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TwoNiphargusspecies,Niphargus khayyamisp. nov. andNiphargus khwarizmisp. nov., are morphologically analysed and described. Both species are found in western Iran, which represents the easternmost border of the distributional area for this subterranean amphipod genus. We were unable to attributeN. khayyamisp. nov. to any of 80Niphargusspecies that were analysed for 28S ribosomal DNA sequences; sequencing ofN. khwarizmisp. nov. failed. Niphargid findings from west Asia recorded in 5 years imply that almost one half of the range of this large freshwater amphipod genus is still unexplored.http://www.zoobank.org/urn:lsid:zoobank.org:pub:9E9E7CC9-83E2-419F-A394-57197305E1EF [ABSTRACT FROM AUTHOR]

Subterranean and surface habitats are in stark contrast in several environmental factors. Therefore, adaptation to the subterranean environment typically impedes the (re)colonisation of surface habitats. The genus Niphargus includes amphipod crustaceans that primarily occupy subterranean habitats. All its species show typical adaptations to the subterranean environment. However, some Niphargus species occur in surface-subterranean ecotones. To understand whether (i) habitat-based phenotypic divergence is present between the cave and the ecotone species and (ii) similar phenotypes emerge independently in each ecotone, we studied morphological divergence between four cave and four ecotone Niphargus species based on 13 functional morphological traits. To account for different selection acting on the sexes, we included both males ( N  = 244) and females ( N  = 222). Nine out of 13 traits showed habitat-divergence. Traits related to feeding and crawling were shorter, while traits related to oxygenation were larger in ecotone species. Eleven out of 13 traits were sexually dimorphic. Traits related to oxygenation and crawling were larger in females, while the trait related to swimming was larger in males. We found that the extent of sexual dimorphism differs between the habitats in eight traits related to sensing, feeding, oxygenation and crawling. Additionally, we found that in certain traits related to sensing and oxygenation, habitat-related differences are only present in one sex, but not the other. We conclude that the detected differences between the cave and the ecotone species indicate divergent evolution, where similarities among the different species within habitat type indicate convergent evolution. The high degree of sexual dimorphism paired with differences in sexual dimorphism between the habitats in certain traits suggest that sexual and fecundity selections have comparable effects to environmental selection. Thus, studies of habitat-dependent adaptations investigating one sex only, or not considering sexual dimorphism, can lead to erroneous conclusions., Competing Interests: The authors declare no competing interests. All authors have read and agreed to the published version of the manuscript., (© 2024 The Author(s). Ecology and Evolution published by John Wiley & Sons Ltd.)

Sexual dimorphism can evolve in response to sex-specific selection pressures that vary across habitats. We studied sexual differences in subterranean amphipods Niphargus living in shallow subterranean habitats (close to the surface), cave streams (intermediate), and cave lakes (deepest and most isolated). These three habitats differ because at greater depths there is lower food availability, reduced predation, and weaker seasonality. Additionally, species near the surface have a near-even adult sex ratio (ASR), whereas species from cave lakes have a female-biased ASR. We hypothesized (a) a decrease in sexual dimorphism from shallow subterranean habitats to cave lake species because of weaker sexual selection derived from changes in the ASR and (b) an increase in female body size in cave lakes because of stronger fecundity selection on account of oligotrophy, reduced predation, and weaker seasonality. We measured body size and two sexually dimorphic abdominal appendages for all 31 species and several behaviours related to male competition (activity, risk-taking, exploration) for 12 species. Species with an equal ASR that live close to the surface exhibited sexual dimorphism in all three morphological traits, but not in behaviour. The body size of females increased from the surface to cave lakes, but no such trend was observed in males. In cave lake species, males and females differed neither morphologically nor behaviourally. Our results are consistent with the possibility that sexual and fecundity selection covary across the three habitats, which indirectly and directly, respectively, shape the degree of sexual dimorphism in Niphargus species., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Evolutionary Biology.)

Groundwater represents a vast, but mostly hidden and inaccessible ecosystem. Although often overlooked in freshwater research, groundwater organisms form a significant part of freshwater biodiversity, whereas their functions are crucial in different ecosystem processes. Knowledge on functional traits is generally lacking for most groundwater species worldwide, yet European groundwater amphipods, particularly the family Niphargidae, are an exception. They are well-researched and used as a model system in ecological and evolutionary studies. We focused on this group to assemble a first functional trait dataset dedicated to groundwater species. We gathered data for eight morphological functional traits quantified through 27 measurements for 1123 individuals which represent 180 species and 314 MOTUs. Besides functional trait data, every entry is accompanied with locality information, including habitat type, and DNA sequences if available. The structure of the dataset and data processing information provided along enable wide applicability and extension to other amphipod taxa. When coupled with phylogeny, the dataset may further enhance different aspects of groundwater research, including biodiversity patterns, community assembly processes, and trait evolution., (© 2024. The Author(s).)

