Paraphyly and budding speciation in the hairy snail (Pulmonata, Hygromiidae)

Next step in Monachacantiana (Montagu, 1803) phylogeography: northern French and Dutch populations (Eupulmonata, Stylommatophora, Hygromiidae)

Features of shell and genitalia as well as nucleotide sequences of selected mitochondrial and nuclear genes of specimens of Monachacantiana from ten northern French and two Dutch populations were compared with the same features of British and Italian populations. They were found to be very similar to populations previously identified as belonging to the CAN-1 lineage of M.cantiana. This confirms previous suggestions that M.cantiana was introduced to western Europe (England, France and the Netherlands) in historical times.

Cryptic diversity begets challenges and opportunities in biodiversity research

How many species of life are there on Earth? This is a question that we want to know but cannot yet answer. Some scholars speculate that the number of species may reach 2.2 billion when considering cryptic diversity and that each morphology-based insect species may contain an average of 3.1 cryptic species. With nearly two million described species, such high estimates of cryptic diversity would suggest that cryptic species are widespread. The development of molecular species delimitation has led to the discovery of a large number of cryptic species, and cryptic biodiversity has gradually entered our field of vision and attracted more attention. This paper introduces the concept of cryptic species, how they evolve, and methods by which they may be discovered and confirmed, and provides theoretical and methodological guidance for the study of hidden species. A workflow of how to confirm cryptic species is provided. In addition, the importance and reliability of multi-evidence-based integrated taxonomy are reaffirmed as a way to better standardize decision-making processes. Special focus on cryptic diversity and increased funding for taxonomy is needed to ensure that cryptic species in hyperdiverse groups are discoverable and described. An increased focus on cryptic species in the future will naturally arise as more difficult groups are studied, and thereby, we may finally better understand the rules governing the evolution and maintenance of cryptic biodiversity.

Integrative taxonomy reveals the conspecific status of Xerotricha madritensis (Rambur, 1868) and Helicella candoni Thach, 2018 (Gastropoda, Geomitridae)

The Mediterranean region is a biodiversity hotspot. Mollusks represent the second most diverse phylum, with high species richness, endemism, and significant numbers of threatened species. The non-marine species are an especially vulnerable group. New taxa are frequently described although the descriptions often lack biological support. This is true for Helicella candoni Thach, 2018, originally described from Puerto de Santa María, Cádiz, Spain. Thatch (2018) considered H. candoni to be similar to Xerotricha madritensis (Rambur, 1868) but the comparison was made on the basis of basic conchological characters. The present study analyzed topotypes of X. madritensis and H. candoni using integrative taxonomy to evaluate the relationship of the two taxa and their status within Helicella A. Férussac, 1821 and Xerotricha Monterosato, 1892 respectively. A matrix of the mitochondrial cytochrome c oxidase subunit I (COI) yielded a total of 618 bp. Bayesian and Maximum Likelihood analyses showed that H. candoni and X. madritensis clustered closely together along with Helicella itala. Mean sequence divergence for COI between H. candoni and X. madritensis was 1.42 %. Both taxa are similar in shell shape and colour. Genitalia dimensions of H. condoni were very similar to those of X. madritensis. These data indicate that H. candoni is a junior synonym of X. madritensis. The phylogenetic analyses showed that, despite its morphological similarities, X. madritensis is a species of Helicella instead of Xerotricha.

DNA barcoding as a tool to monitor the diversity of endangered spring snails in an Austrian National Park

