What can the cold-induced transcriptomes of Arctic Brassicaceae tell us about the evolution of cold tolerance?

By studying the molecular basis of cold response in plants adapted to some of the world’s coldest biomes, we can gain insight into the evolution of cold tolerance - an important factor in determining plant distributions worldwide.Although cold tolerance in temperate plants have been extensively studied, little is known about the evolutionary changes needed to transition from temperate to the more extreme polar zones.Here, we conducted a time series experiment to examine the transcriptional responses of three Arctic Brassicaceae to low temperatures. RNA was sampled before onset of treatment, and after 3h, 6h, and 24h with 2 °C. We identified sets of genes that were differentially expressed in response to cold and compared them between species, as well as to published data from the temperate Arabidopsis thaliana.We found that the cold response is highly species-specific. Among thousands of differentially expressed genes, ∼200 genes were shared among the three Arctic species and A. thaliana, and only ∼100 genes were specific to the three Arctic species alone. This pattern was also reflected in the functional comparison.Our results show that the cold response of Arctic plant species has mainly evolved independently, although it likely builds on a conserved basis found across Brassicaceae. The findings also confirm that highly polygenic traits, such as cold tolerance, may show less repeatable patterns of adaptation than traits involving only a few genes.

Effects of competitive pressure and habitat heterogeneity on niche partitioning between Arctic and boreal congeners

The rapidly changing climate in the Arctic is expected to have a major impact on the foraging ecology of seabirds, owing to changes in the distribution and abundance of their prey but also that of competitors (e.g. southerly species expanding their range into the Arctic). Species can respond to interspecific competition by segregating along different niche axes. Here, we studied spatial, temporal and habitat segregation between two closely related seabird species: common guillemot Uria aalge (a temperate species) and Brünnich’s guillemot Uria lomvia (a true Arctic species), at two sympatric sites in Iceland that differ in their total population sizes and the availability of marine habitats. We deployed GPS and temperature-depth recorders to describe foraging locations and behaviour of incubating and chick-rearing adults. We found similar evidence of spatial segregation at the two sites (i.e. independent of population sizes), although segregation in environmental space was only evident at the site with a strong habitat gradient. Unexpectedly, temporal (and, to a limited extent, vertical) segregation appeared only at the least populated site. Overall, our results show complex relationships between the levels of inferred competition and that of segregation.

Bryozoa of the Laptev and East Siberian seas: modern research

The new data about bryozoan fauna of the Siberian seas (Laptev Sea and East Siberian Sea) are obtained. 48 species of Bryozoa were identified in the samples, collected in the MMBI RAS expedition (2014) at 50 stations: 45 – in the Laptev Sea and 16 – in the East Siberian Sea. The taxonomic and biogeographic composition, the features of distribution of Bryozoa are analyzed. A comparative analysis of the studies of the end of the 20th century (1986, 1987 and 1993–1998) based on literature data is carried out (Gontar, 1990, 1994, 2004, 2015а,б, 2016). There was a significant increase 60 in the share of boreal-arctic species due to a significant decrease of arctic species (by almost a third), which probably reflects the climate change towards warming , observed at the beginning of the 21st century.

Winter-Spring Development of the Zooplankton Community Below Sea Ice in the Arctic Ocean

The impact of the rapidly changing Arctic on zooplankton community structure and seasonal behaviour is not yet understood. Here we examine 6 months of under-ice zooplankton observations from the N-ICE2015 expedition (January to June 2015) in the Nansen Basin and on the Yermak Plateau north of Svalbard. Stratified sampling in the water column was done with MultiNet during the entire expedition, and sampling in the upper 5 m below sea ice was performed during April-May by divers using a hand-held net. Hydrographic conditions were dominated by northward-flowing warm and saline Atlantic Water at intermediate depth, and southward-flowing cold Polar Surface Water in the upper 100 m. The mesozooplankton was dominated by copepods. Most numerous were the small ubiquitous Oithona similis in the upper 200 m, with Microcalanus spp. and Triconia borealis further down the water column. Calanus finmarchicus dominated among the Calanus species while Metridia longa was also numerous. The most abundant deep-water copepods were Paraeuchaeta spp. and Spinocalanus spp. Arrow worms (Chaetognatha) and comb jellies (Ctenophora) were the most numerous non-copepods. The mesozooplankton community was more dependent on surrounding water mass characteristics, such as salinity and depth, than geographical location. Algal food availability, which was closely linked to seasonality, explained the community changes seen in surface waters in May and June due to seasonal ascent and recruitment. Seasonal changes from winter to spring mostly involved an increase in the herbivorous C. finmarchicus and its nauplii in the upper 200 m of the water column coinciding with the peak of the phytoplankton bloom in late May. The Yermak Plateau and adjacent Nansen Basin were characterised by oceanic North Atlantic and Arctic species, many of which are deep water specialists. Despite the late onset of the spring bloom due to consolidated sea ice, both North Atlantic and Arctic species successfully reproduced in the study area. This explains the species-rich mesozooplankton community in this region as opposed to the less productive central Arctic Ocean. Future prospects of less sea ice and earlier onset of the bloom will likely be positive for the overall secondary production by both Arctic and boreal zooplankton in this region.