Subterranean ecosystems (comprising terrestrial, semi-aquatic, and aquatic components) are increasingly threatened by human activities; however, the current network of surface-protected areas is inadequate to safeguard subterranean biodiversity. Establishing protected areas for subterranean ecosystems is challenging. First, there are technical obstacles in mapping three-dimensional ecosystems with uncertain boundaries. Second, the rarity and endemism of subterranean organisms, combined with a scarcity of taxonomists, delays the accumulation of essential biodiversity knowledge. Third, establishing agreements to preserve subterranean ecosystems requires collaboration among multiple actors with often competing interests. This perspective addresses the challenges of preserving subterranean biodiversity through protected areas. Even in the face of uncertainties, we suggest it is both timely and critical to assess general criteria for subterranean biodiversity protection and implement them based on precautionary principles. To this end, we examine the current status of European protected areas and discuss solutions to improve their coverage of subterranean ecosystems., (© 2024. The Author(s).)

Groundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium-to-high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science-policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change., (© 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Body size is one of the main characteristics of any organism and influences various aspects of individual's biology. In animal ecology, it represents a key functional trait that can be quantified using different measures and is often used as a proxy for different organismal functions. The way we quantify body size is critical in any study using this measure alone or to scale other organismal traits. It is especially important in groups that act as model systems across different fields of biological research. One of such groups are amphipods, which are at focus in many ecological studies where appropriate quantification of body size is needed. Here, we explored the relationship between body length and body mass in the largest freshwater amphipod genus Niphargus, and evaluated whether the two measures lead to different conclusions in a putative ecological study of species coexistence. We selected 16 species inhabiting two different subterranean habitats, cave lakes and cave streams. The relationship between log-transformed body mass and body length was linear in all species, but body mass increased steeper among species from cave lakes than from cave streams, reflecting the stouter body shape of the former. In the simulated ecological study, the comparisons of the two measures showed that they may yield different results: in 10 % of cases, body length detected differences between species when body mass did not and vice versa (13 %). Usage of body length or body mass can thus lead to different conclusions. We recommend avoiding direct transformations between body length and body mass in ecological studies. Whenever needed, such transformations should be done with caution using habitat-specific body mass - body length ratios., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Climate change affects all ecosystems, but subterranean ecosystems are repeatedly neglected from political and public agendas. Cave habitats are home to unknown and endangered species, with low trait variability and intrinsic vulnerability to recover from human-induced disturbances. We studied the annual variability and cyclicity of temperatures in caves vis-à-vis surface in different climatic areas. We hypothesize that cave temperatures follow the average temperature pattern at the surface for each location with a slight delay in the signal, but we found three different thermal patterns occurring in caves: (1) high positive correlation and a similar thermal pattern to the surface, (2) low correlation and a slight thermal delay of the signal from the surface, and (3) high negative correlation with an extreme delay from the surface. We found daily thermal cycles in some caves, which may potentially control the circadian rhythms of cave organisms. Our results show that caves had lower thermal amplitude than the surface, and that thermal averages within caves approximately correspond to the to the annual average of surface temperature. Caves buffer external temperature and act as refugia for biota in extreme climatic events. Likewise, temperature increases at surface will lead to increment in caves, threatening subterranean biota and ecosystem services., (© 2023. The Author(s).)

The advent of genetic methods has led to the discovery of an increasing number of species that previously could not be distinguished from each other on the basis of morphological characteristics. Even though there has been an exponential growth of publications on cryptic species, such species are rarely considered in ecotoxicology. Thus, the particular question of ecological differentiation and the sensitivity of closely related cryptic species is rarely addressed. Tackling this question, however, is of key importance for evolutionary ecology, conservation biology, and, in particular, regulatory ecotoxicology. At the same time, the use of species with (known or unknown) cryptic diversity might be a reason for the lack of reproducibility of ecotoxicological experiments and implies a false extrapolation of the findings. Our critical review includes a database and literature search through which we investigated how many of the species most frequently used in ecotoxicological assessments show evidence of cryptic diversity. We found a high proportion of reports indicating overlooked species diversity, especially in invertebrates. In terrestrial and aquatic realms, at least 67% and 54% of commonly used species, respectively, were identified as cryptic species complexes. The issue is less prominent in vertebrates, in which we found evidence for cryptic species complexes in 27% of aquatic and 6.7% of terrestrial vertebrates. We further exemplified why different evolutionary histories may significantly determine cryptic species' ecology and sensitivity to pollutants. This in turn may have a major impact on the results of ecotoxicological tests and, consequently, the outcome of environmental risk assessments. Finally, we provide a brief guideline on how to deal practically with cryptic diversity in ecotoxicological studies in general and its implementation in risk assessment procedures in particular. Environ Toxicol Chem 2023;42:1889-1914. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., (© 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.)

