Isolated populations of postglacial relicts are known from many regions and are typically found on mountains for terrestrial species and in lakes for aquatic species. Among the few aquatic mammalian relicts, the Saimaa ringed seal (Pusa hispida saimensis) has been land-locked in Lake Saimaa, Finland, for the last 10,000 years. Saimaa ringed seals show genetic, behavioral, and morphological differences to the other ringed seal subspecies, but the extent these differences stem from the end of the last glacial period remains unclear. Here, we demonstrate with comprehensive sampling and state-of-the-art genomic methods that the Saimaa ringed seals are much older than the lake they inhabit, having formed a separate evolutionary branch for at least 60,000 years ago. This deep evolutionary origin of the Saimaa ringed seals is further underscored by our ecomorphological analyses revealing adaptively distinct features in their dentition and tongue. Overall, glacial relicts, many threatened by extinction, may harbor a richer selection of evolutionary history than might be expected from their recent isolation history alone. ### Competing Interest Statement The authors have declared no competing interest.

Freshwater bivalves (FWB) are attracting scientific and societal attention given their essential ecosystem services, ecological functions, and poor conservation status. Current knowledge of the spatial distribution of West Palearctic FWB is poor preventing the understanding of biogeography and conservation planning. One of the priorities of the pan-European networking project "CONFREMU - Conservation of freshwater mussels: a pan-European approach" funded by the European Union, was to fill the knowledge gap on the distribution of FWB in Europe and adjacent regions. Based on the efforts of this network of scientists, we provide the most complete, taxonomically, and geographically accurate distribution of FWB species for the entire West Palearctic. The dataset contains 270,287 geo-referenced records of 93 native and 8 non-native FWB from 1674 to 2023. The dataset compiles information from private records from 82 specialists and multiple sources (e.g., published articles, grey literature, biodiversity databases, and scientific collections). This dataset, available online, represents an important data source for future studies on the biodiversity, biogeography, and conservation of these important organisms.

Cnidarians are among the most successful aquatic invaders, and the freshwater jellyfish Craspedacusta sowerbii is a prime example from non-marine systems. The hydrozoan has spread through northern temperate latitudes worldwide, and in the 1990s, the first records from Finland marked its northernmost distribution in Europe. Since then, no systematic monitoring of C. sowerbii’s distribution and genetic identity has been made. We compiled and analysed occurrence data that had mainly accumulated through community science websites to the FinBIF data warehouse. By 2024, over 65 reports of freshwater jellyfish from 19 locations across southern Finland were received. Numerically, most reports were from a few artificial swimming ponds in the vicinity of population centres, whereas most locations were shallow lakes or bays scattered through rural southern Finland. The number of reports has sharply increased in recent years, along with overall increases in community science observations and an upward trend in average surface water temperature of lakes and coastal sea. Most of the observations were from late summer (mid-July to September). The northernmost record (in 2020) was from 62.82°N, 250 km north of the initial public record in 1999. We also assessed the phylogeographic relationship of Finnish samples from the COI gene. The global mitochondrial C. sowerbii diversity comprises three deep lineages all distributed on multiple continents. The Finnish specimens represent a branch within the most widespread lineage, with a sequence identical or nearly identical to ones from Czechia, Greece, Singapore, and China. As spreading is predicted to continue with global warming, monitoring efforts in freshwater systems are advised.

Pacific herring Clupea pallasii and Atlantic herring C. harengus are sister species of Pliocene origin that now both occur in northeastern Europe. Atlantic herring is represented by a huge oceanic population and several small coastal populations in Norway, whereas Pacific herring prevails in the Eastern Barents Sea and White Sea. Two populations in Northern Norway, one in the marine Balsfjord and the other, a putatively unique landlocked Clupea population in the neighboring meromictic Lake Rossfjordvatn, are phenotypically similar to C. pallasii. The Balsfjord herring is predominantly of C. pallasii genetic ancestry, but with 25

