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) 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 farC. If divided, close is better than far D. If divided, distances should be equalD. If divided, distances should be equal E. Corridors are better than no corridorsE. Corridors are better than no corridors F. Circular is better than narrow (low perimeter to area ratio)F. Circular is better than narrow (low perimeter to area ratio)

Size Better Worse

Fragmentation Better Worse

Distance Better Worse

Clustered Better Worse

Connectivity Better Worse

Shape Better Worse

The SLOSS Debate S ingle L arge O r S everal S mall of the same total area

Megareserves for large predators >10 6 ha 100 km linear extent

Simberloff & 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

Simberloff & Abele 1976 Area m 2 Spp A A A A38047 A Archipelago A > 77!!

Simberloff & Abele 1976 Area m 2 Spp B B17136 B28732 Archipelago B < 56!!

Immediate Complaints Diamond, Terborgh, Whitcomb Not all spp equalNot all spp equal –Some extinction prone, Total Spp not the best measure of success –Large predators need 100s-1000s km 2 –Colonial nesters, Migrating spp, Spp dependent on core Small reserves lose the same Spp, so become more similar to each other, more overlap, spp lists are nestedSmall reserves lose the same Spp, so become more similar to each other, more overlap, spp lists are nested

Species are Not Equal: Incidence functions -- Diamond

Nested Species Lists Deterministic extinctionsDeterministic extinctions –Sites lose species in a predictable sequence based on site area Area sensitivityArea sensitivity –Small areas all lose the same species –Sites lose species in a predictable sequence based on isolation Isolation sensitivityIsolation sensitivity Nesting of species lists reduces distance decay and SL > SSNesting of species lists reduces distance decay and SL > SS

Biological Dynamics of Forest Fragments Project Manaus, Brazil, est. 1979Manaus, Brazil, est fragments: 1 ha 10 ha 100 ha avg. 280 tree species per ha (~200 in NY!)

Biological Dynamics of Forest Fragments Project

Results: complex!Results: complex! Some species suffered immediately:Some species suffered immediately: –Large mammals, primates, understory birds, certain large-range insects (beetles, ants, termites, bees, butterflies) Some species unaffected regardless of fragment sizeSome species unaffected regardless of fragment size –Small mammals, frogs

Biological Dynamics of Forest Fragments Project EDGE EFFECTSEDGE EFFECTS Microclimate changes impacted species in smallest fragments (esp. plants, insects, understory birds); favored other ‘gap species’Microclimate changes impacted species in smallest fragments (esp. plants, insects, understory birds); favored other ‘gap species’ Matrix matters: patches surrounded by cattle pastures more affected than those surrounding by regrowth forestsMatrix matters: patches surrounded by cattle pastures more affected than those surrounding by regrowth forests

Single Large vs. 2 Half Reserves A = 1 vs. A = ½ AA = 1 vs. A = ½ A Z =.263Z =.263 S H = c (A/2) z = A z /1.2 =.83 S LS H = c (A/2) z = A z /1.2 =.83 S L If total overlap, 2 * S H =.83 S LIf total overlap, 2 * S H =.83 S L –S L WINS! If no overlap, 2 * S H = 1.66 S LIf no overlap, 2 * S H = 1.66 S L –S H WINS!

z (log-log slope of the species-area relation) Shared species, 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 Diversity Inventory Diversity α, γ, δ Differentiation Diversity β

β diversity measures β = γ / α, β = γ – αβ = γ / α, β = γ – α β = (log [sim 0 ] – log [sim min ])/ log 2β = (log [sim 0 ] – log [sim min ])/ log 2 –Half change beta α γ

β diversity measures β = γ / α, β = γ – αβ = γ / α, β = γ – α β = the distance decay of similarityβ = the distance decay of similaritySimilarity Differentiation diversity (β)Differentiation diversity (β) –Jaccard’s Index –Sørensen’s Index –Matching Coefficient a c b d

β diversity measures β = γ / α, β = γ – αβ = γ / α, β = γ – α β = the distance decay of similarityβ = the distance decay of similaritySimilarity The first law of geography: the similarity between two observations decreases or decays with distance S d = S 0 e -cd, d is distance, c is the rate of distance decay, S 0 is the initial similarity a c b d

Circumpolar Boreal Forest

Plants on 300 x 300 m plots Upland spruce forest (LaRoi 1966)

C=-0.27 C=-0.43 C=-0.23 C=-0.25 Spore/microOther PlumoseNut/berry Rate of decay: Nut/berry>Mosses, Small, Wind

Distance decay in Spruce-fir forests along the Appalachians is 2.7x the Boreal forest rate C=-0.25 C=-0.67

What causes distance decay?

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

SLOSS?? It depends! Several Small Species overlap (similarity) among islands Simberloff & Abele 1972 Rate of distance decay of similarity Nekola & White 1999, 2002 Body size, vagility, gene flow Nestedness Boecklen 1997

CONSERVATION STRATEGY Both grain and extent are critical! Grain: Ecological integrity, Population viability Hydrology, Black bears, Vagile species Extent: variation in environment and history Local endemics, Poorly dispersed species Representativeness SLOSS is here to stay because grain & extent maximize different contributions to biodiversity