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An intricate interplay between evolutionary and demographic processes has frequently resulted in complex patterns of genetic and phenotypic diversity in alpine lineages, posing serious challenges to species delimitation and biodiversity conservation planning. Here we integrate genomic data, geometric morphometric analyses and thermal tolerance experiments to explore the role of Pleistocene climatic changes and adaptation to alpine environments on patterns of genomic and phenotypic variation in diving beetles from the taxonomically complex Agabus bipustulatus species group. Genetic structure and phylogenomic analyses revealed the presence of three geographically cohesive lineages, two representing trans‐Palearctic and Iberian populations of the elevation‐generalist A. bipustulatus and another corresponding to the strictly‐alpine A. nevadensis, a narrow‐range endemic taxon from the Sierra Nevada mountain range in southeastern Iberia. The best‐supported model of lineage divergence, along with the existence of pervasive genetic introgression and admixture in secondary contact zones, is consistent with a scenario of population isolation and connectivity linked to Quaternary climatic oscillations. Our results suggest that A. nevadensis is an alpine ecotype of A. bipustulatus, whose genotypic, morphological and physiological differentiation likely resulted from an interplay between population isolation and local altitudinal adaptation. Remarkably, within the Iberian Peninsula, such ecotypic differentiation is unique to Sierra Nevada populations and has not been replicated in other alpine populations of A. bipustulatus. Collectively, our study supports fast ecotypic differentiation and incipient speciation processes within the study complex and points to Pleistocene glaciations and local adaptation along elevational gradients as key drivers of biodiversity generation in alpine environments. [ABSTRACT FROM AUTHOR]

Simple Summary: We studied the flight dispersal of two congeneric beetle species (Ochthebius quadricollis and Ochthebius lejolisii) living in Mediterranean coastal rockpools; temporary and fragmented habitats with extreme environmental conditions (high salinity, high temperature, and strong desiccation). We used a multi-approach (experimental flying assays, wing morphology, and genetic markers) to measure flight capacity. We found that both species had similar flight behaviour, with most individuals flying when water was heated. Females had larger body sizes and wing areas and lower wing loading than males, which suggested higher dispersal capacity. The wing shape of both species was also shown to be an efficient adaptation to flight. However, the molecular data point to passive dispersal assisted by wind at small-to-medium spatial scales (<100 km). Flight dispersal is ecologically relevant for the survival of supratidal rockpool insects. Dispersal has important consequences for colonisation, gene flow, and evolutionary divergence. Here, we compared the flight dispersal capacity of two congeneric beetle species (Ochthebius quadricollis and Ochthebius lejolisii) that exclusively inhabit these temporary, fragmented, and extreme habitats. We estimated flight capacity and inferred dispersal in both species using different approaches: experimental flying assays, examination of wing morphology, and comparison of microsatellite markers between species. Our findings revealed that both species exhibited similar flight behaviour, with 60 to 80% of the individuals flying under water heating conditions. Notably, females of both species had larger body sizes and wing areas, along with lower wing loading, than males in O. quadricollis. These morphological traits are related to higher dispersal capacity and more energetically efficient flight, which could indicate a female-biassed dispersal pattern. The wing shapes of both species are characterised by relatively larger and narrower wings in relation to other species of the genus, suggesting high flight capacity at short distances. Molecular data revealed in both species low genetic divergences between neighbouring populations, non-significant differences between species, and no isolation by distance effect at the study scale (<100 km). These results point to passive dispersal assisted by wind. [ABSTRACT FROM AUTHOR]