Isolated populations of postglacial relicts are known from many regions and are typically found on mountains for terrestrial species and in lakes for aquatic species. Among the few aquatic mammalian relicts, the Saimaa ringed seal (Pusa hispida saimensis) has been landlocked in Lake Saimaa, Finland, for the last 10,000 y. Saimaa ringed seals show genetic, behavioral, and morphological differences from the other ringed seal subspecies, but the extent these differences stem from the end of the last glacial period remains unclear. Here, we demonstrate with comprehensive sampling and state-of-the-art genomic methods that the Saimaa ringed seals are much older than the lake they inhabit, having formed a separate evolutionary branch for at least 60,000 y. This deep evolutionary origin of the Saimaa ringed seals is further underscored by anatomical differences, including our ecomorphological analyses revealing adaptively distinct features in their dentition and tongue. Overall, glacial relicts may harbor a richer selection of evolutionary history than might be expected from their recent isolation history alone.

A central goal of molecular studies on ancient lake faunas is to resolve the origin and phylogeny of their strikingly diverse endemic species flocks. Another equally intriguing goal is to understand the integrity of individual morphologically diagnosed species, which should help to perceive the nature and speed of the speciation process, and the true biological species diversity. In the uniquely diverse Lake Baikal amphipod crustaceans, molecular data from shallow-water species have often disclosed their cryptic subdivision into geographically segregated genetic lineages, but the evidence so far is mainly based on mitochondrial DNA. We now present a lake-wide parallel survey of both mitochondrial and multilocus nuclear genetic structuring in the common shoreline amphipod Eulimnogammarus verrucosus, known to comprise three deep, parapatric mtDNA lineages. Allele frequencies of seven nuclear allozyme loci divide the data into three main groups whose distributions exactly match the distributions of the main mitochondrial lineages S, W, and E and involve a further division of the W cluster into two subgroups. The inter-group differences involve one to four diagnostic loci and additional group-specific alleles. The transition zones are either abrupt (1 km), occur over a long segment of uninhabitable shoreline, or may be gradual with non-coincident clinal change at different loci. Mitochondrial variation is hierarchically structured, each main lineage further subdivided into 2–4 parapatric sublineages or phylogroups, and patterns of further local segregation are seen in some of them. Despite the recurring observations of cryptic diversity in Baikalian amphipods, the geographical subdivisions and clade depths do not match in different taxa, defying a common explanation for the diversification in environmental history.

Ancient lakes are hotspots of species diversity, posing challenges and opportunities for exploration of the dynamics of endemic diversification. Lake Baikal in Siberia, the oldest lake in the world, hosts a particularly rich crustacean fauna, including the largest known species flock of harpacticoid copepods with some 70 species. Here, we focused on exploring the diversity and evolution within a single nominal species, Harpacticella inopinata Sars, 1908, using molecular markers (mitochondrial COI, nuclear ITS1 and 28S rRNA) and a set of qualitative and quantitative morphological traits. Five major mitochondrial lineages were recognized, with model-corrected COI distances of 0.20-0.37. A concordant pattern was seen in the nuclear data set, and qualitative morphological traits also distinguish a part of the lineages. All this suggests the presence of several hitherto unrecognized cryptic taxa within the baikalian H. inopinata, with long independent histories. The abundances, distributions and inferred demographic histories were different among taxa. Two taxa, H. inopinata CE and H. inopinata CW, were widespread on the eastern and western coasts, respectively, and were largely allopatric. Patterns in mitochondrial variation, that is, shallow star-like haplotype networks, suggest these taxa have spread through the lake relatively recently. Three other taxa, H. inopinata RE, RW and RW2, instead were rare and had more localized distributions on either coast, but showed deeper intraspecies genealogies, suggesting older regional presence. The rare taxa were often found in sympatry with the others and occasionally introgressed by mtDNA from the common ones. The mitochondrial divergence between and within the H. inopinata lineages is still unexpectedly deep, suggesting an unusually high molecular rate. The recognition of true systematic diversity in the evaluation and management of ecosystems is important in hotspots, as it is everywhere else, while the translation of the diversity into a formal taxonomy remains a challenge.

