Anna Seniczak

Peatlands are unique and complex ecosystems of global significance, essential for biodiversity conservation and for maintaining key ecological functions such as carbon storage, water retention, and water purification. These functions have become especially critical in the context of contemporary global change, including rising CO2 emissions, increasing water scarcity, and accelerating biodiversity loss—three of the most urgent environmental challenges facing humanity today. Although Sphagnumdominated peatlands are often considered species-poor due to their waterlogged and acidic conditions, they support rich and abundant communities of Oribatida mites, including numerous habitat specialists rarely found elsewhere. This study provides baseline knowledge on the diversity of Oribatida mites in Norwegian peatlands, offering a foundation for evaluating peatland degradation and guiding future restoration efforts. Norwegian peatlands were investigated between 2020 and 2023 as part of a project funded by the Norwegian Taxonomy Initiative. Samples of Sphagnum mosses were collected in Atlantic raised bogs—ecosystems that are rare and largely destroyed across Europe but remain relatively intact in many Norwegian regions, although they are increasingly threatened. Sampling was carried out in six peatlands in nearly pristine condition, located across southern, central, and northern Norway, providing a broad geographical representation. In addition to the newly collected material, historical specimens stored in the University Museum of Bergen were also examined. Oribatida mites occurred in very high abundances, averaging approximately 50,000 individuals per square meter, and strongly dominated the mite assemblages, accounting for about 97% of all specimens collected. Species richness was also high: in total, around 150 oribatid species were recorded, many of them restricted to peatland habitats. The material included 19 species newly recorded for Norway and three species new to science. Juvenile stages constituted nearly 40% of all oribatid specimens, highlighting the importance of including them in analyses to fully understand peatland diversity and ecological processes. The mite communities also showed clear vertical stratification within the Sphagnum layers, and more than 20% of the species were found exclusively in deeper layers. These findings emphasize that sampling deeper peat layers is essential for accurately assessing the full diversity of oribatid mites in peatland ecosystems.

Arctic ecosystems, such as those in Svalbard, are facing diverse stressors, being at the forefront of global warming while also facing increasing anthropogenic impacts. This poses a variety of threats to biodiversity, including soil microarthropod communities, which play a crucial role in the functioning of the Arctic ecosystems. Monitoring these groups in Svalbard is challenging due to limited baseline knowledge, logistically demanding and costly sampling, and the difficult and time‐consuming identification of soil microarthropod communities. In contrast, vegetation maps are relatively fast and easy to construct, often relying on remote sensing, and there are comprehensive vegetation maps available. These vegetation maps integrate numerous environmental characteristics into one vegetation community describing vegetation biodiversity. While relationships between soil microarthropod communities and vegetation communities have been documented in other regions, it remains unclear whether such patterns hold in the Arctic and whether existing vegetation maps could serve as proxies for soil microarthropod community composition and macroecology analyses. To address this question, we analyzed 172 soil samples collected from 33 localities across latitudinal and longitudinal gradients, representing 11 vegetation classes. In total, nearly 180,000 microarthropods were recorded, including approximately 63,000 Acari (87% Oribatida, 2% Mesostigmata, 10% Trombidiformes) and 116,000 Collembola. Oribatida and Mesostigmata were identified to family, while other groups were counted. Our analysis reveals that location is more important to soil microarthropod communities than vegetation community per se, indicating that these groups respond differently to local conditions. The variability of the Acari family abundances was mostly explained by Sørkapp, the southernmost and climatically harsh locality, followed by Fjortendejulibukta (northwestern Svalbard), which has a relatively mild climate but is subject to human disturbance. Locality also affected Oribatida diversity, mainly explained by Tjuvfjord in eastern Svalbard. At a larger scale, the approach of vegetation community classifications proved to be only weak proxies for the Acari and Collembola communities.