The late Pliensbachian (Early Jurassic) ammonoid Amaltheus in Japan: systematics and biostratigraphic and paleobiogeographic significance

The genus Amaltheus, one of the representative late Pliensbachian ammonoids, has biostratigraphic and paleobiogeographic significance in Japan. Four species, Amaltheus stokesi (Sowerby, 1818), A. margaritatus de Montfort, 1808, A. repressus Dagis, 1976, and A. orientalis new species, have been found in the Kuruma Group in central Japan; A. stokesi and A. margaritatus are also from the Toyora Group in southwest Japan. On the basis of taxonomic analysis of the genus Amaltheus, we distinguish two successive ammonoid biozones in the lower part of the Teradani Formation of the Kuruma Group: the Amaltheus stokesi–Amaltheus repressus and the Amaltheus margaritatus assemblage zones, in stratigraphic ascending order. This study also establishes the presence of the Amaltheus stokesi Assemblage Zone in the Higashinagano Formation of the Toyora Group. The stokesi–repressus and the stokesi assemblage zones correspond biostratigraphically to the Amaltheus stokesi Standard Subzone of the margaritatus Zone. The margaritatus Assemblage Zone is correlated with the Amaltheus subnodosus and Amaltheus gibbosus standard subzones. The Japanese early–middle late Pliensbachian ammonoid faunas are composed almost entirely of pan-Boreal and Arctic species of the genus Amaltheus. This faunal composition has an affinity with that of the Northeast Russian region, and thus suggests a strong paleobiogeographic relationship between East Asian and Northeast Russian faunas throughout this time interval. UUID: http://zoobank.org/5F08121F-1DAF-4B24-BCBE-B08F7101CF29

Increased functional diversity warns of ecological transition in the Arctic

As temperatures rise, motile species start to redistribute to more suitable areas, potentially affecting the persistence of several resident species and altering biodiversity and ecosystem functions. In the Barents Sea, a hotspot for global warming, marine fish from boreal regions have been increasingly found in the more exclusive Arctic region. Here, we show that this shift in species distribution is increasing species richness and evenness, and even more so, the functional diversity of the Arctic. Higher diversity is often interpreted as being positive for ecosystem health and is a target for conservation. However, the increasing trend observed here may be transitory as the traits involved threaten Arctic species via predation and competition. If the pressure from global warming continues to rise, the ensuing loss of Arctic species will result in a reduction in functional diversity.

Variability in nitrogen-derived trophic levels of Arctic marine biota

Stable isotopes are often used to provide an indication of the trophic level (TL) of species. TLs may be derived by using food-web-specific enrichment factors in combination with a representative baseline species. It is challenging to sample stable isotopes for all species, regions and seasons in Arctic ecosystems, e.g. because of practical constraints. Species-specific TLs derived from a single region may be used as a proxy for TLs for the Arctic as a whole. However, its suitability is hampered by incomplete knowledge on the variation in TLs. We quantified variation in TLs of Arctic species by collating data on stable isotopes across the Arctic, including corresponding fractionation factors and baseline species. These were used to generate TL distributions for species in both pelagic and benthic food webs for four Arctic areas, which were then used to determine intra-sample, intra-study, intra-region and inter-region variation in TLs. Considerable variation in TLs of species between areas was observed. This is likely due to differences in parameter choice in estimating TLs (e.g. choice of baseline species) and seasonal, temporal and spatial influences. TLs between regions were higher than the variance observed within regions, studies or samples. This implies that TLs derived within one region may not be suitable as a proxy for the Arctic as a whole. The TL distributions derived in this study may be useful in bioaccumulation and climate change studies, as these provide insight in the variability of trophic levels of Arctic species.

Increasing importance of climate change and other threats to at-risk species in Canada

In a previous analysis, six major threats to at-risk species in Canada were quantified: habitat loss, introduced species, over-exploitation, pollution, native species interactions, and natural causes (O. Venter et al. 2006. Bioscience, 56(11): 903–910). Because of rapid environmental change in Canada and an enhanced understanding of the drivers of species endangerment, we updated the 2005 analysis and tested for changes in threats up until the end of 2018. We also expanded the scope to acknowledge climate change as a seventh major threat to species, given its increasing importance for reshaping biological communities. Using information on the COSEWIC (Committee on the Status of Endangered Wildlife in Canada) website, we scored the threats for each of 814 species. Habitat loss remained the most important anthropogenic threat to Canada’s at-risk species, affecting 82% of species, followed by over-exploitation (47%), introduced species (46%), and pollution (35%). Climate change was the least important threat, affecting only 13% of species. However, report writers used less certain language when talking about climate change compared with other threats, so when we included cases where climate change was listed as a probable or future cause, climate change was the fourth most important anthropogenic threat, affecting some 38% of species. The prevalence of threat categories was broadly similar to those for the United States and IUCN listed species. The taxa most affected by climate change included lichens (77%), birds (63%), marine mammals (60%), and Arctic species of all taxa (79%), whereas vascular plants (23%), marine fishes (24%), arthropods (27%), and non-Arctic species (35%) were least affected. A paired analysis of the 188 species with two or more reports indicated that any mention of climate change as a threat increased from 12% to 50% in 10 years. Other anthropogenic threats that have increased significantly over time in the paired analysis included introduced species, over-exploitation, and pollution. Our analysis suggests that threats are changing rapidly over time, emphasizing the need to monitor future trends of all threats, including climate change.