Populations experiencing negligible predation pressure are expected to evolve higher behavioral activity. However, when sexes have different expected benefits from high activity, the adaptive shift is expected to be sex-specific. Here, we compared movement activity of one cave (lack of predation) and three adjacent surface (high and diverse predation) populations of Asellus aquaticus , a freshwater isopod known for its independent colonization of several caves across Europe. We predicted 1) higher activity in cave than in surface populations, with 2) the difference being more pronounced in males as they are known for active mate searching behavior, while females are not. Activity was assessed both in the presence and absence of light. Our results supported both predictions: movement activity was higher in the cave than in the surface populations, particularly in males. Relaxed predation pressure in the cave-adapted population is most likely the main selective factor behind increased behavioral activity, but we also showed that the extent of increase is sex-specific., (© The Author(s) 2022. Published by Oxford University Press on behalf of Editorial Office, Current Zoology.)

Subterranean ecosystems are among the most widespread environments on Earth, yet we still have poor knowledge of their biodiversity. To raise awareness of subterranean ecosystems, the essential services they provide, and their unique conservation challenges, 2021 and 2022 were designated International Years of Caves and Karst. As these ecosystems have traditionally been overlooked in global conservation agendas and multilateral agreements, a quantitative assessment of solution-based approaches to safeguard subterranean biota and associated habitats is timely. This assessment allows researchers and practitioners to understand the progress made and research needs in subterranean ecology and management. We conducted a systematic review of peer-reviewed and grey literature focused on subterranean ecosystems globally (terrestrial, freshwater, and saltwater systems), to quantify the available evidence-base for the effectiveness of conservation interventions. We selected 708 publications from the years 1964 to 2021 that discussed, recommended, or implemented 1,954 conservation interventions in subterranean ecosystems. We noted a steep increase in the number of studies from the 2000s while, surprisingly, the proportion of studies quantifying the impact of conservation interventions has steadily and significantly decreased in recent years. The effectiveness of 31% of conservation interventions has been tested statistically. We further highlight that 64% of the reported research occurred in the Palearctic and Nearctic biogeographic regions. Assessments of the effectiveness of conservation interventions were heavily biased towards indirect measures (monitoring and risk assessment), a limited sample of organisms (mostly arthropods and bats), and more accessible systems (terrestrial caves). Our results indicate that most conservation science in the field of subterranean biology does not apply a rigorous quantitative approach, resulting in sparse evidence for the effectiveness of interventions. This raises the important question of how to make conservation efforts more feasible to implement, cost-effective, and long-lasting. Although there is no single remedy, we propose a suite of potential solutions to focus our efforts better towards increasing statistical testing and stress the importance of standardising study reporting to facilitate meta-analytical exercises. We also provide a database summarising the available literature, which will help to build quantitative knowledge about interventions likely to yield the greatest impacts depending upon the subterranean species and habitats of interest. We view this as a starting point to shift away from the widespread tendency of recommending conservation interventions based on anecdotal and expert-based information rather than scientific evidence, without quantitatively testing their effectiveness., (© 2022 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

Secondary salinization of freshwater is becoming a growing environmental problem. Currently, there is few data available on the effects of salinisation on subterranean crustaceans that are vital for the maintenance of groundwater ecosystem functioning. In this study, the sensitivity of subterranean Niphargus amphipods to NaCl was investigated. We expected that cave-dwelling species would be more sensitive as surface-subterranean boundary species. Eight ecologically different Niphargus species were tested: four live at the boundary between the surface and subterranean ecosystems (N. timavi, N. krameri, N. sphagnicolus, N. spinulifemur), three live in cave streams (N. stygius, N. scopicauda, N. podpecanus), and one species (N. hebereri) lives in anchialine caves and wells. The organisms were exposed to five concentrations of NaCl for 96 h and afterwards the immobility, mortality, and electron transfer system (ETS) activity (a measure for metabolic rate of animals) were evaluated. As expected, the most tolerant species was N. hebereri dwelling in naturally high-salinity habitat. However, contrary to our expectations, the species collected at the surface-subterranean boundary were more sensitive as cave stream species when their immobility and mortality were assessed. Interestingly, the majority of Niphargus tested were more NaCl tolerant as can be deduced from currently available data for subterranean and surface crustaceans. We could not observe a clear trend in ETS activity changes between groups of surface-subterranean boundary and cave streams species after exposure to NaCl stress, but it appears that osmotic stress-induced metabolic rate changes are species-specific. This study shows that amphipods Niphargus can be a valuable subterranean environmental research model and further ecotoxicity research is of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Predator-prey interactions are among the most important biotic interactions shaping ecological communities and driving the evolution of defensive traits. These interactions and their effects on species received little attention in extreme and remote environments, where possibilities for direct observations and experimental manipulation of the animals are limited. In this paper, we study such type of environment, namely caves of the Dinarides (Europe), combining spatial and phylogenetic methods. We focused on several species of Niphargus amphipods living in phreatic lakes, as some of them use the dorsal spines as putative morphological defensive traits. We predicted that these spines represent a defense strategy against the olm (Proteus anguinus), a top predator species in the subterranean waters. We tested for spatial overlap of the olm and Niphargus species and showed that spined species live in closer proximity to and co-occur more frequently with the olm than non-spined species. Modeling of the evolution of the spines onto Niphargus phylogeny implies coevolution of this trait in the presence of olm. We conclude that these spines likely evolved as defensive traits in a predator-prey arms race. Combining multiple analyses, we provide an example for a methodological framework to assess predator-prey interactions when in-situ or laboratory observations are not possible., (© 2021. The Author(s).)

