Phylogeography of the insular populations of common octopus, Octopus vulgaris Cuvier, 1797, in the Atlantic Macaronesia

Oceanic islands act as drivers for the genetic diversity of marine species: Cardita calyculata (Linnaeus, 1758) in the NE Atlantic as a case-study

Geographic distribution, as well as evolutionary and biogeographic processes and patterns of marine invertebrate benthic species are strongly shaped by dispersal ability during the life cycle. Remote oceanic islands lie at the brink of complex biotic and abiotic interactions which have significantly influenced the biodiversity patterns we see today. The interaction between geological environmental change and taxon-specific dispersal modes can influence species evolutionary patterns, eventually delimiting species-specific biogeographic regions. In this study, we compare the population genetic patterns of the marine bivalve Cardita calyculata in the northeast Atlantic, discussing the role of Macaronesian islands during past climatic cycles. The genetic structure and diversity patterns were outlined based on SSR-GBAS loci of 165 individuals and on the mitochondrial COI marker of 22 individuals from the Canary Islands, Madeira, Azores and the Mediterranean. The highly structured genetic pattern found among regions and within archipelagos suggests the central role of oceanic islands in promoting the divergence of the species in both the NE Atlantic and the Mediterranean. The high degree of divergence in the COI dataset (> 7%) suggests the existence of potential cryptic speciation that needs to be further explored with a more comprehensive sampling. Such patterns are only congruent with a scenario where C. calyculata populations were maintained during glacial/interglacial cycles, supporting the role of the studied archipelagos as drivers of diversity for marine biota. We stress the importance of developing studies for species with various life history and dispersal modes. In such a way, a more profound understanding of the biogeographic and evolutionary significance of oceanic islands can catalyse directed conservation efforts, especially in the context of the ongoing climate crisis.

Insights on the Evolutionary History and Genetic Patterns of Octopus vulgaris Cuvier, 1797 in the Northeastern Atlantic Using Mitochondrial DNA

Octopus vulgaris is one of the most harvested octopus species in the world. In the Iberian Peninsula, there are several small-scale fisheries that have a long-term tradition of harvesting octopus. The Asturias fleet (in Northern Spain) has an internationally recognized MSC label for its exploitation. Of concern, genetic assessments of exploited stocks are currently scarce, which could prevent the implementation of adequate managing strategies. We use two mitochondrial regions (cytochrome oxidase subunit 1 and control region) to analyze the genetic status and evolutionary events that conditioned octopus populations' characteristics in the Northeastern Atlantic. A total of 90 individuals were sampled from three different localities in the Iberian Peninsula as well as a location in Macaronesia. Temporal genetic analyses on Asturias and Algarve populations were also performed. Results indicated the absence of fine spatial genetic structuring but showed the Canary Islands (in Macaronesia) as the most distinct population. Our analyses detected two distinct clades, already described in the literature, but, for the first time, we confirmed the presence of the α-southern haplogroup in the Northern Iberian Peninsula. This result indicates a more continuous cline for the distribution of these two haplogroups than previously reported. Temporal changes in the distribution of both haplogroups in contact zones were also detected.

Evaluating the taxonomic status of the large sized Tricolia Risso, 1826 in the Northeast Atlantic and Mediterranean Sea

Despite a long history of taxonomic studies on the genus Tricolia Risso, 1826, there is a shortfall on thorough systematic molecular reviews of the taxon from the NE Atlantic and Mediterranean coasts. Aiming to assess the genetic distinctness among morphospecies and the taxonomic status of currently accepted large sized species in these areas, we conducted a molecular phylogenetic analysis of the genus based on one mitochondrial (cox1) and two nuclear (28S and ITS2) markers. Seven Tricolia species were consistently retrieved in the analyses, including a new genetic lineage in the NE Atlantic designated as Tricolia sp. 1. Molecular analyses revealed that only one species, T. azorica, occurs in the NE Atlantic archipelagos. The sister taxa T. pullus (Mediterranean) and T. picta (NE Atlantic) should be classified as distinct species, instead of subspecies of the T. pullus group (sensu Gofas 1982). Tricolia miniata is also a complex of species in the Mediterranean and future studies across the distribution range are necessary to clarify its status.

Genetic monitoring on the world's first MSC eco-labeled common octopus (O. vulgaris) fishery in western Asturias, Spain

Octopus vulgaris (Cuvier, 1797) is a cephalopod species with great economic value. In western Asturias (northwest of Spain), O. vulgaris artisanal fisheries are relatively well monitored and conditionally eco-labeled by the Marine Stewardship Council (MSC). Despite this, the Asturian octopus stocks have not been genetically assessed so far. In order to improve the current fishery plan and contrast the octopus eco-label validity in Asturias, 539 individuals from five regions of the O. vulgaris geographic distribution, including temporal samplings in Asturias, were collected and genotyped at thirteen microsatellite loci. All the samples under analysis were in agreement with Hardy-Weinberg expectations. Spatial levels of genetic differentiation were estimated using F-statistics, multidimensional scaling, and Bayesian analyses. Results suggested that the O. vulgaris consists of at least four genetically different stocks coming from two ancestral lineages. In addition, temporal analyses showed stability in terms of genetic variation and high N_E (> 50) for several generations in different localities within Asturias, pointing out to indeed sustainable fishery exploitation levels. Even though, the current Asturias fishery plan shows no significant genetic damages to the stocks, the regional-specific management plans need systematic genetic monitoring schemes as part of an efficient and preventive regional fishery regulation strategy.