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Patterns, causes, and consequences of marine larval dispersal

  1. Peter M. Bustona
  1. aDepartment of Biology and Marine Program, Boston University, Boston, MA 02215;
  2. bDepartment of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853;
  3. cDepartment of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106

  1. Edited by Nancy Knowlton, Smithsonian Institution, DC, Washington, and approved October 1, 2015 (received for review July 15, 2015)

Significance

Networks of marine protected areas (MPAs) have been widely implemented to combat global population declines. Although their efficacy largely depends on larval exchange between populations, quantitative analyses of dispersal have been limited due to the difficulties of tracking larvae. Here, we systematically measure dispersal in the fish Elacatinus lori, producing the first robust estimate of a dispersal kernel. We find that dispersal declines exponentially, with most larvae traveling less than 2 km from their parents. Remarkably, the distance an individual travels is unrelated to the number of days it spends in the larval phase. These results suggest that simple distance-based models may be useful conservation tools and that MPAs that are close in space will accommodate short-distance dispersers.

Abstract

Quantifying the probability of larval exchange among marine populations is key to predicting local population dynamics and optimizing networks of marine protected areas. The pattern of connectivity among populations can be described by the measurement of a dispersal kernel. However, a statistically robust, empirical dispersal kernel has been lacking for any marine species. Here, we use genetic parentage analysis to quantify a dispersal kernel for the reef fish Elacatinus lori, demonstrating that dispersal declines exponentially with distance. The spatial scale of dispersal is an order of magnitude less than previous estimates—the median dispersal distance is just 1.7 km and no dispersal events exceed 16.4 km despite intensive sampling out to 30 km from source. Overlaid on this strong pattern is subtle spatial variation, but neither pelagic larval duration nor direction is associated with the probability of successful dispersal. Given the strong relationship between distance and dispersal, we show that distance-driven logistic models have strong power to predict dispersal probabilities. Moreover, connectivity matrices generated from these models are congruent with empirical estimates of spatial genetic structure, suggesting that the pattern of dispersal we uncovered reflects long-term patterns of gene flow. These results challenge assumptions regarding the spatial scale and presumed predictors of marine population connectivity. We conclude that if marine reserve networks aim to connect whole communities of fishes and conserve biodiversity broadly, then reserves that are close in space (<10 km) will accommodate those members of the community that are short-distance dispersers.

Footnotes

  • ↵1Present address: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S3G5.

  • ↵2To whom correspondence should be addressed. Email: cassidy.daloia{at}gmail.com.

  • Author contributions: C.C.D., S.M.B., R.G.H., and P.M.B. designed research; C.C.D., S.M.B., R.K.F., J.E.M., and P.M.B. performed research; C.C.D. analyzed data; and C.C.D. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1513754112/-/DCSupplemental.

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