Four mitochondrial phylogroups are distinguished in the European pine marten (Martes martes), two of which, FNR1/2, are shared with the more easterly sister species, the sable (Martes zibellina). Here, we found that the phylogroup frequencies differed markedly between the southern Finland and western Russia populations in the eastern part of the range of Martes martes, suggesting differential introgression from M. zibellina in these regions. We also examined the diversity of a protein-coding gene, MHC class II DRB, in these two Martes species. We detected 16 functional Martes martes DRB alleles (Mama-DRBs), including several codons that seem to have undergone positive selection, and eight presumed pseudogenes (Mama-DRB*PSs); some alleles/pseudogenes were geographically widespread and others restricted. In a broader carnivoran DRB tree, all Mama-DRBs grouped within a mustelid clade, four in a basal group comprising alleles from early-diverged species and the others in a derived group containing alleles from more recently diverged species. Many alleles showed trans-species polymorphism, suggesting that Mama-DRBs have evolved under pathogen-driven balancing selection. Three of six Mama-DRBs and one of four pseudogenes shared with Martes zibellina were restricted to the FNR1/2 mitochondrial DNA phylogroups, pointing to the possibility that genetic introgression from Martes zibellina might have contributed to Mama-DRB diversity and thus adaptability.

The Saimaa ringed seal (Pusa hispida saimensis) is endemic to Lake Saimaa in Finland. The subspecies is thought to have originated when parts of the ringed seal population of the Baltic region were trapped in lakes emerging due to postglacial bedrock rebound around 9000 years ago. During the 20th century, the population experienced a drastic human-induced bottleneck. Today encompassing a little over 400 seals with extremely low genetic diversity, it is classified as endangered. We sequenced sections of the mitochondrial control region from 60 up to 125-years-old museum specimens of the Saimaa ringed seal. The generated dataset was combined with publicly available sequences. We studied how genetic variation has changed through time in this subspecies and how it is phylogenetically related to other ringed seal populations from the Baltic Sea, Lake Ladoga, North America, Svalbard, and the White Sea. We observed temporal fluctuations in haplotype frequencies and loss of haplotypes accompanied by a recent reduction in female effective population size. In apparent contrast with the traditionally held view of the Baltic origin of the population, the Saimaa ringed seal mtDNA variation also shows affinities to North American ringed seals. Our results suggest that the Saimaa ringed seal has experienced recent genetic drift associated with small population size. The results further suggest that extant Baltic ringed seal is not representative of the ancestral population of the Saimaa ringed seal, which calls for re-evaluation of the deep history of this subspecies.

Atlantic herring (Clupea harengus) and Pacific herring (C. pallasii) are sister species that split from a common ancestor about 2 million years ago. Balsfjord, a subarctic fjord in Northern Norway, harbors an outpost population of Pacific herring within the range of the Atlantic herring. We used whole genome sequencing to show that gene flow from Atlantic herring into the Balsfjord population has generated a stable hybrid population that has persisted for thousands of generations. The Atlantic herring ancestry in Balsfjord was estimated in the range 25-26%. The old age and large proportion of introgressed regions suggest there are no obvious genetic incompatibilities between species. Introgressed regions were widespread in the genome and large, with some in excess of 1 Mb, and they were overrepresented in low-recombination regions. We show that the distribution of introgressed material is non-random; introgressed sequence blocks in different individuals are shared more often than expected by chance. Furthermore, introgressed regions tend to show elevated divergence (F-ST) between Atlantic and Pacific herring. Together, our results suggest that introgression of genetic material has facilitated adaptation in the Balsfjord population. The Balsfjord population provides a rare example of a stable interspecies hybrid population that has persisted over thousands of years.

