Dataset Information

Origins of the Greenland shark (Somniosus microcephalus): Impacts of ice-olation and introgression.

ABSTRACT: Herein, we use genetic data from 277 sleeper sharks to perform coalescent-based modeling to test the hypothesis of early Quaternary emergence of the Greenland shark (Somniosus microcephalus) from ancestral sleeper sharks in the Canadian Arctic-Subarctic region. Our results show that morphologically cryptic somniosids S. microcephalus and Somniosus pacificus can be genetically distinguished using combined mitochondrial and nuclear DNA markers. Our data confirm the presence of genetically admixed individuals in the Canadian Arctic and sub-Arctic, and temperate Eastern Atlantic regions, suggesting introgressive hybridization upon secondary contact following the initial species divergence. Conservative substitution rates fitted to an Isolation with Migration (IM) model indicate a likely species divergence time of 2.34 Ma, using the mitochondrial sequence DNA, which in conjunction with the geographic distribution of admixtures and Pacific signatures likely indicates speciation associated with processes other than the closing of the Isthmus of Panama. This time span coincides with further planetary cooling in the early Quaternary period followed by the onset of oscillating glacial-interglacial cycles. We propose that the initial S. microcephalus-S. pacificus split, and subsequent hybridization events, were likely associated with the onset of Pleistocene glacial oscillations, whereby fluctuating sea levels constrained connectivity among Arctic oceanic basins, Arctic marginal seas, and the North Atlantic Ocean. Our data demonstrates support for the evolutionary consequences of oscillatory vicariance via transient oceanic isolation with subsequent secondary contact associated with fluctuating sea levels throughout the Quaternary period-which may serve as a model for the origins of Arctic marine fauna on a broad taxonomic scale.

SUBMITTER: Walter RP

PROVIDER: S-EPMC5632604 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Publications

Origins of the Greenland shark (Somniosus microcephalus): Impacts of ice-olation and introgression.

Walter Ryan P RP Roy Denis D Hussey Nigel E NE Stelbrink Björn B Kovacs Kit M KM Lydersen Christian C McMeans Bailey C BC Svavarsson Jörundur J Kessel Steven T ST Biton Porsmoguer Sebastián S Wildes Sharon S Tribuzio Cindy A CA Campana Steven E SE Petersen Stephen D SD Grubbs R Dean RD Heath Daniel D DD Hedges Kevin J KJ Fisk Aaron T AT

Ecology and evolution 20170908 19

Herein, we use genetic data from 277 sleeper sharks to perform coalescent-based modeling to test the hypothesis of early Quaternary emergence of the Greenland shark (Somniosus microcephalus) from ancestral sleeper sharks in the Canadian Arctic-Subarctic region. Our results show that morphologically cryptic somniosids S. microcephalus and Somniosus pacificus can be genetically distinguished using combined mitochondrial and nuclear DNA markers. Our data confirm the presence of ...[more]

PMID: 29043060

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Project description:The Greenland shark (Somniosus microcephalus) is the main bycatch species in established and exploratory inshore longline fisheries for Greenland halibut (Reinhardtius hippoglossoides) on the east coast of Baffin Island, Canada. Bycatch and entanglement in longline gear has at times been substantial and post-release survival is questionable when Greenland sharks are released with trailing fishing gear. This study investigated the effect of the type of fishing line used in the gangion and gangion breaking strength on catch rates of Greenland shark and Greenland halibut in bottom set longlines. Circle (size 14/0, 0° offset) hooks were used throughout the study. Behavior of captured sharks, mode of capture (i.e., jaw hook and/or entanglement), level of entanglement in longline gear, time required to disentangle sharks and biological information (sex, body length and health status) were recorded. Catch rates of Greenland shark were independent of monofilament nylon gangion breaking strength and monofilament gangions captured significantly fewer Greenland sharks than the traditional braided multifilament nylon gangion. Catch rates and body size of Greenland halibut did not differ significantly between gangion treatments. Although most (84%) of the Greenland sharks were hooked by the jaw, a high percentage (76%) were entangled in the mainline. The mean length of mainline entangled around the body and/or caudal peduncle and caudal fin was 28.7 m. Greenland sharks exhibited cannibalistic behavior with 15% of captured sharks cannibalized. All remaining sharks were alive and survived the disentanglement process which can be attributed to their lethargic behavior and lack of resistance when hauled to the surface. Thus, as a conservation measure fishers should be encouraged to remove trailing fishing gear prior to release. Our results are used to demonstrate benefits to the fishing industry with regard to an overall reduction in the period of time to disentangle sharks and damage to fishing gear by switching from braided multifilament to monofilament gangions in Greenland halibut longline fisheries.

Dataset Information

Origins of the Greenland shark (Somniosus microcephalus): Impacts of ice-olation and introgression.

Publications

Origins of the Greenland shark (<i>Somniosus microcephalus</i>): Impacts of ice-olation and introgression.

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