The Kalkalpen National Park is situated in Upper Austria and contains more than 800 springs. The international importance of this Park is, from the perspective of nature conservation directives, highly significant (European Nature Reserve Natura 2000, recognised wetland of the Ramsar convention). In the current study, the hydrobioid fauna ('spring snails') of the Kalkalpen National Park was evaluated. These tiny snails are difficult to determine; however, their investigation is especially desirable, as several species are threatened and as they are important for water quality assessment. Snails collected in 39 selected springs were examined with classical morphological methods (shell and genital anatomy) and, subsequently, by DNA analysis. For this task, the DNA barcode, a partial sequence of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene (length of the sequence 658-682 bp), was PCR amplified and sequenced. From 107 specimens, the DNA barcoding sequence could be obtained and compared with already existing DNA sequences. The (sub)endemic species Bythinellaconica, Hauffeniakerschneri, Hauffeniawienerwaldensis and Belgrandiellaaulaei could be clearly identified. For Bythiospeumnocki, despite the ambitious collecting effort, only empty shells were found in four springs (including the locus typicus spring) in the Park and its surroundings. The genus Bythinella was detected in 36 springs. From 25 of these localities, DNA barcodes could be created, which matches those of Bythinellaconica (comparison data from ABOL). It is, therefore, concluded that the species occurs widely in the Kalkalpen National Park. The genus Hauffenia was sampled from 16 springs. From one, the haplotype of Hauffeniawienerwaldensis could be identified (spring is 5 km outside the Park) and from six, the haplotype of Hauffeniakerschneri. Belgrandiellaaulaei was found in three springs, which all lie outside the boundaries and are, therefore, not included in the protection measures of the National Park. The data and analyses obtained contribute to the assessment of the taxonomic status of the species studied. The present study gives a good baseline for further monitoring of the hydrobioids in the Kalkalpen National Park, which is important to evaluate current as well as to decide on future protection measures for this group.

Multi-locus phylogeny and species delimitations of the striped-back shrew group (Eulipotyphla: Soricidae): Implications for cryptic diversity, taxonomy and multiple speciation patterns

The striped-back shrew group demonstrates remarkable variation in skull and body size, tail length, and brightness of the dorsal stripe; and karyotypic and DNA variation has been reported in recent years. In this study, we investigated the phylogenetic structure of the group, as well as speciation patterns and demographic history in Mountains of Southwestern China and adjacent mountains, including the southern Himalayas, Mts. Bashan, Wushan, and Qinling. We sequenced a total of 462 specimens from 126 localities in the known range of the group, which were sequenced and analyzed based on 6.2 kb of sequence data from two mitochondrial, six nuclear, and two Y chromosome markers. Phylogenetic analyses of the concatenated mtDNA data revealed 14 sympatric and independently evolving lineages within the striped-back shrew group, including Sorex bedfordiae, S. cylindricauda, S. excelsus, S. sinalis and several cryptic species. All concatenated data (ten genes) showed a consistent genetic structure compared to the mtDNA lineages for the group, whereas the nuclear and the Y chromosome data showed a discordant genetic structure compared to the mtDNA lineages for the striped-back shrew group. Species delimitation analyses and deep genetic distance clearly support the species status of the 14 evolving lineages. The divergence time estimation suggested that the striped-back shrew group began to diversify from the middle Pleistocene (2.34 Ma), then flourished at approximately 2.14 Ma, followed by a series of rapid diversifications through the Pleistocene. Our results also revealed multiple mechanisms of speciation in the Mountains of Southwestern China and Adjacent Mountains with complex landscapes and climate. The uplifting of the Qinghai-Tibetan Plateau, Quaternary climate oscillations, riverine barriers, ecological elevation gradients, topographical diversity, and their own low dispersal capacity may have driven the speciation, genetic structure, and phylogeographic patterns of the striped-back shrew group.

Temporal variation in climatic factors influences phenotypic diversity of Trochulus land snails

Organisms with limited dispersal capabilities should show phenotypic plasticity in situ to keep pace with environmental changes. Therefore, to study the influence of environmental variation on the phenotypic diversity, we chose land snails, Trochulus hispidus and T. sericeus, characterized by high population variability. We performed long-term field studies as well as laboratory and common garden experiments, which revealed that temporal environmental changes generate visible variation in shell size and shape of these snails. Many shell measurements of T. hispidus varied significantly with temperature and humidity in individual years. According to this, the first generation of T. hispidus, bred in controlled laboratory conditions, became significantly different in higher spire and narrower umbilicus from its wild parents. Interestingly, offspring produced by this generation and transplanted to wild conditions returned to the ‘wild’ flat and wide-umbilicated shell shape. Moreover, initially different species T. hispidus and T. sericeus transferred into common environment conditions revealed rapid and convergent shell modifications within one generation. Such morphological flexibility and high genetic variation can be evolutionarily favored, when the environment is heterogeneous in time. The impact of climate change on the shell morphometry can lead to incorrect taxonomic classification or delimitation of artificial taxa in land snails. These findings have also important implications in the context of changing climate and environment.