Organisms colonizing new habitats can undergo adaptive change due to novel selective landscapes encountered in the new environment. Examples in nature where the development of the same traits has repeatedly occurred on multiple independent occasions upon colonizing a novel habitat represent instances of parallel evolution. Here we test whether the colonization of spring habitat by the principally lacustrine amphipod crustacean Pallaseopsis quadrispinosa has resulted in parallel evolution in armature traits using empirical data on morphology and mitochondrial DNA and through a breeding experiment. Analysis of mtDNA CO1 sequences shows that the spring populations share no common history and have evolved in isolation from each other and from their neighbouring lake populations since deglaciation approximately 12,000 years ago and are now fixed for different haplogroups. Dorsal spines and lateral projections were absent or less developed in all spring populations than in lake populations. Variation in armature development also could be explained by predator presence as populations with fish predators exhibited more developed spines than those without fish. In a laboratory breeding experiment, hybrid Spring x Lake F1 offspring had intermediate development of armature compared to offspring of Lake x Lake and Spring x Spring matings. The results support the hypothesis that armature reduction has independently evolved on multiple occasions in P. quadrispinosa. Recent research has questioned the degree to which parallel evolution actually explains variance in traits. Taking into account the predation regime, sexual dimorphism and mineral composition of the trait, a more precise understanding of the factors influencing parallel evolution emerges.

We provide an overview of the World Amphipoda Database (WAD), a global species database that is part of the World Register of Marine Species (WoRMS). Launched in 2013, the database contains entries for over 10,500 accepted species names. Edited currently by 31 amphipod taxonomists, following WoRMS priorities, the WAD has at least one editor per major group. All accepted species are checked by the editors, as is the authorship available for all of the names. The higher classification is documented for every species and a type species is recorded for every genus name. This constitutes five of the 13 priorities for completion, set by WoRMS. In 2015, five LifeWatch grants were allocated for WAD activities. These included a general training workshop in 2016, together with data input for the superfamily Lysianassoidea and for a number of non-marine groups. Philanthropy grants in 2019 and 2021 covered more important gaps across the whole group. Further work remains to complete the linking of unaccepted names, original descriptions, and environmental information. Once these tasks are completed, the database will be considered complete for 8 of the 13 priorities, and efforts will continue to input new taxa annually and focus on the remaining priorities, particularly the input of type localities. We give an overview of the current status of the order Amphipoda, providing counts of the number of genera and species within each family belonging to the six suborders currently recognized.

The chemical industry is the leading sector in the EU in terms of added value. However, contaminants pose a major threat and significant costs to the environment and human health. While EU legislation and international conventions aim to reduce this threat, regulators struggle to assess and manage chemical risks, given the vast number of substances involved and the lack of data on exposure and hazards. The European Green Deal sets a 'zero pollution ambition for a toxic free environment' by 2050 and the EU Chemicals Strategy calls for increased monitoring of chemicals in the environment. Monitoring of contaminants in biota can, inter alia: provide regulators with early warning of bioaccumulation problems with chemicals of emerging concern; trigger risk assessment of persistent, bioaccumulative and toxic substances; enable risk assessment of chemical mixtures in biota; enable risk assessment of mixtures; and enable assessment of the effectiveness of risk management measures and of chemicals regulations overall. A number of these purposes are to be addressed under the recently launched European Partnership for Risk Assessment of Chemicals (PARC). Apex predators are of particular value to biomonitoring. Securing sufficient data at European scale implies large-scale, long-term monitoring and a steady supply of large numbers of fresh apex predator tissue samples from across Europe. Natural science collections are very well-placed to supply these. Pan-European monitoring requires effective coordination among field organisations, collections and analytical laboratories for the flow of required specimens, processing and storage of specimens and tissue samples, contaminant analyses delivering pan-European data sets, and provision of specimen and population contextual data. Collections are well-placed to coordinate this. The COST Action European Raptor Biomonitoring Facility provides a well-developed model showing how this can work, integrating a European Raptor Biomonitoring Scheme, Specimen Bank and Sampling Programme. Simultaneously, the EU-funded LIFE APEX has demonstrated a range of regulatory applications using cutting-edge analytical techniques. PARC plans to make best use of such sampling and biomonitoring programmes. Collections are poised to play a critical role in supporting PARC objectives and thereby contribute to delivery of the EU's zero-pollution ambition.

