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?


Immigration Rates = DistanceExtincton Rates = Area


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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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.


Southwestern Sky Islands In Equilibrium

Lomolino, Brown, Davis, 1989. Island biogeography of montane forest mammals in the American Southwest. Ecology 70:18-194.


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


Speciation vs. ImmigrationVolcanicvs.Mature Islands

Thornton 1996. Krakatau: The destruction and reassembly of an island ecosystem. MA, Harvard.


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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


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.


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.


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.


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.


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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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


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.


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


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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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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Island Biogeography 2

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