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Download Species, Area, & the Equilibrium Theory of Island Biogeography
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Species, Area, & the Equilibrium Theory of Island Biogeography as a foundation paradigm in conservation biology Part 2… Preserve Design Guidelines IBT & Design • • • • A. Large is better than small B. Undivided is better than divided C. If divided, close is better than far D. If divided, distances should be equal • E. Corridors are better than no corridors • 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 IBT & Design The SLOSS Debate Single Large Or Several Small of the same total area Several Small > Single Large Florida scrub vertebrates--McCoy & Mushinsky 1994 Butterflies, Spain--Baz & Garcia-Boyera 1996 Plants, Norway--Saetersdal 1994 Plants in mires, Finland--Virolainen et al. 1998 Birds--Loman & von Schantz 1991 Sequoia-Kings Canyon NP vs. CA State Parks -- Species Richness From Stohlgren & Quinn 1993 SEKI CA State Parks 4000 Area Area and Number of Species 3500 3341 3000 Plants 2500 1951 2000 1485 1500 1402 Birds 1000 434 500 195 0 1 2 Comparision 3 Megareserves for large predators >106 ha 100 km linear extent Simberloff & Abele 1976 • • • • Island A becomes Archipelago A Island B becomes Archipelago B For A, SS > SL For B, SL > SS Simberloff & Abele 1976 Area m2 Spp A 475 77 -------------------------------A1 119 51 A2 133 48 A3 80 47 A4 102 50 Archipelago A 434 81 81 > 77!! Simberloff & Abele 1976 Area m2 Spp B 168 56 -------------------------------B1 71 36 B2 87 32 Archipelago B 158 47 47 < 56!! Immediate Complaints Diamond, Terborgh, Whitcomb • Not all spp equal – Some extinction prone, Total Spp not the best measure of success – Large predators need 100s-1000s km2 – Colonial nesters, Migrating spp, Spp dependent on core • Small reserves loose the same Spp, so become more similar to each other, more overlap, Spp lists are nested SLOSS?? It depends! Several Small Species overlap (similarity) among islands Simberloff & Abele 1972 • The Diamond Isles • The Lack Archipelago • The Tallahassee Archipelago Scale dependence 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 The Umbrella Concept Protecting large animals that require large areas & play important ecosystem roles --large bird & mammalian predators— protects all species Does the Umbrella Species Idea Work? Carnivore plan would protect 43% of North American invertebrates No better than random placement Kerr 1997 Plants > birds as the umbrella group for other taxa, S California Ryti 1992 Vertebrates missed lower plant diversity Portugal Araujo 1999 Rare species captured common species; Common species did not capture rare Rebelo & Siegfried 1992 Other island-like models • Gene flow • Metapopulations • Landscape ecology Other SLOSS-like debates • GLOSS: Is it better to sample genes from one population or from several small populations of the same total size (number of individuals sampled)? • SLOPP: Is it better to protect one large population or several small populations of the same total size? • FLOSS: Is it better to introduce a species as one large release or several small releases? Conservation as sampling • By definition we conserve a subset of the original • What is the best conservation sample? • What are the consequences of fragmentation? • Thing and process The Two Triangles The Constraint of Size A continuum of area sensitivity Starting with large predators, 106 ha Headwaters of streams Disturbance regimes, pattern and process Dependence on multiple habitats; seasonal movements Exceptions: rare species dependent on rare habitat; air pollution; alien invasions; climate synchronization; long distance migration Size: completeness, wholeness, integrity, health Costs of management and conservation success Conservation as sampling: bigger areas are better samples Feasible restoration goals depend on size BUT any site can play a role…dependent on size The Two Triangles Continued Small areas Small area requiring species, habitats Connectors, stepping stones Representation: more places Air, Water, Soil quality Environment: temperature Human-nature connections Human well-being