The Geology Collection is part of the national collections of the Finnish Museum of Natural History Luomus. General principles and guidelines for the collections are defined in the General Collection Policy of Luomus. The Geology Collection Policy is subordinate to the General Collection Policy of Luomus, clarifying its content with reference to the special characteristics of the geological collections. The Geological Collection includes mineral, rock, and meteorite specimens worldwide and from all geologic ages to support Finnish research and educational projects. The coverage emphasizes specimens from Finland, Scandinavia, Africa, and Antarctica. The Geology Collection Policy defines the purpose of the collections, the objectives, the distribution of responsibilities for collection management and maintenance in the organisation, and the principles of collection accumulation, preservation, accessibility and use to public.

Cryptic and hybridizing species may lack diagnostic taxonomic characters leaving researchers with semi-diagnostic ones. Identification based on such characters is probabilistic, the probability of correct identification depending on the species composition in a mixed population. Here we test the possibilities of applying a semi-diagnostic conchological character for distinguishing two cryptic species of blue mussels, Mytilus edulis and M. trossulus. These ecologically, stratigraphically and economically important molluscs co-occur and hybridize in many areas of the North Atlantic and the neighboring Arctic. Any cues for distinguishing them in sympatry without genotyping would save much research effort. Recently these species have been shown to statistically differ in the White Sea, where a simple character of the shell was used to distinguish two mussel morphotypes. In this paper, we analyzed the associations between morphotypes and species-specific genotypes based on an abundant material from the waters of the Kola Peninsula (White Sea, Barents Sea) and a more limited material from Norway, the Baltic Sea, Scotland and the Gulf of Maine. The performance of the “morphotype test” for species identification was formally evaluated using approaches from evidence-based medicine. Interspecific differences in the morphotype frequencies were ubiquitous and unidirectional, but their scale varied geographically (from 75% in the White Sea to 15% in the Baltic Sea). In addition, salinity-related variation of this character within M. edulis was revealed in the Arctic Barents Sea. For every studied region, we established relationships between the proportions of the morphotypes in the populations as well as between the proportions of the morphotypes in samples and the probabilities of mussels of different morphotypes being M. trossulus and M. edulis. We provide recommendations for the application of the morphotype test to mussels from unstudied contact zones and note that they may apply equally well to other taxa identified by semi-diagnostic traits.

Comparative phylogeography has become a powerful approach in exploring hidden or cryptic diversity within widespread species and understanding how historical and biogeographical factors shape the modern patterns of their distribution. Most comparative phylogeographic studies so far focus on terrestrial and vertebrate taxa, while aquatic invertebrates (and especially freshwater invertebrates) remain unstudied. In this article, we explore and compare the patterns of molecular diversity and phylogeographic structure of four widespread freshwater copepod crustaceans in European water bodies: the harpacticoids Attheyella crassa, Canthocamptus staphylinus and Nitokra hibernica, and the cyclopoid Eucyclops serrulatus, using sequence data from mtDNA COI and nuclear ITS/18S rRNA genes. The three taxa A. crassa, C. staphylinus and E. serrulatus each consist of deeply diverged clusters and are deemed to represent complexes of species with largely (but not completely) non-overlapping distributions, while in N. hibernica only little differentiation was found, which may however reflect the geographically more restricted sampling. However, the geographical patterns of subdivision differ. The divisions in A. crassa and E. serrulatus follow an east–west pattern in Northern Europe whereas that in C. staphylinus has more of a north–south pattern, with a distinct Fennoscandian clade. The deep mitochondrial splits among populations of A. crassa, C. staphylinus and E. serrulatus (model-corrected distances 26–36%) suggest that divergence of the lineages predate the Pleistocene glaciations. This study provides an insight into cryptic diversity and biogeographic distribution of freshwater copepods.

