dispersed - smaller is better
Plants (bigger, simpler)loss of pappus, heavier, less resistant to saltwater
(precintiveness)Become Trees
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Evolutionary Trends on Islands
Body Size Change on Islands
Dwarfismreduced resource needbetter shelter in treeless islands
Gigantismtraits that allowed dispersal (small size a disadvantage)wider range of preygreater energy and water reserves for famines
The Island Rule: "the big get smaller & the small get bigger"
Optimal size 250 grams (red squirrel)Predators: canids, felids - dwarfism
reduced resourcesRodents - gigantism
immigrant selection: small animals disperse moreeasilyecological release: small size not needed to avoidpredators
EVOLUTIONARY TRENDS
Size variation
squirrel size vs. island area
Heaney, L.R. 1978. Island area and body size of insular mammals: Evidence from the t ri-colored squirrel (Callisciurus prevosti) of
Southwest Africa. Evolution 32: 29-44.
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EVOLUTIONARY TRENDS
Size variation
mouse size vs. isolation
Ebenhard, T. 1988. Introduced birds and mammals and their ecological effects. Swedish Wildlife Research 13: 1-107.
EVOLUTIONARY TRENDS
Size variation
lizard size vs. number of lizards per island
Soul, M.E. 1966. Trends in insular radiation of a lizard. American Midland Nat. 100: 47-64.
EVOLUTIONARY TRENDS
Taxon Cycles
Island speciation ends in extinctionInvasion of Most Islands1.Speciation and Range Restriction2.Few Relictual Populations3.Replaced by new Stage 1 Species4.
Wilson, E.O. 1959. Adaptive shift and dispersal in a tropical island fauna. Evolution 13: 122-144.
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