Accelerated mitochondrial evolution and asymmetric fitness of hybrids contribute to the persistence of Helix thessalica in the Helix pomatia range.

Interbreeding and introgression between recently diverged species is common. However, the processes that prevent these species from merging where they co-occur are not well understood. We studied the mechanisms that allowed an isolated group of populations of the snail Helix thessalica to persist within the range of the related Helix pomatia despite high gene flow. Using genomic cline analysis, we found that the nuclear gene flow between the two taxa across the mosaic hybrid zone was not different from that expected under neutral admixture, but that the exchange of mtDNA was asymmetric. Tests showed that there is relaxed selection in the mitochondrial genome of H. thessalica and that the substitution rate is elevated compared to that of H. pomatia. A lack of hybrids that combine the mtDNA of H. thessalica with a mainly (>46%) H. pomatia genomic background indicates that the nuclear-encoded mitochondrial proteins of H. pomatia are not well adapted to the more rapidly evolving proteins and RNAs encoded by the mitochondrion of H. thessalica. The presumed reduction of fitness of hybrids with the fast-evolving mtDNA of H. thessalica and a high H. pomatia ancestry, similar to 'Darwin's Corollary to Haldane's rule', resulted in a relative loss of H. pomatia nuclear ancestry compared to H. thessalica ancestry in the hybrid zone. This probably prevents the H. thessalica populations from merging quickly with the surrounding H. pomatia populations and supports the hypothesis that incompatibilities between rapidly evolving mitochondrial genes and nuclear genes contribute to speciation.

Holding in the stream: convergent evolution of suckermouth structures in Loricariidae (Siluriformes).

Suckermouth armoured catfish (Loricariidae) are a highly speciose and diverse freshwater fish family, which bear upper and lower lips forming an oral disc. Its hierarchical organisation allows the attachment to various natural surfaces. The discs can possess papillae of different shapes, which are supplemented, in many taxa, by small horny projections, i.e. unculi. Although these attachment structures and their working mechanisms, which include adhesion and interlocking, are rather well investigated in some selected species, the loricariid oral disc is unfortunately understudied in the majority of species, especially with regard to comparative aspects of the diverse oral structures and their relationship to the ecology of different species. In the present paper, we investigated the papilla and unculi morphologies in 67 loricariid species, which inhabit different currents and substrates. We determined four papilla types and eight unculi types differing by forms and sizes. Ancestral state reconstructions strongly suggest convergent evolution of traits. There is no obvious correlation between habitat shifts and the evolution of specific character states. From handling the structures and from drying artefacts we could infer some information about their material properties. This, together with their shape, enabled us to carefully propose hypotheses about mechanisms of interactions of oral disc structures with natural substrates typical for respective fish species.

Speciation of rock-dwelling snail species: Disjunct ranges and mosaic patterns reveal the importance of long-distance dispersal in Chilostoma (Cingulifera) in the European Southern Alps.

To better understand the origin of the high diversity and endemism in the Southern Alps of Europe, we investigated the phylogeny and population structure of the rock-dwelling snail group Chilostoma (Cingulifera) in the Southern Alps. We generated genomic ddRAD data and mitochondrial sequences of 104 Cingulifera specimens from 28 populations and 14 other Ariantinae. Until recently, about 30 Cingulifera taxa were classified as subspecies of a single polytypic species. The phylogenetic and population genetic analyses of the ddRAD data and mitochondrial sequences revealed that Cingulifera in the Southern Alps is differentiated into three species. Each of the three Chilostoma (Cingulifera) species occupies disjunct sub-areas, which are separated by areas occupied by other Chilostoma taxa. Neighbouring populations of different species show little or no admixture. Tests indicating that the genetic differentiation of the three Cingulifera taxa cannot be explained by isolation by distance confirmed their species status. The disjunct range patterns demonstrate the importance of stochastic events such as passive long-distance dispersal for the evolution of population structure and speciation in these snails, and of priority effects and ecological competition as important factors influencing species distributions.

