Cryptic speciation and genetic structure of widely distributed brittle stars (Ophiuroidea) in Europe

• Published in: Zoologica Scripta
• Main Authors: Pérez-Portela, R., Almada, Vitor C., Turon, Xavier
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley-Blackwell 2013
• Subjects: North Atlantic; Northeast Atlantic
• Online Access: http://hdl.handle.net/10261/67268; https://doi.org/10.1111/j.1463-6409.2012.00573.x

19 páginas, 3 tablas, 4 figuras. The development of molecular techniques has led to the detection of numerous cases of cryptic speciation within widely distributed marine invertebrate species and important taxonomic revisions in all the major marine taxa. In this study, we analysed a controversial marine species complex in the genus Ophiothrix, a widespread taxon in European waters traditionally assigned to two nominal species, Ophiothrix fragilis and O. quinquemaculata. These species are important components of the rocky shores and deep marine benthos along the North Atlantic and Mediterranean littoral. Their status (including variants of both species) has remained contentious due to overlapping variability in morphological characters. In this study, we analysed the genetic and morphological differences of Ophiothrix lineages along the Atlantic and Mediterranean coasts. We also assessed population genetic structure in the Atlantic and Mediterranean basins by sequencing two mitochondrial genes, the 16S rRNA gene and COI gene, of 221 specimens from 13 locations. Phylogenetic analyses demonstrated the existence of two genetically distinct lineages, attributable to two different species although unrelated to previous taxonomic distinctions. Morphological differences could also be detected between these lineages. Samples from the Northeast Atlantic and one from the deep Mediterranean grouped within Lineage I, whereas Lineage II pooled together the southern Atlantic and rocky shallow Mediterranean samples. In the northern region of the Iberian Peninsula and at a deep locality in the Mediterranean, both lineages overlap. Speciation processes likely happened during the Mio–Pliocene transition (about 4.8–7.5 million years ago), when marine-level oscillations led to the blockage of major marine corridors in Europe and promoted genetic isolation by vicariance. Secondary contact between lineages following sea-level increases and recolonization during the refilling of the Mediterranean after the Miocene salinity crisis ...