Island biogeography II: the application Bio 415/615

Island biogeography II: the application

Bio 415/615

Questions

1. Why would one large reserve be better than small ones of equal total area?

2. How are spatial grain and extent related to the SLOSS debate?

3. How does distance decay of similarity apply to SLOSS?

4. How do properties of species contribute to SLOSS?

IBT & Design (Diamond)IBT & Design (Diamond)• A. Large is better than smallA. Large is better than small• B. Undivided is better than dividedB. Undivided is better than divided• C. If divided, close is better than C. If divided, close is better than

farfar• D. If divided, distances should be D. If divided, distances should be

equalequal• E. Corridors are better than no E. Corridors are better than no

corridorscorridors• F. Circular is better than narrow F. Circular is better than narrow

(low perimeter to area ratio)(low perimeter to area ratio)

SizeSize

Better Worse

FragmentationFragmentation

Better Worse

DistanceDistance

Better Worse

ClusteredClustered

Better Worse

ConnectivityConnectivity

Better Worse

ShapeShape

Better Worse

TheThe SLOSSSLOSS DebateDebate

SSingleingle LLargearge

OOrr

SSeveraleveral SSmall mall

of the same total areaof the same total area

Megareserves for large predatorsMegareserves for large predators>10>1066 ha ha100 km linear extent100 km linear extent

Simberloff & Abele 1976Simberloff & Abele 1976

• Island A becomes Archipelago AIsland A becomes Archipelago A• Island B becomes Archipelago BIsland B becomes Archipelago B• For A, SS > SLFor A, SS > SL• For B, SL > SSFor B, SL > SS


Area mArea m22 SppSppAA 475475 7777

----------------------------------------------------------------A1A1 119119 5151A2A2 133133 4848A3A3 8080 4747A4A4 102102 5050

Archipelago AArchipelago A 434434 818181 > 77!!81 > 77!!


Area mArea m22 SppSpp

BB 168168 5656

----------------------------------------------------------------

B1B1 7171 3636

B2B2 8787 3232

Archipelago BArchipelago B 1581584747

47 < 56!!47 < 56!!

Immediate ComplaintsImmediate ComplaintsDiamond, Terborgh, Diamond, Terborgh,

WhitcombWhitcomb• Not all spp equalNot all spp equal

– Some extinction prone, Total Spp not the Some extinction prone, Total Spp not the best measure of successbest measure of success

– Large predators need 100s-1000s kmLarge predators need 100s-1000s km22

– Colonial nesters, Migrating spp, Spp Colonial nesters, Migrating spp, Spp dependent on coredependent on core

• Small reserves lose the same Spp, so Small reserves lose the same Spp, so become more similar to each other, become more similar to each other, more overlap, spp lists are nestedmore overlap, spp lists are nested

Species are Not Equal: Species are Not Equal: Incidence functions -- Incidence functions --

DiamondDiamond

Nested Species ListsNested Species Lists• Deterministic extinctionsDeterministic extinctions

– Sites lose species in a predictable Sites lose species in a predictable sequence based on site areasequence based on site area• Area sensitivityArea sensitivity

– Small areas all lose the same speciesSmall areas all lose the same species– Sites lose species in a predictable Sites lose species in a predictable

sequence based on isolationsequence based on isolation• Isolation sensitivityIsolation sensitivity

• Nesting of species lists reduces Nesting of species lists reduces distance decay and SL > SSdistance decay and SL > SS

Biological Dynamics of Biological Dynamics of Forest Fragments ProjectForest Fragments Project

• Manaus, Brazil, est. 1979Manaus, Brazil, est. 197911 fragments:

1 ha

10 ha

100 ha

avg. 280 tree species per ha

(~200 in NY!)



• Results: complex!Results: complex!• Some species suffered immediately:Some species suffered immediately:

– Large mammals, primates, understory Large mammals, primates, understory birds, certain large-range insects birds, certain large-range insects (beetles, ants, termites, bees, (beetles, ants, termites, bees, butterflies)butterflies)

• Some species unaffected regardless Some species unaffected regardless of fragment sizeof fragment size– Small mammals, frogsSmall mammals, frogs


• EDGE EFFECTSEDGE EFFECTS• Microclimate changes impacted Microclimate changes impacted

species in smallest fragments (esp. species in smallest fragments (esp. plants, insects, understory birds); plants, insects, understory birds); favored other ‘gap species’favored other ‘gap species’

• Matrix matters: patches surrounded Matrix matters: patches surrounded by cattle pastures more affected by cattle pastures more affected than those surrounding by regrowth than those surrounding by regrowth forestsforests

Single Large Single Large vs. 2 Half Reservesvs. 2 Half Reserves

• A = 1 vs. A = ½ AA = 1 vs. A = ½ A• Z = .263Z = .263

• SSH H = c (A/2)= c (A/2)z z = A= Azz/1.2 = .83 S/1.2 = .83 SL L

• If total overlap, 2 * SIf total overlap, 2 * SH H = .83 S= .83 SLL

– SSLL WINS! WINS!

