Baltic Sea genetic biodiversity: Current knowledge relating to conservation management

1. The Baltic Sea has a rare type of brackish water environment which harbours unique genetic lineages of many species. The area is highly influenced by anthropogenic activities and is affected by eutrophication, climate change, habitat modifications, fishing and stocking. Effective genetic management of species in the Baltic Sea is highly warranted in order to maximize their potential for survival, but shortcomings in this respect have been documented. Lack of knowledge is one reason managers give for why they do not regard genetic diversity in management.
2. Here, the current knowledge of population genetic patterns of species in the Baltic Sea is reviewed and summarized with special focus on how the information can be used in management. The extent to which marine protected areas (MPAs) protect genetic diversity is also investigated in a case study of four key species.
3. Sixty‐one species have been studied genetically in the Baltic Sea, but comprehensive genetic information exists for only seven of them. Genetic monitoring shows genetic stability in some species but fluctuations and genetic changes in others. About half of the scientific studies published during the last 6 years provide conservation advice, indicating a high interest in the scientific community for relating results to practical management.
4. Populations in MPAs do not differ genetically from populations outside MPAs, indicating that MPAs in the Baltic Sea do not protect genetic diversity specifically, but that populations in MPAs are a representative subset of populations in the Baltic Sea.
5. Recommendations are provided for cases where genetic information is available but not used in management, particularly for non‐commercial species with important ecosystem function.
6. Improved channels for effective communication between academia and practical management on Baltic Sea genetic biodiversity are needed. A web page that can be used for knowledge transfer is highlighted here.

     

Habitats for the Atlantic sturgeons in Russia

1. The critically endangered Atlantic sturgeon, Acipenser sturio, inhabited the Russian section of the Baltic Sea basin until recent times. Eight rivers were indicated as their habitats in local literature.
2. The Atlantic surgeon disappeared in Russia because of overfishing, not because of habitat loss.
3. Nowadays, potential spawning grounds for sturgeons occur in six rivers of the Russian section of the Baltic Sea basin. The largest river (Neva) is not blocked by dams and the whole river provides the ecological requirements of sturgeons on a stretch 75 km long.
4. Restocking of other sturgeon species in Russia demonstrated that the release of reared fishes into the sea is ineffective, whereas the release into rivers could result in successful acclimatization.
5. Recent climatic changes are rather favourable for sturgeon restocking in the Baltic Sea area. The main problem for the restoration of sturgeon populations is the intensive fishery.

     

Niche‐based species distribution models and conservation planning for endangered freshwater crayfish in south‐western Germany

1. Niche‐based species distribution models (SDMs) can help conservation planning by forecasting environmental suitability for an endangered species. Here, SDMs were constructed for stone crayfish (Austropotamobius torrentium) and white‐clawed crayfish (Austropotamobius pallipes s. str.) to identify catchments in south‐western Germany where environmental conditions are favourable for reintroduction.
2. Maximum‐entropy modelling (Maxent) was used with presence‐only data to forecast environmental suitability for the two crayfish species based on five climate variables, slope, land cover, and a human impact index.
3. SDMs showed good to excellent performance and were able to capture the range of both Austropotamobius species. Presence probabilities were mostly determined by climate variables, and climate niches partly overlap, with white‐clawed crayfish occurring at conditions with less extreme winter temperatures and lower temperature seasonality than stone crayfish. Human impact contributed between 10 and 27% to the models and was negatively related to presence probabilities. Contribution of land cover was low (5%) but showed a positive relationship with deciduous broadleaf forest in both species.
4. Both SDMs indicated several catchments with high predicted environmental suitability but no present occurrence records. Subsequent crayfish and habitat surveys in these catchments revealed four streams considered suitable for reintroduction and led to discovery of five previously unknown white‐clawed crayfish populations. Overall, SDMs proved to be a powerful tool for conservation planning of freshwater crayfish species.

     

A critical reflection on the success of rearing and culturing juvenile freshwater mussels with a focus on the endangered freshwater pearl mussel (Margaritifera margaritifera L.)

