Genetic data support independent glacial refugia and open ocean barriers to dispersal for the Southern Ocean sea spider Austropallene cornigera (Möbius, 1902)

The diversity and distribution of Antarctic life has been strongly influenced by climatic events, in particular by large scale extension of ice sheets onto the continental shelf during repeated glacial cycles. It has been suggested that populations of benthic marine biota in the Antarctic were limited to very few refugia because the Antarctic shelf was covered with ice. Using the broadly-distributed pycnogonid Austropallene cornigeraas a model, in this study we tested different hypotheses for possible locations of glacial refugia ( ex situon the peri-Antarctic islands or in situon the Antarctic shelf). We sampled 64 individuals of A. cornigerafrom peri-Antarctic islands, the Weddell Sea and East Antarctica. The phylogeographic structure was analysed using partial sequences of the nuclear ribolomal genes 18S and 28S and the mitochondrial cytochrome coxidase subunit I gene (COI). The 18S and 28S sequences were highly conserved. Sequences of the COI were variable and revealed highest haplotype diversity for populations on the Antarctic shelf and lowest for the population from the remote island of Bouvetøya. In addition, the data showed clear genetic distances between the island and shelf populations. Our data are consistent with the hypothesis of survival in situ. The results also suggest that gene flow within A. cornigerais limited, hinting at possible speciation processes acting independently on the Antarctic continental shelf and the peri-Antarctic islands

Combining morphological and genomic evidence to resolve species diversity and study speciation processes of the Pallenopsis patagonica (Pycnogonida) species complex

Background: Pallenopsis patagonica (Hoek, 1881) is a morphologically and genetically variable sea spider species whose taxonomic classification is challenging. Currently, it is considered as a species complex including several genetic lineages, many of which have not been formally described as species. Members of this species complex occur on the Patagonian and Antarctic continental shelves as well as around sub-Antarctic islands. These habitats have been strongly influenced by historical large-scale glaciations and previous studies suggested that communities were limited to very few refugia during glacial maxima. Therefore, allopatric speciation in these independent refugia is regarded as a common mechanism leading to high biodiversity of marine benthic taxa in the high-latitude Southern Hemisphere. However, other mechanisms such as ecological speciation have rarely been considered or tested. Therefore, we conducted an integrative morphological and genetic study on the P. patagonica species complex to i) resolve species diversity using a target hybrid enrichment approach to obtain multiple genomic markers, ii) find morphological characters and analyze morphometric measurements to distinguish species, and iii) investigate the speciation processes that led to multiple lineages within the species complex. Results: Phylogenomic results support most of the previously reported lineages within the P. patagonica species complex and morphological data show that several lineages are distinct species with diagnostic characters. Two lineages are proposed as new species, P. aulaeturcarum sp. nov. Dömel & Melzer, 2019 and P. obstaculumsuperavit sp. nov. Dömel, 2019, respectively. However, not all lineages could be distinguished morphologically and thus likely represent cryptic species that can only be identified with genetic tools. Further, morphometric data of 135 measurements showed a high amount of variability within and between species without clear support of adaptive divergence in sympatry. Conclusions: We generated an unprecedented molecular data set for members of the P. patagonica sea spider species complex with a target hybrid enrichment approach, which we combined with extensive morphological and morphometric analyses to investigate the taxonomy, phylogeny and biogeography of this group. The extensive data set enabled us to delineate species boundaries, on the basis of which we formally described two new species. No consistent evidence for positive selection was found, rendering speciation in allopatric glacial refugia as the most likely model of speciation

