Arctic bird nesting traces back to the Cretaceous

Our understanding of the earliest stages of crown bird evolution is hindered by an exceedingly sparseavian fossil record from the Mesozoic era. The most ancient phylogenetic divergences among crown birds are known to have occurred in the Cretaceous period1-3, but stem-lineage representatives of the deepest subclades of crown birds-Palaeognathae (ostriches and kin), Galloanserae (landfowl and waterfowl) and Neoaves (all other extant birds)-are unknown from the Mesozoic era. As a result, key questions related to the ecology4,5, biogeography3,6,7 and divergence times1,8-10 of ancestral crown birds remain unanswered. Here we report a new Mesozoic fossil that occupies a position close to the last common ancestor of Galloanserae and fills a key phylogenetic gap in the early evolutionary history of crown birds10,11. Asteriornis maastrichtensis, gen. et sp. nov., from the Maastrichtian age of Belgium (66.8-66.7 million years ago), is represented by a nearly complete, three-dimensionally preserved skull and associated postcranial elements. The fossil represents one of the only well-supported crown birds from the Mesozoic era12, and is the first Mesozoic crown bird with well-represented cranial remains. Asteriornis maastrichtensis exhibits a previously undocumented combination of galliform (landfowl)-like and anseriform (waterfowl)-like features, and its presence alongside a previously reported Ichthyornis-like taxon from the same locality13 provides direct evidence of the co-occurrence of crown birds and avialan stem birds. Its occurrence in the Northern Hemisphere challenges biogeographical hypotheses of a Gondwanan origin of crown birds3, and its relatively small size and possible littoral ecology may corroborate proposed ecological filters4,5,9 that influenced the persistence of crown birds through the end-Cretaceous mass extinction.

Polar environments can be among the simplest environments on Earth, making them excellent models to understand ecosystem processes and the responses of microorganisms to environmental perturbations. This vulnerability and the rate of the ongoing change make polar environments a priority in climate change and bioremediation studies. This chapter covers studies based on large-scale 16S rRNA gene libraries, environmental microarrays, large-insert clone libraries, and shotgun genome sequencing that are applying metagenomic techniques to characterize and understand polar ecosystems. A recent study at sites ranging from the Falkland Islands all the way to the base of the Antarctic Peninsula used 454 GS FLX Titanium sequencing of the 16S rRNA gene to compare the bacterial community structure and diversity in warmed versus control plots. This study revealed that soil warming induced significant shifts in the major soil bacterial groups like Acidobacteria and α-Proteobacteria, which led to changes in soil respiration. A recent shotgun metagenomic study in the Canadian High Arctic sequenced a permafrost sample and its overlying active-layer soil and focused particularly on genes that might be important for greenhouse gas emissions following permafrost thaw. The only metagenomic study of polar freshwater ecosystems published to date looked at the viral communities of an Antarctic lake. This study revealed that a large proportion of the viral sequences retrieved from the lake were from eukaryotic viruses and not from bacteriophages. Emerging technologies could also be interesting to apply to polar environments. For instance, bioremediation studies could benefit from metabolomics, proteomics, and newly developed reactome arrays.

Context Soil fungi and bacteria play a crucial role in decomposing soil organic matter (SOM) and providing nutrients to terrestrial ecosystems. However, in polar environments, their relative contributions to decomposition remain unclear. Aims This study aimed to determine whether fungi or bacteria contributes more to humic substances (HS) decomposition (the largest constituent of SOM) in maritime Antarctic soils under controlled laboratory conditions with elevated temperature and moisture levels. Methods Soil culturing method was used to select for soil microbes that efficiently degrade HS. During culturing at 18°C for 30 days, Antarctic soils were treated with selective antimicrobials to manipulate microbial communities. After culturing, HS degradation and bacterial communities were analysed. The effects of soil culturing on plant growth were also evaluated using Arabidopsis thaliana as a surrogate for Antarctic plants. Key results HS decomposition and solubilisation were more pronounced in antifungal-treated soils compared to antibacterial-treated soils. Antifungal treatment reduced bacterial alpha diversity, altered bacterial composition, and increased the abundance of rhizosphere-associated Saccharibacteria. Bacterial growth resumed quickly after antibacterial treatment indicating resilience to antimicrobials. Soil culturing resulted in a higher water-soluble HS fraction, which significantly enhanced the fresh and dry weights of A. thaliana. Conclusions Antarctic bacteria exhibit higher degradative activity and resilience to antimicrobials compared to fungi, promoting HS decomposition and solubilisation. This indicates that bacteria have a greater impact on Antarctic soil functioning than fungi. Implications These findings highlight the critical role of bacteria in nutrient cycling and plant growth in polar ecosystems.

