Aquatic ecosystems are particularly vulnerable to the introduction of non-indigenous species (NIS), leading to multi-faceted ecological, economic and health impacts worldwide. The Iberian Peninsula comprises an exceptionally biodiverse Mediterranean region with a high number of threatened and endemic aquatic species, most of them strongly impacted by biological invasions. Following a structured approach that combines a systematic review of available information and expert opinion, we provide a comprehensive and updated multi-taxa inventory of aquatic NIS (fungi, macroalgae, vascular plants, invertebrates and vertebrates) in Iberian inland waters. Moreover, we assess overall patterns in the establishment status, introduction pathways, native range and temporal introduction trends of listed NIS. In addition, we discuss the legal coverage provided by both national (Spanish and Portuguese) and European NIS regulations. We inventoried 326 aquatic NIS in Iberian inland waters, including 215 established, 96 with uncertain establishment status and 15 cryptogenic taxa. Invertebrates (54.6%) and vertebrates (24.5%) were the groups with the highest number of NIS, with Arthropoda, Mollusca, and Chordata being the most represented phyla. Recorded NIS originated from diverse geographic regions, with North and South America being the most frequent. Vertebrates and vascular plants were mostly introduced through intentional pathways (i.e. release and escape), whereas invertebrates and macroalgae arrived mostly through unintentional ways (i.e. contaminant or stowaway). Most of the recorded NIS were introduced in Iberian inland waters over the second half of the 20^th century, with a high number of NIS introductions being reported in the 2000s. While only 8% of the recorded NIS appear in the European Union list of Invasive Alien Species of Union concern, around 25% are listed in the Spanish and Portuguese NIS regulations. This study provides the most updated checklist of Iberian aquatic NIS, meeting the requirements set by the EU regulation and providing a baseline for the evaluation of its application. We point out the need for coordinated transnational strategies to properly tackle aquatic invasions across borders of the EU members.

Coastal habitats are amongst the most dynamic on Earth, due to their simultaneous exposure to terrestrial, oceanic and atmospheric processes. Coastal taxa are therefore often ecologically specialised and adapted to withstand frequent shifts in sea level, wave exposure, temperature or salinity. This specialisation often resulting in significant cryptic diversity. Previous molecular studies have suggested that genetic differentiation in non-marine coastal organisms may be influenced by oceanic currents and fronts, but the extent to which such processes affect dispersal and evolution of such taxa remains unclear. Here we explore whether population genetic structure in two supralittoral rockpool beetle species (genus Ochthebius) can be predicted from the general circulation pattern of the marine currents and associated oceanic fronts. We simulated dispersal using a Lagrangian particle tracking model and compared this with population genetic structure inferred from COI (mitochondrial) and wingless (nuclear) genes applying linear models and Mantel tests. We show that a biophysical model based on oceanic currents and fronts in the western Mediterranean Sea is a much better predictor of observed population genetic structure than isolation by distance in both species. Our results show that oceanic processes, besides shaping contemporary population connectivity in fully marine organisms, also exert a meaningful influence on terrestrially-derived coastal taxa such as supralittoral rockpool beetles — the first time this mode of dispersal has been demonstrated in an insect.

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.

Here we focused on the co-occurrence pattern on regional and local scales, and on the niche differences of two species of congeneric beetles (Ochthebius quadricollis and O. lejolisii, Hydraenidae) exclusive of supratidal rockpools. Abundances of adults and larval stages from both species and environmental variables were obtained in 10 pools from 12 localities along the Iberian Mediterranean coast. To determine the local co-existence pattern, we monthly sampled two localities in an annual cycle. On regional and local scales, we found negative correlations between both species’ pool abundances, which suggest spatio-temporal segregation based on their different environmental responses. The OMI analysis detected interspecific niche differences, larger in larvae than adults. The best regression models obtained for O. quadricollis larvae included depth, conductivity, and fine sediments as the main explanatory variables with a positive effect, and distance to sea and CPOM with a negative effect. For O. lejolisii larvae, the best models included CPOM and periphyton with positive effects, while pool area, depth and conductivity negatively affected. Our results suggest that subtle interspecific differences in ecological niches, mainly those related to pool hydroperiod and salinity, could determine spatio-temporal storage effects as the principal mechanisms of co-existence on local and regional scales.

A checklist of water beetles of the family Hydrochidae from Morocco is presented. The study compiles data gathered from a deep literature review and field surveys at 397 freshwater localities between 1985 and 2023. The checklist also contains information concerning type localities and detailed distributions for the eight species found. We include a detailed redescription of Hydrochus cf. obtusicollis Fairmaire, 1877, currently listed as a synonym of H. flavipennis Küster, 1852, but clearly representing a different species. In addition, a key, based largely on male genitalia, is presented for Moroccan species. This work is the first detailed study of the family Hydrochidae in Morocco, which can provide a basis for future progress in the knowledge of Moroccan aquatic Coleoptera, an insect group of great ecological interest.

Arthropods constitute the bulk of global biodiversity, being the most diverse metazoan phylum on the planet. Despite the relevance of arthropods, our knowledge about them remains limited, partly due to the scarcity of reliable faunistic data. The Iberian Peninsula is part of one of the global biodiversity hotspots, the Mediterranean Basin. However, very little is known on the ecology and spatial distribution of many Iberian arthropod species. We provide a database on the distribution of Ibero-Balearic arthropods (the IberArthro database) belonging to 10 taxonomic groups: Coleoptera (Aquatic), Coleoptera (Scarabaeoidea), Collembola, Hymenoptera (Apoidea), Lepidoptera (Noctuoidea), Lepidoptera (Papilionoidea), Neuropterida, Opiliones, Plecoptera and Trichoptera. The database contains 1 006 768 records with associated geographic data (at 10 × 10 km grid squares), compiled from various sources and validated by specialists in each group. These records cover 4612 species and subspecies, spanning from the 18th century to February 2024. This database represents an unprecedented advance in understanding the distribution of Iberian arthropod biodiversity and its conservation. The complete dataset is provided in Darwin Core Archive format and is available through the Global Biodiversity Information Facility (GBIF).