COS 89-3
Connectivity structures local population dynamics: A long-term empirical test in a large metapopulation network

Wednesday, August 12, 2015: 2:10 PM
338, Baltimore Convention Center
Max C.N. Castorani, Marine Science Institute, University of California, Santa Barbara, , USA
Daniel C. Reed, Marine Science Institute, University of California, Santa Barbara, ,
Filipe Alberto, Department of Biological Sciences, University of Wisconsin-Milwaukee, ,
Tom W. Bell, Earth Research Institute, University of California, Santa Barbara, Santa Barbara, CA, USA
Rachel D. Simons, Earth Research Institute, University of California, Santa Barbara, ,
Kyle C. Cavanaugh, Department of Geography, University of California, Los Angeles, ,
David A. Siegel, Earth Research Institute, University of California, Santa Barbara, , ; Marine Science Institute, University of California, Santa Barbara, ,
Peter T. Raimondi, Department of Biology, University of California, Santa Cruz, ,
Background/Question/Methods

Ecological theory predicts that demographic connectivity structures the dynamics of local populations within metapopulation systems, but empirical support has been constrained by major limitations in data and methodology. We tested this prediction for giant kelp Macrocystis pyrifera—a key habitat-forming species in temperate coastal ecosystems worldwide—in southern California by combining a long-term (22 y), large-scale (~500 km coastline), high-resolution census of abundance with novel patch delineation methods and innovative connectivity measures incorporating oceanographic transport and source fecundity.

Results/Conclusions

Connectivity strongly predicted local dynamics—well-connected patches had lower probabilities of extinction and higher probabilities of colonization, leading to greater likelihoods of occupancy—but this relationship was mediated by patch size. Moreover, the relationship between connectivity and local population dynamics varied over time, possibly due to temporal variation in oceanographic processes. Surprisingly, connectivity had a smaller influence on colonization relative to extinction, possibly because local ecological factors differ greatly between extinct and extant patches. Our results provide the first comprehensive evidence that southern California giant kelp populations function as a metapopulation system, challenging the view that populations of this important foundation species are predominantly governed by self-replenishment.