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Fine-scale geomorphic pattern and biodiversity Duane A. Griffin and Phil Marquis Bucknell University Lewisburg, PA
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Plant Biodiversity Patterns
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Explanations
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With Apologies: One More! Competitive uncoupling hypothesis Fine-scale habitat structure can disrupt interactions between individuals sharing a habitat. If interactions are negative (competition, allelopathy, pathogen spread…), fragmentation should disrupt trajectories towards exclusion, thereby increasing diversity.
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How does this individual interact with others in its habitat?
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Direct interactions with immediate neighbors (competition)
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Seed dispersal and microsite colonization Direct interactions with immediate neighbors (competition) Mostly Deterministic Mostly Stochastic
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y = f(x)
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What if habitat patches are discrete and isolated at fine scales?
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Colonization neighborhood remains the same
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Resource competition neighborhood is smaller
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y = f(x)
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Testing: GeoSim Individual-Based Spatially Explicit Reaction-Diffusion Model Diffusion Reaction Seed Dispersal Colonization Lottery Competition Seed Production ABA A B A BAA
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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Seed Dispersal Colonization Lottery CompetitionSeed Production
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123 456 78 9 Landscapes
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Experiment 2 species: “a” & “b” –Asymmetric competition ( α ab = 10, α ba = 1) –Symmetric fecundity and dispersal parameters 100 runs in each of: –9 unfragmented landscapes –9 fragmented landscapes Aggregation Index (Landscape statistics: APACK v. 2.23 (Mladenoff and DeZonia 2004)
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Results: Area Effect
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Results: Time to Extinction
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Results
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Conclusion Fine-scale habitat fragmentation facilitates coexistence of competitively asymmetric species. In a digital landscape, at least.
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Does this happen in real landscapes?
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Yes.
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Fragmentation, Diversity, Space, and Time Fragmentation disrupts the processes governing membership in ecological communities. –Negatively –Positively Allopatric speciation Competitive uncoupling (?)
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Space Time + Uncoupling + Allopatric speciation Fragmentation, Diversity, Space, and Time + “Spatial insurance” (Metapopulations) − Habitat fragmentation → relaxation − ?
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Might Uncoupling Emerge at Broader Scales?
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Some Implications Rare species may gain refuge in habitats with fine-scale fragmentation. Habitats with fine-scale fragmentation may provide immigration points for exotic species. It’s worth looking into this…
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Acknowledgements Office of the President, Bucknell University Office of the Dean, Bucknell University College of Arts and Sciences Bryn Scriver and John Stoddard
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Thank you.
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