Migration and isolation during the turbulent Ponto‐Caspian Pleistocene create high diversity in the crustacean Paramysis lacustris

The Ponto‐Caspian brackish‐water fauna inhabits estuaries and rivers of the Black, Azov and Caspian seas and is fragmented by higher salinity waters and a major interbasin watershed. The fauna is known for the high levels of endemism, complex zoogeographic histories, and as a recent source of successful invasive species. It remains debated whether the Black and Azov Sea brackish‐water populations survived unfavourable Pleistocene conditions in multiple separate refugia or whether the two seas were (repeatedly) recolonized from the Caspian. Using microsatellite and mtDNA markers, we demonstrate deep among‐ and within‐basin subdivisions in a widespread Ponto‐Caspian mysid crustacean Paramysis lacustris. Five genetic clusters were identified, but their relationships did not reflect the geography of the region. The Azov cluster was the most distinct (4–5% COI divergence), despite its geographic position in the corridor between Black and Caspian seas, and may represent a new species. In the northern Black Sea area, the Dnieper cluster was closer to the Caspian cluster than to the neighbouring Danube–Dniester–Bug populations, suggesting separate colonizations of the Black Sea. Overall, the data implied a predominant gene flow from the east to the Black Sea and highlight the importance of Caspian Sea transgressions in facilitating dispersal. Yet, the presence of distinct lineages in the Black Sea points to the persistence of isolated refugial populations that have gained diagnostic differences under presumably high mutation rates and large population sizes. The unfavourable Pleistocene periods in the Black Sea therefore appear to have promoted diversification of the brackish‐water lineages, rather than extirpated them.     

History of aquatic invertebrate invasions in the Caspian Sea

Incorporation of the fossil record and molecular markers into studies of biological invasions provides new historical perspectives on the incidence of natural and human-mediated invasions of nonindigenous species (NIS). Palaeontological, phylogeographic, and molecular evidence suggests that the natural, multiple colonizations of the Caspian basin via transient connections with the Black Sea and other basins played an important role in shaping the diversity of Caspian fauna. Geographically isolated, conspecific Ponto-Caspian lineages that currently inhabit fragmented habitats in the Ponto-Caspian region show limited genetic divergence, implying geologically recent episodes of gene flow between populations during the Pliocene to Pleistocene. Several molluscan lineages in the Caspian Sea may have descended from Lake Pannon stock before the Late Miocene isolation of the Caspian depression, about 5.8 million years ago. Anthropogenic activities during the 20th century were responsible for a 1800-fold increase in the rate of establishment of new aquatic species in the Caspian Sea compared to the preceding two million years of natural colonization. The observed success of NIS invasions during the 20th century was due primarily to human-mediated transport mechanisms, which were dominated by shipping activities (44%). Human-mediated species transfer has been strongly asymmetrical, toward the Volga Delta and Caspian Sea from or through Black and Azov Seas. Global and regional trade, particularly that mediated by commercial ships, provides dispersal opportunities for nonindigenous invertebrates, indicating that future invasions in the Caspian Sea are anticipated.     

Aral Sea Ostracoda as environmental indicators

Fluctuations in the level and chemistry during its history have played a major part in shaping the floral and faunal communities of the Aral Sea. Of the eleven species of Ostracoda (Crustacea) known to have been living in the Aral Sea in 1960, only one survives today due to the anthropogenically induced salinity increase of the past three decades. The origins of a mixed fresh- and brackish-water ostracod fauna are discussed, and it is concluded that some of the major faunal elements must have reached the Aral Sea Basin during a past high water level phase when connection existed with the Caspian Sea. The taxonomic position of key taxa is clarified, and the major elements of the pre-1960 Aral Sea ostracod fauna are illustrated from Holocene sequences. Aral Sea, Ostracoda, Holocene, palaeolimnology.     

