Taming the terminological tempest in invasion science.

Standardised terminology in science is important for clarity of interpretation and communication. In invasion science - a dynamic and rapidly evolving discipline - the proliferation of technical terminology has lacked a standardised framework for its development. The result is a convoluted and inconsistent usage of terminology, with various discrepancies in descriptions of damage and interventions. A standardised framework is therefore needed for a clear, universally applicable, and consistent terminology to promote more effective communication across researchers, stakeholders, and policymakers. Inconsistencies in terminology stem from the exponential increase in scientific publications on the patterns and processes of biological invasions authored by experts from various disciplines and countries since the 1990s, as well as publications by legislators and policymakers focusing on practical applications, regulations, and management of resources. Aligning and standardising terminology across stakeholders remains a challenge in invasion science. Here, we review and evaluate the multiple terms used in invasion science (e.g. 'non-native', 'alien', 'invasive' or 'invader', 'exotic', 'non-indigenous', 'naturalised', 'pest') to propose a more simplified and standardised terminology. The streamlined framework we propose and translate into 28 other languages is based on the terms (i) 'non-native', denoting species transported beyond their natural biogeographic range, (ii) 'established non-native', i.e. those non-native species that have established self-sustaining populations in their new location(s) in the wild, and (iii) 'invasive non-native' - populations of established non-native species that have recently spread or are spreading rapidly in their invaded range actively or passively with or without human mediation. We also highlight the importance of conceptualising 'spread' for classifying invasiveness and 'impact' for management. Finally, we propose a protocol for classifying populations based on (i) dispersal mechanism, (ii) species origin, (iii) population status, and (iv) impact. Collectively and without introducing new terminology, the framework that we present aims to facilitate effective communication and collaboration in invasion science and management of non-native species.

The remarkable Ponto-Caspian amphipod diversity of the lower Durso River (SW Caucasus) with the description of Litorogammarus dursi gen. et sp. nov.

The first insight into the unexpectedly diverse amphipod assemblage of the Durso River (Novorossiysk area) in the SW mountainous pre-Caucasian area is presented. The presence of six species is revealed, including three new records for the area and one species new to science. The phylogenetic relationships of all studied species and their relatives were examined based on the divergence of the COI mtDNA gene marker (barcoding). The conducted research clearly showed that the coastal part of the Black Sea and the adjacent pre-Caucasian river/land areas harbors a significant undescribed diversity, and that the transitional sea/river brackish biotopes are important reservoirs of the endemicity. A new genus, Litorogammarus gen. nov. is proposed for native pebble-dwelling species, namely Echinogammarus karadagiensis Grintsov, 2009, Echinogammarus mazestiensis Marin & Palatov, 2021 and the newly discovered Litorogammarus dursi sp. nov., from the lower (estuarine) part of the Durso River and adjacent coastal areas. These three species form a strongly supported molecular clade and share a number of characters such as smooth body without carinae and setae, antenna II armed with dense curled setae, lacking calceoli, pereopods III-VII with sparse, short setation, epimeral plates armed with spines only, telson lobes longer than broad, gradually tapering, bearing only spines. Pectenogammarus oliviiformis (Greze, 1985) comb. nov. is also discovered in the area and is re-described herein. Although this is probably one of the most abundant and common coastal pebble-dwelling species along the northeastern coasts of the Black Sea, it was previously poorly described and thus overlooked by researchers.

Cryptic Species in Ecotoxicology.

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.

Morphology, nuclear SNPs and mate selection reveal that COI barcoding overestimates species diversity in a Mediterranean freshwater amphipod by an order of magnitude.

