Holotypes for three Caspian gastropods of the family Hydrobiidae tracked down: description and taxonomic interpretations.

Type series of three nominal taxa of the hydrobiid gastropods inhabiting the Caspian Sea were traced recently in the uncatalogued part of the malacological collection of the Zoological Institute of Russian Academy of Sciences, Saint-Petersburg. Images of the holotypes and some paratypes of Pyrgula isseli Logvinenko Starobogatov, 1969, P. sowinskyi Logvinenko Starobogatov, 1969 and P. derzhavini Logvinenko Starobogatov, 1969 are presented. The first two species belong to the genus Clathrocaspia (subfamily Caspiinae) and P. sowinskyi is considered a junior synonym of C. pallasii (Clessin W. Dybowski in W. Dybowski, 1887). The attribution of the third species, P. derzhavini, to Laevicaspia (Pyrgulinae) is confirmed based on the newly discovered type material. Based on the additional information we update ecological data and distribution ranges of the species, provide comments on their nomenclature, systematic position and taxonomic rank.

A revision of the Pontocaspian gastropods of the subfamily Caspiinae (Caenogastropoda: Hydrobiidae).

The Caspiinae comprise small gastropod species inhabiting low-salinity environments of the Pontocaspian region, specifically the Caspian Sea and the limans, estuaries and lower river reaches of the northern Black Sea Basin. There is considerable discrepancy in the literature as to which taxa are attributed to this hydrobiid subfamily, which of them are valid and what rank they have. Moreover, the generic classification is not agreed upon. Here, we aim at elucidating systematic relationships and species identities by a thorough taxonomic and systematic revision of the Caspiinae, including a detailed morphological study along with information on biogeography, ecology, conservation and fossil record. We use historical and recent collections from all around the Pontocaspian region acquired over the past 170 years, including several type series that were only recently discovered as well as selected Pleistocene and Holocene materials. Several of the species are illustrated properly here for the first time, using both macrophotographs and scanning electron microscopy images to facilitate evaluation of morphological details. The genus Andrusovia, which has been classified in a number of different families and even gastropod subclasses before, is here attributed to the Caspiinae. By designating a lectotype for the type species, A. dybowskii, we finally fix the identity of this previously ambiguous species and genus. Our revision yields four genera and eleven accepted species of Caspiinae for the modern Pontocaspian fauna: Andrusovia (1), Caspia (1), Clathrocaspia (7) and Ulskia (2). In addition, two species of uncertain status (1 nomen dubium, 1 taxon inquirendum) are discussed, and two species introduced as Caspiinae are here found not to belong in that group. Andrusovia antecessor sp. nov. and Andrusovia cyrensis sp. nov. are introduced as new (sub)fossil species from the Caspian Sea.

Decline of unique Pontocaspian biodiversity in the Black Sea Basin: A review.

The unique aquatic Pontocaspian (PC) biota of the Black Sea Basin (BSB) is in decline. The lack of detailed knowledge on the status and trends of species, populations, and communities hampers a thorough risk assessment and precludes effective conservation. This paper reviews PC biodiversity trends in the BSB (Bulgaria, Romania, Moldova, Ukraine, and Russia) using endemic mollusks as a model group. We aim to assess changes in PC habitats, community structure, and species distribution over the past century and to identify direct anthropogenic threats. The presence/absence data of target mollusk species were assembled from literature, reports, and personal observations. Pontocaspian biodiversity trends in the northwestern BSB coastal regions were established by comparing 20th- and 21st-century occurrences. The direct drivers of habitat and biodiversity change were identified and documented. We found that a pronounced decline of PC species and communities is driven by (a) damming of rivers, (b) habitat modifications that disturbed previous natural salinity gradients and settings in the studied area, (c) pollution and eutrophication, (d) invasive alien species, and (e) climate change. Four out of the 10 studied regions, namely, the Danube Delta-Razim Lake system, Dniester Liman, Dnieper-Bug estuary, and Taganrog Bay-Don Delta, contain favorable ecological conditions for PC communities and still host threatened endemic PC mollusk species. Distribution data are incomplete, but the scale of deterioration of PC species and communities is evident from the assembled data, as are major direct threats. Pontocaspian biodiversity in the BSB is profoundly affected by human activities. Standardized observation and collection data as well as precise definition of PC biota and habitats are necessary for targeted conservation actions. This study will help to set the research and policy agenda required to improve data collection to accommodate effective conservation of the unique PC biota.

Social network analysis and the implications for Pontocaspian biodiversity conservation in Romania and Ukraine: A comparative study.

