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Low levels of diversity and endemism, when compared to red or brown algae, have been reported for Antarctic green marine macroalgae (Chlorophyta). However, recent studies including the use of molecular markers have allowed us to revisit the taxonomical status of species thought to be well known, underlying the existence of unexpected Antarctic flora diversity at local and regional scale. In the present study, samples of green macroalgae along the Western Antarctic Peninsula (from the 62°S down to the 66°S) were sequenced for two genetic markers regularly used for species determination and barcoding in Chlorophyta (i.e., the plastid genes tufA and rbcL). From the 122 specimens of Chlorophyta sampled, 85 were sequenced for the gene tufA and 16 for the gene rbcL. Using the NCBI Nucleotide Blast Tool to compare our sequences to the ones available in public data depositories allowed the identification of 11 species. Three new species were reported for the area: Rosenvingiella radicans (Kütz.) Rindi, L.McIvor & Guiry, Urospora wormskioldii (Mertens) Rosenvinge and Ulvella islandica R.Nielsen & K.Gunnarsson. Furthermore, molecular identification revealed strong match (> 95%) between our Antarctic sequences and the ones obtained for samples from the northern hemisphere for Acrosiphonia arcta (Dillwyn) Gain, Prasiola crispa (Lightfoot) Kützing, Prasiola antarctica Kützing 1849, R. radicans, Ulva sp. A-GW, U. islandica, Urospora penicilliformis (Roth) Areschoug and U. wormskioldii confirming the amphipolar distribution of various taxa of Antarctic Trebouxiophyceae and Ulvophyceae. Amphipolar distribution seems more common in green than red or brown Antarctic seaweeds, so here we hypothesize that recurrent occurrence of long dispersal events could explain the low level of endemism observed for this phylum along the Antarctic coasts. [ABSTRACT FROM AUTHOR]

Plocamium Lamouroux is a widespread genus for which 45 species are currently recognized. However, classical taxonomy based only on morphological characters, is problematic within this genus. The use of molecular tools has uncovered cryptic genetic species, mistakenly grouped under the name of morphological species that are common and widespread (including the generitype Plocamium cartilagineum (Linnaeus) P.S.Dixon). The aim of this work was to evaluate the species diversity of Plocamium in Southern Chile. For this purpose, three independent molecular markers were sequenced in samples collected from seven populations located between 41°S and 54°S. The species diversity was evaluated using phylogenetic reconstructions and two independent methods for species delimitation (ABGD and GMYC). The outcomes of each method were congruent, suggesting the presence of three species in Southern Chile. One species, named Plocamium sp. 1, is restricted to Punta Guabún, the only locality sampled north of the biogeographic barrier of the 42°S. The other two species, Plocamium sp. 2 and 3 are distributed in sympatry in Patagonia and Tierra del Fuego. The three Chilean species form a clade phylogenetically close to sequences obtained from New Zealand and Australia and a divergence along the coasts of Chile after past transoceanic dispersal is proposed. We propose that divergence in glacial microrefugia could have subsequently happen in the southern part of the coast, this hypothesis being supported by the strong impact of glacial maxima on population dynamics, especially in Plocamium sp. 3. [ABSTRACT FROM AUTHOR]

La flore marine de la zone Antarctique est supposée bien connue car relativement peu d' espèces y sont observées par rapport à d'autres régions du monde. En utilisant la taxonomie traditionnelle combinée aux outils moléculaires, nous avons étudié la diversité et biogéographie des communautés de macroalgues rouges le long de la côte Ouest de la Péninsule Antarctique (WAP) et des îles Shetlands du Sud (SShs) en considérant un gradient bathymétrique. Nous avons également comparé nos deux méthodes d'identification en terme de précision et de nombre de taxa identifiés. Nos résultats ont démontré de faibles et homogènes niveaux de diversité à l'échelle de la zone d'étude comme à échelle locale, avec au total environ 50 taxa identifiés. Nous avons également détecté trois complexes d'espèces cryptiques chez les genres Callophyllis, Curdiea et Georgiella, et amélioré l'identification de nos spécimens puisque 98% ont été identifiés jusqu'à l'espèce grÃce grace aux outils moléculaires. Nos résultats ont aussi permis de révéler des différences significatives entre les assemblages de macroalgues rouges appartenant à trois sub-régions, correspondant à des latitudes différentes: SShs et partie Nord de la WAP (≈63°S), la partie centrale de la WAP (≈64°S) et la partie Centre-Sud de la WAP (≈67°S). Nos sub-régions ne correspondent pas à la séparation classique entre SShs/WAP proposée dans les études antérieures, et suggèrent d'une part, que le détroit de Bransfield n'est pas une barrière biogéographique forte pour les macroalgues rouge et d'autre part, que la dynamique actuelle et passée de la couverture de glace a pu jouer un rôle déterminant dans la distribution actuelle des assemblages de macroalgues rouges. Finalement, notre travail a permis de construire une banque de données génétiques associée à un herbier de collection de spécimens, et va permettre d'appuyer des travaux futurs pour mieux comprendre la diversité et distribution des communautés d'algues rouges dans la zone d'étude. The Antarctic marine flora is well known as a flora composed of relatively few species in comparison with other marine realms. Using molecular taxonomy as complementary tool for traditional taxonomy, we studied red macroalgal diversity and biogeography along the Western Antarctic Peninsula (WAP) and South Shetlands Islands (SShs) coasts and across a bathymetric gradient; in addition, we compared both methods of identification in terms of accuracy and number of observed taxa. Our results show low diversity levels at the regional and local scales, with around 50 taxa registered in total. Molecular tools allowed us to detect putative cryptic species within the genera Callophyllis, Curdiea and Georgiella, and to identify 98% of our specimens at species level. Our results also allowed us to identify significant differences between red macroalgal assemblages of three distinct biogeographic sub-regions: SShs and Northern part of the WAP (at ≈63°S), Central part of the WAP (at ≈64°S) and Central-Southern part of the WAP (at ≈67°S). Our sub-regions do not correspond to the classical separation of SShs/WAP reported in previous studies and suggest that the Bransfield Strait is not a strong biogeographic barrier for red macroalgae. Since our three sub-regions correspond to three latitude levels, we propose that past and present-day dynamics of sea-ice disturbance may have shaped the observed differences in red algal communities. We believe that the construction of accessible genetic dataset associated with voucher specimens in the present work will benefit future studies of macroalgal diversity and distribution in the region. [ABSTRACT FROM AUTHOR]