Studying parallel evolution (repeated, independent evolution of similar phenotypes in similar environments) is a powerful tool to understand environment-dependent selective forces. Surface-dwelling species that repeatedly and independently colonized caves provide unique models for such studies. The primarily surface-dwelling Asellus aquaticus species complex is a good candidate to carry out such research, because it colonized several caves in Europe. By comparing 17 functional morphological traits between six cave and nine surface populations of the A. aquaticus species complex, we investigated population divergence in morphology and sexual dimorphism. We found habitat-dependent population divergence in 10 out of 17 traits, likely reflecting habitat-driven changes in selection acting on sensory systems, feeding, grooming, and antipredator mechanisms. Sexual dimorphism was present in 15 traits, explained by sexual selection acting on male traits important in male-male agonistic behavior or mate guarding and fecundity selection acting on female traits affecting offspring number and nursing. In eight traits, the degree of sexual dimorphism was habitat dependent. We conclude that cave-related morphological changes are highly trait- and function-specific and that the strength of sexual/fecundity selection strongly differs between cave and surface habitats. The considerable population variation within habitat type warrants further studies to reveal cave-specific adaptations besides the parallel patterns., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

Sex allocation theory predicts that the proportion of daughters to sons will evolve in response to ecological conditions that determine the costs and benefits of producing each sex. All else being equal, the adult sex ratio (ASR) should also vary with ecological conditions. Many studies of subterranean species reported female-biased ASR, but no systematic study has yet been conducted. We test the hypothesis that the ASR becomes more female-biased with increased isolation from the surface. We compiled a data set of ASRs of 35 species in the subterranean amphipod Niphargus, each living in one of three distinct habitats (surface-subterranean boundary, cave streams, phreatic lakes) representing an environmental gradient of increased isolation underground. The ASR was female-biased in 27 of 35 species; the bias was statistically significant in 12 species. We found a significant difference in the ASR among habitats after correction for phylogeny. It is most weakly female-biased at the surface-subterranean boundary and most strongly female-biased in phreatic lakes. Additional modelling suggests that the ASR has evolved towards a single value for both surface-subterranean boundary and cave stream-dwelling species, and another value for 9 of 11 phreatic lake dwellers. We suggest that a history of inbreeding in subterranean populations might lower inbreeding depression such that kin selection favours mating with siblings. This could select for a female-biased offspring sex ratio due to local mate competition among brothers. The observed patterns in sex ratios in subterranean species make them a group worthy of more attention from those interested in sex allocation theory., (© 2021 European Society for Evolutionary Biology.)

Adaptive radiations are bursts of evolutionary species diversification that have contributed to much of the species diversity on Earth. An exception is modern Europe, where descendants of ancient adaptive radiations went extinct, and extant adaptive radiations are small, recent and narrowly confined. However, not all legacy of old radiations has been lost. Subterranean environments, which are dark and food-deprived, yet buffered from climate change, have preserved ancient lineages. Here we provide evidence of an entirely subterranean adaptive radiation of the amphipod genus Niphargus, counting hundreds of species. Our modelling of lineage diversification and evolution of morphological and ecological traits using a time-calibrated multilocus phylogeny suggests a major adaptive radiation, comprised of multiple subordinate adaptive radiations. Their spatio-temporal origin coincides with the uplift of carbonate massifs in South-Eastern Europe 15 million years ago. Emerging subterranean environments likely provided unoccupied, predator-free space, constituting ecological opportunity, a key trigger of adaptive radiation. This discovery sheds new light on the biodiversity of Europe.

Five decades ago, a landmark paper in Science titled The Cave Environment heralded caves as ideal natural experimental laboratories in which to develop and address general questions in geology, ecology, biogeography, and evolutionary biology. Although the 'caves as laboratory' paradigm has since been advocated by subterranean biologists, there are few examples of studies that successfully translated their results into general principles. The contemporary era of big data, modelling tools, and revolutionary advances in genetics and (meta)genomics provides an opportunity to revisit unresolved questions and challenges, as well as examine promising new avenues of research in subterranean biology. Accordingly, we have developed a roadmap to guide future research endeavours in subterranean biology by adapting a well-established methodology of 'horizon scanning' to identify the highest priority research questions across six subject areas. Based on the expert opinion of 30 scientists from around the globe with complementary expertise and of different academic ages, we assembled an initial list of 258 fundamental questions concentrating on macroecology and microbial ecology, adaptation, evolution, and conservation. Subsequently, through online surveys, 130 subterranean biologists with various backgrounds assisted us in reducing our list to 50 top-priority questions. These research questions are broad in scope and ready to be addressed in the next decade. We believe this exercise will stimulate research towards a deeper understanding of subterranean biology and foster hypothesis-driven studies likely to resonate broadly from the traditional boundaries of this field., (© 2020 Cambridge Philosophical Society.)

