European Habitats Research Articles

Some wood-inhabiting Basidiomycota from the primeval forests with Pinus cembra in Ukraine

The Pinus cembra communities belong to the rarest and least studied woody habitats in Europe. This article reports 30 species of lignicolous Basidiomycota revealed in primeval spruce stands with the admixture of arolla pine in Gorgany Nature Reserve (the Ukrainian Carpathians). Five species, namely Aphanobasidium subnitens, Ceraceomyces eludens, Hyphoderma occidentale, Hypochnicium albostramineum and H. cremicolor, are firstly reported in Ukraine. The records of Cystostereum murrayi, Phellinus viticola and Pycnoporellus fulgens deserve particular attention due to their value as bioindicators of natural forest ecosystems. The species composition of Basidiomycota per individual fallen log turned out to be rather poor. The fungi forming thin resupinate corticioid basidiocarps on the substrate underside prevail among the finds, indicating a lack of moisture in the surveyed treeline stands. Detailed descriptions of the substrate and collection site are given for each find. An overview of previous research on the diversity of lignicolous Basidiomycota in arolla pine forests is provided.

Coastal Biodiversity Assessment Aided by Citizen Science Volunteers: A Look at the Italian Central Adriatic

Coastal ecosystems, encompassing land and marine environments and hosting substantial biodiversity, are among the most threatened worldwide. The European Habitats Directive prioritises coastal habitats and species, requiring legislative, direct protection, monitoring, and informational measures. Accurate habitat and species monitoring is crucial to conservation efforts, yet biodiversity research in complex, ever-changing environments like coastal areas is difficult. Citizen Science may bridge biodiversity assessment and eco-friendly monitoring by incorporating non-scientists into the data collection for scientists and stakeholders. A Citizen Science approach supported by a dedicated iNaturalist project (called Wild Coast CASCADE) was implemented to obtain a complete monitoring framework that includes observations of many taxa in terrestrial, aquatic, and transitional dynamic coastal environments in the Central Italian Adriatic coast. We explored data gathered focusing on the IUCN Red List species, the species and habitats of European conservation concern, and the non-native species. Between 2020 and 2023, we collected 3784 records covering 742 species, with 81% meeting the “research grade criteria”, and these were retained for subsequent research. Citizen Science volunteers have collected 291 georeferenced animal records from the global IUCN Red List, 51 plant species from 14 species that are indicators of the presence of habitats of European Conservation Concern, and 44 non-native plants and animals. Our results provide evidence that citizen research projects can effectively assist in monitoring coastal–marine habitats and species. They also underline the potential of Citizen Science for biodiversity conservation and emphasize the importance of public engagement in conservation efforts.

Over 200,000 kilometers of free-flowing river habitat in Europe is altered due to impoundments

European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats. Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions.

Phosphorus enrichment enabled Amorpha fruticosa to invade on the floodplain of the Tagliamento River, Italy

The North American nitrogen-fixing shrub Amorpha fruticosa (false indigo) is an aggressive invader of riverine habitats in Europe, though the reasons for its success are poorly understood. We hypothesized that its spread on the floodplain of the Tagliamento River in Northern Italy was enabled by anthropogenic phosphorus (P) enrichment. To investigate this hypothesis, we surveyed seed production at different locations along the river and performed a growth chamber experiment in which seedlings of three common floodplain shrubs (A. fruticosa, Salix eleagnos and Buddleja davidii) were grown at 10 levels of both nitrogen (N) and P. As a bioassay of N and P availabilities, we analyzed concentrations of these nutrients in Salix eleagnos leaves collected at different positions along the river. P availability was significantly higher in the lower reaches of the river, where A. fruticosa was abundant, than at its upstream limit. Numbers of A. fruticosa seeds per inflorescence increased strongly in a downstream direction and there was a trend for higher seed weight. In the growth experiment, A. fruticosa was more P-demanding than the other species, producing little biomass and no rhizobial nodules at low P. It also exhibited greater plasticity than the other species in both root mass fraction and ratio of longest root length to root mass. We conclude that anthropogenic P enrichment enabled A. fruticosa to invade what was originally a very oligotrophic environment. This N2-fixing shrub exhibits greater phenotypic plasticity than native S. eleagnos, giving it a competitive advantage under conditions of high P availability.