Phylogeny and evolution of the land snail tribe Clausiliini (Gastropoda: Clausiliidae).

The phylogenetic relationships within the land snail group Clausiliini were analysed based on an almost complete taxon sampling (28 of 29 extant species) and a set of mitochondrial and nuclear markers. The phylogenetic analyses and character state reconstructions revealed several trends in the group that resulted in repeated convergences. The N-type closing apparatus was convergently transformed into a G-type clausilial apparatus in Graciliaria, Ruthenica + Micridyla and probably three times within Neostyriaca. There were parallel changes in the length of the male copulatory organs and repeated reductions of the basal keel in several lineages. Such trends resulting in repeated convergences are characteristic for several radiations of stylommatophoran land snails. They may reflect parallel adaptations of related lineages to similar environmental constraints. However, it is also possible that some of these transformations are not adaptive, but represent random changes in a restricted morphospace. We explored the timing of the Clausiliini radiation using different calibration strategies. Despite large numbers of fossils of Clausiliidae from Western and Central Europe, the results of these analyses and the fossil evidence for a Cretaceous origin of the Clausiliidae indicate that there are large gaps in the fossil record of the Clausiliini. Especially the origin and early evolution of the Clausiliini in Southeastern Europe is obscured by our insufficient knowledge of Neogene deposits there.

The role of Anatolia in the origin of the Caucasus biodiversity hotspot illustrated by land snails in the genus Oxychilus.

Several taxa that are distributed in the Caucasus and/or the adjacent Pontic Mountains also have representatives in the East Mediterranean region. These disjunctions could have been caused by long-distance dispersal or be the result of extinctions in Central Anatolia caused by the aridification of the Anatolian Plateau during the Pliocene. We studied the Longiphallus-Hiramia group of Oxychilus as an example showing such distribution patterns. Phylogenetic analyses of the Oxychilus species previously classified in Longiphallus, Hiramia and related subgenera resulted in a new delimitation of these taxa and the recognition of Anatoloxychilus Neiber, Walther & Hausdorf n. subgen. as an additional clade. Based on phylogenetic and population genetic analyses, O. reticulatus from Mingrelia is revalidated and the populations from the Pontic Mountains previously identified with O. mingrelicus koutaisanus are recognised as a distinct species. Three species pairs of the Longiphallus-Hiramia group with deep splits predating the aridification of the Anatolian Plateau during the Pliocene show disjunctions between the Caucasus/Pontic region and the Mediterranean. The majority of taxa with such a distribution pattern probably had more continuous distributions before the aridification started. The relationships between the Hiramia species from the Caucasus, the Pontic Mountains and the East Mediterranean highlight the importance of the Anatolian land as a source area for the colonisation of the Caucasus region. The dating of the divergences of the Caucasian Hiramia species in the middle to late Miocene indicated that they colonised the Caucasus when it was still an island in the Paratethys Sea and that their divergence was triggered by the orogenesis of the Greater Caucasus. A common pattern within the Caucasus region, also found in Hiramia, is the separation of taxa in the north-western Greater Caucasus from taxa inhabiting the southern slopes of the central Greater Caucasus.

Evaluating Species Delimitation Methods in Radiations: The Land Snail Albinaria cretensis Complex on Crete.

