Díaz A et al. (2018), Genetic structure and demographic inference of ...

ECB-ART-46392

PLoS One 2018 Jan 01;136:e0197611. doi: 10.1371/journal.pone.0197611.

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Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: The role of the last glaciation.

Díaz A , Gérard K , González-Wevar C , Maturana C , Féral JP , David B , Saucède T , Poulin E .

Abstract
One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Adélie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica.

PubMed ID: 29874287
PMC ID: PMC5991379
Article link: PLoS One

Species referenced: Echinodermata
Genes referenced: LOC100887844 LOC576414

Article Images: [+] show captions

References [+] :

Aljanabi, Universal and rapid salt-extraction of high quality genomic DNA for PCR-based techniques. 1997, Pubmed

	Fig 1. Map of localities.Localities analyzed of the species Sterechinus neumayeri in Antarctica.
	Fig 2. Network.General median joining haplotype network including 174 Sterechinus neumayeri mtDNA COI sequences. Each haplotype is represented by a colored circle indicating the main area where it was collected and the size of the circle is proportional to its frequency in the whole dataset. ° = median vector (theoretical haplotype that has not been collected but should exist).
	Fig 3. Networks for each area.Median-joining haplotype networks and the distribution of mean number of pairwise differences (mismatch) for each area included in the analyses. *To compare among areas, 18 individuals were randomly selected from the Antarctic Peninsula.
	Fig 4. Historical demographic trends.Historical demographic trends of effective population size (Ne) constructed using a Bayesian skyline plot approach based on COI haplotypes of S. neumayeri, with two mutation rates (5.1% and 7.2%). The y-axis is the product of effective population size (Ne) and generation length in a log scale while the x-axis is the time in 103 before present. The median estimate (solid black line) and 95% highest probability density (HPD) limits (gray/pink area) are shown. The thick dashed line represents the time of the most recent ancestor (trcma) and the thin dashed line represents time for the expansion in the species.