Global environmental change is altering the soils and ecosystems of polar regions, leading to significant consequences for microarthropods. Here, we report the invertebrate fauna from nests of Arctic – nesting light geese, and describe the invertebrate communities represented by these nests. The data are the first of their kind for Ross’s Geese (Anser rossii) and Lesser Snow Geese (A. caerulescens; hereafter, Snow Geese) and were collected in 1994 from 38 nests, at Karrak Lake, Nunavut. The number of individual invertebrates ranged widely in nests of both goose species, and there were no effects of habitat type on number of invertebrates found in the nests. The most common groups of invertebrates found, with 100% percentage occurrence in nests, were mites (Acari) and springtails (Collembola). Diptera (flies) were found in 94 – 95% of nests of both goose species, but no taxonomic level within Diptera was found in more than 50% of the nests. Among these groups, the number of individuals was highly variable among nests, with all three, on average, more numerous among Snow Goose nests. Acari 1 and Acari 2a (orb) were found in 89% of nests of both goose species, and Onychiurid 1 was found in 85% and 72% of Ross’s and Snow Goose nests, respectively. The Siphonapteran larva of Ceratophyllus vagabundus vagabundus were conspicuously more common in Snow Goose nests (78%) than Ross’s Goose nests (35%), with adults found in 44% and 25% of the goose nests, respectively. Other percent occurrences of operational taxonomic units generally were similar between the goose species. The number of individual invertebrates was independent of nest size, regardless of goose species. Our data are an important snapshot of past invertebrate communities and provide a baseline for future studies of microarthropods in the high Arctic.

The River Habitat Survey (RHS) is a method used to assess the condition of river channels and valleys by considering hydromorphological factors. It evaluates the degree of naturalness or anthropogenic alterations based on physical and landscape data. The study hypothesized that the quality of river habitats, as demonstrated by the RHS, should correlate with the composition of aquatic bugs (Heteroptera) fauna. The research was conducted in the River Krąpiel, a small lowland river in north-western Poland, across 6 sites and 43 sub-sites. Our analyses suggest that the RHS method can predict the composition and quality of aquatic bug fauna. Other indicators, such as the Habitat Quality Assessment (HQA) and the Riverine Habitat Quality Index (RHQI), are associated with different habitat types. Depending on the geographic location and river type, these indicators may reflect differences between habitats associated with the mainstream river and mineral substrates versus those covered by vegetation with relatively slow water flow. Linking the size and character of the river, RHS may be a good method for estimating the water bug fauna.

The family Brachychthoniidae was established by the Norwegian entomologist, Sig Thor. Studies on the Norwegian Brachychthoniidae started nearly 100 years ago in Svalbard where Thor found two species, including one new to science. Nowadays, 32 species and seven genera of Brachychthoniidae are known in Norway. One species, Brachychthonius laetepictus Berlese, 1910 has been considered species inquirenda and its taxonomic status needs to be clarified. Five species new to Norway are reported herein, including the smallest oribatid mite known from Norway, Sellnickochthonius cricoides (Weis-Fogh, 1948), the adults of which are only 135–165 µm long, and other species found during projects from the Norwegian Taxonomy Initiative [Brachychthonius impressus Moritz, 1976, Liochthonius evansi (Forsslund, 1958), S. honestus (Moritz, 1976)] and at the University Museum of Bergen [S. rostratus (Jacot, 1936)]; their distribution and ecology are presented. Based on the lists of Brachychthoniidae from Sweden and Finland, which include ten species and two genera unknown in Norway, we can expect more species of this family in Norway, but sampling from new areas and habitats is necessary.

The long-term persistence of obligate asexual lineages represents one of the most enduring and critical paradoxes in evolutionary biology. Sexual reproduction, through meiotic recombination and segregation, enables the efficient removal of deleterious mutations and facilitates rapid adaptation to shifting environmental pressures. Lineages that lose sex are therefore classically predicted to experience genomic decay and face rapid extinction. Oribatid mites (Acari, Sarcoptiformes) represent a unique system for testing these predictions, as they feature multiple, ancient, and independent transitions to asexuality, providing a natural experiment on the evolutionary fate of asexual genomes. We compared four sets of sister sexual and asexual species using high-quality nuclear genome assemblies to investigate the genomic consequences of long-term asexuality. Our study revealed a profound, reproductive-mode-dependent dichotomy in the evolution of genome architecture. Contrary to their expected genomic decay, asexual species have mostly streamlined genomes with less novel genes than their sexual sister species. In contrast, sexual species have acquired genetic innovations, encompassing both gene and transposable element content. These results challenge classical expectations of genomic deterioration in asexual species and might explain the long-term evolutionary persistence of oribatid mites.