Delimiting species in radiations is notoriously difficult because of the small differences between the incipient species, the star-like tree with short branches between species, incomplete lineage sorting, and the possibility of introgression between several of the incipient species. Next-generation sequencing data may help to overcome some of these problems. We evaluated methods for species delimitation based on genome-wide markers in a land snail radiation on Crete. Species delimitation in the Albinaria cretensis group was based exclusively on shell characters until now and resulted in classifications distinguishing 3-9 species. We generated sequences of 4270 loci for 140 specimens of the A. cretensis group from 48 populations by double-digest restriction site-associated DNA sequencing. We evaluated three methods for species discovery. The multispecies coalescent approach implemented in the program Bayesian Phylogenetics and Phylogeography resulted in a drastic overestimating of the number of species, whereas Gaussian clustering resulted in an overlumping. Primary species hypotheses based on the maximum percentage of the genome of the individuals derived from ancestral populations as estimated with the program ADMIXTURE moderately overestimated the number of species, but this was the only approach that provided information about gene flow between groups. Two of the methods for species validation that we applied, BFD* and delimitR, resulted in an acceptance of almost all primary species hypotheses, even such based on arbitrary subdivisions of hypotheses based on ADMIXTURE. In contrast, secondary species hypotheses, resulting from an evaluation of primary species hypotheses based on ADMIXTURE with isolation by distance tests, approached the morphological classification, but also uncovered two cryptic species and indicated that some of the previously delimited units should be combined. Thus, we recommend this combination of approaches that provided more detailed insights in the distinctness of barriers between the taxa of a species complex and the spatial distribution of admixture between them than the other methods. The recognition and delimitation of undersampled species remained a major challenge. [ADMIXTURE; Clausiliidae; delimitR, Gaussian clustering; isolation-by-distance; land snails; multispecies coalescent; species delimitation.].

Natural history collections recapitulate 200 years of faunal change.

Changing species assemblages represent major challenges to ecosystems around the world. Retracing these changes is limited by our knowledge of past biodiversity. Natural history collections represent archives of biodiversity and are therefore an unparalleled source to study biodiversity changes. In the present study, we tested the value of natural history collections for reconstructing changes in the abundance and presence of species over time. In total, we scrutinized 17 080 quality-checked records for 242 epibenthic invertebrate species from the North and Baltic Seas collected throughout the last 200 years. Our approaches identified eight previously reported species introductions, 10 range expansions, six of which are new to science, as well as the long-term decline of 51 marine invertebrate species. The cross-validation of our results with published accounts of endangered species and neozoa of the area confirmed the results for two of the approaches for 49 to 55% of the identified species, and contradicted our results for 9 to 10%. The results based on relative record trends were less validated. We conclude that, with the proper approaches, natural history collections are an unmatched resource for recovering early species introductions and declines.

Incorporating palaeogeography into ancestral area estimation can explain the disjunct distribution of land snails in Macaronesia and the Balearic Islands (Helicidae: Allognathini).

The systematics and biogeographical history of the Eastern Mediterranean and Macaronesian land snail tribe Allognathini (Helicidae: Helicinae) is investigated based on mitochondrial and nuclear DNA sequence data. Our molecular phylogenetic analyses indicate that the genus-group systematics of the tribe needs to be revised. We show for the first time that the narrow-range endemics Lampadia and Idiomela from the Madeira Archipelago belong to Allognathini and represent together the sister group of the diverse Canary Island Hemicycla radiation. We therefore suggest synonymising Lampadiini with Allognathini. Sister to these Macaronesian genera was the Balearic Island Allognathus radiation. Pseudotachea was not recovered as a monophyletic group and the two currently recognised species clustered in Iberus. Similarly, Adiverticula was not recovered as a monophyletic group and clustered in Hemicycla. We therefore suggest synonymising Pseudotachea with Iberus and Adiverticula with Hemicycla. The six genera in Allognathini, which we distinguish here (Cepaea, Iberus, Allognathus, Hemicycla, Idiomela and Lampadia), originated in Western to South-western Europe according to our ancestral area estimation and the fossil record. The disjunct distribution of the Balearic Islands and Macaronesian sister clades and the mainly Iberian Iberus clade that separated earlier can be explained by the separation of the Betic-Rif System from the Iberian Peninsula during the late Oligocene to early Miocene, along with independent Miocene dispersals to the Balearic Islands and Macaronesia from the Iberian Peninsula, where the ancestral lineage became extinct.

One, two or three? Integrative species delimitation of short-range endemic Hemicycla species (Gastropoda: Helicidae) from the Canary Islands based on morphology, barcoding, AFLP and ddRADseq data.