Despite Greece being a global hotspot of subterranean biodiversity, its hypogean fauna is largely neglected from both an ecological and conservational point of view. An overview of the Niphargidae occurring in Greece is presented as an annotated list of all available published records. These records have resulted in an updated species list reflecting taxonomic corrections and species distribution range in the Greek peninsula. A total of 23 species, attributed to 3 genera, is up to date known from Greece with a high rate of endemicity found particularly in Crete. The endemic species of Greece amount to 21 (91% of total species richness), with the remaining species distributing also in the Republic of North Macedonia. Currently, none of them is listed in the national, European or global IUCN Red Lists of Threatened Species. Considering the increasing habitat degradation due to anthropic pressure, groundwater harvesting and climate change we could lose rare and endemic species without even acknowledging their existence.

Locomotion is an important, fitness-related functional trait. Environment selects for type of locomotion and shapes the morphology of locomotion-related traits such as body size and appendages. In subterranean aquatic arthropods, these traits are subjected to multiple, at times opposing selection pressures. Darkness selects for enhanced mechano- and chemosensory systems and hence elongation of appendages. Conversely, water currents have been shown to favor short appendages. However, no study has addressed the variation in locomotion of invertebrates inhabiting cave streams and cave lakes, or questioned the relationship between species' morphology and locomotion. To fill this knowledge gap, we studied the interplay between habitat use, morphology and locomotion in amphipods of the subterranean genus Niphargus. Previous studies showed that lake and stream species differ in morphology. Namely, lake species are large, stout and long-legged, whereas stream species are small, slender and short-legged. We here compared locomotion mode and speed between three lake and five stream species. In addition, we tested whether morphology predicts locomotion. We found that the stream species lie on their body sides and move using slow crawling or tail-flipping. The species inhabiting lakes move comparably faster, and use a variety of locomotion modes. Noteworthy, one of the lake species almost exclusively moves in an upright or semi-upright position that resembles walking. Body size and relative length of appendages predict locomotion mode and speed in all species. We propose that integrating locomotion in the studies of subterranean species might improve our understanding of their morphological evolution., Competing Interests: Declaration of Competing Interest Authors declare no conflict of interest., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

The ecological radiation of amphipods is striking among crustaceans. Despite high diversity, global distribution and key roles in all aquatic environments, little is known about their ecological transitions, evolutionary timescale and phylogenetic relationships. It has previously been proposed that the amphipod ecological diversification began in the Late Palaeozoic. By contrast, due to their affinity for cold/oxygenated water and absence of pre-Cenozoic fossils, we hypothesized that the ecological divergence of amphipods arose throughout the cool Late Mesozoic/Cenozoic. We tested our hypothesis by inferring a large-scale, time-calibrated, multilocus phylogeny, and reconstructed evolutionary patterns for major ecological traits. Although our results reveal a Late Palaeozoic amphipod origin, diversification and ecological divergence ensued only in the Late Mesozoic, overcoming a protracted stasis in marine littoral habitats. Multiple independent post-Jurassic radiations took place in deep-sea, freshwater, terrestrial, pelagic and symbiotic environments, usually postdating deep-sea faunal extinctions, and corresponding with significant climatic cooling, tectonic reconfiguration, continental flooding, and increased oceanic oxygenation. We conclude that the profound Late Mesozoic global changes triggered a tipping point in amphipod evolution by unlocking ecological opportunities that promoted radiation into many new niches. Our study also provides a solid, time-calibrated, evolutionary framework to accelerate research on this overlooked, yet globally important taxon., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Aim: Common species contribute more to species richness patterns (SRPs) than rare species in most studies. Our aim was to test this hypothesis using a novel model system, species living exclusively in subterranean habitats. They consist of mainly rare species (small ranges), only a few of them being common (large ranges), and challenge whether rare species are less important for the development of SRPs in this environment. We separately analyzed aquatic and terrestrial species., Location: Western Balkans in southeastern Europe., Methods: We assembled two datasets comprising 431 beetle and 145 amphipod species, representing the model groups of subterranean terrestrial and aquatic diversity, respectively. We assessed the importance of rare and common species using the stepwise reconstruction of SRPs and subsequent correlation analyses, corrected also for the cumulative information content of the subsets based on species prevalence. We applied generalized linear regression models to evaluate the importance of rare and common species in forming SRPs. Additionally, we analyzed the contribution of rare and common species in species-rich cells., Results: Patterns of subterranean aquatic and terrestrial species richness overlapped only weakly, with aquatic species having larger ranges than terrestrial ones. Our analyses supported higher importance of common species for forming overall SRPs in both beetles and amphipods. However, in stepwise analysis corrected for information content, results were ambiguous. Common species presented a higher proportion of species than rare species in species-rich cells., Main Conclusion: We have shown that even in habitats with the domination of rare species, it is still common species that drive SRPs. This may be due to an even spatial distribution of rare species or spatial mismatch in hotspots of rare and common species. SRPs of aquatic and terrestrial subterranean organisms overlap very little, so the conservation approaches need to be habitat specific., Competing Interests: None declared., (© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