Review of the indexes to assess the ecological quality of coralligenous reefs: towards a unified approach

There is an urgent need to better understand the stressors, namely heatwaves, changes in thermohaline circulation and mucilage events, that are rapidly re-shaping bioconstructions, such as coralligenous assemblages. This calls for increased monitoring efforts in these invaluable habitats that will improve our understanding of the resistance and resilience of bioconstructions. Since 2009, 16 indexes have been designed to assess the ecological quality of Mediterranean coralligenous reefs. The main objective of this work is to propose a framework to support the development of a shared, cost-effective, and practical index to assess the status of the coralligenous biocenosis. To achieve this, studies conceiving these 16 indexes were reviewed: comparing their objectives, metrics, and applied methodologies. A standardized nomenclature of anthropogenic pressures is supplied, using, when possible, definitions from the European Habitat Directive, Marine Strategy Framework Directive and Water Framework Directive. Additionally, given the unprecedented climatic conditions, we highlight that a common index should give particular attention to the response of the coralligenous to thermal stress and mucilage. A list of priority anthropogenic pressures/environmental stressors and relative indicators and metrics are suggested. This review stresses the urgency to align the methodologies at basin scale and highlights the pros and cons of the preexisting indexes that must be considered in the design of a new, shared procedure to evaluate the status of coralligenous assemblages.

Applying molecular genetic data at different scales to support conservation assessment of European Habitats Directive listed species: A case study of Eurasian otter in Austria.

Evaluating intraspecific genetic structure and diversity is fundamental to assessing a species' conservation status, but direct incorporation of such information into legal frameworks such as the EU's Habitats Directive is surprisingly rare. How genetic structure aligns with EU member state boundaries or biogeographic regions may be very important in designing management plans or achieving legislative goals. The Eurasian fish otter experienced a sharp population decline during the 20th century but is currently re-expanding in several countries. The species is listed under Annex II and IV of the European Habitats Directive, and member states are obliged to assess the species separately across different biogeographic regions. We genotyped 2492 otter spraints across four provinces in Austria, collected between 2017 and 2021. A total of 384 different genotypes were identified, supporting densities along river habitats from 0.1 to 0.47 otters per river km (mean: 0.306), with a resampling-based simulation supporting limited density overestimation at survey lengths of 20 km or more. Three distinct genetic clusters were revealed, two of them presumably reflecting two relict populations whereas the source of the third cluster is unknown. The geographic extent of the three clusters does not coincide with provincial or biogeographic boundaries, both relevant for assessment and management within existing national or European legislative frameworks. We advocate more consideration of genetic structure in the assessment and conservation management planning of species listed in the European Habitats Directive.

Property rights and marine protected areas

Property rights in the marine environment differ from those on land and this difference has an impact on the legal framework for marine protected areas. The Site of Special Scientific Interest designation, which underpins terrestrial nature conservation in the UK, is only relevant at sea for intertidal sites and a few subtidal extensions. Legislation for Marine Nature Reserves, based on that for terrestrial National Nature Reserves, was unworkable because of government reluctance to designate sites in the face of stakeholder opposition. Regulations for the protection of European Marine Sites were made to implement the European Habitats Directive which covers very few marine habitats or species. The lacuna in legal protection was filled by the creation of the Marine Conservation Zone designation but the emphasis on features of particular value detracts from the objective of wider ecosystem protection. Protection for all types of marine protected areas is constrained by the need to consider the socio-economic consequences of regulation. The new pilot Highly Protected Marine Areas in England could tip the balance in favour of conservation but the rejection of two out of five candidate sites on the basis of the socio-economic concerns does not augur well for the future.