Resilience in polar ecosystems: From drivers to impacts and changes

This paper argues that southern Africa was a remote part of the Old World in the late Pleistocene (125-10 ka ago). Because of this isolated position there was continuity without significant replacement in the resident population. Isolation and the relatively recent spread of agriculture to the region has allowed a section of this population to survive into the present. They are the Bushmen (San). Studies of geographic patterning in conventional genetic markers and mitochondrial DNA indicate that the Bushman clade has a long evolutionary history in southern Africa. Estimates of more than 100 ka for the continued presence of this population in the region are supported in archaeological investigations of sites with long sequences such as Klasies River main site and Border Cave. Human remains dating to the earlier part of the late Pleistocene have been recovered from these sites and the samples form a morphological series with the Klasies River remains possibly 20 ka older than those from Border Cave. There is no fossil record for the later Pleistocene, however, at a period when selection for a gracile morphology may have been pronounced. The cultural associations in the earlier late Pleistocene are with the Middle Stone Age. Expressions of cultural 'style' and the occurrence of similar artefact design types in the Middle and Later Stone Ages can be interpreted with reference to the ethnographic present. Temporal continuity can be shown in the geographical distribution of stylistic markers and this suggests participation in a shared cognitive system.(ABSTRACT TRUNCATED AT 250 WORDS)

Climate change posed a significant threat to global biodiversity, affecting wildlife across terrestrial, marine, and polar ecosystems. This review aimed to synthesize the mechanisms through which climate change impacted wildlife and to evaluate recent empirical evidence (2020–2025). A structured literature search was conducted using major scientific databases, and studies were categorized based on climatic drivers and ecological responses. The synthesis indicated that rising temperatures, altered precipitation patterns, extreme weather events, and oceanic changes were driving shifts in species distributions, phenology, and population dynamics. Case studies revealed increasing risks of trophic mismatches, habitat loss, and species decline across diverse ecosystems. The review further evaluated conservation strategies, highlighting the roles of climate mitigation, habitat connectivity, and ecosystem-based adaptation. The inclusion of literature up to early 2025 ensured that the review reflected the most recent scientific findings and evolving climate impacts on wildlife. These findings underscored the need for integrated, evidence-based approaches to enhance wildlife resilience under accelerating climate change.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 557:189-206 (2016) - DOI: https://doi.org/10.3354/meps11868 Carry-over effects of ocean acidification in a cold‑water lecithotrophic holothuroid Katie Verkaik1, Jean-François Hamel2, Annie Mercier1,* 1Department of Ocean Sciences, Memorial University, St John’s, Newfoundland and Labrador, A1C 5S7 Canada 2Society for the Exploration & Valuing of the Environment (SEVE), St Philips, Newfoundland and Labrador, A1M 2B7 Canada *Corresponding author: amercier@mun.ca ABSTRACT: Ocean acidification (OA) due to anthropogenic CO2 emissions is predicted to affect the world’s oceans in the near future. To date, knowledge remains limited on the response of species that are weakly calcified, produce lecithotrophic (non-feeding) larvae and live in polar/subpolar environments. The cold-water sea cucumber Cucumaria frondosa represents an ideal model for such investigations. One of the most abundant echinoderms in the world, it is annually-spawning, slow-growing and has been commercially exploited in the North Atlantic for over 35 yr. The present study examined the effects of predicted near-future OA scenarios on gametogenesis, spawning and embryonic development of C. frondosa, as well as on processes that may compete or coincide with reproductive effort such as ossicle formation and lipid synthesis. Sea cucumbers were exposed to a 0.4 unit pH decrease over 19 wk using a fully open flow-through design allowing for natural fluctuations in pH, light, temperature, salinity and nutrient levels. There were 2 treatment groups, ambient pH (7.9–8.2; pCO2 430–470 µatm) and low pH (7.5–7.7; pCO2 1330–1530 µatm). Results indicate that low pH/high pCO2 interferes with gamete synthesis, leading to discrepancies in oocyte/embryo buoyancy and morphology and developmental tempo, translating into 100% mortality before the blastula stage. Differences in the microstructural appearance of ossicles and the lipid contents of muscles, gonads and spawned oocytes were also highlighted. Such findings draw attention to previously understudied impacts of OA, including transgenerational effects in cold-water species with maternally provisioned eggs, and the resulting implications for temperate, subpolar and polar ecosystems. KEY WORDS: Ocean acidification · pH · Sea cucumber · North Atlantic · Reproduction · Lecithotrophic development · Polar environments Full text in pdf format Supplementary material PreviousNextCite this article as: Verkaik K, Hamel JF, Mercier A (2016) Carry-over effects of ocean acidification in a cold‑water lecithotrophic holothuroid. Mar Ecol Prog Ser 557:189-206. https://doi.org/10.3354/meps11868 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 557. Online publication date: September 28, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Phytoplankton communities of polar regions–Diversity depending on environmental conditions and chemical anthropopressure