Two lineages of bivalve transmissible neoplasia (BTN), BTN1 and BTN2, are known in blue mussels Mytilus . Both lineages derive from the Pacific mussel M. trossulus and are identified primarily by their unique genotypes of the nuclear gene EF1α. BTN1 is found in populations of M. trossulus from the Northeast Pacific, while BTN2 has been detected in populations of other Mytilus species worldwide but not in M. trossulus itself. Here we examined M. trossulus from the Sea of Japan (Northwest Pacific) for the presence of BTN. Using hemocytology and flow cytometry of the hemolymph, we confirmed the presence of disseminated neoplasia in our specimens. Cancerous mussels possessed the BTN2 EF1α genotype and two mitochondrial haplotypes with different recombinant control regions, similar to that of common BTN2 lineages. This is the first report of BTN2 in its original host species M. trossulus. A comparison of all available BTN and M. trossulus COI sequences suggests a common and recent origin of BTN2 diversity in populations of M. trossulus outside the Northeast Pacific, possibly in the Northwest Pacific.

The amphi‐boreal faunal element comprises closely related species and conspecific populations with vicarious distributions in the North Atlantic and North Pacific basins. It originated from an initial trans‐Arctic dispersal in the Pliocene after the first opening of the Bering Strait, and subsequent inter‐oceanic vicariance through the Pleistocene when the passage through the Arctic was severed by glaciations and low sea levels. Opportunities for further trans‐Arctic dispersal have risen at times, however, and molecular data now expose more complex patterns of inter‐oceanic affinities and dispersal histories. For a general view on the trans‐Arctic dynamics and of the roles of potential dispersal–vicariance cycles in generating systematic diversity, we produced new phylogeographic data sets for amphi‐boreal taxa in 21 genera of invertebrates and vertebrates, and combined them with similar published data sets of mitochondrial coding gene variation, adding up to 89 inter‐oceanic comparisons involving molluscs, crustaceans, echinoderms, polychaetes, fishes and mammals. Only 39% of the cases correspond to a simple history of Pliocene divergence; in most taxonomical groups, the range of divergence estimates implies connections through the entire Pliocene–Pleistocene–Holocene time frame. Repeated inter‐oceanic exchange was inferred for 23 taxa, and the latest connection was usually post‐glacial. Such repeated invasions have usually led to secondary contacts and occasionally to widespread hybridization between the different invasion waves. Late‐ or post‐glacial exchange was inferred in 46% of the taxa, stressing the importance of the relatively recent invasions to the current diversity in the North Atlantic. Individual taxa also showed complex idiosyncratic patterns and histories, and several instances of cryptic speciation were recognized. In contrast to a simple inter‐oceanic vicariance scenario underlying amphi‐boreal speciation, the data expose complex patterns of reinvasion and reticulation that complicate the interpretation of taxon boundaries in the region.

The herbarium collections are sub-collections of the Finnish Museum of Natural History Luomus that manages national natural history collections, as referred to in the Universities Act. The general collections policy defines the overall principles and guidelines concerning the collections practices. The sub-collections policies specify its guidelines and instructions, considering the special nature of the sub-collections. The policy for the botanical and mycological herbarium collections guides the activities related to all botanical, mycological and phycological collections in herbaria, hence excluding digital collections, DNA and tissue samples as well as living collections, which have separate policies. The herbarium collections policy defines and outlines the purpose of the collections as is to accrue and preserve natural specimens representing biodiversity for research and university-level teaching. The policy defines the objectives and content of related activities, the division of responsibilities for the administration and care of the collections within the organisation, and the general principles and practices for the acquisition, preservation, availability and use of the collections.

As part of its quality management and goal-driven strategic development, the Finnish Museum of Natural History Luomus drafts policy documents to guide its operational sectors. The purpose of such policies is to define the content and procedures of the Museum’s activities. They answer the questions “what”, “why”, “who” and “for whom” about the activities they discuss, which is to say that they define and delimit the scope of the operational sector, provide the operations with a purpose and determine their content, describe the allocation of responsibilities in the sector under the Luomus organisation and identify the target groups. The policies provide general objectives and thus form the basis for target programmes and any action plans which in turn answer the question “How can we reach the designated goals?”. Policies are not tied to a schedule, unlike target programmes, even though they must be dynamic and updated periodically to better serve the organisation. The core activities at Luomus are: (1) maintenance of the scientific collections, (2) research and (3) expert services. The General Collections Policy sets guidelines for the maintenance of the scientific collections based on the mission of the University of Helsinki and Luomus.