Soil fertility and landscape surrounding former arable fields drive the ecological resilience of Mediterranean dry grassland plant communities

IntroductionSemi-natural dry grasslands are among the species-richest and most diverse habitats in Europe especially in the Mediterranean Basin. They evolved with long-term severe environmental constraints, either biotic (e.g., grazing or mowing) or abiotic (e.g., dryness or oligotrophy). Their recovery after sever anthropogenic disturbance, such as cultivation is often very slow and incomplete. A deeper understanding of the processes driving the recovery would be of great benefit to better restore or conserve these grasslands. We used the filter model as a framework to assess the relative importance of dispersion, abiotic and biotic filters as drivers of this recovery.MethodsWe studied the medium-term dynamics of 37 Mediterranean dry grassland plant communities after an episode of cultivation in the plain of La Crau (Southern France) by two census: after 25 years of abandonment, and revisited 10 years later (35 years of abandonment). Our aims were to characterize the temporal medium-term dynamics of these communities, to measure their taxonomic resilience and to identify the drivers. We performed structural equation modeling to measure the importance of the various drivers, with cover of remnant dry grasslands surrounding each studied community as a proxy for the dispersion filter, soil pH and phosphorus content as proxies for the abiotic filter and cover of the most dominant species as a proxy for the biotic filter.Results and DiscussionOur results show that former arable field vegetation do not recover after more than 40 years. The three filters drive the recovery of dry grassland vegetation: former arable fields that have lower phosphorus content (abiotic filter) have a lower cover of dominant species (biotic filter), a higher species richness and a higher similarity with remnant dry grassland plant communities, especially if the former arable fields are surrounded by remnant dry grasslands (dispersion filter).

Catalogue of specimens of Rhysodes sulcatus (Fabricius, 1787) (Coleoptera, Carabidae) deposited in the State Museum of Natural History NASU, Lviv, Ukraine

Rhysodinae is a subfamily in the family Carabidae with 19 genera and at least 380 described species. Genus Rhysodes native to the Palearctic (including Europe) and the Near East. Rhysodes sulcatus (Fabricius, 1787) distributed in Central, Southern and Eastern Europe (Spain (Pyrenees), France, Italy, Germany, Austria, Hungary, Poland, Czechia, Slovakia, Romania, Bulgaria, countries of the former Yugoslavia, mountain part of Greece, Sweden, Turkey, Ukraine, Belarus and Russia), Asia Minor, the Caucasus and Western Siberia (Крыжановский, 1983; Sienkiewicz, 2004, 2012). The wrinkled bark beetle Rhysodes sulcatus (Fabricius, 1787) (Coleoptera, Carabidae) is an endangered saproxylic beetle listed in the European Habitats Directive (annex II of Council Directive 92/43/EEC), in the Bern Convention (Annex II) and is also listed in the IUCN red list of Threatened species (Nieto, Alexander, 2010; Méndez, Dodelin, Petrakis, Schlaghamersky, Nardi, 2010), classified as EN (Endangered) in the EU 27 and as DD (Data Deficient) for the whole continent. It is considered a relict of primeval forests and belongs among the most threatened saproxylic beetles in Europe (Мателешко, 2003, 2005; Kostanjsek, Sebek, Baranova, Jalaska, Riedl, Cizek, 2018; Mazzei, Audisio, Vigna Taglianti, Brandmayr, 2019). Included in the Red Data Book of Poland (Sienkiewicz, 2004). In the Red Data Book of Ukraine the species were listed in 2021 with vulnerable status (Наказ…, 2021). Before that the species were included in the Red Data Book of the Ukrainian Carpathians (Мателешко, 2011). At the regional level Rhysodes sulcatus (Fabricius, 1787) is protected in the Kharkiv oblast (province) (Різун, 2010). In Ukraine Rhysodes sulcatus (Fabricius, 1787) occurs in the Ukrainian Carpathians, in Polissia region, in the Kharkivska oblast (province) and in the Crimean Mountains. The analysis shows that the presence of the beetle is affected mainly by the diameter of dead wood as well as its humidity, as Rhysodes sulcatus (Fabricius, 1787) was almost exclusively found in large, moist and well rotten fallen logs with a diameter greater than 60 cm. The collection of the State Museum of Natural History, National Academy of Sciences in Lviv contains 12 specimens of this species. Five of them are collected in South-Eastern part of Poland, six in Western part of Ukraine and one has an undefined location. Ten specimens were collected in the period from the second half of the 19th century to 1939, and two beetles in 1987 (Poland) and 2016 in Lviv oblast (province) (Ukraine). Identified collectors were I. Verkhratskyi, ?M. Łomnicki, T. Trella, A. Stöckl, D. Kubisz, V. Rizun.