Romania and Ukraine share the Black Sea coastline, the Danube Delta and associated habitats, which harbor the endemic, aquatic Pontocaspian biota. Currently, this biota is diminishing both in numbers of species and their abundance because of human activities, and its future persistence strongly depends on the adequacy of conservation measures. Romania and Ukraine have a common responsibility to address the conservation of Pontocaspian biodiversity. The two countries, however have different socio-political and legal conservation frameworks, which may result in differences in the social network structure of stakeholder institutions with different implications for Pontocaspian biodiversity conservation. Here, we study the social network structure of stakeholder organizations involved in conservation of Pontocaspian biodiversity in Romania and the implications of network structure for conservation outcomes. Then we compare the findings from Romania to an earlier similar study from Ukraine. We apply a mix of qualitative and quantitative social network analysis methods to combine the content and context of the interactions with relational measures. We show that Pontocaspian biodiversity plays a minor and mostly incidental role in the inter-organizational interactions in Romania. Furthermore, there is room for improvement in the network structure through e.g. more involvement of governmental and nongovernmental organizations and increased motivation of central stakeholders to initiate conservation actions. Social variables, such as lack of funding, hierarchical, non-inclusive system of conservation governance and continuous institutional reforms in the public sector are consequential for the network relations and structure. Social network of stakeholders in Ukraine is more connected and central stakeholders utilize their favorable positions. However, neither in Ukraine is the Pontocaspian biodiversity a driver of organizational interactions. Consequently, both networks translate into sub-optimal conservation actions and the roads to optimal conservation are different. We end with sketching out conservation implications and recommendations for improved national and cross-border conservation efforts.

Old lake versus young taxa: a comparative phylogeographic perspective on the evolution of Caspian Sea gastropods (Neritidae: Theodoxus).

The Caspian Sea has been a highly dynamic environment throughout the Quaternary and witnessed major oscillations in lake level, which were associated with changes in salinity and habitat availability. Such environmental pressures are considered to drive strong phylogeographic structures in species by forcing populations into suitable refugia. However, little is actually known on the effect of lake-level fluctuations in the Caspian Sea on its aquatic biota. We compared the phylogeographic patterns of the aquatic Neritidae snail genus Theodoxus across the Pontocaspian region with refugial populations in southern Iran. Three gene fragments were used to determine relationships and divergence times between the sampled populations in both groups. A dated phylogeny and statistical haplotype networks were generated in conjunction with the analyses of molecular variance and calculations of isolation by distance using distance-based redundancy analyses. Extended Bayesian skyline plots were constructed to assess demographic history. Compared with the southern Iranian populations, we found little phylogeographic structure for the Pontocaspian Theodoxus group, with more recent diversification, homogeneity of haplotypes across the Pontocaspian region and a relatively stable demographic history since the Middle Pleistocene. Our results argue against a strong influence of Caspian Sea low stands on the population structure post the early Pleistocene, whereas high stands may have increased the dispersal possibilities and homogenization of haplotypes across the Pontocaspian region during this time. However, during the early Pleistocene, a more dramatic low stand in the Caspian Sea, around a million years ago, may have caused the reduction in Theodoxus diversity to a single lineage in the region. In addition, our results provide new insights into Theodoxus taxonomy and outlooks for regional conservation.

Mollusc species from the Pontocaspian region - an expert opinion list.

Defining and recording the loss of species diversity is a daunting task, especially if identities of species under threat are not fully resolved. An example is the Pontocaspian biota. The mostly endemic invertebrate faunas that evolved in the Black Sea - Caspian Sea - Aral Sea region and live under variable salinity conditions are undergoing strong change, yet within several groups species boundaries are not well established. Collection efforts in the past decade have failed to produce living material of various species groups whose taxonomic status is unclear. This lack of data precludes an integrated taxonomic assessment to clarify species identities and estimate species richness of Pontocaspian biota combining morphological, ecological, genetic, and distribution data. In this paper, we present an expert-working list of Pontocaspian and invasive mollusc species associated to Pontocaspian habitats. This list is based on published and unpublished data on morphology, ecology, anatomy, and molecular biology. It allows us to (1) document Pontocaspian mollusc species, (2) make species richness estimates, and (3) identify and discuss taxonomic uncertainties. The endemic Pontocaspian mollusc species richness is estimated between 55 and 99 species, but there are several groups that may harbour cryptic species. Even though the conservation status of most of the species is not assessed or data deficient, our observations point to deterioration for many of the Pontocaspian species.