Untangling the Octopus vulgaris species complex using a combined morphological and genomic approach

Despite their commercial value of $US1/2 billion per annum, the benthic octopuses of the family Octopodidae suffer from extensive unresolved taxonomies that impede the management of this global fisheries resource. The type... [ view full abstract ]

Despite their commercial value of $US1/2 billion per annum, the benthic octopuses of the family Octopodidae suffer from extensive unresolved taxonomies that impede the management of this global fisheries resource. The type species of the genus Octopus, Octopus vulgaris, has historically been considered a cosmopolitan species inhabiting Australasia, Europe, Africa, Asia and the Americas. However, recent discoveries suggest populations previously treated as O. vulgaris may represent a complex of morphologically similar yet genetically distinct vulgaris-like species (the “Octopus vulgaris complex”). We employed a global scale sampling strategy to investigate the true taxonomic diversity within the O. vulgaris species complex using unprecedented levels of morphological and genomic data, resulting in the most comprehensive investigation into Octopus vulgaris taxonomy to date. Discrete differences in morphology (based on up to 33 traits) were useful in delimiting the Mediterranean/NE Atlantic group from Asia, regardless of locality within each group or sex investigated. However, comparisons of Asian and South Brazilian groups revealed delimiting power was restricted to males. South Brazilian and Mediterranean/NE Atlantic groups were unable to be distinguished, however comparisons of locations within each group revealed certain male localities were able to be delimited. In fact, all localities of the Mediterranean/NE Atlantic group differed significantly from each other, with up to 49.8% of morphological variation being explained by the variation in environmental data (latitude, longitude, SST, SBT, salinity and depth), suggesting strong morphological plasticity within a single species, which may be driven by local abiotic factors. Furthermore, preliminary phylogenetic analyses of reduced representation genomic data (double digest RADseq) provide further evidence that the O. vulgaris species complex comprises several cryptic species, which are currently being mistreated under a single species name. The resulting multi-locus phylogeny provides new insights and species resolution, which existing mitochondrial based phylogenies are unable to provide.