The amphipod genus Niphargus (Amphipoda: Niphargidae Bousfield, 1977) is the most species-rich genus of freshwater amphipods in the World. Species of this genus, which live almost exclusively in subterranean water, offer an interesting model system for basic and applied biodiversity science. Their use, however, is often limited due to the hitherto unresolved taxonomy within the whole genus. As a comprehensive taxonomic revision of the currently >425 Niphargus species is too demanding, it has been suggested that the taxonomy of the genus could be advanced in smaller steps, by reviewing regional faunas, that would eventually integrate into a global revision. In this study, we provide such a revision of Niphargus in Switzerland. First, we molecularly delimited, morphologically diagnosed, and formally described two new species, namely Niphargus luchoffmanni sp. n. and Niphargus tonywhitteni sp. n. Second, we updated and revised a checklist of Niphargus in Switzerland with new findings, and prepared a list of reference sequences for routine molecular identification, available at BOLD and GenBank. All available specimens of 22 known species from the area were morphologically examined, and their morphological variation was compiled in a data file of DEscription Language for TAxonomy, which can be used for automated generation of dichotomous or interactive keys. The data file is freely available at the World Amphipoda Database. Together, the checklist, the library of reference sequences, the DELTA file, but also a list of hitherto unresolved aspects are an important step towards a complete revision of the genus within a well-defined and biogeographically interesting area in Central Europe.

Niphargidae is among the largest families of freshwater subterranean amphipods in the world, and one of the most important macroinvertebrate groups in European groundwaters. The knowledge of their species diversity on a country level is often incomplete due to demanding taxonomy. In this paper we critically evaluated species diversity of the family in Belgium, using published records and samples from our own field work. Morphology-based identifications confirmed the presence of genera Microniphargus and Niphargus, represented with one and eight species, respectively. Most of the species found in Belgium belonged to complexes of cryptic species, which are still awaiting their taxonomic epilogue. Four species belong to phylogenetic lineages distributed also across British Isles, whereas three species belong to lineages distributed in the west-continental Europe. Identity of one species was doubtful, and two populations, partially illustrated herein, showed distinct morphology and might belong to a new species. All together, Niphargidae were found at 172 localities, with 80% of sites harboring one species only. At 12 localities three to six species co-occurred. When mapped onto 10x10 km grid, up to seven different species were recorded per quadrate. Species richest quadrates were situated in the southeastern part of the country. Paucity of records from the northern part of the country imply lack of research, rather than absence of Niphargidae. Conservation status of Belgian Niphargidae has not been evaluated so far; assessment of this status would require further sampling and detailed taxonomic work.

The species concept is the cornerstone of biodiversity science, and any paradigm shift in the delimitation of species affects many research fields. Many biologists now are embracing a new "species" paradigm as separately evolving populations using different delimitation criteria. Individual criteria can emerge during different periods of speciation; some may never evolve. As such, a paradigm shift in the species concept relates to this inherent heterogeneity in the speciation process and species category-which is fundamentally overlooked in biodiversity research. Cryptic species fall within this paradigm shift: they are continuously being reported from diverse animal phyla but are poorly considered in current tests of ecological and evolutionary theory. The aim of this review is to integrate cryptic species in biodiversity science. In the first section, we address that the absence of morphological diversification is an evolutionary phenomenon, a "process" counterpart to the long-studied mechanisms of morphological diversification. In the next section regarding taxonomy, we show that molecular delimitation of cryptic species is heavily biased towards distance-based methods. We also stress the importance of formally naming of cryptic species for better integration into research fields that use species as units of analysis. Finally, we show that incorporating cryptic species leads to novel insights regarding biodiversity patterns and processes, including large-scale biodiversity assessments, geographic variation in species distribution and species coexistence. It is time for incorporating multicriteria species approaches aiming to understand speciation across space and taxa, thus allowing integration into biodiversity conservation while accommodating for species uncertainty., (© 2018 John Wiley & Sons Ltd.)

