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Global phylogeography of the scalloped hammerhead shark ( Sphyrna lewini )
Author(s) -
DUNCAN K. M.,
MARTIN A. P.,
BOWEN B. W.,
DE COUET H. G.
Publication year - 2006
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/j.1365-294x.2006.02933.x
Subject(s) - biology , biological dispersal , philopatry , population , ecology , mtdna control region , genetic structure , phylogeography , evolutionary biology , zoology , haplotype , genetic variation , phylogenetics , demography , biochemistry , sociology , gene , genotype
Large marine fishes typically have little population genetic structure. The exceptions are associated with sedentary behaviour, disjunct distributions, or reproductive philopatry. Scalloped hammerhead sharks ( Sphyrna lewini ) incorporate the contrasting traits of oceanic habitat (usually associated with high dispersal) and possible fidelity to nursery grounds (for reproductive females). To evaluate the expectations of these contrasting behaviours, we examined the global genetic structure of S. lewini based on collections ( n = 271 individuals) from 20 nursery areas. A 548‐bp fragment of mitochondrial DNA control region revealed 22 polymorphic sites, 24 haplotypes, and three lineages distinguished by 2.56–3.77% sequence divergence. Coalescence analyses based on a provisional molecular clock indicate an origin in the Indo‐West Pacific with late Pleistocene radiations into the central Pacific (Hawaii) and eastern Pacific (Central America), as well as recent interchange between oceans via southern Africa. Population subdivisions are strong (overall Φ ST = 0.749, P < 0.0001 and among oceans Φ ST = 0.598, P < 0.0098). Genetic discontinuity within oceans (Φ ST = 0.519, P < 0.0001) is primarily associated with oceanic barriers (migration across oceans M ≈ 0), with much less structure along continental margins (M > 10). We conclude that nursery populations linked by continuous coastline have high connectivity, but that oceanic dispersal by females is rare. Although we cannot rule out philopatry to natal nurseries, oceanic barriers appear to have a much stronger influence on the genetic architecture of this species and may indicate a mechanism for recent evolutionary radiations in the genus Sphyrna .