Fine-scale geomorphic pattern and biodiversity Duane A. Griffin and Phil Marquis Bucknell University Lewisburg, PA

Plant Biodiversity Patterns

Explanations

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.

How does this individual interact with others in its habitat?

Direct interactions with immediate neighbors (competition)

Seed dispersal and microsite colonization Direct interactions with immediate neighbors (competition) Mostly Deterministic Mostly Stochastic

y = f(x)

What if habitat patches are discrete and isolated at fine scales?

Colonization neighborhood remains the same

Resource competition neighborhood is smaller

y = f(x)

Testing: GeoSim Individual-Based Spatially Explicit Reaction-Diffusion Model Diffusion Reaction Seed Dispersal Colonization Lottery Competition Seed Production ABA A B A BAA

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Seed Dispersal Colonization Lottery CompetitionSeed Production

Landscapes

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 (Mladenoff and DeZonia 2004)

Results: Area Effect

Results: Time to Extinction

Results

Conclusion Fine-scale habitat fragmentation facilitates coexistence of competitively asymmetric species. In a digital landscape, at least.

Does this happen in real landscapes?

Yes.

Fragmentation, Diversity, Space, and Time Fragmentation disrupts the processes governing membership in ecological communities. –Negatively –Positively Allopatric speciation Competitive uncoupling (?)

Space Time + Uncoupling + Allopatric speciation Fragmentation, Diversity, Space, and Time + “Spatial insurance” (Metapopulations) − Habitat fragmentation → relaxation − ?

Might Uncoupling Emerge at Broader Scales?

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…

Acknowledgements Office of the President, Bucknell University Office of the Dean, Bucknell University College of Arts and Sciences Bryn Scriver and John Stoddard

Thank you.