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The relationship between water quality and indigenous and alien crayfish distribution in the Czech Republic: patterns and conservation implications

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Genetic population structure of pike (Esox lucius Linnaeus, 1758) in the brackish lagoons of the southern Baltic Sea

The Baltic Sea is a unique ecosystem and the largest body of brackish water in the world. It is inhabited by several originally freshwater fish species, one of them being pike (Esox lucius), which is adapted to the mesohaline conditions of the southern Baltic Sea and colonises its south‐western bays and lagoons. Using twelve microsatellite markers, we analysed the genetic structure of 407 Baltic Sea pike collected from ten locations in the coastal zone of the southern Baltic region and adjacent rivers and nearby lakes. We used traditional F‐statistics and a Bayesian approach implemented in STRUCTURE to investigate spatial structuring. Our results show an overall isolation by distance pattern with two distinct coastal clusters. The border area between the two clusters is characterised by a sharp salinity leap, indicating that the dispersal barrier is not physical, but physiological in nature. A third cluster was formed by three lake populations, presumably as a result of past stocking measures. Additional otolith microchemical studies demonstrate the brackish origin and residency of the majority of the pike from the coastal lagoons, supporting previous studies which suggest that the anadromous pike “ecotype” is scarce in this area of the Baltic Sea. Our results contribute to current knowledge on the population genetics of Baltic Sea pike in a previously unsampled area.     

Insights into population genetics,connectivity and demographic history of the longnosed skate Dipturus oxyrinchus (Linnaeus, 1758) in the western Mediterranean Sea

1. Genetic information is crucial for the conservation of Dipturus oxyrinchus (Linnaeus, 1758), a threatened large skate with declining populations over most of its geographical range. The main aim of the present study was to investigate the genetic structure, connectivity and demographic history of the longnosed skate in Sardinia (western Mediterranean Sea).
2. Patterns of population structure were assessed in 175 specimens from six sampling sites. Variation in two mitochondrial genes (cytochrome c oxidase subunit I (COI) and control region) highlighted high genetic diversity and low but significant genetic differentiation among sites, which clustered into three groups corresponding to the north‐west, north‐east and south Sardinian coasts.
3. The observed genetic structuring could presumably depend on a combination of past geological events, contemporary restrictions to dispersal and biological characteristics of the species (e.g. site‐fidelity, no pelagic larval stage, limited dispersal of juveniles and/or adults).
4. Demographic analyses showed signs of past population expansion, but substantial current stability of Sardinian populations. From a conservation perspective, these results are encouraging, and indicate that Sardinian populations are still large and stable, and seem not to have suffered negative side‐effects from the ever‐growing fishing pressure in the region.
5. The occurrence of genetic structuring strongly supported the close monitoring of populations to identify any erosion of their gene pool, and high genetic variability of the Sardinian D. oxyrinchus populations could thus represent priority populations for conservation purposes, providing potential sources for recolonization in cases of local extinctions in other areas of the distribution range of the species.
6. When the sequences from Sardinia were compared with those available from other areas, the data seem to exclude the possibility that the Atlantic and Mediterranean host totally isolated populations or even different species, as recently suggested. However, additional markers and a larger sampling sites are needed to confirm these findings.

     

Genetic structure of Spanish white‐clawed crayfish (Austropotamobius pallipes) populations as determined by RAPD analysis: reasons for optimism

• 1. Spanish populations of the white‐clawed crayfish have declined sharply over the last three decades. Although Austropotamobius pallipes was once widely distributed and very abundant in most of the limestone basins of the country, outbreaks of crayfish plague since 1978 have reduced its populations, and now only some 500–600 small populations are left.
• 2. Consequently, the species now enjoys protection under national legislation. Management decisions regarding the conservation of a threatened species require an understanding of the genetic structure of its populations.
• 3. Using random amplified polymorphic DNA (RAPD) fingerprinting the genetic variability of 11 populations of A. pallipes was assessed over the species' range in Spain, and their phylogenetic relationships determined.
• 4. Substantial genetic differentiation was detected among the populations tested; no clear relationship was found between patterns of genetic variability and hydrological basin. The RAPD markers showed the degree of genetic variability of these populations to be similar to, and in some cases slightly higher than, that reported in previous studies on other Spanish and European populations of A. pallipes.
• 5. The results offer hope for the recovery of this species in Spain, and provide information that might be useful in the management of crayfish reintroduction programmes.