Groundwater is an extreme environment due to its absence of light, resource scarcity and highly fragmentary nature. Successful groundwater colonizers underwent major evolutionary changes and exhibit eye and pigment loss (troglomorphies). Consequently, their chances of dispersal and survival in the well-connected surface waters are greatly decreased, resulting in significant endemism. The West Palaearctic subterranean amphipod genus Niphargus comprises hundreds of narrowly endemic and troglomorphic species. Nevertheless, a few are known to occur in surface waters, two of which, N. hrabei and N. valachicus, have extremely large ranges that even exceed those of many surface-water amphipods. We tested if this pattern results from a secondary colonization of the relatively well-connected epigean environment, and whether this ecological shift promoted the large-scale dispersal of these species. Results showed that despite their ecological and zoogeographic similarities, N. hrabei and N. valachicus are not closely related and independently colonized surface waters. Their phylogeographic patterns indicate Middle to Late Pleistocene dispersal episodes throughout the Danube lowlands, and relatively modest yet significant genetic differentiation among populations. Clustering based on morphology revealed that the two species are phenotypically closer to each other than they are to most other epigean congeners. We presume that the ecological shift to surface environments was facilitated by their ability to thrive in hypoxic waters where rheophilic competitors from the family Gammaridae cannot survive. In conclusion, our results indicate that adaptation to groundwater is not a one-way evolutionary path and that troglomorphic species can occasionally recolonize and widely disperse in surface waters., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Mahmood Mamaghani-Shishvan, Somayeh Esmaeili-Rineh, and Cene Fišer (2017) The cave-dwelling fauna of Zagros region (Northern Iran) has been insuf ciently studied. Most of the known cave-specialized species (15 out of 21) belong to the genus Niphargus Schiödte, 1849, yet species composition of this genus is not resolved. In this research, we studied Niphargus specimens from two recently sampled caves, Shoei and Darvish-Olya Caves, from Kurdistan Province in Iran. The specimens belong to a single, yet undescribed species, which can be diagnosed using mitochondrial (COI) and nuclear sequences (28S rDNA gene sequences) as well as several morphological traits. Based on combined evidence from morphology and molecular characters, we described and named new species, N. kurdistanensis sp. nov.. The newly described species is phylogenetically nested within the clade comprising Iranian species. We provide a new and revised identification key for Niphargus from the Middle East region.

Molecular taxonomy often uncovers cryptic species, reminding us that taxonomic incompleteness is even more severe than previous thought. The importance of cryptic species for conservation is poorly understood. Although some cryptic species may be seriously threatened or otherwise important, they are rarely included in conservation programs as most of them remain undescribed. We analysed the importance of cryptic species in conservation by scrutinizing the South European cryptic complex of the subterranean amphipod Niphargus stygius sensu lato. Using uni- and multilocus delineation methods we show that it consists of 15 parapatric and sympatric species, which we describe using molecular diagnoses. The new species are not mere "taxonomic inflation" as they originate from several distinct branches within the genus and coexist with no evidence of lineage sharing. They are as evolutionarily distinct as average nominal species of the same genus. Ignoring these cryptic species will underestimate the number of subterranean endemics in Slovenia by 12 and in Croatia by four species, although alpha diversity of single caves remains unchanged. The new taxonomy renders national Red Lists largely obsolete, as they list mostly large-ranged species but omit critically endangered single-site endemics. Formal naming of cryptic species is critical for them to be included in conservation policies and faunal listings.

New species of the genus Niphargus is described and named as N. kermanshahi sp. nov. from a karst spring in west of Iran. This species is identified based on the analysis of morphological characters and 28S ribosomal DNA sequences. Taxonomic status and phylogenetic position of this species is discussed in comparison to other Iranian species of Niphargus genus.

Boundaries of species distributions are the result of colonization-extinction processes. Survival on the boundary depends on how well individuals discriminate optimal from suboptimal habitat patches. Such behaviour is called habitat choice and was only rarely applied to macroecology, although it links species ecological niche and species distribution. Surface and subterranean aquatic species are spatially strongly segregated, even in the absence of physical barriers. We explored whether a behavioural response to light functions as a habitat choice mechanism that could explain species turnover between surface and subterranean aquatic ecosystems. In a controlled laboratory experiment, we studied the behavioural response to light of ten pairs of surface and subterranean amphipods that permanently co-occur in springs. Surface species showed a weak photophobic, photoneutral, and in one case, photophilic response, whereas all subterranean species showed a strong photophobic response. Eyeless subterranean but not eyed surface amphipods appear to orient themselves with light cues. On a local scale, this difference possibly diminishes harmful interactions between the co-occurring amphipods, whereas on a regional scale, photophobia could explain limited dispersal and a high degree of endemism observed among subterranean species.

