Biology subjects

Lydersen, C.

Publications and source records attributed to Lydersen, C..

6 recordsLinked to original sources

bioRxiv2026

Habitat discontinuity and fidelity to migratory routes shape narwhal genetic structure and diversity

Rapid Arctic warming is reshaping marine ecosystems and altering the evolutionary trajectories of ice-associated species. Narwhals (Monodon monoceros) are Arctic endemics that are thought to be vulnerable to climate change. We present the first nuclear genomic assessment of narwhals across their distribution to evaluate population structure, demographic history, local adaptation, inbreeding and genetic load. Using genomes from 117 individuals, we identified three populations: Canadian Arctic Archipelago/West Greenland, Northeast Greenland/Svalbard and Southeast Greenland. Demographic reconstructions indicated low effective population size over at least 600,000 years, followed by population growth during the last glacial period. Our results suggest that population structure is maintained by habitat discontinuities and fidelity to migration routes. The latter may promote local adaptation, as genes related to long-term memory were found in regions putatively under selection in Canadian Arctic Archipelago/West Greenland narwhals, which undertake the longest migrations. Genome-wide diversity was uniformly low across populations. Inbreeding levels were inversely related to estimated population sizes. The small and rapidly declining Southeast Greenland population exhibited elevated recent inbreeding. Deleterious mutations were primarily masked in heterozygous genotypes, raising concerns for this population. Together, our results demonstrate that past climate, habitat discontinuities and migration fidelity jointly structure narwhal populations.

evolutionary biology↗

bioRxiv2025

Impact of tusk anomalies on the long-term foraging ecology of narwhals

Male narwhals are unique in having one long, spiralled tusk, while females of the species do not have a tusk. However, a small number of individuals develop tusk anomalies, including two-tusked males or females with a tusk. In this study, we combine genetic sexing and bone collagen stable isotope ({delta}13C and {delta}15N) analysis to evaluate whether these tooth anomalies impact foraging ecology. Our analysis of individuals collected in the waters around Greenland showed no systematic impacts; nine of ten two-tusked male narwhals, and all three one-tusked female narwhals were within the normal range of known isotopic diversity from the sampled geographic regions. Two specimens with other forms of unusual dentition both showed stable isotope values outside the range of narwhals, suggesting their diet was different. Our findings underscore how DNA data retrieved from museum specimens can elucidate biological questions of interest, such as the sex of anomalous individuals. They also show how stable isotope analysis can be used to assign individuals with unknown provenance to their geographic region of origin.

zoology↗

bioRxiv2025

Tracing the drivers of range-wide bowhead whale genomic structure and diversity

Understanding how past environmental and anthropogenic factors shaped contemporary genetic patterns is essential for assessing the vulnerability of species in the face of ongoing climate change. The bowhead whale (Balaena mysticetus) - the only baleen whale found in the Arctic year-round - has a strong association with sea ice, long history of human exploitation, and a circumpolar distribution, making it a valuable model for investigating how these factors have shaped population structure in the marine Arctic. We analysed both nuclear and mitochondrial genomes from bowhead whale individuals sampled across the species circumpolar range, encompassing all four recognized management stocks. Our results reveal three not four genetically differentiated populations: the Sea of Okhotsk stock; the East Greenland-Svalbard-Barents Sea stock; and a combined population containing the Bering-Chukchi-Beaufort Seas and East Canada-West Greenland stocks. We utilised ecological niche modeling and bowhead whale telemetry data to model stock connectivity over the past 11,700 years, and identify past habitat connectivity as a key driver of current population structure. Despite centuries of intensive commercial whaling, the three bowhead whale populations exhibit little-to-no evidence of recent inbreeding and retain high genetic diversity relative to other mammalian species. The lowest genetic diversity, most inbreeding, and highest realised genetic load being in the Sea of Okhotsk population. Collectively, our findings shed light on the recent population history and dynamics of bowhead whales, and offer valuable baseline data on present-day genetic structure and diversity to support effective conservation and management strategies.

evolutionary biology↗

bioRxiv2025

The Greenland shark genome: insights into deep-sea ecology and lifespan extremes

The Greenland shark (Somniosus microcephalus) is known for its slow metabolism and deep-sea habitat. It is considered the longest-lived vertebrate on Earth, with an estimated lifespan of 392{+/-}120 years. Despite its remarkable longevity and lifestyle, there have been no genomic studies on this species. Here, we report the first, chromosome-level assembly of the Greenland shark genome, which is 5.9 Gb in size with an N50 length of 233 Mb, and contains 37,125 predicted genes with a completeness score of 86.5%. We found that the copy numbers of three gene families (TNF, TLR, LRRFIP), which are involved in activating the NF-{kappa}B signaling pathway, are significantly increased in the Greenland shark compared to short-lived shark species. In the rhodopsin of this deep-sea dweller, we detected amino acid substitutions that result in spectral tuning for the so-called blue shift, suggesting adaptive evolution to dim-light vision. We also elucidate the dynamics of the effective population size (Ne) of the Greenland shark and its close relative, the Pacific sleeper shark (Somniosus pacificus). These genomic analyses offer new insights into the molecular basis of the exceptional longevity of the Greenland shark and highlight potential genetic mechanisms that could inform future research into longevity.

genomics↗

bioRxiv2024

Four centuries of commercial whaling eroded 11,000 years of population stability in bowhead whales

The bowhead whale, an Arctic endemic, was heavily overexploited during commercial whaling between the 16th-20th centuries1. Current climate warming, with Arctic amplification of average global temperatures, poses a new threat to the species2. Assessing the vulnerability of bowhead whales to near-future predictions of climate change remains challenging, due to lacking data on population dynamics prior to commercial whaling and responses to past climatic change. Here, we integrate palaeogenomics and stable isotope ({delta}13C and{delta} 15N) analysis of 201 bowhead whale fossils from the Atlantic Arctic with palaeoclimate and ecological modelling based on 823 radiocarbon dated fossils, 151 of which are new to this study. We find long-term resilience of bowhead whales to Holocene environmental perturbations, with no obvious changes in genetic diversity or population structure, despite large environmental shifts and centuries of whaling by Indigenous peoples prior to commercial harvests. Leveraging our empirical data, we simulated a time-series model to quantify population losses associated with commercial whaling. Our results indicate that commercial exploitation induced population subdivision and losses of genetic diversity that are yet to be fully realised; declines in genetic diversity will continue, even without future population size reductions, compromising the species resilience to near-future predictions of Arctic warming.

evolutionary biology↗

bioRxiv2018

Strong and lasting impacts of past global warming on baleen whale and prey abundance

AbstractThe demography of baleen whales and their prey during the past 30 thousand years was assessed to understand the effects of past rapid global warming on marine ecosystems. Mitochondrial and genome-wide DNA sequence variation in eight baleen whale and seven prey species revealed strong, ocean-wide demographic changes that were correlated with changes in global temperatures and regional oceanographic conditions. In the Southern Ocean baleen whale and prey abundance increased exponentially and in apparent synchrony, whereas changes in abundance varied among species in the more heterogeneous North Atlantic Ocean. The estimated changes in whale abundance correlated with increases in the abundance of prey likely driven by reductions in sea-ice cover and an overall increase in primary production. However, the specific regional oceanographic environment, trophic interactions and species ecology also appeared to play an important role. Somewhat surprisingly the abundance of baleen whales and prey continued to increase for several thousand years after global temperatures stabilized. These findings warn of the potential for dramatic, long-term effects of current climate changes on the marine ecosystem.\n\nOne Sentence SummaryThe effects of past global warming on marine ecosystems were drastic, system-wide and long-lasting.

evolutionary biology↗