Genetic structuring of Eunicella singularis populations along a bathymetric gradient

Phenotypic plasticity refers to the ability of an organism to express different morphologies depending on the abiotic and biotic environment. Depth integrating many variables (e.g. temperature, light and hydrodynamics), may affect population structure and dynamics of the populations, as well as connectivity patterns and genetic diversity. Eunicella singularis is a Mediterranean arborescent gorgonian who plays an important rule as engineer species providing biomass and complexity to coralligenous habitats. It has a wide bathymetric distribution ranging from shallow rocky bottoms to deep sublittoral reefs. The species shows two depth-related morphotypes which taxonomic status is not yet clarified. The aim of the study is to analyses genetic variability and/or structuring along a vertical gradient to test the presence of the two morphotypes. Furthermore, a preliminary analyses of the phylogenetic relationship among species of the genus Eunicella has been done. Six populations of Eunicella singularis were sampled from 10 to 60 m depth in Cap de Creus and individuals belonging to Eunicella cavolinii, E. verrucosa, E. racemosa and E. stricta aphyta were collected. The genetic analyses were carried out using five microsatellite loci and ITS-1 sequence polymorphism. The results showed a reduction of genetic variability along the vertical gradient. A threshold in connectivity was observed across 30 - 40 m depth, confirming the presence of two different Eunicella singularis morphotypes. The two morphological forms could be due to phenotypic plasticity, which allowed populations to suit different environmental conditions, or to a break in gene flow that determined the isolation of the two populations and an accumulation of genetic differences. The molecular markers used were not able to clarify the phylogenetic relationship among Eunicella species and the systematic position of the two morphotypes, conversely they risen the question on the existence of single species of Mediterranean Eunicella.

Phylogeny and phylogeography of the family Hyalidae (Crustacea: Amphipoda) along the northeast Atlantic coasts

The family Hyalidae comprises more than one hundred species, distributed worldwide. They are common and abundant in the littoral and shallow sublittoral habitats and they play an important role in the coastal food chain. Most studies about this family were dealing with taxonomy and ecology, while very little is known about phylogenetic relationship among genera and species. In the present study we aim to achieve the first approach of the phylogenetic patterns of this family in NE Atlantic Ocean and Mediterranean Sea, and to perform the first insight into the phylogeography Apohyale prevostii along both the North Atlantic coasts. In order to do that, eight species belonging to the genera Apohyale, Hyale, Serejohyale and Protohyale were investigated using the mitochondrial COI-5P barcode region. Specimens were collected along European and Moroccan Atlantic rocky shores, including Iceland, the British Isles, Macaronesia and in the Mediterranean Sea. Sequences of A. prevostii, from the NW Atlantic Ocean, available in BOLD and GenBank, were retrieved. As expected, phylogenetic analyses showed highly-divergent clades, clearly discriminating among different species clusters, confirming their morphology-based identifications. Although, within A. perieri, A. media, A. stebbingi, P. (Protohyale) schmidtii and S. spinidactylus, high genetic diversity was found, revealing putative cryptic species. The clade of A. prevostii and A. stebbingi appears well supported and divided from the other two congeneric species, and P. (Protohyale) schmidtii shows a basal divergence. The north-western Atlantic coasts were recently colonized by A. prevostii after the last glacial maximum from the European populations showing also a common haplotype in every population analysed. The use of the COI-5P as DNA barcode provided a good tool to underline the necessity of a revision of this emblematic family, as well as to discern taxonomically the possible new species flagged with this molecular device.