Increased spatial resolution of sampling in the Carpathian basin helps to understand the phylogeny of central European stream-dwelling gudgeons

Distribution and diversity of fishes and lampreys in Transylvania (Romania): a complete survey and suggestions for new protected areas

Freshwater fishes are in a serious state of decline across the world, making them one of the most threatened groups of vertebrates. The Danube River catchment area in Europe holds the richest freshwater fish community, but our knowledge of the current distribution of these species is limited. Transylvania, the largest region of Romania, is one of the important tributaries of the Danube, from where 77 fish and two lamprey species were recorded until now. Despite this large diversity of freshwater fishes, there is a lack of systematic survey of the fish fauna in this region for the past 50 years. In this study, we present data on the occurrence and distribution of fishes and lampreys collected in Transylvania from 2007 to 2022. This data covers 43% of Romania's surface and includes all major rivers from Transylvania. 65 species of fish and three species of lampreys are recorded, and an additional nine fish species are also reported based on information from competent people. Of the 77 fish and lamprey species recorded 19 (24.7%) are non-native, although their relative abundance was low (5.1%) compared to other similar regions in Europe. The first records of Eudontomyzonmariae, Neogobiusmelanostomus, Piaractusbrachypomus, Pygocentrusnattereri, and Salvelinusalpinus in Transylvanian rivers are presented, as well as the first record of Cobitiselongata outside the Nera River basin (from the Caraș River) and the detection of three new populations of the vulnerable Umbrakrameri. Data on changes in distribution that have occurred since the last comprehensive survey 50 years ago are also provided and the importance of our results in conservation planning are discussed, including the designation of new protected areas for freshwater bodies and the compilation of the Romanian Red List of fishes.

A comprehensive DNA barcode inventory of Austria’s fish species

Austria is inhabited by more than 80 species of native and non-native freshwater fishes. Despite considerable knowledge about Austrian fish species, the latest Red List of threatened species dates back 15 years and a systematic genetic inventory of Austria’s fish species does not exist. To fulfill this deficit, we employed DNA barcoding to generate an up-to-date and comprehensive genetic reference database for Austrian fish species. In total, 639 newly generated cytochrome c oxidase subunit 1 (COI) sequences were added to the 377 existing records from the BOLD data base, to compile a near complete reference dataset. Standard sequence similarity analyses resulted in 83 distinct clusters almost perfectly reflecting the expected number of species in Austria. Mean intraspecific distances of 0.22% were significantly lower than distances to closest relatives, resulting in a pronounced barcoding gap and unique Barcode Index Numbers (BINs) for most of the species. Four cases of BIN sharing were detected, pointing to hybridization and/or recent divergence, whereas in Phoxinus spp., Gobio spp. and Barbatula barbatula intraspecific splits, multiple BINs and consequently cryptic diversity were observed. The overall high identification success and clear genetic separation of most of the species confirms the applicability and accuracy of genetic methods for bio-surveillance. Furthermore, the new DNA barcoding data pinpoints cases of taxonomic uncertainty, which need to be addressed in further detail, to more precisely assort genetic lineages and their local distribution ranges in a new National Red-List.

The mixed phylogenetic origin of northern pike (Esox lucius Linnaeus 1758) populations in the Middle Danubian drainage

BACKGROUND

Pikes, members of genus Esox, are widespread freshwater predators of the northern hemisphere, and important sport fish also. From the Carpathian basin only one species, the northern pike (E. lucius) is noted. At the same time the pike stocks living in this area show high level of phenotypic variance (e.g. various body pattern) and its growth varies highly both among and within populations. These features usually explained by the environmental diversity of the area. Whereas we think that genetic reasons -e.g. the appearance of other/new pike species in the area- may also be responsible for these observed features. Since as no detailed information have been published from the pike populations of this area, so far; we conducted phylogenetic and morphological assay on 88 pike specimens, collected from 49 Middle Danubian sampling sites.

RESULTS

Our phylogenetic surveys showed that the northern pike appear in the study area solely, but all the three of its major lineages (Northern, Circumpolar, Southern) were indicated. Only six specimens represent the Northern lineage, collected from the western part of the study area. The Circumpolar and Southern lineages were common in the Carpathian basin, but the Southern lineage showed higher levels of haplotype diversity than the Circumpolar clade. Which indicates that only the Southern lineage is native in the area, while the other two groups could have appeared in the Middle Danubian system either spontaneously or by human introduction. Moreover, the different clades appeared in the same populations, suggesting the opportunity of inter-lineage hybridisation. From the studied morphologicalal features, the number of scales on the lateral line and the head length showed significant differences among the lineages. At the same time the body pattern of the studied individuals seems to be rather influenced by the ontogenic changes than phylogeny.

CONCLUSIONS

The high phenotypic variability of Middle Danubian northern pike populations may be due that all of its three major clades appeared and came in secondary contact in the area. In the within watershed spread of the non-native lineages the human stocking/transfer may play a considerable role.

Infirm effect of phylogeny on morphometric features in a cryptic Gobio species complex

Several recent notes prove that taxonomic relations of close relative animal groups (species complexes or cryptic species) can be revealed by the combined use of genetic and morphologic methodologies. At the same time scarce information can be found about how phylogeny, population origin, and sexual dimorphism affect the morphometric features of these species. In our present work, we performed simultaneous phylogenetic and morphological studies on the taxonomically still questionable Carpathian stream dwelling gudgeons (Cyprinidae, Gobio) by using two different methodologies (distance based and geometric morphometry). Our results were in correspondence with the previous findings, showing the presence of three phylogenetically more or less distinct groups in the area. The results of the whole-body geometric and the traditional, distance-based morphometry reflected the extent of phylogenetic differences. While the results of geometric scale morphometry did not correspond with the genetic subdivisions. Results of three way PERMANOVA analyses showed that the phylogenetic effects on morphometry is less considerable as the population origin or the sexual dimorphism at these cyprinid taxa. Our investigation contributed to the better understanding of the taxonomy of fish stocks in the Carpathian Basin, and to their conservation, but additional investigations will be needed to clarify the exact taxonomic position of the gudgeons (’Gobio sp1’) dominating the eastern part of the studied drainage.