Genetic and oceanographic tools reveal high population connectivity and diversity in the endangered pen shell Pinna nobilis

Abstract

For marine meta-populations with source-sink dynamics knowledge about genetic connectivity is important to conserve biodiversity and design marine protected areas (MPAs). We evaluate connectivity of a Mediterranean sessile species, Pinna nobilis. To address a large geographical scale, partial sequences of cytochrome oxidase I (COI, 590 bp) were used to evaluate phylogeographical patterns in the Western Mediterranean, and in the whole basin using overlapping sequences from the literature (243 bp). Additionally, we combined (1) larval trajectories based on oceanographic currents and early life-history traits and (2) 10 highly polymorphic microsatellite loci collected in the Western Mediterranean. COI results provided evidence for high diversity and low inter-population differentiation. Microsatellite genotypes showed increasing genetic differentiation with oceanographic transport time (isolation by oceanographic distance (IBD) set by marine currents). Genetic differentiation was detected between Banyuls and Murcia and between Murcia and Mallorca. However, no genetic break was detected between the Balearic populations and the mainland. Migration rates together with numerical Lagrangian simulations showed that (i) the Ebro Delta is a larval source for the Balearic populations (ii) Alicante is a sink population, accumulating allelic diversity from nearby populations. The inferred connectivity can be applied in the development of MPA networks in the Western Mediterranean.

Gene pool and connectivity patterns of Pinna nobilis in the Balearic Islands (Spain, Western Mediterranean Sea): Implications for its conservation through restocking

“…In 2011, the current pattern was very different, with a major loss of larvae offshore towards southern waters predicted, likely leading to high mortality of larvae of that year class and a substantial decrease in recruitment. According to Wesselmann et al (), no isolation of the Balearic P. nobilis populations with the mainland was recorded. In fact, the locality of Ibiza appeared to be a key population in order to ensure connectivity, receiving genes from the mainland (the Ebro Delta, Alicante and Murcia) and exporting them to Mallorca.…”

“…However, no locality from our target region, the Spanish Western Mediterranean Sea, was included in any of these studies. Wesselmann et al () focused on population genetics of P. nobilis working at two spatial scales: (a) wide scale along the Mediterranean Sea using mitochondrial DNA (COI gene), and (b) small scale, including part of the Western Mediterranean Sea (Mediterranean Spanish coast and Balearic Islands) using 10 microsatellites. Microsatellite results showed isolation by oceanographic distance between sampling localities.…”

“…In fact, the locality of Ibiza appeared to be a key population in order to ensure connectivity, receiving genes from the mainland (the Ebro Delta, Alicante and Murcia) and exporting them to Mallorca. Migration rate estimates pointed to the Ebro Delta as a source population, exporting genes to Ibiza and from Ibiza to Mallorca (Wesselmann et al, ).…”

Identification of potential recruitment bottlenecks in larval stages of the giant fan mussel Pinna nobilis using specific quantitative PCR

“…However, the results are suggestively robust considering some of the tested samples are from as far away as France. Additionally, Wesselmann et al (2018) demonstrated using microsatellite markers that populations of P. nobilis from across the Mediterranean have low inter-population diversity, while genetically having high connectivity, which suggests this marker will be useful for areas outside the Ebro Delta and into the Eastern Mediterranean.…”

“…Studies of genetic diversity may find this region useful since regions rich in repeat sequences, such as those found here, frequently expand or contract during the course of evolution (Read et al, 2004); this being the basis for microsatellite analysis. Previous phylogenetic studies related to this genus have used more standard genetic markers such as cytochrome oxidase (Sanna et al, 2013(Sanna et al, , 2014, microsatellite DNA (Gonzalez-Wanguemert et al, 2015;Wesselmann et al, 2018), or nuclear and mitochondrial ribosomal genes (Lemer et al, 2014). In the case of the latter study, cryptic species were identified within the family Pinnidae.…”