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Several studies reported that gametophytes and tetrasporophytes of Gigartinaceae produce different carrageenan types, as observed in Sarcopeltis species although they have isomorphic haploid and diploid phases. Cystocarpic and non-fertile plants of Sarcopeltis (ex Gigartina) skottsbergii produced kappa-carrageenans, while tetrasporophytes produced lambda-carrageenans, and yields were higher in cystocarpic and sterile specimens than in tetrasporophytes. However, comparison on the other primary metabolites among different life history phases still needed to be investigated. Then, we tested the hypothesis if the variation on primary metabolites (pigments, proteins and carbohydrates) are related to the life history phases of Sarcopeltis antarctica and Sarcopeltis skottsbergii, and/or are influenced by abiotic factors. Primary metabolites of S. antarctica varied according to the life-history phases: non-fertile specimens presented higher phycobiliprotein concentrations, tetrasporophytes presented higher chlorophyll a concentrations, and cystocarpic specimens presented higher concentrations of proteins, polysaccharides and floridean starch. However, primary metabolites of S. skottsbergii varied in response to some abiotic factors (nutrients, temperature and salinity), since principal component analysis evidenced two groups; one was related by the higher nitrate and phosphate concentrations, and the other was related to the higher temperatures and lower salinities. Concentrations of floridean starch, low molecular weight carbohydrates, and polysaccharides are higher in S. antarctica than in S. skottsbergii, which could be related to the protective role of these compounds against salinity variation and low temperatures faced in the Antarctic extreme environments.

Abstract The paradigm of past climate-driven range shifts structuring the distribution of marine intraspecific biodiversity lacks replication in biological models exposed to comparable limiting conditions in independent regions. This may lead to confounding effects unlinked to climate drivers. We aim to fill in this gap by asking whether the global distribution of intraspecific biodiversity of giant kelp (Macrocystis pyrifera) is explained by past climate changes occurring across the two hemispheres. We compared the species’ population genetic diversity and structure inferred with microsatellite markers, with range shifts and long-term refugial regions predicted with species distribution modelling (SDM) from the last glacial maximum (LGM) to the present. The broad antitropical distribution of Macrocystis pyrifera is composed by six significantly differentiated genetic groups, for which current genetic diversity levels match the expectations of past climate changes. Range shifts from the LGM to the present structured low latitude refugial regions where genetic relics with higher and unique diversity were found (particularly in the Channel Islands of California and in Peru), while post-glacial expansions following ~ 40% range contraction explained extensive regions with homogenous reduced diversity. The estimated effect of past climate-driven range shifts was comparable between hemispheres, largely demonstrating that the distribution of intraspecific marine biodiversity can be structured by comparable evolutionary forces across the global ocean. Additionally, the differentiation and endemicity of regional genetic groups, confers high conservation value to these localized intraspecific biodiversity hotspots of giant kelp forests.

Measurement(s) microbial diversity • microbial abundances • cations and anions • trace elements Technology Type(s) MiSeq sequencing 16S rRNA gene • Real Time PCR • HPLC • ICP-MS Sample Characteristic - Organism bacteria • archaea Sample Characteristic - Environment lake water • lake sediment • wetland • peatland • soil • pond Sample Characteristic - Location Western Siberia • Alaska • Patagonia • Cape Horn province • Magellanic subantarctic ecoregion

These extensive kelps forest are among the most productive and diverse habitats on the planet, playing an important ecological role in marine ecosystems. These habitats have been affected by anthropogenic factors worldwide and directly by environmental variations resulting from climate change. The Magellan ecoregion has the southernmost kelp forests in the world, dominated by the species Macrocystis pyrifera. This species presents high ecophysiological plasticity being able to inhabit heterogeneous environments, characteristic of the fjord and channel systems of the region, and has high ecological, sociocultural, and economic importance for local coastal communities. To understand the ecophysiological acclimation strategies of M. pyrifera, samples from different blades were collected at different depths at four locations in the Magellan Ecoregion: Possession Bay, Skyring Sound, Otway Sound, and Puerto del Hambre seasonally. Abiotic measurements (salinity, temperature, and PAR light) were carried out for each location sampled. Measurements of photosynthetic parameters, Fv/Fm, rETRmax, Ek and α; pigment analysis of Chl a, Chl c, and fucoxanthin; and fecundity analysis of the sporophylls of each population studied were carried out on the M. pyrifera sporophytes. Significant differences were observed between seasons, locality, and depth of blades. Each population generally showed different photoacclimation processes, depending on the local conditions such as salinity values and probably tidal cycles. This is reflected in the photosynthetic, pigment, and fecundity values obtained during this study. The higher Fv/Fm values in all populations during the winter and autumn seasons and the differences in Chl c and fucoxanthin concentration during the winter period in Otway Sound and Puerto del Hambre population suggest the marked seasonal acclimation of M. pyrifera. In addition, the coastal environmental heterogeneity observed in the Magellan ecoregion related to salinity gradients (Skyring Sound) or wide tidal amplitudes (Possession Bay) influences the acclimation strategy of each population of M. pyrifera. Therefore, the characteristics of each population should be considered in order to promote its sustainability in times of social and climate change.