The thermal limits to life on Earth

Living organisms on Earth are characterized by three necessary features: a set of internal instructions encoded in DNA (software), a suite of proteins and associated macromolecules providing a boundary and internal structure (hardware), and a flux of energy. In addition, they replicate themselves through reproduction, a process that renders evolutionary change inevitable in a resource-limited world. Temperature has a profound effect on all of these features, and yet life is sufficiently adaptable to be found almost everywhere water is liquid. The thermal limits to survival are well documented for many types of organisms, but the thermal limits to completion of the life cycle are much more difficult to establish, especially for organisms that inhabit thermally variable environments. Current data suggest that the thermal limits to completion of the life cycle differ between the three major domains of life, bacteria, archaea and eukaryotes. At the very highest temperatures only archaea are found with the current high-temperature limit for growth being 122 °C. Bacteria can grow up to 100 °C, but no eukaryote appears to be able to complete its life cycle above ∼60 °C and most not above 40 °C. The lower thermal limit for growth in bacteria, archaea, unicellular eukaryotes where ice is present appears to be set by vitrification of the cell interior, and lies at ∼−20 °C. Lichens appear to be able to grow down to ∼−10 °C. Higher plants and invertebrates living at high latitudes can survive down to ∼−70 °C, but the lower limit for completion of the life cycle in multicellular organisms appears to be ∼−2 °

Sea spiders (Arthropoda, Pycnogonida) from ten recent research expeditions to the Antarctic Peninsula, Scotia Arc and Weddell Sea - data

This dataset contains information on specimens of Southern Ocean Pycnogonida (Arthropoda), that were collected from ten different research cruises, spanning 13 years. The individual aims and objectives of each cruise can be found in their cruise reports. The specimens have been collated into a single dataset, forming the basis of J. Maxwell’s PhD. The dataset will be used to investigate the community structure of Antarctic pycnogonids and the factors which influence its composition. This dataset is published by SCAR-AntOBIS under the licence CC-BY 4.0. Please follow the guidelines from the SCAR and IPY Data Policies (https://www.scar.org/excom-meetings/xxxi-scar-delegates-2010-buenos-aires-argentina/4563-scar-xxxi-ip04b-scar-data-policy/file/) when using the data. If you have any questions regarding this dataset, please do not hesitate to contact us via the contact information provided in the metadata or via [email protected]

Cryptic dispersal of Cyanidiophytina (Rhodophyta) in non-acidic environments from Turkey

Cyanidiophytina are a group of polyextremophilic red algae with a worldwide, but discontinuous colonization. They are restricted to widely dispersed hot springs, geothermal habitats, and also some human-altered environments. Cyanidiophytina are predominant where pH is prohibitive for the majority of eukaryotes (pH 0.5-3). Turkey is characterized by areas rich in volcanic activity separated by non-volcanic areas. Here we show that Cyanidiophycean populations are present in thermal baths located around Turkey on neutral/alkaline soils. All known genera and species within Cyanidiophytina were detected in Turkey, including Galdieria phlegrea, recorded up to now only in Italian Phlegrean Fields. By phylogenetic analyses, Turkish G. sulphuraria strains are monophyletic with Italian and Icelandic strains, and with Russian G. daedala strains. G. maxima from Turkey clustered with Icelandic, Kamchatka, and Japanese populations. The discovery of Cyanidiophytina in non-acidic Turkish soils raises new questions about the ecological boundaries of these extremophilic algae. This aids in the understanding of the dispersal abilities and distribution patterns of this ecologically and evolutionarily interesting group of algae

Mechanisms of Acido-Tolerance and Characteristics of Photosystems in an Acidophilic and Thermophilic Red Alga, Cyanidium Caldarium

In this chapter, we describe the mechanisms of acido-tolerance in an acidophilic- and thermophilic red alga, Cyanidium caldarium. In spite of the extremely acidic environments it inhabits, the intracellular pH of Cyanidium cells is kept neutral by pumping out the protons previously leaked into the cells according to the steep pH gradient. The H+ pump is driven by the plasma membrane ATPase, utilizing intracellular ATP produced by both oxidative phosphorylation and cyclic photophosphorylation via photosystem I. We also describe the characteristics and function of the two photosystems, Photosystem I (PSI) and II (PSII), in Cyanidium caldarium in comparison with those of cyanobacteria, other eukaryotic algae, and higher plants, based on the crystal structures of the two complexes reported so far

Guided Evocation

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library