A new Paratethyan genus of the ostracod subfamily Loxoconchinae (Podocopida,Cytheroidea)

A new ostracod genus established in a Loxoconchinae fauna from the Eastern Paratethys, with two species known from the Pliocene–post-Pliocene and Recent of the Caspian Sea and Dnieper–Bug estuary of the Black Sea Basin is described. Comparative morphological analysis of four Loxoconchinae genera from a brackish-water fauna of the Paratethyan basins is performed and the trends in morphological evolution of their hinge structures are revealed.     

A Late Miocene Paratethyan mollusc fauna from the Denizli Basin (southwestern Anatolia, Turkey) and its regional palaeobiogeographic implications

We report on a Late Miocene mollusc fauna from a single locality in the Denizli Basin in southwestern Turkey that is composed of ten presumably euryhaline species and three freshwater species. The fauna is remarkably distinct from faunas of the adjacent Late Miocene Aegean and Euxinian Basins, and has elements in common with the modern Caspian Sea fauna in the form of Didacna species. The suggested age of the fauna (Late Miocene) would extend the stratigraphic range of the lymnocardiid genus Didacna (hitherto Calabrian-Extant) considerably. The palaeobiogeographic significance of the Denizli fauna is discussed.     

Sturgeon abundance and distribution in the Caspian Sea.

The number of sturgeons and their distribution on feeding grounds in the Caspian Sea were assessed. Data were collected between 1991 and 1996 on environmental factors, species composition, and population sizes in the Northern, Middle and Southern Caspian Sea except for Iranian waters. The results show a drastic decline of the sturgeon populations on the feeding grounds at sea. In order to preserve the Caspian Sea sturgeon populations, efforts of all States surrounding the Caspian Sea must be increased and harmonised to serve a single system of fishery management, stock conservation and enhancement measures based on natural reproduction and artificial propagation.     

Biogeographic zonation of the Black Sea and Caspian Sea basin based on Mysid fauna (Crustacea: Mysidacea)

A biogeographic analysis of the Black Sea and Caspian Sea basin and adjacent Aegean Sea and the Sea of Marmara was conducted based on the distribution of 55 mysid species. The Black and Caspian Sea basin proper is inhabited by 35 mysid species belonging to 12 genera, among them 26 species and 3 genera are endemic to the region. Ponto-Caspian and Caspian species are predominant. The explored areas were included into two provinces of the Mediterranean subrealm of the East-Atlantic Subtropical realm and three provinces of the Ponto-Caspian realm.     

Present status of commercial stocks of sturgeons in the Caspian Sea basin

Catches for the last 25 years are analyzed for beluga Huso huso, stellate sturgeon A. stellatus and Russian sturgeon Acipenser gueldenstaedtii, which are the three commercially important species of sturgeons found in the Caspian Sea Basin. Population sizes for generations born between 1961 and 1970 are estimated, and found to depend on natural reproduction and the number of young fish stocked annually from sturgeon hatcheries located in the Volga River Delta. A ban on sea fishing from 1962 to 1991 positively impacted the number and total biomass of commercial stocks. Sturgeon growth rates depend on water levels in the Caspian Sea. In order to preserve Caspian Sea sturgeon populations, it will be necessary to coordinate efforts of all countries surrounding the Caspian Sea to achieve rational harvests, preserve juveniles, and produce at least 100 million juveniles annually from hatcheries.     

The problem of invaders in the Caspian Sea in the context of the findings of new zoo- and phytoplankton species from the Black Sea