On the verge of extinction - revision of a highly endangered Swiss alpine snail with description of a new genus, Raeticella gen. nov. (Gastropoda, Eupulmonata, Hygromiidae)

The phylogenetic status of the alpine land snail Fruticicolabiconica has remained questionable since it was described by Eder in 1917. Considered a microendemic species from mountain tops in Central Switzerland, the shell is specially adapted for life under stones. Herein, we show via molecular and anatomical investigations that F.biconica neither belongs to the land snail genus Trochulus, nor to any other genus within Trochulini, but rather warrants placement within the newly established genus Raeticella Kneubühler, Baggenstos & Neubert, 2022. Phylogenetic analyses reveal that R.biconica is clearly separated from Trochulus. These findings are supported by morphological investigations of the shell and genitalia.

Two new pseudocryptic species in the medium-sized common European land snails, Fruticicola Held, 1838; as a result of phylogeographic analysis of Fruticicola fruticum (O. F. Müller, 1774) (Gastropoda: Helicoidea: Camaenidae)

Fruticicola fruticum (O. F. Müller, 1774), a medium-sized helicoid snail in the Bradybaenidae, has a wide range in Europe, reaching from the Urals and the Caucasus to the Balkans, and from the southern part of Scandinavia, through Central Europe to eastern and central France and northern Italy. There are numerous studies on its distribution, biology, life cycle, etc., but little is known about the genetic diversity of this taxon. Here, we studied the phylogeny and phylogeography of F. fruticum using two mitochondrial markers: cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S); and four nuclear markers: 18S ribosomal RNA (18S), 28S ribosomal RNA (28S), internal transcribed spacer (ITS-2), and histone 3 (H3). The study was based on 59 populations sampled across the range. Whereas nuclear markers showed little differentiation, phylogenetic analysis of COI sequences clearly confirmed the distinctness of the European Fruticicola and Asian Bradybaena (p-distance 0.229). Within Fruticicola 54 haplotypes were detected, haplotype diversity (Hd) = 0.973±0.006, nucleotide diversity (π) = 0.137±0.005. ABGD and PTP delimitation analyzes distinguished eight mOTUs. Two sequences (our mOTU C) from Russia were published in the GenBank as two distinct species: F. schrenckii and F. transbaicalia. Seven further mOTUs identified in our study formed three distinct lineages, regarded as species. The first (mOTU A and mOTU B), represented by 40 populations, occupies a wide range across northern and central Europe, extending east to Ukraine and south to northern Croatia (mOTU B). It encompasses the type locality of F. fruticum, and can be recognized as F. fruticum sensu stricto. Another lineage (mOTU D and mOTU E), represented by six populations in central Romania, appears to form another species. Both mOTUs were found together in one population. A third lineage, containing mOTUs F, G and H, represented by 14 populations, was distributed across the Balkans from N.E. Croatia to Bulgaria. p-distances between the three species ranged from 0.172 to 0.219, and between all the mOTUs, pooled together, from 0.172 to 0.258. The highest genetic diversity was found in species 3 (0.112) and the lowest in species 1 (0.025), despite its largest geographic distribution. Pairwise p-distances, Tamura 3-parameter distances, composite likelihood distances, as well as the coancestry coefficient F_ST, calculated for all populations pooled together were significantly associated with geographic distance, but this was not the case within each of these three species. The significant association for all populations reflected high diversity between the species coupled with high geographic distances between their populations, not the character of intraspecies diversity. With a few exceptions, there hold a rather infinite island model with low migration. AMOVA detected 78% of the variance between the three species, 18% among populations within the species, and only 3.6% within the populations. The low genetic diversity of widespread F. fruticum s. stricto, compared with much higher diversity of two narrowly distributed newly found species of Fruticicola, may reflect the rapid spread of the former into previously uninhabitable regions, while the latter were able to maintain populations in glacial refugia. The estimated time of divergence between the three species, 1.7-2.19 mya, suggests their ancestors' isolation in southern European refugia during the lower Pleistocene, the Gelasian/Calabrian. There was no clear association of variation in shell morphology and lineage or mOTU identity; on external characters, these species are semicryptic, subtle differences in reproductive anatomy among them were found.

