Morphology and Genetics of the Ciscoes (Actinopterygii: Salmoniformes: Salmonidae: Coregoninae: Coregonus) from the Solovetsky Archipelago (White Sea) as a Key to Determination of the Taxonomic Position of Ciscoes in Northeastern Europe

Background: The characteristic feature of the genus <i>Coregonus</i> is the multitude of nominal species of obscure identity. The northeastern Europe is inhabited by, inter alia—the vendace, <i>Coregonus albula</i> (Linnaeus, 1758)—considered the European cisco—and the least cisco, <i>C. sardinella</i> Valenciennes, 1848—often referred to as the Siberian species. There is a large area in where the ranges of both species overlap. Using morphological- as well as genetic tools we attempted to test the working hypothesis that the <i>Coregonus</i> fish (ciscoes) inhabiting the above-mentioned transitional zone represent a single species. Materials and methods: Within 1995–2009 we collected 344 ciscoes from five lakes in Bolshoy Solovetsky Island and determined diagnostic morphological traits for the two species. For some samples, the polymorphism of the creatine kinase isoloci (<i>CK-A1,2</i>*) and the fragment of mitochondrial DNA (mtDNA) encoding the subunit 1 of NADH-dehydrogenize complex (<i>ND-1</i> fragment) was also studied. Results: According to one of the main taxonomical characteristics—the number of vertebrae—the cisco of Solovetsky Island occupies an intermediate position between <i>C. albula</i> and <i>C. sardinella</i>. The molecular markers,however, did not reveal any differences between the ciscoes of Bolshoy Solovetsky Island and the vendace found elsewhere. All specimens had the type allele of creatine kinase <i>(CK-A*100)</i> which was considered to be typical for C. albula at other locations as well as the haplotype E of mtDNA widespread in vendace populations. Conclusion: The cisco from Solovetsky Island is more similar to typical vendace. Differences in some morphological traits between Solovetsky Island populations and the vendace from elsewhere are likely to reflect adaptation to environmental conditions. Thus it appears that morphological criteria do not allow reliable differentiation between two forms of ciscoes as well as between least cisco and vendace because they are influenced by environmental conditions. We believe that the presence of populations with intermediate features is a strong argument for combining <i>C. albula</i> and <i>C. sardinella</i> into a single species (<i>C. albula</i>)

How an Ecological Race Is Forming: Morphological and Genetic Disparity among Thermal and Non-Thermal Populations of Aquatic Lymnaeid Snails (Gastropoda: Lymnaeidae)

Hot (geothermal) pools and streams, a specific type of aquatic biotopes having almost worldwide distribution, maintain rich faunas of animals belonging to various taxa. Snails (Gastropoda) represent one of such groups, which form populations in geothermal waterbodies of all continents. Some freshwater snail species produce morphologically distinct hot-water populations, whose rank is often debated (full species or thermal ‘ecotype’, or ‘race’). In this study, we used six species of pond snails (family Lymnaeidae) to investigate the morphological and genetic consequences of infiltration of freshwater snails into geothermal habitats. In particular, we aimed at studying the changes in shell shape and proportions as well as the formation of unique hot-water haplotypes and the occurrence of the latter beyond geothermal waterbodies. All six species studied demonstrate diminutive body size in hot sites accompanied, in four species, by apparent alterations in shell proportions. A phenomenon of phenotypic ‘juvenilization’, when adult and able to reproduce individuals demonstrate shell proportions characteristic for full-grown individuals living under ‘normal’ conditions, is described. Unique ‘thermal’ haplotypes, not found beyond the geothermal sites, were normally restricted to a single locality, and no signs of frequent ‘travels’ of snails from one thermal habitat to another are seen. In the vast majority of cases, these exclusive haplotypes are separated from their ancestors by only a few (1–3) mutational steps, which may indicate their relatively recent origin. We are inclined to relate both size reduction and ‘juvenilization’ to the life-cycle re-adjustment following the penetration of lymnaeids to thermal habitats. The ecological (‘thermal’) intraspecific races of different species, forming in geothermal habitats, exhibit, to a great extent, evolutionary predictability (=convergent evolution; =parallelisms). The dilemma ‘ecological race vs. young species’ in application to the taxonomy of these hot-water populations is briefly discussed

