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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]

A molecular taxonomic study of the bladed Bangiales of the South Eastern Pacific (coast of Chile) was undertaken based on sequence data of the mitochondrial COI and chloroplast rbc L for 193 specimens collected from Arica (18°S) in the north to South Patagonia (53°S) in the south. The results revealed for the first time that four genera, Porphyra , Pyropia , Fuscifolium and Wildemania were present in the region. Species delimitation was determined based on a combination of a General Mixed Yule Coalescence model (GMYC) and Automatic Barcode Gap Discovery (ABGD) coupled with detection of monophyly in tree reconstruction. The overall incongruence between the species delimitation methods within each gene was 29%. The GMYC method led to over-splitting groups, whereas the ABGD method had a tendency to lump groups. Taking a conservative approach to the number of putative species, at least 18 were recognized and, with the exception of the recently described Pyropia orbicularis , all were new to the Chilean flora. Porphyra and Pyropia were the most diverse genera with eight ‘species’ each, whereas only a ‘single’ species each was found for Fuscifolium and Wildemania . There was also evidence of recently diverging groups: Wildemania sp. was distinct but very closely related to W. amplissima from the Northern Hemisphere and raises questions in relation to such disjunct distributions. Pyropia orbicularis was very closely related to two other species, making species delimitation very difficult but provides evidence of an incipient speciation. The difference between the ‘species’ discovered and those previously reported for the region is discussed in relation to the difficulty of distinguishing species based on morphological identification. [ABSTRACT FROM AUTHOR]

The article discusses research being done on the impact of climate change on seaweeds. It references the study "Upswelling Areas as Climate Change Refugia for the Distribution and Genetic Diversity of a Marine Macroalgia," by C. R. Lourenco et al. in the 2016 issue. The variables considered include the role of sea surface temperatures (SST) in pelagic plankton richness, the geographic range of the seaweed Fucus guiryi and the effects of decreasing population density on fitness.

Molecular studies have reported the coexistence of two species of Agarophyton in New Zealand: the newly described A.transtasmanicum with an apparently restricted distribution to some sites in the North Island, and the more widespread A.chilense. Here, we compared the distribution, genetic diversity, and structure of both Agarophyton species throughout the archipelago using sequences of the nuclear Internal Transcribed Spacer 2 (ITS2) marker. Agarophyton chilense's distribution was continuous and extensive along the North and South Islands, Stewart Island, and Chatham Island, and the genetic clusters were mostly concordant with boundaries between biogeographic regions. In contrast, specimens of A.transtasmanicum were collected in four sites broadly distributed in both the North and South Islands, with no clear spatial structure of the genetic diversity. Populations, where the species co‐occurred, tended to display similar levels in genetic diversity for the two species. Demographic inferences supported a postglacial demographic expansion for two A.chilense genetic clusters, one present in the South Island and the eastern coast of the North Island, and the other present in northern South Island. A third genetic cluster located on the western coast of the North Island had a signature of long‐term demographic stability. For A.transtasmanicum, the skyline plot also suggested a postglacial demographic expansion. Last, we developed a new molecular tool to quickly and easily distinguish between the two Agarophyton species, which could be used to ease future fine‐scale population studies, especially in areas where the two species coexist. [ABSTRACT FROM AUTHOR]

The genus Ectocarpus (Ectocarpales, Phaeophyceae) contains filamentous algae widely distributed in marine and estuarine habitats of temperate regions in both hemispheres. While E. siliculosus has become a model organism for genomics and genetics of the brown macroalgae, accurate species delineation, distribution patterns and diversity for the genus Ectocarpus remain problematic. In this study, we used three independent species delimitation approaches to generate a robust species hypothesis for 729 Ectocarpus specimens collected mainly along the European and Chilean coasts. These approaches comprised phylogenetic reconstructions and two bioinformatics tools developed to objectively define species boundaries (General Mixed Yule Coalescence Method and Automatic Barcode Gap Discovery). Our analyses were based on DNA sequences of two loci: the mitochondrial cytochrome oxidase subunit 1 and the nuclear internal transcribed spacer 1 of the ribosomal DNA. Our analyses showed the presence of at least 15 cryptic species and suggest the existence of incomplete lineage sorting or introgression between five of them. These results suggested the possible existence of different levels of reproductive barriers within this species complex. We also detected differences among species in their phylogeographic patterns, range and depth distributions, which may suggest different biogeographic histories (e.g., endemic species or recent introductions). [ABSTRACT FROM AUTHOR]