Jasna Vukić

Nuclear and mitochondrial DNA sequence data reveal the evolutionary history of Barbus (Cyprinidae) in the ancient lake systems of the Balkans.

Freshwater fauna of ancient lakes frequently contain endemic taxa thought to have originated during the long existence of these lakes, yet uncertainties remain as to whether they represent distinct genetic lineages with respect to more widespread relatives and to the relative roles of isolation and dispersal in their evolution. Phylogenetic analyses of sequence variation at nuclear and mitochondrial genes were used to examine these issues for the freshwater fish genus Barbus in two European ancient lake systems on the Balkan Peninsula. The nuclear and mitochondrial data yielded concordant phylogeographic patterns though incomplete sorting of nuclear haplotypes between some mitochondrial clades was detected. The distributions of two currently recognized species investigated here do not match the distributions of evolutionary lineages revealed by phylogenetic analyses. The Prespa barbel, Barbus prespensis, is not endemic to the lakes Prespa as previously thought but is instead found to be widespread in the south-eastern Adriatic Sea basin, with a distribution largely corresponding to the basin of the now extinct Lake Maliq historically connected with Lake Prespa. On the other hand, a cryptic phylogenetic subdivision in a widespread species, B. rebeli, was discovered to be more distant from B. rebeli than from other Barbus species and to be endemic to the system of connected lakes Ohrid and Shkodra. The division coincides with the hydrogeographical boundary delimiting distributions of other freshwater fishes, and we suggest that this newly discovered evolutionary lineage represents a distinct species. These findings support the emerging pattern that endemic taxa have evolved not through isolation of individual lakes, but in systems of currently and historically interconnected lakes and their wider basins.

Evolutionary stability of sex chromosomes in snakes.

Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms.

Conservation of sex chromosomes in lacertid lizards.

Sex chromosomes are believed to be stable in endotherms, but young and evolutionary unstable in most ectothermic vertebrates. Within lacertids, the widely radiated lizard group, sex chromosomes have been reported to vary in morphology and heterochromatinization, which may suggest turnovers during the evolution of the group. We compared the partial gene content of the Z‐specific part of sex chromosomes across major lineages of lacertids and discovered a strong evolutionary stability of sex chromosomes. We can conclude that the common ancestor of lacertids, living around 70 million years ago (Mya), already had the same highly differentiated sex chromosomes. Molecular data demonstrating an evolutionary conservation of sex chromosomes have also been documented for iguanas and caenophidian snakes. It seems that differences in the evolutionary conservation of sex chromosomes in vertebrates do not reflect the distinction between endotherms and ectotherms, but rather between amniotes and anamniotes, or generally, the differences in the life history of particular lineages.

A multilocus assessment of nuclear and mitochondrial sequence data elucidates phylogenetic relationships among European spirlins (Alburnoides, Cyprinidae).

The phylogenetic relationships and taxonomy of the spirlins in the genus Alburnoides are examined by comparative sequencing analysis of mitochondrial and nuclear markers. Molecular analyses revealed 17 Eurasian lineages divided into two main clades, termed the Ponto-Caspian and European in accordance with the lineage distribution. The indel diagnostics of β-actin and S7 markers and translation of cyt b to the amino acid chain were evaluated as a reliable identifying tool for most of the recognised lineages. Lineage richness is closely connected with the existence of known glacial refugia in most cases. The underestimation of species richness in the genus Alburnoides is confirmed: the genetic analyses support the validity of 11 morphologically accepted species; apart from them, four phylogenetic lineages requiring descriptions as separate species were revealed. The distribution area of the nominotypical species A. bipunctatus s. stricto is newly defined. Two diverging phylogenetic lineages, A. ohridanus, and A. prespensis complex, were observed in the Southeast Adriatic Freshwater Ecoregion, confirmed as a hotspot of endemic biodiversity. A. ohridanus demonstrates high divergence from the A. prespensis complex, represented by three similar mitochondrial lineages with the same nuclear haplotypes and sympatric occurrence. The range restricted endemism was confirmed for at least seven species. The Albanian river systems, as well as the wider Ponto-Caspian basin exhibit complications among definite species delineations and gaps in understanding of microevolutionary processes; these areas require further investigations.