Sponge Fauna of the Apulian Marine Caves (Southern Italy): Current State of Knowledge

Submerged and semi-submerged marine caves are considered a European habitat of Community Interest as they preserve one of the most important biodiversity heritages in the Mediterranean and serve as refugia for endemic and/or “relict” species. Among sessile benthic taxa, caves represent significant reservoirs of sponge species richness and are well representative of the entire poriferan Mediterranean fauna. In order to assess the current knowledge of sponge species in marine caves along the Apulian coast, this study gathered data from the available literature (national and international scientific publications and grey literature) with original data, surveying 26 marine caves in the area. A total of 145 Porifera species were reported in marine caves on the Apulian coast, including 117 in the Tremiti archipelago, 33 along the Adriatic coast of Bari and 73 along the Salento Peninsula. Original data includes new records for nine species in the Corvine cave, two in the Murene cave and one in the Zinzulusa cave. Our results suggest that marine cave communities along the Apulian coast are not uniformly surveyed, being the caves of the Tremiti Islands and those of the Salento Peninsula among the best studied, while large stretches of the regional coast, although particularly rich in marine caves, are poorly investigated for their sponge fauna.

Drivers of variability in Blue Carbon stocks and burial rates across European estuarine habitats

The implementation of climate change mitigation strategies based on the conservation and restoration of Blue Carbon ecosystems requires a deep understanding of the magnitude and variability in organic carbon (Corg) storage across and within these ecosystems. This study explored the variability in soil Corg stocks and burial rates across and within intertidal estuarine habitats of the Atlantic European coast and its relation to biotic and abiotic drivers. A total of 136 soil cores were collected across saltmarshes located at different tidal zones (high marsh, N = 45; low marsh, N = 30), seagrass meadows (N = 17) and tidal flats (N = 44), and from the inner to the outer sections of five estuaries characterized by different basin land uses. Soil Corg stocks were higher in high-marsh communities (65 ± 3 Mg ha−1) than in low-marsh communities (38 ± 3 Mg ha−1), seagrass meadows (40 ± 5 Mg ha−1) and unvegetated tidal flats (46 ± 3 Mg ha−1) whereas Corg burial rates also tended to be higher in high marshes (62 ± 13 g m−2 y−1) compared to low marshes (43 ± 15 g m−2 y−1) and tidal flats (35 ± 9 g m−2 y−1). Soil Corg stocks and burial rates decreased from inner to outer estuarine sections in most estuaries reflecting the decrease in the river influence towards the estuary mouth. Higher soil Corg stocks were related to higher content of silt and clay and higher proportion of forest and natural land within the river basin, pointing at new opportunities for protecting coastal natural carbon sinks based on the conservation and restoration of upland ecosystems. Our study contributes to the global inventory of Blue Carbon by adding data from unexplored regions and habitats in Europe, and by identifying drivers of variability across and within estuaries.