Copyright © 2007 John Wiley & Sons, Ltd.     

Going,going, gone? Loss of genetic diversity in two critically endangered Australian freshwater fishes,Scaturiginichthys vermeilipinnis and Chlamydogobius squamigenus,from Great Artesian Basin springs at Edgbaston,Queensland, Australia

1. Artesian springs are particularly sensitive freshwater ecosystems, characterized by specialized flora and fauna which, owing to their isolation, are often endemic. Thus, protection of spring habitats and endemic spring biota is important for biodiversity conservation, particularly because human impacts such as invasive species, habitat destruction, and fragmentation can have such devastating effects.
2. This study investigated the mitochondrial DNA (mtDNA) genetic diversity and structure of two critically endangered (IUCN) freshwater fish species: red‐finned blue‐eye Scaturiginichthys vermeilipinnis, and Edgbaston goby Chlamydogobius squamigenus, with the aim of assisting management agencies to establish relocated populations that conserve the genetic integrity and evolutionary potential of both species.
3. 2862 bp from multiple mtDNA genes were amplified from 111 red‐finned blue‐eye individuals (17 from the 1990s and 94 from 2010), and a 660 bp segment of mtDNA cytochrome b was amplified from 111 Edgbaston goby individuals (from 2010). In total, 14 concatenated mtDNA haplotypes were identified in red‐finned blue‐eye and three cytb haplotypes were identified in Edgbaston goby.
4. Overall assessment of the genetic diversity and structure of the endemic fish fauna from the Edgbaston springs revealed low levels of diversity in both species and a loss of haplotypes in red‐finned blue‐eye over time. In addition, both species displayed significant genetic structure: at the spring scale for red‐finned blue‐eye and at the spring group scale for Edgbaston goby. It is concluded that without the appropriate management of relocated populations, such as considering genetic structure and diversity and selecting high quality habitats, these species are at a severe risk of losing evolutionary potential and becoming extinct. This study provides a valuable example for conservation managers of the contribution that population genetic studies can make regarding the adaptive management of endangered species.

Copyright © 2016 John Wiley & Sons, Ltd.     

The potential exceptional role of a small Baltic boulder reef as a solitary habitat in a sea of mud

1. In this study, non‐destructive seafloor imaging techniques were employed to assess the benthic community structure of a recently discovered boulder reef within the central Arkona Basin of the Baltic Sea.
2. Data indicate that geographical isolation, water column stratification and temporary oxygen deficiency create an exceptional reef habitat in a sea of mud.
3. The reef forms a saline refuge for the deepest and easternmost known population of the plumose sea anemones (Metridium dianthus Ellis, 1768) in the Baltic Sea.
4. Limited connectivity to other reefs and dominance of the aggressively colonizing and planktivorous M. dianthus hamper the recruitment of other species and lead to an overall low invertebrate richness.
5. Large boulders attract ecologically and economically important fish like Baltic cod (Gadus morhua Linnaeus, 1758) that find shelter in the otherwise heavily fished Arkona Basin.
6. Despite this very first exploration being only a snapshot of the observed community, findings imply a potential conservation importance of this Germany's deepest known natural habitat type 1170 (‘reefs’).

     

Crayfish in central and southern Ukraine with special focus on populations of indigenous crayfish Astacus pachypus (Rathke, 1837) and their conservation needs

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Single nucleotide polymorphisms found in the red alga Furcellaria lumbricalis (Gigartinales): new markers for population and conservation genetic analyses

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Management of a highly unlikely native fish: The case of arctic charr Salvelinus alpinus from the Southern Alps