Hemicycla mascaensis and H. diegoi are short-range endemics that occur allopatrically in small areas in the Teno Mountains in the western part of Tenerife (Canary Islands). Both taxa have been recognised as distinct species based on differences in shell morphology and genital anatomy. Preliminary molecular analyses using mitochondrial markers suggested a potential paraphyly of H. diegoi with regard to H. mascaensis. We here use multilocus AFLP data and ddRADseq data as well as distribution data, data on shell morphology and genital anatomy to assess the status of these taxa using phylogenetic analyses, species tree reconstruction and molecular species delimitation based on the multispecies coalescent as implemented in BFD* and BPP in an integrative approach. Our analyses show that, based on the analysis of multilocus data, the two taxa are reciprocally monophyletic. Species delimitation methods, however, tend to recognise all investigated populations as distinct species, albeit neither lending unambiguous support to any of the species hypotheses. The comparison of the anatomy of distal genital organs further suggests differentiation within H. mascaensis. This highlights the need for a balanced weighting of arguments from different lines of evidence to determine species status and calls for cautious interpretations of the results of molecular species delimitation analyses, especially in organisms with low active dispersal capacities and expected distinct population structuring such as land snails. Taking all available evidence into account, we favour to recognise H. mascaensis and H. diegoi as distinct species, acknowledging, though, that the recognition of both taxa as subspecies (with possibly a third yet undescribed) would also be an option as morphological differentiation is within the limits of other land snail species that are traditionally subdivided into subspecies.

Repeated hybridization increased diversity in the door snail complex Charpentieria itala in the Southern Alps.

The door snail species complex Charpentieria itala is widely distributed in the Southern Alps and subdivided into several morphologically differentiated subspecies. Thus, it can be used as a model group for understanding migration and differentiation processes in the Southern Alps. We generated genome-wide double digest Restriction Site Associated DNA (ddRAD) sequencing data for 166 specimens from 36 populations of the door snail Charpentieria itala and for 8 specimens of the other three Charpentieria species to reconstruct their evolutionary history and phylogeography. Phylogenetic and structure analyses based on the ddRAD data indicated that the repeated separation of the populations in western and eastern groups by the Garda glacier during the glacials was the process that most strongly shaped the population structure of C. itala. This process may also explain a similar phylogeographic boundary in many other southern Alpine animal and plant species. Our study revealed that some populations that resemble Charpentieria stenzii morphologically and ecologically, the 'stenzioid' subspecies, originated by a hybridization event with Charpentieria stenzii. A further hybridization event between stenzioid populations that survived the glacials in mountain refuges and non-stenzioid populations that probably came into contact with stenzioid populations as a result of climate warming during an interglacial resulted in the origin of a hybrid subspecies that is adapted to intermediate altitudes. Our study demonstrated that the origin of new differentiated taxa by hybridization, is more frequent than previously assumed.

Phylogenetic relationships of ghost slugs (Selenochlamys) and overlooked instances of limacization in Western Palaearctic Limacoidei (Gastropoda: Stylommatophora).

We analysed the phylogenetic relationships of the enigmatic ghost slug Selenochlamys with other Western Palaearctic Limacoidei based on mitochondrial and nuclear sequences. Selenochlamys is a carnivorous slug group from the Caucasus region. Until now, it has been classified in Trigonochlamydidae, which includes several carnivorous slug groups from the Caucasus region. However, the molecular phylogenetic analyses revealed that Selenochlamys originated from omnivorous snails belonging to Oxychilidae. The similarities of Selenochlamys and Trigonochlamydidae are convergences resulting from limacization, the evolutionary transition from shelled snails to slugs, and from the transition from herbivory or detritivory via omnivory to obligate carnivory. These two evolutionary trends occurred repeatedly within the Limacoidei. Phylogenetic analyses based on morphological characters are prone to underestimate the instances with which such recurrent evolutionary trends occurred, as they depend on the parsimony criterion. The molecular phylogenetic analyses revealed that Limacoidea and Parmacelloidea, which were at least partly based on characters associated with limacization, are polyphyletic. The molecular phylogenetic tree implied that 5-7 independent limacizations occurred in the Western Palaearctic Limacoidei. Half of these limacizations remained undetected in a previous parsimony analysis based on morphological characters. Moreover, the analyses revealed that Godwiniinae belong to Gastrodontidae, not Oxychilidae.