Plastic pollution poses a threat to terrestrial ecosystems, even impacting soils from remote alpine and arctic areas. Biodegradable plastics are a promising solution to prevent long-term accumulation of plastic litter. However, little is known about the decomposition of biodegradable plastics in soils from alpine and polar ecosystems or the microorganisms involved in the process. Plastics in aquatic environments have previously been shown to form a microbial community on the surface of the plastic distinct from that in the surrounding water, constituting the so-called ‘plastisphere’. Comparable studies in terrestrial environments are scarce. Here, we aimed to characterize the plastisphere microbiome of three types of plastics differing in their biodegradability in soil using DNA metabarcoding. Polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and polyethylene (PE) were buried in two different soils, from the Swiss Alps and from Northern Greenland, at 15°C for eight weeks. While physico-chemical characteristics of the polymers only showed minor (PLA, PBAT) or no (PE) changes after incubation, a considerably lower α-diversity was observed on the plastic surfaces and prominent shifts occurred in the bacterial and fungal community structures between the plastisphere and the adjacent bulk soil not affected by the plastic. Effects on the plastisphere microbiome decreased with greater biodegradability of the plastics, from PLA to PE. Copiotrophic taxa within the phyla Proteobacteria and Actinobacteria benefitted the most from plastic input. Especially taxa with a known potential to degrade xenobiotics, including Burkholderiales, Caulobacterales, Pseudomonas, Rhodococcus and Streptomyces, thrived in the plastisphere of the Alpine and Arctic soils. In addition, Saccharimonadales (superphylum Patescibacteria) was identified as a key taxon associated with PLA. The association of Saccharibacteria with plastic has not been reported before, and pursuing this finding further may shed light on the lifestyle of this obscure candidate phylum. Plastic addition affected fungal taxa to a lesser extent since only few fungal genera such as Phlebia and Alternaria were increased on the plastisphere. Our findings suggest that the soil microbiome can be strongly influenced by plastic pollution in terrestrial cryoenvironments. Further research is required to fully understand microbial colonization on plastic surfaces and the biodegradation of plastic in soils.