1. As a result of ancient introductions, some alien species are erroneously considered native. Salvelinus alpinus (Linnaeus, 1758) is hypothesized to have survived as a postglacial relic in the northern European Alps, although documented ancient introductions contradict its native status in a few mountain lakes from the southern Alps (Trentino Alto Adige, Italy). Regardless of its uncertain origin, its recent expansion across the southern Alps (introduced into >170, mainly originally fishless, high‐altitude lakes) was the result of management and alleged conservation actions.
2. The present study is a review of the origin of S. alpinus in the southern Alps, and of the appropriateness of management and conservation actions.
3. The autochthony of S. alpinus in this region is rejected by multiple lines of evidence and its presence is most likely the result of historical introductions. Only the origin of two populations occurring at lower altitude is uncertain, as they may be native.
4. Residual uncertainty makes it difficult to evaluate the conservation status and value of the Italian populations of S. alpinus, but it does not prevent the highlighting of several errors in the past and the present management of this species.
5. Past and present introductions have altered the original genetics of the ancient populations and have contributed to the invasion of montane aquatic habitats by modern domestic fish. Although it is now timely to consider the adverse ecological consequences of fish stocking, the many introductions of S. alpinus are associated with a misleading conservation rhetoric, providing ambiguous educational messages to people and relevant stakeholders, and probably diverting resources intended for biodiversity conservation.
6. A non‐intervention approach (i.e. not to stock or fish S. alpinus) would have been the wiser strategy to preserve ancient populations, their supposed conservation value, and their actual cultural value. Even now, this strategy is probably the best option, while planning definitive research.

     

Population genetic divergence of bonnethead sharks Sphyrna tiburo in the western North Atlantic: Implications for conservation

1. Sharks are a priority for conservation because numerous species, including small-sized coastal species, are being heavily exploited by commercial and recreational fisheries. Understanding the genetic population structure of sharks is key to effective management, maximizing their evolutionary potential in a rapidly changing environment and preventing population declines.
2. Limited dispersal is an important factor promoting population divergence for several coastal shark species. The genetic variation in 14 microsatellite loci and 21,006 single nucleotide polymorphisms genotyped using restriction-site-associated DNA sequencing was analysed to assess the genetic structure of the bonnethead shark, Sphyrna tiburo, in the western North Atlantic.
3. Genetic differences were identified among three well-defined regions: the western Florida coast, the south-eastern US Atlantic coast, and the southern Gulf of Mexico. Results support previous studies based on mitochondrial DNA sequences in defining differences among these regions and suggest limitations of bonnethead sharks in routinely performing long-distance migrations.
4. The limited connectivity among regions explains the pattern of genetic divergence but also reported divergence at the species/subspecies level. These genetically discrete bonnethead populations have independent evolutionary histories that may include local adaptations to specific areas.
5. Bonnethead sharks are currently managed as two stocks in the USA owing to recent genetic, tagging, and life history studies; however, no stock assessments or management plans exist for Mexico. These results not only serve to reinforce US management strategies and provide critical data about the extent of gene flow and sex dispersal among populations, but also begin the process of effective management in the waters of Mexico to ensure the long-term productivity and resilience of this species. With an absence of gene flow between populations from US waters and the southern Gulf of Mexico, there is a need for management plans based upon independent biological and population dynamics data since limited or no opportunities for populations to interchange individuals may occur to re-establish population viability.

     

On sightings of (vagrant?) monk seals,Monachus monachus,in the Mediterranean Basin and their importance for the conservation of the species

1. In ancient times, the distribution range of the Mediterranean monk seal (Monachus monachus) extended all over the coasts of the Mediterranean, the Black Sea and parts of the north‐eastern Atlantic coast.
2. Nowadays, the species is classified as Endangered and the current total world population is stated to consist of ~700 animals, though numbers mostly express best estimates. Distribution patterns in documents of international authorities from the last 15 years indicate the species' extinction in a number of Mediterranean countries, whereas in some of them only a few individuals are thought to survive and in others the status is unknown.
3. This study analyses recent monk seal sightings over the period from 2000 to 2014 in the Mediterranean Basin. The locations of the sightings cover most of the study area and indicate a spreading of individual seals or a more stable presence in regions where the species was considered extinct.
4. The investigation pointed out that efforts for the protection of monk seals, the most endangered marine mammal in Europe, should encompass all areas where monk seal sightings have been recorded, including the protection and conservation of potential suitable habitats in countries where the species apparently no longer exists.
5. Appropriate conservation measures, such as the establishment of marine protected areas and sustainable management of fisheries, will aid natural recolonization and enhance gene flow between distant regions throughout the Mediterranean Basin, allowing the reconnection of distant populations or individual animals.

