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Trabajo presentado en el XI Congreso de Ficología de Latinoamérica y El Caribe y la IX Reunión Iberoamericana de Ficología, celebrado en Cali (Colombia), del 5 al 10 de noviembre de 2017, Dictyota fasciola is a relatively common species of eulittoral pools and the shallow subtidal in the NE Atlantic and the Mediterranean Sea. Dictyota mediterranea is a rarer species, endemic from the coasts of the Mediterranean Sea where it occupies a similar habitat than the preceding species. As occurs in the majority of Dictyota species, these two taxa are notoriously difficult to identify based on morphological, anatomical, or reproductive characters. Indeed, D. mediterranea was reduced to a synonym of D. fasciola by Feldmann (1937) on the basis of similarities in color, width of the axes, and shape of the apices. However, D. mediterranea shows a terete thallus at the base and the apex – but complanate in the middle part – and a multilayered medulla. In contrast, axes of D. fasciola are all complanate, and a multilayered medulla is restricted to the basal parts of the thallus. Previous molecular phylogenetic studies indicated that both species are closely related (Tronholm et al. 2010), but results pointed out clear genetic differentiation among them. In our current project, we aim to examine the evolutionary relationship between these two species from phylogeographic and systematic points of view, Financial support was provided by Fundación Biodiversidad

Dictyota cyanoloma has recently been described from the Mediterranean Sea and Macaronesia but doubt had arisen as to whether this species was truly native in Europe. The species is mainly found on non-natural substrata (harbour walls, marinas, boat hulls, etc.), strongly suggesting that it is an introduction. Molecular sequence information from historical herbarium samples proves the presence of D. cyanoloma in the Adriatic Sea as early as 1935. Since approximately the year 2000, however, the number of records as well as the geographic range of the species has expanded significantly. The present-day distribution of D. cyanoloma occupies most of the Mediterranean Sea, Macaronesia, NW Africa and southern Portugal, but recent records from Galicia and SW England (Falmouth, Cornwall) indicate that the species is rapidly expanding northward. Collections from Australia demonstrated that the species is also present from Perth in Western Australia, over much of the southern Australian coastline up to Minnie Water in New South Wales. Phylogenetic analyses resolve D. cyanoloma in a sister clade to a previously unreported Australian Dictyota species. Analysis of genetic diversity of the mitochondrial markers (nad6–nad11 and atp9–orf11) reveals that even though Australian populations contain a much higher haplotype richness, European populations are also fairly diverse. Furthermore, only two out of 25 haplotypes are shared between both regions. These somewhat counterintuitive results could be indicative of a more complicated introduction history.

Dictyota cyanoloma has recently been described from the Mediterranean Sea and Macaronesia but doubt had arisen as to whether this species was truly native in Europe. The species is mainly found on non-natural substrata (harbour walls, marinas, boat hulls, etc.), strongly suggesting that it is an introduction. Molecular sequence information from historical herbarium samples proves the presence of D. cyanoloma in the Adriatic Sea as early as 1935. Since approximately the year 2000, however, the number of records as well as the geographic range of the species has expanded significantly. The present-day distribution of D. cyanoloma occupies most of the Mediterranean Sea, Macaronesia, NW Africa and southern Portugal, but recent records from Galicia and SW England (Falmouth, Cornwall) indicate that the species is rapidly expanding northward. Collections from Australia demonstrated that the species is also present from Perth in Western Australia, over much of the southern Australian coastline up to Minnie Water in New South Wales. Phylogenetic analyses resolve D. cyanoloma in a sister clade to a previously unreported Australian Dictyota species. Analysis of genetic diversity of the mitochondrial markers (nad6–nad11 and atp9–orf11) reveals that even though Australian populations contain a much higher haplotype richness, European populations are also fairly diverse. Furthermore, only two out of 25 haplotypes are shared between both regions. These somewhat counterintuitive results could be indicative of a more complicated introduction history.