In April 2004, an expedition to the Caspian Sea discovered the species in the Middle Caspian not previously described in this sea. These species preliminary identified as Oithona similis Claus 1963, Sagitta setosa Muller 1847, and Calanus euxinus (Hulsemann) are the main representatives of edible plankton of the Black Sea; most likely they were introduced into the Caspian Sea with ballast waters of ships passing through the Volga-Don Canal. At present, it is difficult to say if these species will be established in the Caspian Sea; if so, they will clearly become a valuable food resource for planktophagous fish in the Caspian Sea. In addition, we discovered two diatom species typical for the Black Sea phytoplankton, Pseudo-nitzschia seriata (Cleve) H. Peragallo and M. Peragallo and Cerataulina pelagica (Cleve) Hendey which invaded the Caspian Sea in recent years. Pseudo-nitzschia seriata synthesizes a toxin (domoic acid) and can become harmful for the basin in the case of mass bloom. We discuss the problem of spontaneous invasion of alien species from the Black Sea and their effect on the Caspian ecosystem in the context of these findings.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 78–87.Original Russian Text Copyright © 2005 by Shiganova, Musaeva, Pautova, Bulgakova.     

Phylogeography and taxonomic status of trout and salmon from the Ponto‐Caspian drainages,with inferences on European Brown Trout evolution and taxonomy

Current taxonomy of western Eurasian trout leaves a number of questions open; it is not clear to what extent some species are distinct genetically and morphologically. The purpose of this paper was to explore phylogeography and species boundaries in freshwater and anadromous trout from the drainages of the Black and the Caspian Seas (Ponto‐Caspian). We studied morphology and mitochondrial phylogeny, combining samples from the western Caucasus within the potential range of five nominal species of trout that are thought to inhabit this region, and using the sequences available from GenBank. Our results suggest that the genetic diversity of trout in the Ponto‐Caspian region is best explained with the fragmentation of catchments. (1) All trout species from Ponto‐Caspian belong to the same mitochondrial clade, separated from the other trout since the Pleistocene; (2) the southeastern Black Sea area is the most likely place of diversification of this clade, which is closely related to the clades from Anatolia; (3) The species from the Black Sea and the Caspian Sea drainages are monophyletic; (4) except for the basal lineage of the Ponto‐Caspian clade, Salmo rizeensis, all the lineages produce anadromous forms; (5) genetic diversification within the Ponto‐Caspian clade is related to Pleistocene glacial waves; (6) the described morphological differences between the species are not fully diagnostic, and some earlier described differences depend on body size; the differences between freshwater and marine forms exceed those between the different lineages. We suggest a conservative taxonomic approach, using the names S. rizeensis and Salmo labrax for trout from the Black Sea basin and Salmo caspius and Salmo ciscaucasicus for the fish from the Caspian basin.     

The fauna of bloodsucking insects of Northwestern Russia. Characteristics of the ranges

The fauna of the Northwestern region of Russia comprises 285 species of bloodsucking insects. The number of species of mosquitoes and lice in the Northwest constitute 40% of the total numbers in the Russian fauna; that of the biting midges, 38%; horseflies, 35%; blackflies, 30%, and fleas, 19%. Representatives of 4 dipteran families of the “gnus” complex, and also lice and fleas of the Northwestern Russian fauna possess ranges of 12 types, most of which include large part of the Holarctic or Palaearctic; 57 species (20%) of the species have Holarctic ranges; 82 species, or 28%, trans-Palaearctic ranges; 49 species, or 17%, Western-Central Palaearctic ranges; and 73 species, or 25%, Western-Palaearctic ranges. The fraction of species (8) with other range types is 19%. A synopsis of the species groups characterized by these types of ranges is given. Species with ranges extending as far northwards as the tundra zone constitute 13%, those with ranges including the taiga zone, 60%, and those with other range types, 27% of the fauna.     

Genetic diversity of sharpnose mullet <Emphasis Type="Italic">Liza saliens</Emphasis> introduced in southern Caspian Sea in comparison with one native Aegean Sea population

Sharpnose mullet, Liza saliens (Risso, 1810) is one of the valuable species in Caspian shoreline and it was first introduced to Caspian Sea from Black Sea between 1930 and 1934. In the present study, we used six microsatellite markers to obtain genetic information for L. saliens from four localities of southern Caspian Sea and for one native population from Greece coastline (northern Aegean Sea). Results showed lower number of alleles (Na = 5.7–6) and higher observed heterozygosity (Ho = 0.74–0.83) in Caspian Sea samples, related to the native Aegean population (Na = 8, Ho = 0.68). Significant deviations from Hardy-Weinberg expectations were detected in 19 out of 28 tests. Low genetic differentiation (provided Fst values) among samples was detected, but Behshahr sample was significantly differentiated from all the others. The UPGMA tree revealed three major clusters: the Behshahr sample and Greek population were clustered in two different clades, and the remaining three samples formed another cluster. The low genetic variation and spatial differentiation among Caspian Sea samples may be justified by the recent establishment.     