Population Characteristics of Spirlin Alburnoides bipunctatus (Bloch, 1782) in Serbia (Central Balkans): Implications for Conservation

The aim of this study was to evaluate the population characteristics of spirlin, Alburnoides bipunctatus, in Serbia, since this small fish species is facing a severe decline in its abundance and its natural habitats in Europe. We investigated the spirlin population dynamics, including size, age structure, growth pattern, mortality, and exploitation rate. Additionally, we used the Uniform Manifold Approximation and Projection approach with the Decision Tree algorithm to investigate the influence of different environmental parameters on the population parameters to unveil which factors shape the abundance and distribution of spirlin. The results showed that the highest values of production, abundance, and biomass were estimated in sites with low temperature, optimal pH, and well-oxygenated water, even though we found them in heavily polluted waters with extremely high values of conductivity. Moreover, we observed a pattern of migratory behavior, in which spirlin migrate upstream to sites at a higher altitude in early summer and autumn. Despite the putative vulnerability and high sensitivity of spirlin populations, our results showed that the species was abundant, occurring in altered habitats (due to pollution, climate change, anthropogenic pressure, etc.).

Habitat suitability mapping of white stork Ciconia ciconia in one of its key European breeding areas

Due to rapid changes of the agricultural practice, the traditionally managed farmland became currently-one of the most endangered habitats in Europe. Species related to the rural landscape have been facing a great challenge of adaptation to quickly changing conditions. Therefore, recognizing and characterizing highly suitable areas for white storks is very important to plan conservation measures in the era of changes in agriculture and land use. Here, combining nest survey data (811 occupied nest), GIS-data on habitat availability and modelling approach, we characterize the current foraging conditions of the white stork Ciconia ciconia, an indicator of the agricultural habitat biodiversity and an umbrella species for organisms associated with agriculture landscape. The studied population breeds in the Warmińska Refuge Natura 2000 site (N Poland), one of the key breeding areas of this species in Europe. Breeding pair presence was predicted by the area of pasture, meadows, field ponds, and linear water within a 1 km buffer around the nest. The main hotspots of habitat suitability were located in the central and western parts of the study area, characterized by a more traditional model of agriculture. The distance to important foraging habitats does not influence white stork fecundity indicating that landscape composition is important when choosing the breeding site. The pairs with higher number of young were located further from other neighbouring pairs and at the areas with lower density of pairs in general. This is probably linked to the lower competition for food between more distant breeding pairs. Our results show that the traditional agricultural use in mosaics of pastures, meadows and aquatic habitats promotes white storks nesting.

Protected habitats support bats in Mediterranean dry grasslands

The replacement of natural habitats by urbanization and agricultural land reclamation is one of the main drivers of biodiversity loss. Among European habitat types, natural grasslands are particularly prone to anthropogenic pressures, being also recognized as conservation priorities within the Habitats Directive. Nonetheless, little is known on the relationship between grasslands, their conservation quality, and most animals' taxa that may rely upon them. Here we focus on the role of Mediterranean dry grasslands protected by the EU legislation in sustaining bat populations, setting our study in the biodiversity hotspot of Mediterranean Italy. By conducting acoustic surveillance at 48 sites within a protected area devoted to conserve natural and semi-natural grasslands, we found that all the bat species found in the area are regular exploiters of such open environments. Grassland conservation quality, in terms of extent of high-diversity protected habitats, was the key factor shaping the use of grasslands by bats of all the considered guilds, together with several terrain and landscape features, which showed more guild-specific effects. Moreover, our results indicate that bat assemblages are functionally shifted along an ecological gradient from highly modified to well-conserved grassland sites, indicating a prevalence of opportunistic taxa in the former, and higher abundance of species of conservation concern in the latter. Overall, we demonstrate that the effects of EU-listed habitats may extend also onto bats in the case of Mediterranean dry grasslands, highlighting the importance of preserving such habitats as a tool for conserving highly mobile species.