Species delimitation and geography.

Despite the importance of the geographical arrangement of populations for the inference of species boundaries, only a few approaches that integrate spatial information into species delimitation have thus far been developed. Persistent differentiation of sympatric groups of individuals is the best criterion for species status. Species delimitation becomes more prone to error if allopatric metapopulations are considered because it is often difficult to assess whether observed differences between allopatric metapopulations would be sufficient to prevent the fusion of these metapopulations upon contact. We propose a novel approach for testing the hypothesis that the multilocus genetic distances between individuals or populations belonging to two different candidate species are not larger than expected based on their geographical distances and the relationship of genetic and geographical distances within the candidate species. A rejection of this null hypothesis is an argument for classifying the two studied candidate species as distinct species. Case studies show that the proposed tests are suitable to distinguish between intra- and interspecific differentiation. The regression approach proposed here is more appropriate for testing species hypotheses with regard to isolation by distance than (partial) Mantel tests. Our tests assume a linear relationship between genetic and (transformed) geographical distances. This assumption can be compromised by a high genetic variability within populations as found in a case study with microsatellite markers.

Diplommatina boessnecki n. sp. from Nepal (Gastropoda: Diplommatinidae).

Diplommatina Benson, 1849 (Caenogastropoda: Diplommatinidae) is a species-rich genus of terrestrial microsnails with a constriction near the beginning of the last whorl (Kobelt 1902). It includes several hundred species in eastern and southern continental Asia, Japan, Taiwan, Indonesia and the Philippines. Although known for more than a century from the Himalayas and other mountain ranges in India, the first Diplommatina from Nepal were reported not before 1997 (Kuznetsov Schileyko 1997). A recent revision reported 16 species of the genus from Nepal (Budha et al. 2017).

Molecular phylogeny and trait evolution of Madeiran land snails: radiation of the Geomitrini (Stylommatophora: Helicoidea: Geomitridae).

The Geomitrini is the most species-rich group of land snails in the Madeiran Archipelago. The phylogeny of the group is reconstructed based on mitochondrial and nuclear genetic markers. The timing of diversification, the colonisation history of the islands of the Madeiran Archipelago and the evolution of characters of the dart apparatus are studied. The results of the phylogenetic analyses confirm the sister group relationship of Geomitrini and Cochlicellini, but also show that several previously accepted genus-group taxa are not monophyletic. A new classification for the Geomitrini is proposed, including the description of two new genera, Domunculifex Brozzo, De Mattia, Harl & Neiber, n. gen. and Testudodiscula Brozzo, De Mattia, Harl & Neiber, n. gen. The onset of diversification of Geomitrini was dated in our analysis at 13 Ma, which largely coincides with the emergence of the present-day islands. The ancestral state estimation recovered the presence of two appendiculae in the reproductive system as the ancestral state in Geomitrini. One appendicula was lost three times independently within the tribe and is even missing completely in one group. The ancestral area estimation suggests recurrent colonisations of Madeira (and the Ilhas Desertas) from the older island Porto Santo.

Ecological specialization resulting in restricted gene flow promotes differentiation in door snails.