Among living crocodylians, alligatoroids exhibit a wide range of body sizes and a biogeographic distribution that spans tropical‐to‐subtropical climates. The fossil record of alligatoroids, however, reveals even greater diversity, including multiple examples of gigantism and a broader distribution that extends into polar latitudes. Osteohistological studies on extant alligatoroids show that living alligators and caimans both exhibit seasonal growth, with roughly comparable growth rates. However, alligators and caimans diverged from one another over 60 million years ago; the dearth of studies on extinct alligatoroids makes it unclear if the shared condition in extant taxa reflects convergent responses to rapid climatic changes in the recent past or represents the ancestral condition in alligatoroids. Additionally, sample sizes are often limited to one or two individuals, especially in extinct crocodylians, obscuring any intraspecific variation present. To address this uncertainty, we conducted the largest monospecific osteohistological study of an extinct crocodylian to date, based on a sample of nine femora, providing unique insight into the intraspecific variation in growth of the early‐diverging alligatoroid Diplocynodon hantoniensis from the late Eocene of the UK. The bone microanatomy of D. hantoniensis shows moderate compactness, with a well‐defined medullary cavity, and osteohistological features that are generally consistent with those of extant alligatoroids. Samples vary greatly along a continuum in the degree of remodelling and vascularity, highlighting both the importance of evaluating intraspecific variation and limitations of basing histological assessments on singleton samples. Ontogenetic assessment indicates that our sample captures a range of skeletally immature to mature individuals, approximately corresponding to femoral size, but with notable exceptions possibly driven by sexual dimorphism. Body size estimates for D. hantoniensis (1.2–3.4 m) fall within the typical range of living American alligators (Alligator mississippiensis). Reconstruction from cyclical growth marks indicates a similar overall growth rate between D. hantoniensis and A. mississippiensis. As in extant alligatoroids more generally, this is determinate, seasonally‐controlled growth. Femoral circumference scales positively with femoral length in D. hantoniensis, demonstrating similar allometry to A. mississippiensis. This differs from some other extant crocodylians (e.g. Crocodylus niloticus and Crocodylus johnstoni) and suggests conservation of allometric relationships in alligatoroids. This in‐depth look into an early diverging alligatoroid indicates that seasonality and growth rates present in extant members were established near the base of the clade. Furthermore, it highlights the importance of including larger samples of singular species in order to capture potential variation when making clade‐wide interpretations.

Individuals breeding in seasonal environments are under strong selection to time reproduction to match offspring demand and the quality of the post-natal environment. Timing requires both the ability to accurately interpret the appropriate environmental cues, and the flexibility to respond to inter-annual variation in these cues. Determining which cues are linked to reproductive timing, what these cues are predicting and understanding the fitness consequences of variation in timing, is therefore of paramount interest to evolutionary and applied ecologists, especially in the face of global climate change. We investigated inter-annual relationships between climatic variation and the timing of reproduction in Canada's largest breeding population of Arctic common eiders (Somateria mollissima) in East Bay, Nunavut. Warmer spring temperatures predicted both earlier mean annual laying dates and the earlier ice-free conditions required by ducklings for post-natal growth. Warmer springs had higher variation in this temperature cue, and the population laying distribution became increasingly positively-skewed in warmer summers, potentially indicating that more low-quality females had the opportunity to commence laying in warmer years. Females that timed laying to match duckling hatching just prior to fully ice-free conditions obtained the highest duckling survival probability. Inter-annual data on repeated breeding attempts revealed that the individuals examined show a similar degree of laying flexibility in response to climatic variation; however, there was significant individual variation in the absolute timing of laying within an average year. This work sheds light on how reproductive timing is related to and influenced by variation in local climate and provides vital information on how climate-related variation in reproductive timing influence a fitness measure in an Arctic species. Results are especially relevant to future work in polar environments given that global climatic changes are predicted to be most intense at high latitudes.