Simple Summary: Supratidal rockpools stand out as some of the most extreme environments on the planet. These pools are exposed to the wave's action, fluctuations in sea level, dramatic shifts in water temperature, high salinity levels, desiccation, and intense sunshine. As a result, only a handful of species can survive there, with aquatic beetles of the genus Ochthebius being the insects that dominate this kind of habitat on the Mediterranean coast. In this work, we genetically analysed four species (O. lejolisii, O. subinteger, O. celatus, and O. quadricollis) found along the Mediterranean coasts of Spain and Malta to develop microsatellite markers, which are repetitive DNA motifs, for the first time for this genus. Additionally, we obtained the complete mitochondrial genome of three species (O. lejolisii, O. subinteger, and O. quadricollis). These newly developed microsatellite markers and mitochondrial genomes for Ochthebius will be valuable in future studies for evolutionary and ecological research on the diversity of this genus: identification, genetic structure, population connectivity, etc. Here we focus on designing, for the first time, microsatellite markers for evolutionary and ecological research on aquatic beetles from the genus Ochthebius (Coleoptera, Hydraenidae). Some of these non-model species, with high cryptic diversity, exclusively inhabit supratidal rockpools, extreme and highly dynamic habitats with important anthropogenic threats. We analysed 15 individuals of four species (O. lejolisii, O. subinteger, O. celatus, and O. quadricollis) across 10 localities from the Mediterranean coasts of Spain and Malta. Using next-generation sequencing technology, two libraries were constructed to interpret the species of the two subgenera present consistently (Ochthebius s. str., O. quadricollis; and Cobalius, the rest of the species). Finally, 20 markers (10 for each subgenus) were obtained and successfully tested by cross-validation in the four species under study. As a by-catch, we could retrieve the complete mitochondrial genomes of O. lejolisii, O. quadricollis, and O. subinteger. Interestingly, the mitochondrial genome of O. quadricollis exhibited high genetic variability compared to already published data. The novel SSR panels and mitochondrial genomes for Ochthebius will be valuable in future research on species identification, diversity, genetic structure, and population connectivity in highly dynamic and threatened habitats such as supratidal coastal rockpools. [ABSTRACT FROM AUTHOR]

Determining the saline niche of the congeneric and co‐existing species that inhabit supralittoral rockpools subjected to extremely fluctuating saline conditions is a crucial concern to understand their spatial distributions and occurrence, and to predict their ability to face increasing environmental instability due to climate change.Therefore, we compared the realised and fundamental saline niches of Ochthebius quadricollis and Ochthebius lejolisii (Coleoptera: Hydraenidae) on the Mediterranean coast of the Iberian Peninsula.A realised niche was determined using field data on the abundance of the adults and larvae of both species.A fundamental niche was addressed with laboratory experiments by measuring the survival of the adults and larvae and the egg‐hatching success exposed to different salinity treatments (35, 60, 90, 110, 140 and 170 g L−1).Our study found a discordant pattern between realised and fundamental niches. Both species are euryhalines and support extreme salinity fluctuations from 1.80 to almost 140 g L−1, and O. quadricollis larvae in the field withstand up to 180 g L−1.However, physiological tolerance was greater in O. lejolisii than in O. quadricollis, and O. lejolissi adults survived in the laboratory at 170 g L−1 for more than 3 days with 30% egg‐hatching success, whereas O. quadricollis showed a maximum survival time of 2 days and no egg‐hatching success at that salinity.The larvae and eggs of both species were more tolerant than adults.The two studied species exhibited high physiological capacity to tolerate extremely fluctuating salinity, which will be exacerbated by climate change. [ABSTRACT FROM AUTHOR]

The immune response represents a suite of evolved traits that can involve energetic and evolutionary trade‐offs with other energy‐demanding and fitness‐related processes. Here, we tested the hypothesis that aquatic beetles living in inland hypersaline habitats have lower immune capacity than freshwater congeners.Phenoloxidase activity, encapsulation response and antimicrobial peptide activity were compared in freshwater/hypersaline species pairs with differing osmoregulatory capacity and cuticular waterproofing properties in the genera Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae), independent evolutionary lineages that have colonised saline media separately.Hypersaline species (N. ceresyi and E. jesusarribasi) showed significantly lower phenoloxidase activity and antimicrobial peptide responses than their freshwater relatives (N. clarkii and E. salomonis). Encapsulation responses in freshwater species also appeared to be higher than in hypersaline relatives.Our results reinforce the complex nature of immune responses and suggest that adaptation to saline environments may have involved a trade‐off between osmoregulation and investment in immune defences, but also are consistent with relaxed selection pressures on basal immune responses resulting from lower microbial infection load in saline habitats. In addition, the more resistant cuticle of species occupying such habitats may protect against the entry of parasites, reducing selection pressure on immunity.Because the evolution of salinity tolerance is associated with reduced immune capacity, saline specialists may be particularly vulnerable to the dilution of saline waters and consequent changes in pathogen communities and load following colonisation by more generalist microorganisms. [ABSTRACT FROM AUTHOR]

