Plocamium undetermined

Montecinos, Alejandro E., Huanel, Oscar R., RAMĺREZ, María E. & Guillemin, Marie-Laure, 2021, Molecular data reveal the presence of three Plocamium Lamouroux species with complex patterns of distribution in Southern Chile, Cryptogamie, Algologie 20 (1), pp. 1-19 : 7-8

OF CHILEAN PLOCAMIUM SPECIES ANCESTRAL CLADE

In the phylogenetic trees, the three Chilean Plocamium species formed a clade embedded in sequences from the Southern Hemisphere and genetically close to clades from New Zealand and Australia. We propose that the Chilean Plocamium clade has diverged from Australian or New Zealand colonists, after their arrival by rafting in Chile. Transoceanic dispersal has commonly been reported, especially in taxa with high capacity of dispersal, for example fish ( Blower et al. 2012) or crustacea ( Page et al. 2005). Recurrent dispersal, more than vicariance, has indeed been postulated to be the mechanism leading to the biogeographic patterns and disjunct species distributions observed nowadays in the Southern Ocean ( Waters 2008; Fraser et al. 2013). The importance of transoceanic rafting is less recognized in marine species with limited dispersal capacity (i.e., lack of larvae or short lived propagules) even if recent studies have demonstrated that this mechanism, depending on the species physiological/reproductive tolerance, could be highly efficient, allowing rapid expansion of their distribution ranges ( Thiel & Gutow 2005a, b; Fraser et al. 2011;

Fraser et al. 2013; Waters et al. 2013; Guillemin et al. 2014, 2016; Tala et al. 2019). In the Southern Hemisphere, currents are dominated by the Antarctic Circumpolar Current (ACC) and the West Wind Drift (WWD) ( Waters 2008). Recurrent dispersal from Australia and/or New Zealand to Chile have been registered using molecular data in various macroalgae including the buoyant seaweed Durvillaea antarctica (Chamisso) Hariot ( Fraser et al. 2009) , but also the non-buoyant species Bostrychia intricata (Bory) Montagne , Adenocystis utricularis (Bory) Skottsberg ( Fraser et al. 2013) , Capreolia implexa Guiry & Womersley ( Boo et al. 2014) and Agarophyton chilense (C.J.Bird, McLachlan & E.C.Oliveira) Gurgel, J.N.Norris et Fredericq (as Gracilaria chilensis C.J.Bird, McLachlan & E.C.Oliveira ; Guillemin et al. 2014). All these species show genetic signatures of recent west to east dispersal across vast oceanic distances. In the case of the genus Durvillaea Bory there is evidence of a long-distance dispersal event from New Zealand to temperate Chile that was followed by genetic divergence leading to the speciation of D. incurvata (Suhr) Macaya (a species restricted to Chilean temperate waters) some 3 -10 million years ago ( Fraser et al. 2013; Fraser et al. 2019). Studies in other organisms, as in the coastal sac spiders of the genus Amaurobioides O. Pickard-Cambridge , show repeated events of long-distance dispersal along the WWD followed by divergence, revealing a remarkable pattern of “stepping-stone” speciation all around the Southern Ocean ( Ceccarelli et al. 2016).