Biological Flora of Britain and Ireland: Liparis loeselii

Abstract This account presents information on all aspects of the biology of Liparis loeselii (L.) Rich. (Fen Orchid) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of Britain and Ireland: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, and history and conservation. Liparis loeselii is a small terrestrial orchid that has a circumboreal distribution and is widespread in Europe and North America. Despite its wide distribution, the species is locally rare and has declined considerably in most of its range. In Britain, the species has a disjunct distribution and is now known to occur consistently at only six sites in eastern England and three in south Wales. It is absent from Ireland. Its most characteristic habitats in Britain are inland fens and coastal dune slacks, but outside Britain it can also be found in wet meadows, marshes, forested seep springs, at lake borders or on mats of floating peat. Populations of Liparis loeselii in dune slacks tend to be short‐lived, and can rapidly increase in size or decrease and disappear as environmental conditions change. The species does not tolerate high nutrient concentrations or low pH. It is susceptible to drought, which reduces seed germination, seedling recruitment and adult survival. Heavy predation by rabbits and rodents has been observed under drought conditions. Liparis loeselii reproduces both by sexual reproduction, and by vegetative propagation through the production of pseudobulbs. Although flowers are accessible to insects, entomophilous pollination is unusual, and most sexual reproduction is the result of selfing. Fruits ripen late in the growing season (mid‐October) and the dust‐like seeds are dispersed during winter by wind and water. Germination occurs during the following growing season and is supported by a wide variety of mycorrhizal fungi. Since the late 19th century Liparis loeselii has declined considerably in Britain and elsewhere in Europe, primarily due to habitat destruction and loss, natural succession, and habitat desiccation due to drainage. As a result, the species has been listed as endangered in the Bern Convention and the European Habitat Directive (92/43/EEC) and is the focus of intensive conservation efforts in many countries. Restoration of habitat by mowing, extensive grazing and peat removal, and the creation of new habitat by dune slack formation in dune systems and peat removal in fens may prolong population persistence and promote establishment of new populations.

European Habitats Directive has fostered monitoring but not prevented species declines

AbstractStrong biodiversity declines have been reported across the European Union, especially in insects, despite conservation policy such as the Habitats Directive that aims to halt biodiversity loss. Using 50 years of observational data, we examined indicators for the goals of the Directive in terms of improving monitoring efforts and occupancy trends of butterfly and dragonfly annex species in a central European region. We quantified annual monitoring effort and used occupancy‐detection models to compare species trends for 18 years before and after legal implementation of the Directive. Monitoring efforts increased after implementation, while occupancy trends both improved and deteriorated. Contrary to its main goal, the European Habitats Directive did not prevent a worsening of all annex species’ occupancy trends in the studied region. While the increased monitoring efforts aid biodiversity assessments, more serious broad‐scale conservation measures are needed to halt biodiversity loss across Europe.

Natura 2000 Grassland Habitats Mapping Based on Spectro-Temporal Dimension of Sentinel-2 Images with Machine Learning

Habitat mapping is essential for the management and monitoring of Natura 2000 sites. Time-consuming field surveys are still the most frequently used solution for the implementation of the European Habitats Directive, but the use of remote sensing tools for this is becoming more common. The high temporal resolution of Sentinel-2 data, registering the visible, near, and shortwave infrared ranges of the electromagnetic spectrum, makes them valuable material in this context. In this study, we aimed to use multitemporal Sentinel-2 data for mapping three grassland Natura 2000 habitats in Poland. We performed the classification based on spectro-temporal features extracted from data collected from eight different terms within the year 2017 using Convolutional Neural Networks (CNNs), and we also tested other widely used machine learning algorithms for comparison, such as Random Forests (RFs) and Support Vector Machines (SVMs). Based on ground truth data, we randomly selected training and validation polygons and then performed the evaluation iteratively (100 times). The best resulting median F1 accuracies that we obtained for habitats were as follows: 6210, 0.85; 6410, 0.80; and 6510, 0.84 (with SVM). Finally, we concluded that the accuracy of the results was comparable, but we obtained the best results using SVM (median OA = 88%, with 86% for RF and 84% for CNNs). In this work, we confirmed the usefulness of the spectral dimension of Sentinel-2 time series data for mapping grassland habitats, and researchers of future work can further develop the use of CNNs for this purpose.

