Tracing the introduction history of the brown seaweed Dictyota cyanoloma (Phaeophyceae, Dictyotales) in Europe

Abstract

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 presentday 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

Phenological and molecular studies on the introduced seaweed Dictyota cyanoloma (Dictyotales, Phaeophyceae) along the Mediterranean coast of the Iberian Peninsula

“…In 1988, an extensive study on the algal communities from the harbour of �lanes -where D. cyanoloma has currently been found (Table 1) -did not report the occurrence of any Dictyota species (Rodríguez-Prieto et al, 1997). These results contrast with the data from the Croatian coast, where some herbarium records (since 1935) of D. cyanoloma have been found (Steen et al, 2016) suggesting that the colonization of the Spanish coast could have occurred later. Alternatively, the presence of this species along the Mediterranean coast of the Iberian Peninsula could have been overlooked since older times, not expanding its range or frequency until recently.…”

“…Certainly, some environmental characteristics of harbours such as water and sediment pollution, structures providing artificial substrates, altered temperature regime and marine traffic have been associated with increased introduction incidence (Carlton, 1996;Glasby et al, 2007;Schaffelke & Hewitt, 2007). However, despite that the first records of D. cyanoloma in the Mediterranean Sea corresponded to anthropogenic environments, the species has also been recently reported in more natural habitats (Steen et al, 2016). The occurrence of this seaweed outside harbour environments on the Iberian Mediterranean coast needs to be studied more thoroughly.…”

“…The type of D. cyanoloma was a specimen from Palamós harbour (Girona, Spain), and new records of D. cyanoloma from the Canary Islands, Morocco, Madeira, Açores, Southern Portugal, Aegean coast, Adriatic Sea, French Mediterranean, Great �rittany and Spanish North Atlantic coasts were soon reported (Taskin, 2013;�árba-ra et al, 2014;Santolaria, 2014;Steen et al, 2016). Steen et al (2016), based on phylogenetic affinities, haplotype networks and global distributions of Dictyota species, concluded that the species is non-native in the Mediterranean and North Atlantic regions and indicated Australia as its native region.…”

“…Steen et al (2016), based on phylogenetic affinities, haplotype networks and global distributions of Dictyota species, concluded that the species is non-native in the Mediterranean and North Atlantic regions and indicated Australia as its native region. Steen et al (2016) In this study we aim to provide a deeper insight into the dynamics and genetic diversity showed by local populations of D. cyanoloma on the Mediterranean coast of the Iberian Peninsula.…”

“…Steen et al (2016), based on phylogenetic affinities, haplotype networks and global distributions of Dictyota species, concluded that the species is non-native in the Mediterranean and North Atlantic regions and indicated Australia as its native region. Steen et al (2016) In this study we aim to provide a deeper insight into the dynamics and genetic diversity showed by local populations of D. cyanoloma on the Mediterranean coast of the Iberian Peninsula. We therefore conducted: (i) a screening of the principal Spanish herbaria looking for historical records of this species; (ii) a large scale survey of the most important harbours from the Mediterranean Iberian coast to describe the current distribution of D. cyanoloma in the region where the species was first reported; (iii) a one year detailed phenology study of one population from Palamós harbour (Girona, Spain) to characterise the sporophytic and gametophytic reproduction; and (iv) a phylogeographic study in order to assess the variability of D. cyanoloma across the Mediterranean Iberian coast.…”