DNA sequence information has revealed many morphologically cryptic species worldwide. For animals, DNA-based assessments of species diversity usually rely on the mitochondrial cytochrome c oxidase subunit I (COI) gene. However, a growing amount of evidence indicate that mitochondrial markers alone can lead to misleading species diversity estimates due to mito-nuclear discordance. Therefore, reports of putative species based solely on mitochondrial DNA should be verified by other methods, especially in cases where COI sequences are identical for different morphospecies or where divergence within the same morphospecies is high. Freshwater amphipods are particularly interesting in this context because numerous putative cryptic species have been reported. Here, we investigated the species status of the numerous mitochondrial molecular operational taxonomic units (MOTUs) found within Echinogammarus sicilianus. We used an integrative approach combining DNA barcoding with mate selection observations, detailed morphometrics and genome-wide double digest restriction site-associated DNA sequencing (ddRAD-seq). Within a relatively small sampling area, we detected twelve COI MOTUs (divergence = 1.8-20.3%), co-occurring in syntopy at two-thirds of the investigated sites. We found that pair formation was random and there was extensive nuclear gene flow among the ten MOTUs co-occurring within the same river stretch. The four most common MOTUs were also indistinguishable with respect to functional morphology. Therefore, the evidence best fits the hypothesis of a single, yet genetically diverse, species within the main river system. The only two MOTUs sampled outside the focal area were genetically distinct at the nuclear level and may represent distinct species. Our study reveals that COI-based species delimitation can significantly overestimate species diversity, highlighting the importance of integrative taxonomy for species validation, especially in hyperdiverse complexes with syntopically occurring mitochondrial MOTUs.

Turcogammarus aralensis (Uljanin, 1875), a relict pontogammarid amphipod crustacean from the Aralo-Caspian paleobasin: redescription, phylogenetic position and biogeography.

The Ponto-Caspian region harbours the world's second most diverse lacustrine radiation of amphipod crustaceans. The taxonomic position of some of these species is unclear, due to incorrectly defined species limits, poor descriptions, and in some cases, poorly understood characters, such as armament of dorsal integuments. A pertinent example is Turcogammarus aralensis (Uljanin, 1875), which inhabits the Aral Sea and adjacent water bodies like the brackish lake Shalkar (Charkhal), lower reaches of the Syr Darya and Volga, and extends ca. 2500 km westwards in the Black Sea basin. This species has never been properly described, which has led to frequent taxonomic reshuffling. Herein, we provide a full re-description, ascertain its phylogenetic position using the cytochrome c oxidase subunit I (COI) marker, and review its geographical distribution. Our molecular analyses reveal T. aralensis as a sister species to the widespread Obesogammarus crassus (Sars, 1894), and its species status was further confirmed by three molecular species delimitation methods. Turcogammarus aralensis and O. crassus share many similarities such as the setation of the antennae and pereopods 3-4, and poorly setose posterior margin of pereopod 7 basis. Further study is needed to ascertain the validity of the genus Turcogammarus.

Zoogeography of epigean freshwater Amphipoda (Crustacea) in Romania: fragmented distributions and wide altitudinal variability.

Inland epigean freshwater amphipods of Romania are diverse and abundant for this region has a favourable geographical position between the Balkans and the Black Sea. Excluding Ponto-Caspian species originating in brackish waters and freshwater subterranean taxa, there are 11 formally recognized epigean freshwater species recorded from this country. They belong to 3 genera, each representing a different family: Gammarus (Gammaridae, 8 species or species complexes), Niphargus (Niphargidae, 2 epigean species) and Synurella (Crangonyctidae, one species). Their large-scale distribution patterns nevertheless remain obscure due to insufficient data, consequently limiting biogeographical interpretations. We provide extensive new data with high resolution distribution maps, thus improving the knowledge of the ranges of these taxa. Gammarus species display substantial altitudinal variability and patchy, fragmented distribution patterns. They occur abundantly, particularly in springs and streams, from lowlands to sub-mountainous and mountainous regions. In the light of recent molecular research, we hypothesize that the complex geomorphological dynamics of the Carpathian region during the Late Tertiary probably contributed to their allopatric distribution pattern. Contrasting with Gammarus, the genera Niphargus and Synurella exhibit low altitudinal variability, broad ecological valences and overlapping distributions, being widespread throughout the lowlands. The current distribution of N. hrabei and N. valachicus seems to be linked to the extent of the Paratethys during the Early Pliocene or Pleistocene. We further discuss the taxonomic validity of two synonymized and one apparently undescribed taxon, and provide an updated pictorial identification key that includes all taxa and forms discussed in our study. The mosaic distribution of epigean freshwater amphipod species in Romania shows that this region is particularly suitable for phylo- and biogeographical analyses of this group.