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In the Southern Ocean, rapid climatic fluctuations during the Quaternary are thought to have induced range contractions and bottlenecks, thereby instigating genetic divergence and potentially even speciation of marine species. Specifically, ice scouring during glacial events may have had drastic impacts on seaweed communities, thus leading to genetic diversification between algal populations that persisted on the Antarctic shelf in small isolated refugia. Using the mitochondrial Cytochrome c Oxidase I (COI) gene and 279 individual macroalgal specimens collected from five geographic areas along the coasts of the Antarctic Peninsula and the South Shetland Islands, we studied the genetic diversity of six commonly encountered species of red algae. All six algae were characterized by very low genetic diversity, and we found a significant signature of recent population expansion of a single haplotype encountered over more than 450 km. These results reflect the drastic impact of historical perturbations on populations of Antarctic seaweeds. We propose that genetic drift during a glacial bottleneck had a strong effect and could have been amplified by gene surfing effects during spatial expansion after ice sheet retreat. This led to the rapid spread of a single haplotype in the recolonized region. Unfortunately, the very low level of genetic diversity encountered did not allow us to precisely pinpoint the putative location of the glacial refugium inhabited by Antarctic seaweeds. Despite this, we propose that future studies should test the role of active volcanic areas, such as Deception Island, as long-term refugia in the region. [ABSTRACT FROM AUTHOR]

Mazzaella laminarioides is a common haploid-diploid red alga that forms dense beds. This alga has a wide distributional range, covering 3,500 km of the Chilean coast, but is restricted to high rocky intertidal zones. Recently, the existence of three highly divergent genetic lineages was demonstrated for this taxon, and two cytoplasmic markers were used to determine that these lineages are distributed in strict parapatry. Here, using 454 next-generation sequencing, we developed polymorphic microsatellite loci that cross amplify in all three cytoplasmic lineages. Six sites (i.e., two sites within each lineage) were analyzed using nine microsatellite loci. Our work shows that, although substantial cytoplasmic differentiation occurs within M. laminarioides, the microsatellite loci did not retrieve three nuclear genetic clusters as expected. Indeed, while the northernmost and southernmost cytoplasmic lineages form two strongly divergent nuclear groups characterized by diagnostic alleles, the third cytoplasmic lineage did not form a third nuclear independent group. It is possible that inter-lineage gene exchange has occurred, particularly at sites along the contact zone between the different cytoplasmic lineages. This nuclear-cytoplasmic incongruence in M. laminarioides could be explained by incomplete lineage sorting of the nuclear genes or asymmetric introgressive hybridization between the lineages. Finally, highly significant heterozygote deficiencies (suggesting occurrence of intergametophytic selfing) were observed in the three small northernmost sites while the large southernmost sites generally approached panmixia. [ABSTRACT FROM AUTHOR]

The distribution of the Southern Ocean (SO) biota is the result of major geological, oceanographic, and climate changes during the last 50 million years (Ma). Several groups of marine benthic organisms exhibit marked taxonomic similarities between the Antarctic Peninsula and southern South America, where families, genera, and even species are currently co-distributed in these continents. Several species of macroalgae including Gigartina skottsbergii, Plocamium cartilagineum, and Iridaea cordata are currently found on both sides of the Drake Passage. Advances in molecular techniques have allowed estimating phylogenetic relationships, levels of differentiation and divergence time estimates between populations from these continents in order to determine whether they constitute separate evolutionary units. In this study, we determine whether Iridaea cordata represents the same evolutionary unit in southern South America and the Antarctic Peninsula or if populations on the two sides of the Drake Passage represent different genetic lineages. According to our results, I. cordata populations from the Antarctic Peninsula and South America are clearly distinguishable evolutionary units with 8.31% and 3.17% mtDNA and cpDNA molecular divergence, respectively. The separation between Antarctic and South American populations of I. cordata occurred at the end of the Miocene, between 5 Ma (rbcL) and 9 Ma (COI-5P). These results are similar to those reported in G. skottsbergii on both sides of the Drake Passage. Thus, I. cordata populations on the two sides of the Drake Passage should be considered two sister species. Cryptic speciation plays an important role in the evolution of the Southern Ocean; thus, the systematics, biogeography, and biodiversity of the region require major revisions. [ABSTRACT FROM AUTHOR]

Molecular markers belonging to the three different genomes, mitochondrial ( cox2- cox3 spacer), plastid ( rbcL), and nuclear (internal transcribed spacer [ITS] 2 region), were used to compare samples of the two morphologically related species Gracilaria gracilis (Stackh.) Steentoft, L. M. Irvine et Farnham and G. dura (C. Agardh) J. Agardh collected along Atlantic coasts. In northern Europe, the distinction between these two species is ambiguous, and they are currently recognized under the single name of G. gracilis. The low but congruent patterns of genetic divergence observed for markers of the three genomic compartments highly suggest that these two taxa correspond effectively to two different genetic entities as previously described 200 years ago, based on morphological traits. However, thanks to the combination of different DNA markers, occurrence of “incongruent” cytotypes (i.e., mitotypes of G. dura associated with chlorotypes of G. gracilis) in individuals collected from Brittany, suggests interspecific hybridization between the two sibling species studied. [ABSTRACT FROM AUTHOR]