We tested the hypothesis that ecological specialization that affects dispersal promotes diversification by a comparison of the genetic structure of two sister species of door snails across their broadly overlapping ranges in the Crimean Mountains. The hypothesized effect of ecological specialization on diversification is supported by STRUCTURE analyses that showed that Mentissa gracilicosta that is restricted to limestone rocks, is subdivided into several distinct clusters, whereas all populations of the species adapted to more continuous habitat, the forests-dwelling Mentissa canalifera, were assigned to a single cluster. Furthermore, it is supported by AMOVAs that showed that a larger part of the genetic variation of M. gracilicosta is apportioned among populations than in M. canalifera. The stronger genetic differentiation of the M. gracilicosta populations corresponds to their more distinct morphological differentiation that resulted in the classification of M. gracilicosta into several geographical subspecies, whereas the more continuously distributed M. canalifera was not subdivided into subspecies. The stronger differentiation of populations of M. gracilicosta compared to M. canalifera can be ascribed to reduced gene flow between the isolated populations of M. gracilicosta and to founder events associated with the long distance dispersal events that are necessary for the colonization of isolated rocks by M. gracilicosta. In Central Europe, the Pleistocene climatic oscillations selected for species with high dispersal abilities, whereas the more stable climate in southern Europe facilitated the non-adaptive radiation of rock-dwelling door snails. Thus, the intrinsic ecological properties of these species groups contributed to the latitudinal diversity gradient.

Dicharax (?) candrakirana n. sp. (Gastropoda: Cyclophoridae) from Sempu Island, Indonesia.

The Alycaeinae Blanford, 1864 (Gastropoda: Cyclophoridae) is a species-rich group of caenogastropod land snails distributed mainly in Southeast Asia (Kobelt 1902). The Madagascan endemic Boucardicus Fischer-Piette & Bedoucha, 1965 has also been classified in the Alycaeinae (Emberton 2002). The Asian species of Alycaeinae are characterized by a sutural tube on the last whorl that is closed at its posterior end, but is connected to the outside by radial microtunnels opening near the umbilicus. This device is hypothesized to allow gas exchange when the animal is retracted and the operculum seals the shell aperture (Páll-Gergely et al. 2016).

High gene flow despite opposite chirality in hybrid zones between enantiomorphic door snails.

We studied differentiation and geneflow patterns between enantiomorphic door-snail species in two hybrid zones in the Bucegi Mountains (Romania) to investigate the effects of intrinsic barriers (complications in copulation) and extrinsic selection by environmental factors. A mitochondrial gene tree confirmed the historical separation of the examined populations into the dextral Alopia livida and the sinistral Alopia straminicollis in accordance with the morphological classification, but also indicated gene flow between the species. By contrast, a network based on amplified fragment length polymorphisms (AFLP) markers revealed local groups of populations as units independent of their species affiliation. Admixture analyses based on AFLP data showed that the genomes of most individuals in the hybrid zones are composed of parts of the genomes of both parental taxa. The introgression patterns of a notable fraction of the examined markers deviated from neutral introgression. However, the patterns of most non-neutral markers were not concordant between the two hybrid zones. There was also no concordance between non-neutral markers in the two genomic clines and markers that were correlated with environmental variables or markers that were correlated with the proportion of dextral individuals in the populations. Neither extrinsic selection by environmental factors nor intrinsic barriers resulting from positive frequency-dependent selection of the prevailing coiling direction were sufficient to maintain the distinctness of A. straminicollis and A. livida. Despite being historically separated units, we conclude that these taxa now merge where they come into contact.

Molecular phylogeny and biogeography of the land snail family Hygromiidae (Gastropoda: Helicoidea).

