Uncovering the hidden diversity of Amphiglena mediterranea (Annelida: sabellidae): an integrative approach

Abstract

[eng] Amphiglena mediterranea Leydig, 1851 (Annelida: Sabellidae) was described from shallow rocky bottoms in Nice, France. For over a century it was the only species in the genus reported in the Mediterranean Sea. Recent studies in the Italian coast evidenced there are lineages compatible with the unified species concept hidden under an apparently similar morphological group. In order to determine Amphiglena diversity from several understudied localities along the Western Mediterranean and North-East Atlantic, an integrative approach for species delimitation combining genetic, morphological and also geographical data, was implemented. This represents the first integrative study in Amphiglena and the largest genetic study conducted within the genus to date. The mitochondrial gene cytochrome C oxidase subunit I (COI), the so-called universal barcoding gene for animals, of 90 Amphiglena specimens were analyzed. The genetic approach included phylogenetic analyses (Bayesian inference and Maximum Likelihood), and different distance and tree based molecular species delimitation tools (ABGD, ASAP, and PTP, bPTP, mPTP and statistical parsimony haplotype network). The morphological approach included different microscopic techniques (microscopy and SEM) and staining methods. In addition, multivariate analyses (PCA and PCoA) were performed to identify morphological diagnostic attributes for the molecular lineages. Seven undescribed Amphiglena genetic lineages compatible with the unified species concept were found in this study adding to the other seven species already reported in the Italian coasts and Madeira. Western Mediterranean species showed restricted and, in some cases, sympatric distributions, indicating no genetic flow between taxa regardless proximity. Morphological features overlapped in certain molecular groups and only five morphogroups were identified. One morphogroup, included three lineages, and showed very similar morphology with the original description of A. mediterranea. This study reveals that the genus Amphiglena holds a vast genetic and morphological diversity that has been overlooked over the years. In addition, members of the A. mediterranea species complex shows restricted distributions and have not apparently been unintentionally translocated, as expected being a common shallow water species, able to settle and stablish populations quickly on hard substrates including artificial substrates and anthropogenic environments.