Historic speciation and recent colonization of Eurasian monkey gobies (Neogobius fluviatilis and N. pallasi) revealed by DNA sequences,microsatellites, and morphology

Aim Hidden diversity within an invasive ‘species’ can mask both invasion pathways and confound management goals. We assessed taxonomic status and population structure of the monkey goby Neogobius fluviatilis across Eurasia, comparing genetic variation across its native and invasive ranges. Location Native populations were analysed within the Black and Caspian Sea basins, including major river drainages (Dnieper, Dniester, Danube, Don and Volga rivers), along with introduced locations within the upper Danube and Vistula river systems. Methods DNA sequences and 10 nuclear microsatellite loci were analysed to test genetic diversity and divergence patterns of native and introduced populations; phylogenetic analysis of mtDNA cytochrome b and nuclear RAG‐1 sequences assessed taxonomic status of Black and Caspian Sea lineages. Multivariate analysis of morphology was used to corroborate phylogenetic patterns. Population genetic structure within each basin was evaluated with mtDNA and microsatellite data using F_ST analogues and Bayesian assignment tests. Results Phylogenetic analysis of mitochondrial and nuclear sequences discerned a pronounced genetic break between monkey gobies in the Black and Caspian Seas, indicating a long‐term species‐level separation dating to c. 3 million years. This pronounced separation further was confirmed from morphological and population genetic divergence. Bayesian inference showed congruent patterns of population structure within the Black Sea basin. Introduced populations in the Danube and Vistula River basins traced to north‐west Black Sea origins, a genetic expansion pattern matching that of other introduced Ponto‐Caspian gobiids. Main conclusions Both genetic and morphological data strongly supported two species of monkey gobies that were formerly identified as subspecies: N. fluviatilis in the Black Sea basin, Don and Volga Rivers, and the Kumo‐Manych Depression, and Neogobius pallasi in the Caspian Sea and Volga River delta. Genetic origins of introduced N. fluviatilis populations indicated a common invasion pathway shared with other introduced Ponto‐Caspian fishes and invertebrates.     

Variability of Black and Caspian Sea sprat <Emphasis Type="Italic">Clupeonella cultriventris</Emphasis> (Clupeidae) growth in the contemporary range

The size and age composition of the population of Black and Caspian Sea sprat Clupeonella cultriventris, as well as the variation of the growth of fish in the reservoirs of the upper reaches of the Volga, are reported and a comparative analysis of group and individual variability of fish growth within the native (Caspian, Azov, and Black seas) and contemporary (formed due to invasion) ranges is presented. The degree of variability and the asymmetry of sprat body length distribution have been shown to increase under the conditions of large population sizes, deficit of food, and slow growth. Variability was also elevated near the borders of the range of the species, notwithstanding the abundance of food. It is shown that invasion of sea walnut comb jelly Mnemiopsis leydi into the Azov and Caspian Seas had so undermined feed base of sprat, that it is not only decreased its abundance and fecundity but also slowed growth of the fish.     