The giant kelp Macrocystis pyrifera is a cosmopolitan species of cold-temperate coasts. Its South-American distribution ranges from Peru to Cape Horn and Argentina, encompassing a considerable temperature gradient, from 3 to 20°C. Temperature is known to strongly affect survival, growth and reproduction of many kelp species, and ongoing global warming is already eroding their range distribution. Their response to thermal variability was shown to vary among genetically differentiated regions and populations, suggesting a possible adaptive divergence in thermal tolerance traits. This study aimed at testing the existence of local adaptation in the giant kelp, in regions separated by up to 4000km and strong thermal divergence. Two complementary experiments mimicked reciprocal transplants through a common garden approach, each habitat being represented by a given temperature corresponding to the regional average of the sampled populations. Several proxies of fitness were measured in the haploid stage of the kelp, and sympatric versus allopatric conditions (i.e. individuals at the temperature of their region of origin versus in a different temperature and versus individuals from other regions in that temperature) were compared. Additionally, a heat wave at 24°C was applied to measure the tolerance limits of these gametophytes. A significant interaction between experimental temperature and region of origin revealed that temperature tolerance varied among regions. However, depending on the fitness parameter measured, high latitude populations from the sub-Antarctic region were not always less heat resilient than populations from the warmer region of Peru. Even at 24°C, a temperature that is exceptionally reached in the southernmost part of the kelp’s natural habitat, all the gametophytes survived, although with strong differences in other traits among regions and populations within regions. This large range of temperature tolerance supports the idea of kelp gametophytes being a resistant stage. Finally, local adaptation sensu stricto was not detected. Fertility was more influenced by the geographic origin than by temperature, with possible effects of marginal conditions at the extremes of the distribution range. The latter results also suggest that stochastic dynamics such as genetic drift restricts adaptive processes in some populations of M. pyrifera.

Abstract Two species of scallop, Austrochlamys natans (“Ostión del Sur”) and Zygochlamys patagonica (“Ostión patagonico”) are presently exploited in the southern part of the Magallanes Province (MP). The lack of clarity in taxonomic identification and ecological aspects is generating both erroneous extraction statistics and an unperceived harvesting pressure on A. natans and Z. patagonica. We aim to discriminate these Magallanes scallops accurately, improve our understanding of their complex natural history and discuss possible implications for their management and conservation status, given the current fisheries statistics. To achieve these goals, we present a complete review of the historical identification of the Magallanes scallop and a multi-locus molecular phylogeny which allowed us to recover the phylogenetic position of A. natans. We sampled 54 individuals from five localities across the southern Pacific coast of the MP. We calculated the depth of the byssal notch (BND) and shell height (VH) ratio from morphological characters and conducted phylogenetic reconstructions with mitochondrial (12S and 16S) and nuclear markers (28S) using Bayesian and maximum likelihood analyses. Both morphology and molecular phylogeny identified two distinct entities, Z. patagonica and a distinct, highly divergent lineage that corresponds to A. natans. Our study provides integrative evidence to alert the current fishery management and the need for further conservation studies.

Glacial episodes of the Quaternary, and particularly the Last Glacial Maximum (LGM) drastically altered the distribution of the Southern-Hemisphere biota, principally at higher latitudes. The irregular coastline of Patagonia expanding for more than 84.000 km constitutes a remarkable area to evaluate the effect of Quaternary landscape and seascape shifts over the demography of near-shore marine benthic organisms. Few studies describing the biogeographic responses of marine species to the LGM have been conducted in Patagonia, but existing data from coastal marine species have demonstrated marked genetic signatures of post-LGM recolonization and expansion. The kelp-dweller limpet Nacella mytilina is broadly distributed along the southern tip of South America and at the Falkland/Malvinas Islands. Considering its distribution, abundance, and narrow bathymetry, N. mytilina represents an appropriate model to infer how historical and contemporary processes affected the distribution of intraspecific genetic diversity and structure along the southern tip of South America. At the same time, it will be possible to determine how life history traits and the ecology of the species are responsible for the current pattern of gene flow and connectivity across the study area. We conducted phylogeographic and demographic inference analyses in N. mytilina from 12 localities along Pacific Patagonia (PP) and one population from the Falkland/Malvinas Islands (FI). Analyses of the mitochondrial gene COI in 300 individuals of N. mytilina revealed low levels of genetic polymorphism and the absence of genetic differentiation along PP. In contrast, FI showed a strong and significant differentiation from Pacific Patagonian populations. Higher levels of genetic diversity were also recorded in the FI population, together with a more expanded genealogy supporting the hypothesis of glacial persistence of the species in these islands. Haplotype genealogy, and mismatch analyses in the FI population recognized an older and more complex demographic history than in PP. Demographic reconstructions along PP suggest a post-LGM expansion process (7.5 ka), also supported by neutrality tests, mismatch distribution and maximum parsimony haplotype genealogies. Migration rate estimations showed evidence of asymmetrical gene flow from PP to FI. The absence of genetic differentiation, the presence of a single dominant haplotype, high estimated migration rates, and marked signal of recent demographic growth, support the hypothesis of rapid post-glacial expansion in N. mytilina along PP. This expansion could have been sustained by larval and rafting-mediated dispersal of adults from northernmost populations following the Cape Horn Current System. Marked genetic differentiation between PP and FI could be explained through differences in their respective glacial histories. During the LGM, Pacific Patagonia (PP) was almost fully covered by the Patagonian Ice Sheet, while sheet coverage in the FI ice was restricted to small cirques and valleys. As previously recorded in the sister-species N. magellanica, the FI rather than represent a classical glacial refugium for N. mytilina, seems to represent a sink area and/or a secondary contact zone. Accordingly, historical and contemporary processes, contrasting glacial histories between the analyzed sectors, as well as life history traits constitute the main factors explaining the current biogeographical patterns of most shallow Patagonian marine benthic organisms.