Climate Warming as a Possible Trigger of Keystone Mussel Population Decline in Oligotrophic Rivers at the Continental Scale

The effects of climate change on oligotrophic rivers and their communities are almost unknown, albeit these ecosystems are the primary habitat of the critically endangered freshwater pearl mussel and its host fishes, salmonids. The distribution and abundance of pearl mussels have drastically decreased throughout Europe over the last century, particularly within the southern part of the range, but causes of this wide-scale extinction process are unclear. Here we estimate the effects of climate change on pearl mussels based on historical and recent samples from 50 rivers and 6 countries across Europe. We found that the shell convexity may be considered an indicator of the thermal effects on pearl mussel populations under warming climate because it reflects shifts in summer temperatures and is significantly different in viable and declining populations. Spatial and temporal modeling of the relationship between shell convexity and population status show that global climate change could have accelerated the population decline of pearl mussels over the last 100 years through rapidly decreasing suitable distribution areas. Simulation predicts future warming-induced range reduction, particularly in southern regions. These results highlight the importance of large-scale studies of keystone species, which can underscore the hidden effects of climate warming on freshwater ecosystems.Peer reviewe

Cryptic taxonomic diversity and high-latitude melanism in the glossiphoniid leech assemblage from the Eurasian Arctic

Abstract The family Glossiphoniidae is a diverse and widespread clade of freshwater leeches, playing a significant role in functioning of aquatic ecosystems. The taxonomy and biogeography of leeches from temperate, subtropical, and tropical regions attracted much attention of zoologists, while their taxonomic richness and distribution in the Arctic are poorly understood. Here, we present an overview of the Eurasian Arctic Glossiphoniidae based on the most comprehensive occurrence and DNA sequence datasets sampled to date. This fauna contains 14 species, belonging to five genera and three subfamilies. One genus and five species are new to science and described here. The world’s northernmost occurrences of glossiphoniids are situated on the Taymyr Peninsula at 72° N, although further records at higher latitudes are expected. Most Arctic leeches are characterized by broad ranges crossing several climatic zones (e.g., Glossiphonia balcanica and G. nebulosa), although the distribution of two new species may be confined to the high-latitude areas. The Taymyr Peninsula with the nearby Putorana Plateau represents the most species-rich area (totally 9 species), while the European Arctic, Iceland, Kolyma Highland, and Chukotka Peninsula house depleted faunas (2–4 species per subregion). Finally, we show that the high-latitude melanism is a common phenomenon in glossiphoniid leeches

Round-the-World Voyage of the Threespine Stickleback (Gasterosteus aculeatus): Phylogeographic Data Covering the Entire Species Range

A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5&ndash;34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west

Round-the-World Voyage of the Threespine Stickleback (<i>Gasterosteus aculeatus</i>): Phylogeographic Data Covering the Entire Species Range

A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5–34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west

Climate Warming as a Possible Trigger of Keystone Mussel Population Decline in Oligotrophic Rivers at the Continental Scale

The effects of climate change on oligotrophic rivers and their communities are almost unknown, albeit these ecosystems are the primary habitat of the critically endangered freshwater pearl mussel and its host fishes, salmonids. The distribution and abundance of pearl mussels have drastically decreased throughout Europe over the last century, particularly within the southern part of the range, but causes of this wide-scale extinction process are unclear. Here we estimate the effects of climate change on pearl mussels based on historical and recent samples from 50 rivers and 6 countries across Europe. We found that the shell convexity may be considered an indicator of the thermal effects on pearl mussel populations under warming climate because it reflects shifts in summer temperatures and is significantly different in viable and declining populations. Spatial and temporal modeling of the relationship between shell convexity and population status show that global climate change could have accelerated the population decline of pearl mussels over the last 100 years through rapidly decreasing suitable distribution areas. Simulation predicts future warming-induced range reduction, particularly in southern regions. These results highlight the importance of large-scale studies of keystone species, which can underscore the hidden effects of climate warming on freshwater ecosystems.© The Author(s) 201