Examinando por Autor "Gardner, Jonathan P.A."

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    Blue mussels of the Mytilus edulis species complex from South America: The application of species delimitation models to DNA sequence variation
    (Public Library of Science, 2021-09) Oyarzun, Pablo A.; Toro, Jorge E.; Nuñe, José; Suarez-Villota, Elkin Y.; Gardner, Jonathan P.A.
    Smooth-shelled blue mussels, Mytilus spp., have a worldwide antitropical distribution and are ecologically and economically important. Mussels of the Mytilus edulis species complex have been the focus of numerous taxonomic and biogeographical studies, in particular in the Northern hemisphere, but the taxonomic classification of mussels from South America remains unclear. The present study analysed 348 mussels from 20 sites in Argentina, Chile, Uruguay and the Falkland Islands on the Atlantic and Pacific coasts of South America. We sequenced two mitochondrial locus, Cytochrome c Oxidase subunit I (625 bp) and 16S rDNA (443 bp), and one nuclear gene, ribosomal 18S rDNA (1770 bp). Mitochondrial and nuclear loci were analysed separately and in combination using maximum likelihood and Bayesian inference methods to identify the combination of the most informative dataset and model. Species delimitation using five different models (GMYC single, bGMYC, PTP, bPTP and BPP) revealed that the Mytilus edulis complex in South America is represented by three species: native M. chilensis, M. edulis, and introduced Northern Hemisphere M. galloprovincialis. However, all models failed to delimit the putative species Mytilus platensis. In contrast, however, broad spatial scale genetic structure in South America using Geneland software to analyse COI sequence variation revealed a group of native mussels (putatively M. platensis) in central Argentina and the Falkland Islands. We discuss the scope of species delimitation methods and the use of nuclear and mitochondrial genetic data to the recognition of species within the Mytilus edulis complex at regional and global scales. © 2021 Oyarzún et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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    Genetic structure and diversity of the Chilean flat oyster Ostrea chilensis (Bivalvia: Ostreidae) along its natural distribution from natural beds subject to different fishing histories
    (Brazilian Journal of Genetics, 2022) Toro, Jorge E.; Oyarzún, Pablo A.; Toledo, Felipe E.; Navarro, Jorge M.; Illesca, Alex F.; Gardner, Jonathan P.A.
    Ostrea chilensis (Küster, 1844), the flat oyster, is native to Chile and New Zealand. In Chile, it occurs in a few natural beds, from the northern part of Chiloé Island (41 ºS) to the Guaitecas Archipelago (45 ºS). This bivalve is slow growing, broods its young, and has very limited dispersal potential. The Ostrea chilensis fishery has been over-exploited for a number of decades such that in some locations oysters no longer exist. The aim of this study was to study the genetic diversity of the Chilean flat oyster along its natural distribution to quantify the possible impact of the dredge fishery on wild populations. The genetic structure and diversity of Ostrea chilensis from six natural beds with different histories of fishing activity were estimated. Based on mitochondrial (Cytb) and nuclear (ITS1) DNA sequence variation, our results provide evidence that genetic diversity is different among populations with recent history of wild dredge fishery efforts. We discuss the possible causes of these results. Ultimately, such new information may be used to develop and apply new management measures to promote the sustainable use of this valuable marine resource. © Sociedade Brasileira de Genética.