• If no overlap, 2 * SIf no overlap, 2 * SH H = 1.66 S= 1.66 SLL

– SSHH WINS! WINS!

z (log-log slope of the species-area relation)

Sh

ared

sp

ecie

s, P

v

.1 .3

Single Large Reserve

2 Half Reserves

R=1.0

90%

75%

Estimation of critical similarity for SLR>THR as a function of z

Bell & Boecken 1990

2 Kinds of 2 Kinds of DiversityDiversity

Inventory Inventory DiversityDiversity

α, γ, δα, γ, δ

Differentiation Differentiation Diversity Diversity

ββ

ββ diversity measures diversity measures• ββ = = γγ / / αα, , ββ = = γγ – – αα

• ββ = (log [sim= (log [sim00] – log [sim] – log [simminmin])/ ])/ log 2log 2– Half change betaHalf change beta

αα γγ

ββ diversity measures diversity measures• ββ = = γγ / / αα, , ββ = = γγ – – αα• ββ = the distance decay of = the distance decay of

similaritysimilaritySimilaritySimilarity

• Differentiation diversity (Differentiation diversity (ββ))– Jaccard’s IndexJaccard’s Index– Sørensen’s IndexSørensen’s Index– Matching CoefficientMatching Coefficient

a a cc b b dd

ββ diversity measures diversity measures• ββ = = γγ / / αα, , ββ = = γγ – – αα• ββ = the distance decay of = the distance decay of

similaritysimilaritySimilaritySimilarity

The first law of geography:The first law of geography:the similarity between two observations the similarity between two observations decreases or decays with distancedecreases or decays with distance

SSdd = S = S00 e e-cd-cd, d is distance, c is the rate , d is distance, c is the rate of distance decay, Sof distance decay, S00 is the initial is the initial similaritysimilarity

a a cc b b dd

Circumpolar Boreal Circumpolar Boreal ForestForest

Plants on 300 x 300 m Plants on 300 x 300 m plots Upland spruce plots Upland spruce forest forest

(LaRoi 1966)(LaRoi 1966)

C=-0.27

C=-0.43

C=-0.23

C=-0.25

Spore/micro Other

Plumose Nut/berry

Rate of decay: Nut/berry>Mosses, Small, Wind

Distance decay in Distance decay in Spruce-fir forests Spruce-fir forests along the along the Appalachians is 2.7x Appalachians is 2.7x the Boreal forest ratethe Boreal forest rate

C=-0.25

C=-0.67

What causes distance What causes distance decay?decay?

The rate of distance decay, c, varies with Two traits of environment &Two traits of organisms:

Environment Organism traits

Adaptation Gradients Niche

Movement Resistance Vagility

SLOSS?? It depends!SLOSS?? It depends!

Several Small Several Small

Species overlap (similarity) among Species overlap (similarity) among islandsislands


Rate of distance decay of similarityRate of distance decay of similarity

Nekola & White 1999, 2002Nekola & White 1999, 2002

Body size, vagility, gene flow Body size, vagility, gene flow

Nestedness Nestedness

Boecklen 1997Boecklen 1997

CONSERVATION STRATEGYCONSERVATION STRATEGY

Both grain and extent are critical!Both grain and extent are critical!

Grain: Ecological integrity, Population Grain: Ecological integrity, Population viabilityviability

Hydrology, Black bears, Vagile speciesHydrology, Black bears, Vagile species

Extent: variation in environment and Extent: variation in environment and historyhistory

Local endemics, Poorly dispersed Local endemics, Poorly dispersed speciesspecies

RepresentativenessRepresentativeness

SLOSS is here to stay because grain SLOSS is here to stay because grain & extent maximize different & extent maximize different contributions to biodiversitycontributions to biodiversity

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Island biogeography II: the application Bio 415/615