Climate-trait relationships exhibit strong habitat specificity in plant communities across Europe

Ecological theory predicts close relationships between macroclimate and functional traits. Yet, global climatic gradients correlate only weakly with the trait composition of local plant communities, suggesting that important factors have been ignored. Here, we investigate the consistency of climate-trait relationships for plant communities in European habitats. Assuming that local factors are better accounted for in more narrowly defined habitats, we assigned > 300,000 vegetation plots to hierarchically classified habitats and modelled the effects of climate on the community-weighted means of four key functional traits using generalized additive models. We found that the predictive power of climate increased from broadly to narrowly defined habitats for specific leaf area and root length, but not for plant height and seed mass. Although macroclimate generally predicted the distribution of all traits, its effects varied, with habitat-specificity increasing toward more narrowly defined habitats. We conclude that macroclimate is an important determinant of terrestrial plant communities, but future predictions of climatic effects must consider how habitats are defined.

Current Distribution and Conservation Issues of Aquatic Plant Species Protected under Habitats Directive in Lithuania

The European Habitats Directive was adopted to halt the rapid loss of biodiversity and has become an important instrument for protecting biodiversity in the European Union. Three aquatic plant species protected under the European Habitats Directive have so far been found in Lithuania: Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis. Our aim in this study was to evaluate the former and current distribution and the status of conservation of the target species. Screening for the above-mentioned protected aquatic plant species was performed in 73 natural lakes throughout Lithuania in 2019–2021. We confirmed extant populations of Aldrovanda vesiculosa in four lakes, Caldesia parnassifolia in two lakes, and Najas flexilis in four lakes in the northeastern part of the country. We studied Aldrovanda vesiculosa populations three times (2015, 2019, and 2022) in Lake Rūžas and once each in Lake Apvardai and Lake Dysnai (2020). The population density of Aldrovanda vesiculosa ranged from 193.4 ± 159.7 to 224.0 ± 211.0 individuals/m2, the mean length of plants ranged from 12.5 ± 2.1 to 14.3 ± 2.7 cm, and the mean number of apices ranged from 2.0 ± 0.7 to 2.2 ± 0.9 per individual. The habitat of Aldrovanda vesiculosa in Lake Rūžas covered an area of about 3 ha. The number of generative individuals of Caldesia parnassifolia widely varied between years in Lake Rūžas. All populations of Najas flexilis were small, although the potential habitats in the studied lakes cover relatively large areas. We propose designating all lakes with populations of Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis as special areas of conservation, as well as developing and implementing action plans for the conservation of these species and their habitats.

Parasites and their impact on thick-shelled river mussels Unio crassus from two populations in Luxembourg.

The thick-shelled river mussel Unio crassus Philipsson, 1788 is a species native to many European habitats, with declining populations. The impact of parasite communities on health status of this species is poorly understood. In this study, parasites of 30 U. crassus specimens from the Our and Sauer Rivers in Luxembourg were identified morphologically and, in some cases, using molecular genetic methods. The findings were correlated to selected parameters (total length, visceral weight, shell lesions, gonadal stage). The 2 populations did not differ in shell length, visceral weight, number of males and females, gonadal scoring, shell lesions, and the occurrence of glochidia. The prevalence and infestation intensities of detected Trichodina sp., Conchophthirus sp., and freshwater mite larvae did not differ between the 2 populations, whereas the prevalence and infestation intensities of mite eggs, nymphs, and adults were significantly higher in the Sauer River. Rhipidocotyle campanula and European bitterling Rhodeus amarus larvae were only present in the Sauer. Histopathology revealed the destruction of the gonads by R. campanula and tissue damage by the mites. The only significant correlation of the selected parameters was a positive correlation between R. amarus occurrence and total length as well as a negative correlation between R. amarus occurrence and gonadal stage. In the Sauer River, 2 mussels were found to be hermaphrodites.