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

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 highlatitude 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 Φ ST = 0.07−0.87) and all but one pair of the 8 samples also exhibited significantly different haplotype frequencies (pairwise F ST = 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 F ST = 0.03−0.06). There was a significant pattern of IBD for all markers and measures of genetic differentiation (r 2 = 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.

Genetic connectivity and phylogeography of the night shark (Carcharhinus signatus) in the western Atlantic Ocean: Implications for conservation management

“…This is concordant with the maximum distances travelled by tagged individuals ranging between 1000 and 2000 km in the western North Atlantic and Gulf of Mexico, and with no trans‐equatorial movements being detected (Kohler, Casey, & Turner, ). The same isolation of western North Atlantic and western South Atlantic populations at mitochondrial markers also occurred in large coastal shark species such as Sphyrna lewini (Griffith & Smith, 1834); (Chapman, Pinhal, & Shivji, ), Carcharhinus leucas (Müller & Henle, 1839) (Karl et al, ), G. cirratum (Karl et al, ), Negaprion brevirostris (Poey, 1868) (Ashe et al, ), and the semi‐oceanic C. falciformis (Domingues et al, ), but not in epipelagic, oceanic shark species such as Pseudocarcharias kamoharai (Matsubara, 1937) and Carcharhinus longimanus (Poey, 1861) (Camargo et al, ; Ferrette et al, ). Individual based mtCR analyses support an isolation‐by‐distance pattern rather than the complete isolation of populations in night sharks, similar to findings for other shark species such as Carcharhinus melanopterus (Quoy & Gaimard, 1824) (Vignaud, Clua, Mourier, Maynard, & Planes, ), Sphyrna tiburo (Linnaeus, 1758) (Portnoy et al, ), and N. brevirostris (Ashe et al, ).…”

“…Alvarado Bremer, Viñas, Mejuto, Ely, & Plas, ; Domingues et al, ; Martinez, González, Castilho, & Zardoya, ; Portnoy et al, ). The presence of two sympatric clades composed of representatives’ samples from all populations could be attributed to their recent isolation, which mitochondrial frequencies have not yet homogenized, as has been observed in other shark species (Ashe et al, ; Domingues et al, ; Portnoy et al, ).…”

Philopatry and Regional Connectivity of the Great Hammerhead Shark, Sphyrna mokarran in the U.S. and Bahamas

“…Future studies should explore genetic differentiation by examining haplotype frequency of young of the year great hammerheads and adults sampled throughout the region. This will be important in determining if females are returning faithfully to parturition sites and whether there is an absence of female-mediated gene flow, which has consequences for stock management as discussed for other marine species, including sharks Ashe et al, 2015) cetaceans (Baker et al, 2013) and pinnipeds (Lopes et al, 2015).…”

A population genomics insight by 2b‐RAD reveals populations' uniqueness along the Italian coastline in Leptopsammia pruvoti (Scleractinia, Dendrophylliidae)

“…For instance, when considering fish with a Mediterranean–Atlantic distribution, a weak differentiation is often found when comparing populations sampled at thousands of kilometres of distance (i.e., Milano et al, ; Souche et al, ), and extreme differences are found at most across major biogeographic/oceanographic transitions (Patarnello, Volckaert, & Castilho, and references therein). Indeed, for marine fish, F ST values rarely exceed 0.1–0.15 within the Mediterranean Sea, even when considering species with a limited PLD, fragmented habitat and endemism level (Astolfi et al, ; Carreras et al, ; Carreras‐Carbonell, Macpherson, & Pascual, ; Congiu et al, ), and only raise to high values when considering sharks (Ashe et al, ), reptiles (Sethuraman et al, ) and some marine mammals (Fruet et al, ). Similar pictures of low differentiation are common in several benthic invertebrates, such as sponges ( Scopalina lophyropoda , Blanquer & Uriz, ), sea urchins ( Paracentrotus lividus , Maltagliati, Di Giuseppe, Barbieri, Castelli, & Dini, , Penant, Aurelle, Feral, & Chenuil, ), sea cucumbers ( Holothuria mammata , Borrero‐Pérez, Gonzàlez‐Wanguemert, Marcos, & Pérez‐Ruzafa, ), bivalves ( Pinna nobilis , Sanna et al, ) and crustaceans ( Liocarcinus depurator , Pascual et al, ; Carcinus aestuarii , Schiavina, Marino, Zane, & Melìa, ; Pachygrapsus marmoratus , Fratini et al, ).…”