The minnowPhoxinus lumaireul(Leuciscidae) shifts the Adriatic–Black Sea basin divide in the north‐western Dinaric Karst region

Abstract

Karst landscapes are characterized by intermittent and sinking streams. The most common method used to study underground hydrological connections in karst is tracing tests. However, a more biologically oriented approach has been suggested: analysis of the genetic structure of aquatic organisms. Biological tracers can be sought among trogloxenes, that is, surface species that occasionally enter caves and groundwater. One such example is the fish genus Phoxinus, which exhibits high genetic diversity and complex phylogeography in the Balkan Peninsula. In the north‐western Dinaric Karst, the complex hydrological network was digitalized in 2020. Contemporaneously, Phoxinus lumaireul populations in the Slovenian Dinaric Karst were intensively sampled and analysed for fragments of two mitochondrial genes and one nuclear gene. The derived phylogeographic structure and data on hydrological connections were compared to evaluate support for three alternative scenarios: The genetic structure (1) is a consequence of the ongoing geneflow through underground connections, (2) reflects a previous hydrological network or (3) is an outcome of anthropogenic translocations. The results suggest that the first two scenarios seem to have played a major role, while the third has not had profound effects on the genetic composition. Comparison between the genetic structure of Slovenian Dinaric Karst sampling sites and that of hydrologically isolated reference sampling sites indicated a greater genetic connectivity in the former. Moreover, the range of Adriatic (1a) and Black Sea (1c) haplotypes does not correspond to the Adriatic–Black Sea basin divide but is shifted northwards.

Comparative Phylogeography of Phoxinus, Delminichthys, Phoxinellus and Telestes in Dinaric Karst: Which Factors Have Influenced Their Current Distributions?

“…When introduced to non-native rivers and lakes, Phoxinus species quickly spread and are considered invasive in Scandinavia and Spain [52,79,97], attesting again to the adaptability of the genus to new environments [92]. It is clear that Phoxinus species are generalists with a high migratory potential, confirmed also in previous studies [37,39,98], which detected several occasions of the crossing of the Adriatic-Black Sea divide in Dinaric Karst. Especially in lineages 1a and 1b, the genetic structure points to a recurrent, ongoing contact between surface-isolated water systems that are connected underground, keeping the populations in Hardy-Weinberg equilibrium.…”

“…While Leuciscinae in Europe are well represented (>320 species), the closest relatives of Phoxinus are distributed in the Pacific basin [54,106,107]. Morphologically, Phoxinus is, in general, characterized by a low level of phenotypic diversity, in contrast to its high level of genetic diversity [38,98,108], whereas Leuciscinae (including Delminichthys, Phoxinellus and Telestes) are highly phenotypically divergent and taxonomically structured in a complex system that also corresponds to their genetic patterns. Nevertheless, when comparing the distribution ranges with other unrelated taxa spread in the Dinaric Karst, some common patterns emerge.…”

A chromosome-level, haplotype-resolved genome assembly and annotation for the Eurasian minnow (Leuciscidae: Phoxinus phoxinus) provide evidence of haplotype diversity

“…Our high-quality assembly, indicating augmented levels of standing genetic variation, is a testament to this approach. Previous studies have also indicated abundant levels of genetic variation in the Phoxinus genus (Bogutskaya et al, 2020; Reier et al, 2022), potentially enabling more expeditious responses to environmental changes and even greater potential for adaptation across diverse environments (Lai et al, 2019; Matuszewski et al, 2015).…”

“…Our high-quality assembly, indicating increased levels of standing genetic variation, demonstrates the effectiveness of this approach. Previous studies have already indicated abundant levels of genetic variation in the Phoxinus genus (Bogutskaya et al, 2020; Reier et al, 2022).…”

An integrative approach highlights the discrepancy in the genetic, phenotypic, and presumptive taxonomic structure of Phoxinus (Actinopterygii, Leuciscidae, Phoxininae) in Bulgaria

“…Among the highlighted problems to be addressed were the high intraspecific phenotypic diversity, which makes it difficult to diagnose morphologically similar species (Bogutskaya et al, 2019), and the insufficient information provided by the currently analysed molecular markers for final species delimitation (Palandači c et al, 2020). Finally, in contrast to most leuciscid fishes, it was found that the distribution of species (and/or mitochondrial [mt] clades) in European Phoxinus does not follow current zoogeographic patterns and drainage boundaries (Palandači c et al, 2015(Palandači c et al, , 2017a(Palandači c et al, , 2020Reier, Bogutskaya, & Palandači c, 2022;Reier, Kruckenhauser et al, 2022).…”