Morphological comparison of bleaks (Alburnus, Cyprinidae) from the Adriatic Basin with the description of a new species

Abstract. The morphometric, meristic and phenotypical characters of the members of the genus Alburnus from the Adriatic Basin were analyzed on specimens from 11 localities, representing eight watersheds. The number of gill rakers, the number of lateral line scales, the number of branched anal fin rays and the coverage of the ventral keel by scales have the greatest significance in differentiating between species. Significant morphological differences exist between the Alburnus population from Lake Lugano (type locality for Alborella maxima Fatio, 1882) and all the remaining investigated populations. Alburnus from the Neretva River drainage is described as a new species and it is distinguished from other species of the genus Alburnus by the following combination of characters: 13½-15½ branched anal fin rays; 17–26 gill rakers; 40–48 lateral line scales; first anal fin ray below branched dorsal rays 6–10 or located up to one scale after the last dorsal fin ray; ventral keel exposed for at least ⅔ of a distance between the pelvic fin base and the anal aperture. The status of the Neretva River basin populations as a separate species was corroborated by genetic analyses, with p-distance between newly described species and A. arborella from the Zrmanja River 1.8–2.2%.

Different Histories, Different Destinies‒Impact of Evolutionary History and Population Genetic Structure on Extinction Risk of the Adriatic Spined Loaches (Genus Cobitis; Cypriniformes, Actinopterygii).

The region of Balkans is often considered as an ichthyologic “hot spot”, with a great number of species and high portion of endemics living in fresh waters in a relatively small area. The Adriatic watershed in Croatia and Herzegovina is inhabited by six spined loach species (genus Cobitis) whose extinction risk estimations were based solely on their extent of occurrence (and/or area of occupancy) and its fragmentation, and conservation proposals do not consider diversity below species level. In this investigation we employed molecular genetic methods to describe present genetic structure of the Adriatic spined loaches and reveal their demographic history. The divergence of the Adriatic lineages inside the genus Cobitis started in Miocene and lasted until Pleistocene epoch. Geological events responsible for shaping recent diversity of spined loaches in the Adriatic basin are: the Dinarid Mountains upwelling, the evolution of Dinaric Lake system, local tectonic activity, river connections during glaciations and differences in sea level. Even though all the investigated species inhabit karstic rivers located in the same geographic area and that were subject of similar geological events, the results obtained reveal great differences in their genetic diversity and structure and point out the necessity of different conservation measures to ensure their future viability. High level of genetic polymorphism is characteristic for species located more to the south. Two species comprised of more than one population have completely different intraspecific structure; populations of C. illyrica are genetically distinct and represent separate evolutionary significant units, whereas intraspecific structure of C. narentana corresponds to metapopulational pattern. Without population genetic data, evolutionary significant units could be easily misidentified. Furthermore, the obtained results affirm that population genetic measurements are able to detect differences among closely located and related species and estimate extinction risk even more accurately than currently applied IUCN criteria.

Spheroidal carbonaceous particle record in sediments of a small reservoir

The main aims of this study were to determine whether reservoir sediments provide good temporal records of atmospherically deposited spheroidal carbonaceous particles (SCPs), and to examine their spatial distribution within the reservoir. SCPs are produced solely by fossil-fuel burning and are good indicators of the extent of industrial pollution. The site chosen for the study was Drásov Reservoir in the Czech Republic. Sediment cores were taken along two transects within the reservoir. The results suggest that wind- and inlet-induced currents have an important influence on both SCP and sediment distribution in the reservoir, and that the distribution of SCPs is different to that of sediments. The SCP records were most reliable in the down-wind area of the reservoir, and although most detailed SCP record was contained in a deep-water core near the dam, records in shallower-water cores from the down-wind side of the reservoir were also good. The correlation between SCP accumulation rates and solid emissions from local sources was very good (Spearman R=0.867, p=0.001).%