This work presents an updated list of water beetles of the Elmidae and Dryopidae occurring in Morocco. The study is based on an exhaustive review of literature (1914–2021) complemented with field and laboratory investigations on more than 2200 collected individuals between 1997 and 2019. As a result, 30 species belonging to nine genera of Elmidae and Dryopidae are listed with their distribution in Morocco and North Africa. From the 30 species, Elmidae are represented by 21 species and seven genera, whereas Dryopidae are represented by nine species and only two genera. A chorological analysis shows that the Elmidae and Dryopidae from Morocco are essentially Mediterranean (60%), with a very high prevalence of endemics in the broadest sense (77.78%) within this group, whilst those Palearctic species (33.33%) or Afrotropical-Mediterranean (6.67%) are clearly less represented. This chorotype pattern is notably different to that observed in other aquatic beetle families in the same study area, where the percentage of endemic species was much lower. Moroccan Dryopoidea include seven endemic species exclusive to Morocco, six Maghrebian and one Ibero-Maghrebian species. [ABSTRACT FROM AUTHOR]

Morphologically cryptic lineages confound many estimates of global biodiversity and are often discovered in ecologically specialized taxa, subject to strong morphological constraint. Such a situation may apply in many extreme environments, including supralittoral rockpools, where dramatic fluctuations in water availability and salinity impose strong selection pressures on the inhabitants. Here we explore the genetic diversity and phylogeography of supralittoral rockpool Ochthebius beetles in the eastern Atlantic and western Mediterranean, using a combination of mitochondrial and nuclear markers and dense geographical sampling of the three recognized widespread species. Our results point to the existence of morphologically cryptic lineages within all currently named taxa and suggest that the distribution of these is linked to both historical and contemporary marine hydrogeography; a combination of ocean currents and winds apparently driving the spatial patterns observed. The main contemporary barrier to dispersal for Ochthebius is located around the Ibiza Channel, whilst the Messinian Salinity Crisis appears to have been the ultimate driver of lineage diversification in these insects. Our results show that oceanographic processes do not just shape the evolution of fully marine species, but also impact significantly on the terrestrially derived inhabitants of the coastal zone. [ABSTRACT FROM AUTHOR]

Coping with aridity is a physiological challenge for all organisms, including freshwater ones. Aridity shapes distributions of aquatic species at fine and large geographical scales. Specifically, for aquatic beetles, the desiccation resistance of the adults is a potential constraint for the colonisation of arid regions.We assessed the congruence between the fundamental and realised aridity niche in eight species of a Palearctic lineage of water beetles (subgenus Lumetus, genus Enochrus, family Hydrophilidae). We also estimated the relative explanatory capacity of aridity‐related versus other environmental variables in species distributions.Most of the species, even those most sensitive to desiccation stress in laboratory experiments, occur in areas with high aridity within the Palearctic region. Our results suggest a lack of association between the physiological (desiccation resistance) and environmental distance matrix (realised aridity niche), or between either of these and phylogenetic distances. Aridity‐related variables had generally a similar explanatory capacity in explaining the distribution of species than non‐related ones.Our results indicate that desiccation resistance has not been an important physiological constraint for the colonisation of arid environments by this clade and suggest that other non‐physiological factors are more important in shaping their distributions along aridity gradients. The studied beetle lineage might conserve a high basal desiccation resistance from relatively recent terrestrial ancestors, which could have provided a physiological advantage for the colonisation of arid areas. Further research could shed light on whether these unexpected results are common to other groups of aquatic insects living in arid areas or are particular to this group of beetles. [ABSTRACT FROM AUTHOR]

