MEPS 520:203-216 (2015)  -  DOI: https://doi.org/10.3354/meps11069

Local population structure and context-dependent isolation by distance in a large coastal shark

Jimiane L. Ashe1, Kevin A. Feldheim2, Andrew T. Fields1, Eric A. Reyier3, Edward J. Brooks4, Martin T. O’Connell5, Gregory Skomal6, Samuel H. Gruber7,8, Demian D. Chapman1,*

1Institute for Ocean Conservation Science/School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA
2Pritzker Laboratory for Molecular Systematics and Evolution, Field Museum of Natural History,
1400 South Lake Shore Drive, Chicago, IL 60605, USA
3Kennedy Space Center Ecological Program and InoMedic Health Applications, Kennedy Space Center, Cape Canaveral, FL 32920, USA
4Shark Research and Conservation Program, Cape Eleuthera Institute, Eleuthera, The Bahamas
5Nekton Research Laboratory, Pontchartrain Institute for Environmental Sciences, University of New Orleans, New Orleans, LA 70148, USA
6Massachusetts Shark Research Project, Division of Marine Fisheries, 1213 Purchase St., New Bedford, MA 02740, USA
7Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science,
4600 Rickenbacker Causeway, Miami, FL 33149, USA
8Bimini Biological Field Station Foundation, Miami, FL 33176, USA
*Corresponding author:

ABSTRACT: Genetic diversity, population genetic structure and isolation by distance (IBD) were assessed in a viviparous coastal shark (the lemon shark Negaprion brevirostris) across 8 western Atlantic samples spaced between ~150 and 7000 km apart. Juveniles (N = 325) were sequenced at 2 mitochondrial loci (1729 bp) and typed at 9 nuclear encoded microsatellite loci. Analysis of mitochondrial sequences revealed higher diversity at low-latitude island samples compared to high-latitude continental samples, consistent with an equatorial center-of-origin for this species. There were 5 distinct groups across our sampling areas (Brazil, Louisiana, Cape Canaveral, Gullivan Bay and the Florida Keys/Bahamas/Virgin Islands; pairwise ΦST = 0.07-0.87) and all but one pair of the 8 samples also exhibited significantly different haplotype frequencies (pairwise FST = 0.10-0.51). Bayesian analysis indicated that the Brazil and Louisiana samples were generally isolated from the others, but most of the rest were diverged although still connected or recently connected by migration. In contrast, structure was only detected between the most distant sample (Brazil) and all of the others using the microsatellite markers (pairwise FST = 0.03-0.06). There was a significant pattern of IBD for all markers and measures of genetic differentiation (r2 = 0.65-0.81, p < 0.05-0.01), but not after removing the Brazil sample. There was evidence that glacial and post-glacial historical processes and sex-specific differences in philopatry affected IBD. Because of the relatively fine-scale population structure of this and other large coastal shark species more attention should be paid to local processes in the conservation and fisheries management of these species.


KEY WORDS: Mitochondrial DNA · Microsatellites · Phylogeography · Population structure


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Cite this article as: Ashe JL, Feldheim KA, Fields AT, Reyier EA and others (2015) Local population structure and context-dependent isolation by distance in a large coastal shark. Mar Ecol Prog Ser 520:203-216. https://doi.org/10.3354/meps11069

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