1. Spatial synchrony and extinction risk in metapopulations: a spatial “hydra effect” Jeremy Fox University of Calgary dynamicecology.wordpress.com David Vasseur Yale University

2. The “hydra effect”

3. The usual story: intermediate dispersal rates maximize metapopulation persistence Metapopulation persistence time Dispersal rate Zero/lowIntermediateHigh Indep. patches (async.) Coloniz.-extinction (async.) “One big patch” (sync.) Big patch persistent Big patch extinction-prone

4. Yaari et al. 2012 Intermediate dispersal rates maximize metapopulation persistence

5. Huffaker 1958 Intermediate dispersal maximizes metapopulation persistence Holyoak and Lawler 1996:

6. Euplotes patella Tetrahymena pyriformis Protist microcosms: a model system for spatial synchrony

7. Day Prey density (ml -1 ) 072 0 1500 072 Vasseur & Fox 2009; Fox et al. 2011, unpublished Cyclic dynamics are easily synchronized (“phase locked”) by dispersal Dispersal rates <0.5%/prey generation can give synchrony

8. Spatial synchrony in nature Lynx Gypsy moth Collared lemming Measles Blasius et al. 1999, Johnson et al. 2006, Rohani et al. 1999, Paradis et al. 2000, Krebs et al. 2002 Wren

9. A puzzle: How are asynchronous colonization-extinction dynamics possible? An answer: A spatial hydra effect Local extinctions are desynchronizing Anything that reduces synchrony promotes recolonization, and thus persistence Empirical examples of colonization-extinction dynamics involve extinction-prone subpopulations Empirical examples of synchrony at low dispersal rates involve persistent subpopulations

10. An illustration of the spatial hydra effect Nicholson-Bailey host-parasitoid model with demogr. stochas. (Yaari et al. 2012) 4 patches Global density-independent dispersal of both spp. after births & deaths At end of timestep: random subpop. destruction

11. Subpopulation dynamics under low dispersal, no subpop. destruction TimestepHost subpopulation abundance

12. Subpopulation dynamics under intermediate dispersal, no subpop. destruction Timestep Host subpopulation abundance

13. Subpopulation dynamics under high dispersal, no subpop. destruction Timestep Host subpopulation abundance

14. Subpopulation dynamics under high dispersal with random subpopulation destruction Timestep Host subpopulation abundance

15. 0 90 0.00010.0010.010.11 Dispersal rate (log scale) Metapopulation persistence time (mean) Subpopulation destruction rate 0 0.025 0.5 0.075 0.1 A spatial hydra effect

16. Conclusions and future directions Hydras are real Effect can vary in strength, be swamped by other effects -Matter & Roland 2010 Proc Roy Soc B Biological details only matter via effects on colonization and extinction rates Really exists.

17. 0 800 0101 Dispersal rate Mean metapop. persist. time Stochastic RickerStochastic logistic map 0 0.025 0.05 0.075 0.1 Destruct. rate Weak spatial hydra effect

18. Moran Disp. n y n n y y y Low rates of “stepping stone” dispersal phase lock entire metapopulations 0 0.9 1.8 12345 Spatial lag Mean prey synchrony ±SE Fox et al. 2011 Ecol. Lett.

19. Even low dispersal rates can rapidly synchronize cycling populations Fox et al. unpublished