     

Population structure,genetic diversity,and colonization history of the eastern pondmussel,Sagittunio nasutus,in the Great Lakes drainage

1. The eastern pondmussel, Sagittunio nasutus (Bivalvia: Unionida), has declined in abundance and distribution in eastern North America over the last few decades. The declines are predominantly the result of infestation by invasive dreissenid mussels and changes in habitat. The species is now considered imperilled across large portions of its distribution, especially in the Laurentian Great Lakes region.
2. The genetic diversity and structure of the remnant populations in the Great Lakes region were assessed using 10 newly developed microsatellite DNA loci for S. nasutus. Understanding the remaining populations can inform future management projects and determine whether the remnant populations have experienced a genetic bottleneck or a founder effect. We hope that this will inform the conservation of other species in regions founded by, and isolated from, a more genetically diverse source population or with disjointed geographical distributions.
3. Focusing on the Great Lakes region, samples (n = 428) from 62 collection sites in 28 water bodies were collected. Across the locations sampled for S. nasutus 11 genetic populations were identified, with significant genetic differentiation among them. The genetic structure of the species was assessed, with genetic similarities among populations compared and with geographical routes of colonization and gene flow evaluated.
4. Initial colonization from the Atlantic coast into Lake Erie and Lake Ontario is evident, followed by colonization events into nearby inland rivers and lakes. Analyses found evidence of inbreeding in all but one population and evidence of past genetic bottlenecks or strong founder effects in all but four populations. This study deepens our understanding of the genetic past and present of this imperilled species, providing conservation suggestions for the future management of the species.

     

Reintroduction of a dioecious aquatic macrophyte (Stratiotes aloides L.) regionally extinct in the wild. Interesting answers from genetics

1. The reintroduction of a plant species regionally extinct in the wild poses a stimulating conservation challenge. If the species is dioecious and the ex situ preserved population is only of one sex, the challenge is even more difficult. To assess whether the female population of Stratiotes aloides originally studied requires a reinforcement to increase its genetic variation, and to determine from which source male individuals should be taken to re‐establish a viable population, the genetic structure of nine different accessions of S. aloides across Europe and Asia were analysed – six native populations and the last three Italian populations, preserved ex situ.
2. Amplified fragment length polymorphism (AFLP) fingerprinting of 190 individuals from these populations was performed using six primer combinations and chromosome counts.
3. AFLP markers revealed medium to high values of genetic diversity at the population level, unexpectedly including residual ex situ accessions. Neighbour‐joining tree, PCoA and STRUCTURE analyses indicate the presence of three genetic patterns identifiable in the central‐western, central and eastern Europe–Asian populations. Chromosome counts revealed the presence of diploid (2n = 24) and tetraploid (2n = 48) populations.
4. Similarity between populations belonging to different hydrographical basins, and differences between neighbouring populations could be explained through long‐distance bird‐mediated dispersal events. Genetic analysis showed that reinforcement with female individuals from other European populations to increase the genetic diversity of the Italian female population is not necessary. Surprisingly, the geographically closest male population (Bavaria) to the Po basin is not the best option for male reintroduction. Instead, male individuals should be reintroduced from the Rhine basin (Netherlands) and eastern part of the Danube basin (Romania).

Copyright © 2016 John Wiley & Sons, Ltd.     