ABSTRACTFreshwater fish are highly vulnerable to climate change because they are restricted to inland waters and cannot readily disperse across geographical barriers, making them particularly exposed to catastrophic habitat losses. Understanding how environmental changes may affect the distribution of widespread species is critical for anticipating biodiversity responses and informing conservation efforts. In this study, we employed ecological niche models (MaxEnt) to assess the current and future potential distribution of Hoplias malabaricus, a generalist freshwater predator of ecological and fisheries importance in South America. We focus on the Amazon, Tocantins–Araguaia, Guiana Shield, Brazilian Atlantic Coast, and Marajó Island basins, which encompass the current distribution of the species. We used bioclimatic variables derived from the global WorldClim v2.1 dataset under present‐day conditions and two future climate scenarios (SSP1–2.6, a low‐emission pathway, and SSP5–8.5, a high‐emission pathway) to project habitat suitability. The models demonstrated excellent predictive performance (AUC > 0.9), identifying temperature seasonality (BIO4) and elevation as the most influential variables across all scenarios. Results revealed contrasting trends among hydrographic regions. The species showed increasing association with more seasonal environments and highly suitable habitats contracted under the most extreme scenario. Marajó Island exhibited the highest loss of suitable area, highlighting increased isolation risks. Overall, our findings indicate that H. malabaricus may persist under climate change through niche shifts and partial range contractions. However, habitat loss, reduced connectivity, and regional genetic isolation may compromise long‐term viability, particularly under high‐emission scenarios.

Seawater chlorophyll a concentration (size‐fractionated at 20, 2, and 0.2 µm) and temperature have been measured weekly from December 1988 to August 1994 at a nearshore shallow‐water station at Signy Island in the maritime Antarctic. Macronutrients (N, P, Si) were measured monthly, and the microbial community enumerated during a 15‐month period. The duration of winter sea‐ice, summer seawater temperature, and peak chlorophyll biomass all exhibited strong interannual variability. The summer peak of microplankton (>20 µm) chlorophyll was dominated by large diatoms and colonial forms, and there were late summer‐early winter blooms in two of the six seasons examined. Peak concentrations of nanoplankton (20–2 µm) chlorophyll, predominantly from flagellates, were much lower but the bloom lasted longer and winter biomass was higher than in the microplankton. Seasonal macronutrient patterns suggested a preferential utilization of ammonium at the start of spring followed by a major utilization of nitrate by the summer diatom bloom. The microbial community was complex and showed a clear seasonality in all components, although the timing of the summer bloom differed between taxa. Cell numbers were low in winter, increasing in summer with flagellate taxa especially important in late summer. This study emphasizes the complex nature of the nearshore marine ecosystem and highlights the need for year‐round oceanographic studies in the highly seasonal polar marine environment.

Taphonomic and sedimentologic interpretations of the dinosaur-bearing Upper Cretaceous Strata of the Prince Creek Formation, Northern Alaska: Insights from an ancient high-latitude terrestrial ecosystem

The Ponto-Caspian radiation of gammaroid amphipods is one of the world’s most diverse lacustrine crustacean radiations as well as the only lacustrine amphipod radiation with a fossil record (dating back 9 Ma). However, the phyletic relationship between fossils and extant species was never formally investigated, hampering our evolutionary understanding of this diverse clade. Here, we present the first morphology-based phylogeny (114 characters) of Ponto-Caspian gammaroids that includes 99% of extant taxa, all previously known fossils, as well as newly discovered fossil specimens from the Late Miocene (10.5 Ma) of eastern Romania. Our phylogenetic and phenetic results strongly support the monophyly of all fossil taxa. However, despite its widespread Late Miocene distribution throughout the Paratethys Sea, this fossil clade left no modern descendants. Its exact phylogenetic position is ambiguous, although it is nested in the radiation’s crown group. Morphometric analyses further indicate that fossil species occupy a narrower and peripheral morphospace relative to extant taxa. Our results support the assignment of the newly discovered Romanian fossils to a new genus, Eogmelina gen. nov. with two new species Eogmelina moldavica gen. et sp. nov. and Eogmelina prisca gen. et sp. nov. Finally, our findings call for a fundamental systematic restructuring of Ponto-Caspian gammaroids at genus and family level.