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We report a hitherto unknown radiation within the clingfishes (Gobiesocidae), discovered in one of the best-studied marine biomes, the Mediterranean Sea. The monotypic genus Gouania is a Mediterranean endemic inhabiting the interstices of gravel beaches. Using geometric morphometric analyses, we identified two distinct morphotypes (characterized by a slender and a stout body shape, respectively) among Gouania willdenowi sampled from the three major Mediterranean basins (Eastern, Western and Adriatic). Slender and stout G. willdenowi occurred sympatrically in the Adriatic and the Eastern Mediterranean basins. Only the stout morphotype was found in the Western Mediterranean. Morphotypes were further distinguished by relative eye size and number of vertebrae. Based on mitochondrial and nuclear gene sequences, five highly divergent clades (COI-based K2P distances of 8 to 15%) were identified. The clades represented, respectively, stout Adriatic, slender Adriatic, stout Eastern, slender Eastern and stout Western Mediterranean Gouania. This suggests that the genus Gouania comprises at least five different species. Phylogenetic relationships among clades furthermore imply repeated evolution of convergent morphotypes. The onset of the Gouania radiation was dated to 3.23 (95% HPD 2.08-5.90) mya, and may therefore have overlapped with or followed the Messinian salinity crisis., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Mediterranean lotic waters such as rivers, streams and springs are poorly monitored for non-indigenous fish species (NIFS). Since these systems are stressed by multiple anthropogenic pressures, it is important to build robust procedures to track NIFS distribution and spread. This study applies a multi-faceted assessment of NIFS in the lotic ecosystems of Greece at different spatial scales by providing: a) a historical review of temporal patterns and arrival pathways of fish introductions in river basins of Greece (140 basins) across 100years; b) an analysis of occurrence and abundance data of NIFS assemblages at the lotic site scale (644 electrofished sites); c) the mapping of NIFS distributional patterns at river basin (75 basins) and regional scales (7 freshwater ecoregions); and, d) a vector analysis of fish translocations using an ecoregional framework. In total, 55 NIFS were recorded (25 alien and 30 translocated); however, there is a low incidence of NIFS in lotic waters at the site scale (30 NIFS recorded in the field samples; 10 alien and 20 translocated). NIFS introductions in Greece appear to be influenced by specific socio-historical periods, indicating a gradual increase since late 1970s. Despite this increase, our study provides evidence that only four alien species are currently widespread and common in the rivers and streams of Greece: Gambusia holbrooki, Carassius gibelio, Pseudorasbora parva, and Lepomis gibbosus (in order of recorded abundance). NIFS tend to be absent or distributed in very low numbers in upland streams and in smaller river basins. However, the issue of translocated fish species is shown to be a sorely neglected problem that is difficult to track. This review tests a readily transferable screening procedure, contributes to the application of the European Union Regulation on Invasive Alien Species; it suggests gaps and uncertainties, and proposes conservation and management actions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In ecosystems with high fish species endemicity, such as Mediterranean-type rivers, biogeographical differences among ecoregions present serious obstacles to developing broadly-applicable river bioassessment indices. This impediment has contributed to a serious time-lag in developing EU policy-relevant fish-based indices in the Eastern Mediterranean countries. Here we present the first model-based fish index for the Eastern Mediterranean (the Hellenic Fish Index, HeFI) in an effort to overcome biogeographic differences among the area's biotically heterogeneous rivers. The index is based on modelled reference conditions and employs site-specific electrofished fish samples from an extensive dataset from Greece that covers six freshwater ecoregions, including five transboundary river basins flowing through six countries. Environmental and anthropogenic pressure data were procured from 403 sampled river sites and ecologically-relevant traits were defined for 103 collected fish species. For the development of the index, we first diagnosed least degraded sites forming a calibrated reference site dataset and secondly quantified differences of fish metrics between the reference and impaired sites. Four trait-based fish metrics showed the best ability to discriminate between impaired and reference sites. The index performed well in discriminating anthropogenic pressure classes, giving a significant negative linear response to a gradient of anthropogenic degradation. HeFI successfully assessed both small and large rivers in different freshwater ecoregions. This geographically broad-scale index development shows that key trait-based reference conditions can be produced by a predictive model in remarkably heterogeneous rivers where range-restricted fishes dominate. This index promotes a screening-level bioassessment application that may be further developed and refined with relevant monitoring., (Copyright © 2017 Elsevier B.V. All rights reserved.)

While Gobioidei comprises showcases of (adaptive) radiation, the scientific interest they yielded did not ensure full understanding of goby biodiversity. Even in a well-studied region like Europe, wide knowledge gaps remain. Sand gobies represent one of the few clades whose monogenean parasites have been thoroughly studied. However, in the Balkans, part of the sand gobies' centre of endemism, these parasites were unstudied. We focus on Greek and Croatian freshwater gobies. From five sand goby species, the first parasites are reported, describing seven new Gyrodactylus species. Economidichthys pygmaeus harbours Gyrodactylus benedeni sp. n. and Gyrodactylus dorlodoti sp. n. Its congener E. trichonis hosts G. meelkopae sp. n. Knipowitschia milleri was found to host G. charon sp. n., K. thessala is infected by G. bios sp. n., and K. croatica by G. douglasadamsi sp. n. and G. hellemansi sp. n. Gyrodactylus bubyri was found on its type host K. caucasica. A diverse parasite fauna is expected for a region known for its biodiversity and endemism. The contribution of parasites to species richness in such hotspots is overlooked. The observed species richness per host is rather low compared to the better-studied eastern Atlantic sand gobies. Host vicariance is considered to mediate parasite specificity in this fauna. Some new flatworm species display unique morphological features, such as the remarkable size of the marginal hook sickle proper compared to its foot in the Economidichthys parasites, or a characteristically kinked marginal hook sickle in G. douglasadamsi sp. n. These features reflect their hosts' endemism in the Balkans.

Mediterranean river systems are characterised by more diverse fish assemblages and regional ecological processes compared with the rest of Europe. A data set from Mediterranean France, Iberia and Greece (∼2000 sites) was used to describe the characteristics of fish assemblages, explore their responses to anthropogenic disturbance and analyse the implications for river quality assessment. There was a southwards decline in species richness per site, but endemicity and proportion of alien species increased. Sites in the eastern Mediterranean had higher endemicity, lower site richness and lower number of alien species than sites in western Mediterranean Europe. Assemblage composition differed between Mediterranean sub-regions, but was dominated by three major fish types: a salmonid fish type common throughout the study area and two cyprinid-dominated fish types (in some sub-regions, Salmo trutta L. is present but not numerically dominant), corresponding to a gradient in hydrological and temperature regimes. Metric responses to perturbation were compared with those found at the European (larger scale) and basin (smaller scale) levels. Overall metric response was weaker in this Mediterranean application. The best responses to human pressure were usually obtained with abundance-based metrics and included the contribution of naturalised alien species. Some widespread alien species contributed to the response to anthropogenic alteration (notably Cyprinus carpio L. and Lepomis gibbosus (L.)). [ABSTRACT FROM AUTHOR]