Discovery of the oldest Gobius (Teleostei, Gobiiformes) from a marine ecosystem of Early Miocene age

Gobiidae (Gobiiformes, Teleostei) is among the largest families of vertebrates. These fishes are distributed worldwide and contribute significantly to species diversity in marine habitats and reefs. However, their fossil record is sparse prior to the Miocene and little is known about the course of diversification of the clade. Here we report exceptionally well-preserved skeletal remains of the oldest known Gobius from an Early Miocene (Burdigalian) marine ecosystem of Central Europe (Czech Republic). Gobius jarosi Přikryl & Reichenbacher sp. nov. is dated to 19.1–20.4 Ma by biostratigraphical analysis of calcareous nannoplankton from small fragments of the holotype matrix. Gobius jarosi sp. nov. is characterized by a pterygiophore formula of 3-22110 and a premaxilla with a distinctive postmaxillary process, has 11 abdominal and 16–17 caudal vertebrae, six thin spines in the first dorsal fin and one spine and 12 soft rays in the second dorsal fin, one spine and 11 rays in the anal fin, and two anal fin pterygiophores preceding the first haemal spine. Large ctenoid scales cover the body except for its anterior portion and the head. A comparative analysis of meristic and osteological data suggests close affinities between G. jarosi sp. nov. and the extant species G. niger, G. roulei and G. vittatus. Accompanying fish fossils and nannoplankton assemblages indicate that G. jarosi sp. nov., like G. roulei and G. vittatus, lived in an inshore to offshore marine ecosystem. The discovery of such an early member of the lineage leading to the present-day species of Gobius has important implications for the origin and evolution of the Gobiidae, and indicates that diversification of the European Gobiidae began in, but not before, the Early Miocene. http://zoobank.org/urn:lsid:zoobank.org:pub:3229739B-3428-4DFB-9588-4CE875D732D8

Ancient mitochondrial capture as factor promoting mitonuclear discordance in freshwater fishes: A case study in the Genus Squalus (Actinopterygii, Cyprinidae) in Greece

Hybridization and incomplete lineage sorting are common confounding factors in phylogeny and speciation resulting in mitonuclear disparity. Mitochondrial introgression, a particular case of hybridization, may, in extreme cases, lead to replacement of the mitochondrial genome of one species with that of another (mitochondrial capture). We investigated mitochondrial introgression involving two species of the cyprinid genus Squalius in the western Peloponnese region of Greece using molecular and morphological data. We found evidence of complete mitochondrial introgression of Squalius keadicus into two populations recognized as Squalius peloponensis from the Miras and Pamissos River basins and a divergence of mitochondrial genomes of S. keadicus from the Evrotas basin from that of the introgressed populations dating from the Pleistocene. Secondary contact among basins is a possible factor in connection of the species and the introgression event. Morphological analyses support the hypothesis of mitochondrial introgression, as S. keadicus was different from the other three populations recognized as S. peloponensis, although significant differences were found among the four populations. Isolation by geographical barriers arose during Pleistocene in the western Peloponnese were the source of the evolution of the two reciprocally monophyletic subclades found in the S. keadicus mitochondrial clade, and the morphological differences found among the four populations. Along with the lack of structure in the nuclear genome in the three populations ascribed to S. peloponensis, this suggests an incipient speciation process occurring in these Squalius species in the western Peloponnese.

Complete mitochondrial genome of the Greek nine-spined stickleback Pungitius hellenicus (Gasterosteiformes, Gasterosteidae)

Abstract The complete mitochondrial genome of the Greek nine-spined stickleback Pungitius hellenicus was obtained using Illumina high-throughput sequencing of genomic DNA. The genome was 16 713 bp long, and contained 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region. The arrangement of the genes was identical to that of other Gasterosteidae fishes. However, the control region of P. hellenicus contained three copies of imperfect repeated sequences (72–78 bp in single motifs), while P. pungitius and P. tymensis have one or two copies. Nucleotide identity between P. hellenicus and three other Pungitius species across all the 37 genic regions was 93.0% to 95.5%.