Macroalgal domestication and farming can induce significant ecological and biological changes in exploited species. In the red macroalga, Agarophyton chilense, marine farming is based on clonal propagation by cuttings of the largest plants. This type of mass selection by farmers can have a considerable impact on the life history characteristics of cultivated strains. In this study we investigated the potential effect of this type of selection on the reproduction in A. chilense, comparing female gametophytes from the natural and farmed populations. Our results showed strong differences between these two types of populations. As expected, individuals were larger in the farm than in the wild population. On the other hand, the number of cystocarps per centimeters of fronds was ten times lower in the farm than in the natural population. These differences suggest that artificial selection and cultivation environment significantly modify life-history traits in this macroalga. Moreover, the positive relationship between female size and number of cystocarps per centimeters of fronds observed in Dichato point out to the possible existence of cost of reproduction in A. chilense, with bigger females allocating more resources or energy to reproductive structures in natural populations. [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]

The Gracilariaceae is a species-rich family, with a number of members having high commercial value as sources of agar. Members of this family are also known for their phenotypic plasticity and convergent morphologies, resulting in considerable taxonomic confusion. Over the past two decades, two species of Agarophyton (previously part of Gracilaria) have been recognised in New Zealand with very similar morphologies and growth habits, and they have been incorrectly grouped as Agarophyton chilense. Agarophyton chilense is distributed in Chile and New Zealand and is genetically distinct from Agarophyton sp. from Australia and New Zealand. We name this new species A. transtasmanicum sp. nov. Morphologically A. transtasmanicum has fewer medullary cell layers and a more abrupt transition in cell size between cortex and medulla than A. chilense. The cox1 and rbcL dataset grouped A. transtasmanicum as sister to A. tenuistipitatum with high support. Clarifying the distinctions between A. chilense and A. transtasmanicum will enable further research, including investigating differences in distribution patterns, physiology, ecology, and chemical composition of these two Agarophyton species. [ABSTRACT FROM AUTHOR]

In this study, we explored how past terrestrial and marine climate changes have interacted to shape the phylogeographic patterns of the intertidal red seaweed Gracilaria caudata, an economically important species exploited for agar production in the Brazilian north‐east. Seven sites were sampled along the north‐east tropical and south‐east sub‐tropical Brazilian coast. The genetic diversity and structure of G. caudata was inferred using a combination of mitochondrial (COI and cox2‐3), chloroplast (rbcL) and 15 nuclear microsatellite markers. A remarkable congruence between nuclear, mitochondrial and chloroplast data revealed clear separation between the north‐east (from 03° S to 08° S) and the south‐east (from 20° S to 23° S) coast of Brazil. These two clades differ in their demographic histories, with signatures of recent demographic expansions in the north‐east and divergent populations in the south‐east, suggesting the maintenance of several refugia during the last glacial maximum due to sea‐level rise and fall. The Bahia region (around 12° S) occupies an intermediate position between both clades. Microsatellites and mtDNA markers showed additional levels of genetic structure within each sampled site located south of Bahia. The separation between the two main groups in G. caudata is likely recent, probably occurring during the Quaternary glacial cycles. The genetic breaks are concordant with (i) those separating terrestrial refugia, (ii) major river outflows and (iii) frontiers between tropical and subtropical regions. Taken together with previously published eco‐physiological studies that showed differences in the physiological performance of the strains from distinct locations, these results suggest that the divergent clades in G. caudata correspond to distinct ecotypes in the process of incipient speciation and thus should be considered for the management policy of this commercially important species. [ABSTRACT FROM AUTHOR]

During the domestication process, farmers influence the reproduction and care of organisms to ensure a predictable supply of the resource of interest, causing changes in phenotypic and genotypic character frequencies. In Chile, as a result of unconscious selection and domestication process, farmed populations of the red alga Agarophyton chilensis have most likely undergone a reduction in genetic diversity and a modification in life-history traits compared to wild populations. In order to understand the implications that these processes may have in A. chilensis, we investigated how temperature variations (10 °C, 15 °C, and 20 °C) affect growth and photosynthetic responses of natural and farmed populations from three different localities along the Chilean coast. Natural population's growth decreased at low and high temperature levels while all three farmed populations respond in a very similar way to temperature variation. We propose that a possible outcome of farming, in the A. chilensis, vegetatively propagated crops, could have been the selection of general-purpose-genotypes able to perform adequately across the range of temperature tested in our experiment. Furthermore, our results showed that photosynthetic activity was also affected by temperature treatments (e.g., different maximum maximal electron transport rate and quantum yield values depending on the population type and temperature). In a context of climate change, A. chilensis farmed populations may be better able to cope with impacts of anthropogenic activities than natural populations due to the buffer effect of their general-purpose-genotypes, tolerant to a wide range of conditions. [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]