The dominant fish fauna in the North Sea and its determination

The 224 species of fish reported from the North Sea are regarded as being composed of elements of three faunas—Boreal, Lusitanian and Atlantic, and they can be grouped accordingly on both a number of species and a biomass basis. The estimation of biomass of more than 10 important species is based on stock estimates obtained from population data. For 65 non-standard species the estimate is based on a comparison of catch rates for 'standard'and non-standard species from groundfish survey data. This involves assumption about the relative catchability of different sets of species. For the other species the biomass are computed in different ways. An analysis of the dominant fish fauna in the North Sea is attempted. The fish fauna in the area is analysed in two ways: by the conventional total number of species from each zoogeographic area, and by the biomass of the representatives of each fauna. It is concluded that for establishing the dominant faunal element of fish, biomass is a better index than is the number of species. The dominant faunal element of fish in the North Sea is Boreal.     

The endemic molluscs of the Late Miocene Lake Pannon: their origin, evolution, and family-level taxonomy

Long-lived lakes are often sites of spectacular endemic radiations. During the Oligocene to recent history of the Paratethys, large, long-lived (more than a million years) lakes with endemic faunas formed three times, in three different basins: the first in the Pannonian basin, the second in the Euxinian (Black Sea) basin, and the third in the Caspian basin. Because the Euxinian lake inherited much of the fauna of Lake Pannon, the three lakes together hosted two endemic radiations of molluscs. The most long-lived lake in the region was Lake Pannon, which persisted approximately seven million years from the late Middle Miocene to the Early Pliocene. Lake Pannon was formed by isolation from the sea. Changes in hydrological regime and/or water chemistry in addition to the relative lowstand which accompanied (or caused) the isolation almost completely exterminated the restricted marine fauna of the basin. A few highly euryhaline and marginal marine cardiids, dreissenids, and hydrobiids survived this environmental change. As in other fossil and extant long-lived lakes, the originally low-diversity fauna radiated into a high number of related endemic species (‘species flocks’) and genera in the expanding and ecologically vacated lake. Many originally freshwater taxa (unionids, sphaeriids, viviparids, valvatids, melanopsids, lymnaeids, planorbids) entered the lake as well, and some of them also gave rise to endemic clades. Evolution in both relict and freshwater immigrant groups led to the appearance of highly unusual shell shapes. Many lineages exhibit gradual morphological changes over one to several million years. More than 900 endemic mollusc species have been described from Lake Pannon, although this number includes junior synonyms, invalid species names, and highly similar chronospecies. Applying a conservative taxonomy, all these species belong to four bivalve and eight gastropod families. The high degree of endemism, however, is reflected by proposals of some authors to establish as many as five new families based on Lake Pannon endemics.     

Changes in biodiversity of phytoplankton,zooplankton, fishes and macrobenthos in the Southern Caspian Sea after the invasion of the ctenophore <Emphasis Type="Italic">Mnemiopsis Leidyi</Emphasis>

Monitoring for 6 years (2001–2006) showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton. While this decline appeared to have reduced the nourishment of sprat (also known as kilka), it seemed to have affected phytoplankton favorably mainly due to the decrease in grazing pressure. During 2001–2002, when M. leidyi abundance and biomass were at their highest levels, abundance of dinoflagellates and cyanophytes exceeded that of diatoms. Before the invasion (1996) and in some years after the invasion (2003, 2004 and 2006) diatom abundance was higher than the abundance of other groups. In September 2005, an unprecedented bloom of the toxic cyanophyte Nodularia sp. was observed in the southern Caspian Sea. Disappearance of edible zooplankton such as Eurytemora spp. was among the first changes observed after the expansion of M. leidyi in the area. Some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophore. While the biomass of some deposit feeders, such as the polychaete Nereis diversicolor and oligochaete species increased, benthic crustaceans decreased sharply in abundance during 2001–2003 and completely disappeared during 2004–2006. Iranian catches of kilka, the most abundant and widespread zooplanktivorous fish, decreased significantly in the southern Caspian Sea after 1999. Iranian landings of kilka dropped ~70% from 69,070 ± 20,270 t during 1995–2000 to 23,430 ± 12,240 t during 2001–2006, resulting in a loss of at least 125 million US dollars to the economy. There were also changes in the total catches of large predators such as the kutum and mullet, which mainly feed on kilka, between 1991 and 2006.