Gene pool and connectivity patterns of Pinna nobilis in the Balearic Islands (Spain,Western Mediterranean Sea): Implications for its conservation through restocking

1. Pinna nobilis is an endemic bivalve of the Mediterranean Sea, and a vulnerable species registered as endangered and protected under the European Council Directive 92/43/EEC and Barcelona Convention.
2. In early autumn 2016, a mass mortality event impacted P. nobilis populations in the south‐western Mediterranean Sea, including the Balearic Islands. At the time of this study, P. nobilis still maintained high population densities along the Balearic coasts (Western Mediterranean).
3. This study evaluated the connectivity of P. nobilis post‐larvae and adults in seagrass habitats around the Balearic Islands and identified its source and sink populations. These objectives were reached through a multidisciplinary approach including population genetics (10 microsatellites) and hydrodynamic modelling.
4. High genetic diversity was found and significant genetic differentiation (inferred by fixation index F_ST) was detected between post‐larvae samples, but not between adult populations. Significant genic and genotypic differentiation was recorded for adults and post‐larvae.
5. This pattern was confirmed by correspondence analysis using allele frequencies. The genetic connectivity pattern was consistent with marine currents and dispersal models.
6. This work not only improves knowledge of the P. nobilis gene pool in south‐west Mediterranean populations and their connectivity patterns, but is also crucial to help evaluate the possibility of recovery from source populations and the possibility of restocking programmes, as well as provide a solid base to establish effective marine reserve networks.

     

Modelling effects of invasive species and drought on crayfish extinction risk and population dynamics

1. Hydrological alteration, which may be exacerbated by climate change, is known to facilitate aquatic species invasion. Altered hydrology, invasive species, and the additive effects of these stressors pose a threat to aquatic biodiversity.
2. Understanding extinction risk in the context of these stressors is crucial for prioritizing conservation efforts. As case studies, three narrow‐ranged endemic crayfish species of conservation concern (Faxonius marchandi, Faxonius roberti, and Cambarus hubbsi) in the Ozark Highlands of Arkansas and Missouri, USA, were used to examine the effects of invasive species and drought on crayfish population dynamics.
3. The objectives of this study were to model the population dynamics of these imperilled species, assess how these populations may be affected under increased invasion effects and intensified drought, determine potential refuge effects, and examine the sensitivity of quasi‐extinction to model parameters.
4. ramas‐metapop was used to construct stage‐based demographic models. Terminal extinction risk, median time to quasi‐extinction, and metapopulation occupancy were used to assess population viability under different scenarios.
5. Cambarus hubbsi appears to be highly susceptible to decline if survival rates are reduced by simulated drought, as they have low reproductive potential and mature slowly. Models indicated that potential refuges allow F. roberti and C. hubbsi to persist, even when invasion and drought effects were extreme. Conversely, barriers to dispersal for F. marchandi led to reduced quasi‐extinction times and the greatest extinction risk under most invasion scenarios. Quasi‐extinction was most sensitive to changes in juvenile survival for all species examined, which indicates that improved estimates of stage‐specific demographic parameters for crayfish will improve model predictions.
6. An increased understanding of the mechanisms of displacement of native crayfish by invasive crayfish is needed for most crayfish species. Limiting the spread of invasive species, maintaining natural habitat and hydrological regimes, and gaining insight into life histories and demographic parameters will increase the ability to conserve endemic and imperilled crayfish.

     

Crunoecia irrorata (Curtis) (Trichoptera: Lepidostomatidae) and conservation of boreal springs: indications of clustering of red‐listed species

• 1. Crunoecia irrorata is widely dispersed across Europe, but rare and red‐listed in Finland. Its geographical range comprises most of the southern boreal zone in Fennoscandia. The species is confined to springs in the north, but occurs also in lower reaches of headwater streams in central and western Europe. It becomes more rare and less abundant towards the limits of its range across Europe, showing diffusive rarity. Glacial history and climate limit the distribution of the species in the north.
• 2. The most important habitat characteristic for C. irrorata in Finland was the total area of helocrene habitats. Its occurrence was positively related to taxon richness of benthic macroinvertebrates, but not bryophytes. Co‐occurrence of C. irrorata with other red‐listed spring‐dependent taxa was observed, indicating high conservation value of the springs occupied.
• 3. Crunoecia irrorata occurred frequently in moderately disturbed springs, indicating tolerance to human disturbance around springs. However, the effect of the disturbance on population size is not known. Forestry and water and gravel extraction are potential threats to C. irrorata, and only a few of its populations are strictly protected. Therefore, populations of C. irrorata in the boreal zone should be conserved and monitored to ensure the species' survival at the northern limits of its range.

Copyright © 2007 John Wiley & Sons, Ltd.