Population Genetic History of <i>Aristeus antennatus</i> (Crustacea: Decapoda) in the Western and Central Mediterranean Sea

<div><p><i>Aristeus antennatus</i> is an ecologically and economically important deep-water species in the Mediterranean Sea. In this study we investigated the genetic variability of <i>A</i>. <i>antennatus</i> sampled from 10 sampling stations in the Western and Central Mediterranean. By comparing our new samples with available data from the Western area, we aim to identify potential genetic stocks of <i>A</i>. <i>antennatus</i> and to reconstruct its historical demography in the Mediterranean. We analyzed two regions of mitochondrial DNA in 319 individuals, namely COI and 16S. We found two main results: i) the genetic diversity values consistent with previous data within the Mediterranean and the absence of barriers to gene flow within the Mediterranean Sea; ii) a constant long-term effective population size in almost all demes but a strong signature of population expansion in the pooled sample about 50,000 years B.P./ago. We propose two explanation for our results. The first is based on the ecology of <i>A</i>. <i>antennatus</i>. We suggest the existence of a complex meta-population structured into two layers: a deeper-dwelling stock, not affected by fishing, which preserves the pattern of historical demography; and genetically homogeneous demes inhabiting the fishing grounds. The larval dispersal, adult migration and continuous movements of individuals from “virgin” deeper grounds not affected by fishing to upper fishing areas support an effective ‘rescue effect’ contributing to the recovery of the exploited stocks and explain their genetic homogeneity throughout the Mediterranean Sea. The second is based on the reproduction model of this shrimp: the high variance in offspring production calls for a careful interpretation of the data observed under classical population genetics and Kingman’s coalescent. In both cases, management policies for <i>A</i>. <i>antennatus</i> will therefore require careful evaluation of the meta-population dynamics of all stocks in the Mediterranean. In the future, it will be particularly relevant to sample the deepest ones directly.</p></div

Diversity measurement for concatenated 16S rDNA and COI sequences (947bp).

<p>Number of haplotypes (N<i>h</i>); number of polymorphic sites (N<i>p</i>); haplotype diversity (<i>h</i>); nucleotide diversity (<i>π</i>). Tajima’s <i>D</i> and Fu’s <i>Fs</i> neutrality tests.</p><p>* p≤0.05.</p><p>**p≤0.005.</p><p>Diversity measurement for concatenated 16S rDNA and COI sequences (947bp).</p

Results of SAMOVA for five groups (K = 5) using COI sequences.

<p>WM: Western Mediterranean, CM: Central Mediterranean, AO: Atlantic Ocean.</p><p>* Samples from Fernandez et al. (2010). na: not available.</p><p>Results of SAMOVA for five groups (K = 5) using COI sequences.</p

Extended Bayesian Skyline Plot (EBSP) of a concatenated 16S rDNA and COI sequences, Western and Central Mediterranean pooled samples.

<p><i>X</i> axis: calendar years. <i>Y</i> axis: effective population size. Red lines show the 95% HPD limits; black line the median estimate.</p

Results of SAMOVA (10,000 iterations) for concatenated sequences (947 bp) of Western and Central Mediterranean.

<p>We ran the simulated annealing algorithm using different random starting points from two (K = 2) to five groups (K = 5).</p><p>*p≤0.05</p><p>**p≤0.005. C-S = Central-Southern.</p><p>Results of SAMOVA (10,000 iterations) for concatenated sequences (947 bp) of Western and Central Mediterranean.</p

Sampling locations in the Central-Southern Tyrrhenian Sea (Western Mediterranean), North-Western Ionian Sea and Southern Adriatic Sea (Central Mediterranean).

<p>Sampling locations in the Central-Southern Tyrrhenian Sea (Western Mediterranean), North-Western Ionian Sea and Southern Adriatic Sea (Central Mediterranean).</p

Median-joining network of haplotypes detected for the concatenated 16S rDNA and COI sequences.

<p>The area of each circle is proportional to the number of individuals exhibiting that haplotype. Branch length is proportional to the number of mutations occurred. Red dots represent missing or undetected haplotypes. The most frequent haplotypes are shared by individuals from all localities.</p

Length-frequency distribution of <i>Pagellus bogaraveo</i>, <i>Phycis blennoides</i> and <i>Polyprion americanus</i> in the coral megahabitat (C) and non-coral megahabitat (NC) in the SML cold-water coral province.

<p>Length-frequency distribution of <i>Pagellus bogaraveo</i>, <i>Phycis blennoides</i> and <i>Polyprion americanus</i> in the coral megahabitat (C) and non-coral megahabitat (NC) in the SML cold-water coral province.</p

Sampling stations, with mean depth and geographic coordinates in the coral megahabitat (C) and non-coral megahabitat (NC) in the SML coral province during May–June 2010.

<p>Sampling stations, with mean depth and geographic coordinates in the coral megahabitat (C) and non-coral megahabitat (NC) in the SML coral province during May–June 2010.</p

A live colony of <i>Madrepora oculata</i> with the presence of the solitary <i>Desmophillum dianthus</i> corals collected by longline in the coral megahabitat of the SML cold-water coral province.

<p>A live colony of <i>Madrepora oculata</i> with the presence of the solitary <i>Desmophillum dianthus</i> corals collected by longline in the coral megahabitat of the SML cold-water coral province.</p