Evaluating data quality and inventory completeness must be a preliminary step in any biodiversity research, particularly in the case of insects and high biodiversity areas. Yet, this step is often neglected or, at best, assessed only for one insect group, and the degree of congruence of sampling effort ffor different insect groups remains unexplored.We assess the congruence in the spatial distribution of sampling effort for five insect groups (butterflies, caddisflies, dung beetles, moths, and aquatic beetles) in the Iberian Peninsula. We identify well‐surveyed areas for each taxonomic group and examine the degree to which the patterns of sampling effort can be explained by a set of variables related to environmental conditions and accessibility.Irrespective of the general lack of reliable inventories, we found a general but low congruence in the completeness patterns of the different taxa. This suggests that there is not a common geographical pattern in survey effort and that idiosyncratic and contingent factors (mainly the proximity to the workplaces of entomologists) are differentially affecting each group.After many decades of taxonomic and faunistic work, distributional databases of Iberian insects are still in a very preliminary stage, thus limiting our capacity to obtain reliable answers to basic and applied questions.We recommend carrying out long‐term, standardised and well‐designed entomological surveys able to generate a reliable image of the distribution of different insect groups. This will allow us to estimate accurately insect trends and better understand the full extent of global biodiversity loss. [ABSTRACT FROM AUTHOR]

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This checklist summarises our present knowledge on Moroccan distribution of the water beetles of five families: Gyrinidae, Haliplidae, Noteridae, Hygrobiidae and Dytiscidae. It includes all available faunistic data based on material collected by the authors and from the private collections, as well as from the literature, PhD theses, and other unpublished sources covering a period between 1914 and 2018. The checklist of 112 species of 40 genera is presented with species distributions in Morocco and North Africa. Hydroglyphus major (Sharp, 1882) is reported for the first time from Morocco. Six species (Agabus dilatatus (Brullé, 1832), Hydroporus longulus Mulsant and Rey, 1861, H. nigrita (Fabricus, 1792), H. planus (Fabricius, 1782), Bidessus pumilus (Aubé, 1838) and Ilybius fuliginosus (Fabricius, 1792)) are excluded from the country's fauna. A chorological analysis shows that most species are essentially Mediterranean (60%), whilst those whose distribution is wider in Palearctic (25%) or extends into Nearctic (9.29%) or Afrotropical regions (5.71%) are clearly less represented. This chorotype pattern is similar to that observed for other aquatic insects in the same study area. [ABSTRACT FROM AUTHOR]

The study of the genetic makeup and demographic fate of alien species is essential to understand their capacity to recover from founder effects, adapt to new environmental conditions and, ultimately, become invasive and potentially damaging. Here, we employ genomic data to gain insights into key demographic processes that might help to explain the extraordinarily successful invasion of the Western Mediterranean region by the North American boatman Trichocorixa verticalis (Hemiptera: Corixidae). Our analyses revealed the genetic distinctiveness of populations from the main areas comprising the invasive range and coalescent‐based simulations supported that they originated from independent introductions events probably involving different source populations. Testing of alternative demographic models indicated that all populations experienced a strong bottleneck followed by a recent and instantaneous demographic expansion that restored a large portion (>30%) of their ancestral effective population sizes shortly after introductions took place (<60 years ago). Considerable genetic admixture of some populations suggest that hypothetical barriers to dispersal (i.e., land and sea water) are permeable to gene flow and/or that they originated from introductions involving multiple lineages. This study demonstrates the repeated arrival of propagules with different origins and short time lags between arrival and establishment, emphasizing the extraordinary capacity of the species to recover from founder effects and genetically admix in invaded areas. This can explain the demonstrated capacity of this aquatic insect to spread and outcompete native species once it colonizes new suitable regions. Future genomic analyses of native range populations could help to infer the genetic makeup of introduced populations and track invasion routes. [ABSTRACT FROM AUTHOR]