We describe and phylogenetically characterize a new species Niphargus mirocensis from Mt. Miroč, eastern Serbia. This species shows distinct morphology typical for a lake ecomorph of niphargid amphipod, i.e. large and stout body, elongated appendages and raptorial gnathopods and presents the first record of this ecomorph in Carpathian Mountains. Phylogenetic analyses based on Cytochrome Oxidase Subunit 1 gene (COI), Histone (H3) and 28S rRNA (28S) suggests that species is nested within a clade of lake ecomorphs spread in Italy and Central Dinaric Region. The new finding is geographic extension of clade's range, the species of which are generally narrow endemics.

Four new species from the amphipod genus Niphargus are described, namely N. borisi sp. nov., N. bisitunicus sp. nov., N. darvishi sp. nov. and N. sharifi sp. nov. All four species of this predominantly subterranean genus were collected from springs in the Western region of Iran (Zagros region), which is the eastern borderline of the genus range. The species are morphologically diagnosed, described and illustrated. With these newly described species, the total number of Niphargus species in the Middle East reaches twenty-three. In order to facilitate the identification of Niphargus species in the region and to make future taxonomy of the genus easier, we have compiled a database in DEscription Language for TAxonomy (DELTA) using 23 diagnostic traits for these 23 species and subspecies identified in the Middle East. The database is available on the web as supplementary material whereas the dichotomous identification key automatically generated from the database for routine use is provided as a part of the paper.

We describe a new species of an amphipod Niphargus zagorae sp. n. and redescribe its nearest relative and morphologically similar species N. boskovici S. Karaman, 1952. We present the geographic distributions of both species, morphological diagnoses and infer their phylogenetic position within the genus based on COI, 28S and H3 markers.

Recent studies indicate that morphologically cryptic species may be ecologically more different than would be predicted from their morphological similarity and phylogenetic relatedness. However, in biodiversity research it often remains unclear whether cryptic species should be treated as ecologically equivalent, or whether detected differences have ecological significance. In this study, we assessed the ecological equivalence of four morphologically cryptic species of the amphipod genus Niphargus. All species live in a small, isolated area on the Istrian Peninsula in the NW Balkans. The distributional ranges of the species are partially overlapping and all species are living in springs. We reconstructed their ecological niches using morphological traits related to feeding, bioclimatic niche envelope and species' preference for epi-hypogean habitats. The ecological meaning of differences in niches was evaluated using distributional data and co-occurrence frequencies. We show that the species comprise two pairs of sister species. All species differ from each other and the degree of differentiation is not related to phylogenetic relatedness. Moreover, low co-occurrence frequencies in sympatric zones imply present or past interspecific competition. This pattern suggests that species are not differentiated enough to reduce interspecific competition, nor ecologically equivalent to co-exist via neutral dynamics. We tentatively conclude that the question of ecological equivalence relates to the scale of the study: at a fine scale, species' differences may influence dynamics in a local community, whereas at the regional level these species likely play roughly similar ecological roles.

A detailed redescription of two endemic, cave-dwelling niphargid species of the Hungarian Mecsek Mts., Niphargusmolnari Méhely, 1927 and Niphargusgebhardti Schellenberg, 1934 is given based on newly collected material. Morphology was studied under light microscopy and with scanning electon microscopy. Morphological descriptions are complemented with mitochondrial cytochrome c oxidase subunit I (COI) sequences as barcodes for both species and with notes on their ecology. Using three independent molecular markers we showed that Niphargusgebhardti belongs to the clade distributed between Central and Eastern Europe, whereas phylogenetic relationship of Niphargusmolnari to the rest of Niphargus species is not clear. The two species from the Mecsek Mts. are phylogenetically not closely related. Both species need to be treated as vulnerable according to IUCN Red List of Threatened Species.

Phenotypically similar species coexisting in extreme environments like sulfidic water are subject to two opposing eco-evolutionary processes: those favoring similarity of environment-specific traits, and those promoting differences of traits related to resource use. The former group of processes includes ecological filtering and convergent or parallel evolution, the latter competitive exclusion, character displacement and divergent evolution. We used a unique eco-evolutionary study system composed of two independent pairs of coexisting amphipod species (genus Niphargus) from the sulfidic caves Movile in Romania and Frasassi in Italy to study the relative contribution and interaction of both processes. We looked at the shape of the multifunctional ventral channel as a trait ostensibly related to oxygenation and sulfide detoxification, and at body size as a resource-related trait. Phylogenetic analysis suggests that the sulfidic caves were colonized separately by ancestors of each species. Species within pairs were more dissimilar in their morphology than expected according to a null model based on regional species pool. This might indicate competitive interactions shaping the morphology of these amphipod species. Moreover, our results suggest that the shape of the ventral channel is not subject to long-term convergent selection or to the process of environmental filtering, and as such probably does not play a role in sulfide tolerance. Nevertheless, the ancestral conditions reconstructed using the comparative method tended to be more similar than null-model expectations. This shift in patterns may reflect a temporal hierarchy of eco-evolutionary processes, in which initial environmental filtering became later on superseded by character displacement or other competition-driven divergent evolutionary processes.