To date, only adults of Zercon forsslundi have been known. According to the description of this species, it has been the first report of Zercon with clear differences in opisthonotal chaetotaxy between females and males, a unique character in the genus. At the same time, Z. forsslundi belongs to a unique group of Zercon species with dorsal setae J5 in females clearly longer than setae J1 – J4, the latter ones being short and of similar length. Our description is the first-ever report on the full morphological ontogeny of Z. forsslundi, the mite species, the adult which is the most similar to the recently described Zercon hamaricus and to a lesser extent to Zercon polonicus. The morphological closeness of the above-mentioned species has been confirmed in immature stages. We also studied the geographic distribution of Z. forsslundi and its above-mentioned congeners with remarks on their evolutionary affinity on the background of dispersal abilities and faunal dispersal after the Last Glacial Maximum. We also report the occurrence of Z. forsslundi and Z. hamaricus in the Northern Norway for the first time. Ranges of Z. forsslundi and Z. hamaricus overlap in the area of N Norway. Also, the microenvironmental sympatry was confirmed for these taxa. We also proved the niche overlap of these two species, which is probably limited to the northern verge of Eurasia. Zercon polonicus, not present in the current Arctic fauna, probably is a post-glacial relict, inhabiting more southern mountainous areas of Europe (Carpathians and Alps).

Arctic terrestrial invertebrate biodiversity is generally poorly known, but the archipelago of Svalbard has one of the most up-to-date inventories of its terrestrial and freshwater faunas of any Arctic region, offering a baseline for long term monitoring of invertebrate communities in space and time. Since the most recent review of the Svalbard invertebrate fauna was produced in 2014, knowledge of this fauna has developed and this inventory is here critically revised and updated. Our aims are (1) to critically review the inventory based on current taxonomic knowledge, (2) publish the complete species inventory, including cross-referencing to the relevant publications, in an open access data archive (GBIF), and (3) highlight the particular advantages that working in Svalbard may bring for scientists working on terrestrial, freshwater, and cryospheric environments. The inventory contains a total 1091 valid species names or interim names. A gap analysis in the Barcode of Life Data Systems reveals that 50% of the species currently documented from Svalbard lack COI (Cytochrome c oxidase subunit 1) barcode reference sequences in this database. Gaps in our knowledge of the Svalbard fauna and how these may be resolved are discussed.

The morphological ontogeny of Nothrus palustris C.L. Koch, 1839 is redescribed and illustrated. The morphology of this species has already been investigated in the last century, but these descriptions were either general or incomplete, and lack some cupules, lateral aspect of some instars, and leg setation, which are necessary for morphological comparisons. In the larva of N. palustris the bothridium is weakly developed and bothridial seta is short, whereas in the nymphs and adult the bothridium is well-developed, and bothridial seta is setiform and very long. In this species one pair of exobothridial setae is present. In all instars most prodorsal setae are short, with thickened ro and le in the larva, and ro, le, and in in the nymphs and adult. Most gastronotal setae are of medium size or short, except for long f1 and very long h 1 in the larva, and long h1 and very long h2 in the nymphs and adult. All setae are finely barbed in the larva, and smooth in the nymphs and adult, and they are usually covered with phylliform cerotegument. In all instars the femora are with reticulate ornamentation, and some leg setae (d, l, ft) are thickened and finely barbed, whereas the other setae are thin and smooth. Formulae of femoral setae (leg I–IV) are 7-7-4-3 in the deutonymph, 8-8-6-5 in the tritonymph, and 8/9-8-6-5 in the adult. The illustrations of N. palustris are supported by SEM images. We also summarised knowledge on the ecology and compared the molecular data (COI) of N. palustris from different locations, based on our own and public data.

The morphological ontogeny of Oribatula pannonica Willmann, 1949 is described and illustrated. Most prodorsal setae of juveniles are of medium size, and bothridial seta is clavate. The larva has 11 pairs of gastronotal setae, including h2, most are of medium size and barbed, nymphs have 13 pairs (p3 absent), of which most are short and smooth. Basal excentrosclerites are present at nine pairs of gastronotal setae (c1, c2, d-, l-series, h1) in the larva, and at 12 pairs (c1, c2, d-, l-, h-series, p1) in the nymphs. The morphology of adult O. pannonica is compared with congeners with 13 pairs or an unknown number of notogastral setae.