High genetic differentiation of red gorgonian populations from the Atlantic Ocean and the Mediterranean Sea

Phylogeography ofDictyota fasciolaandDictyota mediterranea(Dictyotales, Phaeophyceae): unexpected patterns on the Atlantic-Mediterranean marine transition and taxonomic implications

“…However, as in the case of other Mediterranean organisms (e.g., vertebrates Domingues et al, 2005; echinoderms, Taboada & Pérez-Portela, 2016; or cnidarian, Pilczynska et al, 2017) we cannot discard the hypothesis that the ancestors of the D. fasciola-D.mediterranea complex survived the MSC in the Atlantic Ocean. In this scenario, the arrival of this group of seaweeds to the Mediterranean basin would have happened after the Zanclean re-flooding with Atlantic waters.…”

Not out of the Mediterranean: Atlantic populations of the gorgonian Paramuricea clavata are a separate sister species under further lineage diversification

“…Currently, seven valid species are known to occur along the NE Atlantic and Mediterranean (Carpine & Grasshoff, 1975 ; Grasshoff, 1977 ; WoRMS, 2022 ), with a further two putatively new species recently discovered after re‐examination of natural history collections (Sampaio et al, 2019 ). Two of these, Paramuricea clavata and Paramuricea macrospina , were historically regarded as endemic to the Mediterranean Sea (Carpine & Grasshoff, 1975 ; Grasshoff, 1977 ; Pica et al, 2018 ) despite several recent studies extending the distribution ranges of P. clavata to adjacent Atlantic coastlines (Boavida, Assis, et al, 2016 ; Cúrdia et al, 2012 ; Pilczynska et al, 2019 ; Pilczynska, Cocito, et al, 2017 ) and of P. macrospina potentially to the Cape Verde archipelago (Sampaio et al, 2019 ).…”

“…Spatial genetic structure in P. clavata is congruent with oceanographic barriers to gene flow (AOF: Mokhtar‐Jamaï et al, 2011 ; seasonal cyclonic gyres along the Adriatic: Ledoux et al, 2018 ), and with the limited dispersal ability inherent to a reproductive strategy of larval brooding on maternal colonies (as observed in other brooding corals: Ayre & Hughes, 2000 ; Ledoux, Mokhtar‐Jamaï, et al, 2010 ; Mokhtar‐Jamaï et al, 2013 ; Smilansky & Lasker, 2014 ; Underwood et al, 2007 ). Atlantic populations identified as P. clavata along the Portuguese coast are genetically differentiated from Mediterranean ones and also differentiated between western and southern Portugal (Pilczynska et al, 2019 ; Pilczynska, Cocito, et al, 2017 ). Interestingly, this differentiation between western and southern populations in Portugal appears to coincide with color morphotypes that dominate circalittoral coral gardens in each region (Pilczynska, Cocito, et al, 2017 ), with a yellow morphotype prevalent in the Algarve (southern Portugal) and a purple morphotype dominating communities in western Portugal.…”

“…Atlantic populations identified as P. clavata along the Portuguese coast are genetically differentiated from Mediterranean ones and also differentiated between western and southern Portugal (Pilczynska et al, 2019 ; Pilczynska, Cocito, et al, 2017 ). Interestingly, this differentiation between western and southern populations in Portugal appears to coincide with color morphotypes that dominate circalittoral coral gardens in each region (Pilczynska, Cocito, et al, 2017 ), with a yellow morphotype prevalent in the Algarve (southern Portugal) and a purple morphotype dominating communities in western Portugal. Although both morphotypes can occur in sympatry, our field surveys indicate that the purple morphotype is extremely rare in the south (Dias et al, 2020 ; colonies reported as P. clavata ) and vice‐versa (J. Boavida and M. Coelho, personal observations).…”

“…Although both morphotypes can occur in sympatry, our field surveys indicate that the purple morphotype is extremely rare in the south (Dias et al, 2020 ; colonies reported as P. clavata ) and vice‐versa (J. Boavida and M. Coelho, personal observations). Despite these findings, the existence and exact location of the Atlantic‐Mediterranean break, and the level of divergence across these regions (i.e., whether it represents within‐species population structure or speciation processes) remains unknown in P. clavata due to incomplete geographic sampling and low marker resolution (Mokhtar‐Jamaï et al, 2011 ; Pilczynska et al, 2019 ; Pilczynska, Cocito, et al, 2017 ). Indeed, standard DNA barcoding approaches for species delimitation are poorly suited to resolve closely related or recently diverged octocorals due to slow rates of mitochondrial gene evolution (Calderón et al, 2006 ; Hellberg, 2006 ; Huang et al, 2008 ; McFadden et al, 2011 ; Shearer et al, 2002 ).…”