The Hygromiidae is a highly diverse group of land snails with a distribution range stretching throughout the Palearctic region from the Macaronesian Islands to the Russian Far East and reaching southwards to the north-eastern Ethiopian region. So far, the classification of the family largely rested on the structure of the dart apparatus, an accessory genital organ. We used nuclear and mitochondrial DNA sequences of almost all genera to reconstruct the phylogeny of the Hygromiidae. Several of the clades found in the molecular phylogenetic analyses represent regional radiations that partly show a high variation in the structure of the dart apparatus. Thus, several of the currently accepted subdivisions of the family, which included taxa with similar dart apparatus from different regions, turned out to be polyphyletic. We newly delimit three subfamilies within the family, Hygromiinae, Leptaxinae and Trochulinae on the basis of our phylogenetic analyses. The Hygromiinae are further subdivided into Hygromiini and Perforatellini trib. nov. The Leptaxinae are classified in Leptaxini, Metafruticicolini and Cryptosaccini trib. nov. The Trochulinae are the most diverse group including Ciliellini, Archaicini, Ganulini trib. nov., Urticicolini trib. nov., Trochulini, Caucasigenini trib. nov., Ashfordini trib. nov., Halolimnohelcini and Monachaini. Moreover, two new genera, Coronarchaica gen. nov. from Central Asia and Noricella gen. nov. from the Alps, are described. The Hygromiidae originated in the western Palaearctic, from where the Central Asian mountain regions, the Macaronesian Islands, the Caucasus region and sub-Saharan East Africa were colonized. The radiation of the Hygromiidae as well as those of several other land snail families was dispersal limited. Because of the low dispersal abilities of land snails, the period until an isolated region is colonized by a group by chance dispersal is comparatively longer than the period necessary for morphological and ecological diversification of the group within the newly colonized region. Some of the regional radiations coincided with orogeny in the respective areas and were probably triggered by the development of geographical barriers and new niches.

Helicopsis persica n. sp. from northern Iran (Gastropoda: Geomitridae).

Helicopsis Fitzinger, 1833 is a mainly eastern European genus of the xerophilous Helicellinae (Geomitridae, Helicoidea; for family systematics see Razkin et al. 2015) that is characterized by two symmetrical dart and accessory sacs. This is probably the plesiomorphous character state within the Geomitridae and Hygromiidae. Therefore, the delimitation and relationships of Helicopsis remained questionable (Hausdorf 1996). Most Helicopsis species are characterized by a lateral attachment of the outer layer of the penial papilla at the penis wall so that a cavity is separated in the proximal part of the penis (Schileyko 1978; Giusti et al. 1992; Hausdorf 1996). However, a similar cavity is present in some other Helicellinae (e.g., Pseudoxerophila, Xerolenta, Xeromunda). Giusti et al. (1992) considered these cavities artefacts, but it cannot be excluded that they are actually homologous to the cavity of Helicopsis. Therefore, it is doubtful whether such a cavity can be considered as an autapomorphy of Helicopsis. About ten species of Helicopsis are spread from Turkey and Bulgaria to the Ukraine with a centre of diversity on the Crimean peninsula. Only the type species, Helicopsis striata (Müller, 1774) is more widespread from Alsace in the west, the island Öland in the Baltic Sea in the north to Bulgaria and Turkey in the south and western Russia in the east. Furthermore, species from Morocco, Greece, Cyprus, Iran and the Kopetdag were classified as Helicopsis. The relationships between these species have to be examined in more detail. Here we describe a new Helicopsis species from Iran.

Phylogeographic analyses reveal Transpontic long distance dispersal in land snails belonging to the Caucasotachea atrolabiata complex (Gastropoda: Helicidae).

The phylogeography and population structure of land snails belonging to the Caucasotachea atrolabiata complex in the Caucasus region was investigated to obtain a better understanding of diversification processes in this biodiversity hotspot. So far the complex has been classified into three species, C. atrolabiata from the north-western Caucasus, C. calligera from Transcaucasia and C. intercedens from the eastern Pontus Mountains. Phylogenetic (neighbor-net and neighbor-joining tree) as well as admixture analyses based on AFLP data showed that the complex consists of two population clusters corresponding to C. atrolabiata and C. calligera. The populations assigned to C. intercedens in fact represent hybrids consisting of different proportions of the genomes of C. atrolabiata and C. calligera. There is a broad transition zone between C. atrolabiata and C. calligera in the Pontic Mountains and a second transition zone in Abkhazia. Because of evidence for gene flow, it is suggested to classify the two aforementioned taxa as subspecies, namely C. a. atrolabiata and C. a. calligera. The presence of mitochondrial C. a. atrolabiata haplotypes in Turkey can only be explained by passive dispersal across the Black Sea. The distribution of C. a. atrolabiata and additional cases of land snails with disjunct Transpontic distribution patterns cannot be ascribed to a common cause but are results of long distance dispersal events at different times.