Deep genetic structure at a small spatial scale in the endangered land snail Xerocrassa montserratensis

Species with small geographic ranges do not tend to have a high genetic structure, but some land snail species seem to be an exception. Xerocrassa montserratensis, an endangered land snail endemic to Catalonia (northeastern Iberian Peninsula), is an excellent model to study the processes affecting the phylogeography of specialized species of conservation concern. This species is restricted to xerophilous stony slopes and occurs within a small and fragmented area of ca. 500 km2. We sequenced the COI barcode region of 152 individuals from eight sites covering the entire range of the species. We found four genetic groups mostly coincident with their geographic distribution: a central ancestral group containing shared haplotypes among five localities and three groups restricted to a single locality each. Two of these derived groups were geographically and genetically isolated, while the third and most differentiated group was not geographically isolated. Geomorphologic and paleoclimatic processes during the Pleistocene can explain the divergence found between populations of this low dispersal species with historical fragmentation and secondary contacts. Nonetheless, recent passive large dispersal through streams was also detected in the central group. Overall, our study uncovered four evolutionary units, partially matching morphologically described subspecies, which should be considered in future conservation actions.

Genome-wide nuclear data confirm two species in the Alpine endemic land snail Noricella oreinos s.l. (Gastropoda, Hygromiidae)

The Austrian endemic land snail species Noricella oreinos (formerly Trochulus oreinos) occurs in the Northeastern Calcareous Alps at high elevations. Two morphologically highly similar subspecies N. o. oreinos and N. o. scheerpeltzi have been described. First analyses of mitochondrial and nuclear marker sequences indicated a high genetic divergence between them. In the present study, we aimed to assess gene flow between the two subspecies which should help to re-evaluate their taxonomic status. Sequence data and amplified fragment length polymorphism (AFLP) markers of 255 Noricella specimens covering the whole distribution range were analyzed. A clear geographic separation was found within the potential contact zone, the Haller Mauern mountain range. Samples of all western sites were part of the clade representing N. o. scheerpeltzi and almost all samples from the eastern sites clustered with N. o. oreinos. However, within two sampling sites of the eastern Haller Mauern, a few individuals possessed a COI sequence matching the N. o. oreinos clade whereas at the ITS2 locus they were heterozygous possessing the alleles of both taxa. Contrary to the ITS2 results indicating historical and/or ongoing hybridization, AFLP analyses of 202 individuals confirmed a clear separation of the two taxa congruent with the mitochondrial data. Although they occur on the same mountain range without any physical barrier, no indication of ongoing gene flow between the two taxa was found. Thus, we conclude that the two taxa are separate species N. oreinos and N. scheerpeltzi.

Exploration of phylogeography of Monachacantiana s.l. continues: the populations of the Apuan Alps (NW Tuscany, Italy) (Eupulmonata, Stylommatophora, Hygromiidae)

Two new lineages CAN-5 and CAN-6 were recognised in four populations of Monachacantiana (Montagu, 1803) s.l. from the Italian Apuan Alps by joint molecular and morphological analysis. They are different from other M.cantiana lineages known from English, Italian, Austrian and French populations, i.e. CAN-1, CAN-2, CAN-3 and CAN-4, as well as from the other Italian Monacha species used for comparisons (M.parumcincta and M.cartusiana). Although a definite taxonomic and nomenclatural setting seems to be premature, we suggest that the name or names for these new lineages as one or two species should be found among 19th century names (Helixsobara Mabille, 1881, H.ardesa Mabille, 1881, H.apuanica Mabille, 1881, H.carfaniensis De Stefani, 1883 and H.spallanzanii De Stefani, 1884).

The influence of habitat preferences on shell morphology in ecophenotypes of Trochulus hispidus complex

Trochulus hispidus and T. sericeus are hairy snails widely distributed in Europe. They differ in shell morphology and are usually found in various land habitats. However, their morphology does not match genetic distance as they do not form distinct clades. Therefore, it is interesting to determine to what extent environmental factors can control their phenotypes. We analysed the morphological traits and many environmental features of their habitats to find relationships between these parameters and explain ecological reasons for this plasticity. We found many statistically significant correlations between morphological traits and environmental variables. Illumination, forestation, precipitation and temperature occurred the most important features discriminating habitats of these snails. It turned out that T. sericeus prefers forests and moist shaded places, while T. hispidus chooses more dry habitats and open areas exposed to the sun. T. sericeus is also probably more tolerant to low and variable temperatures. The hair durability is also correlated with their habitats: the shell of T. hispidus is mostly hairless but hairs almost always cover the shell of T. sericeus. These results support the hypothesis that the lack of hairs is associated with the loss of a potential adaptive function due to the change from wet to dry habitats. The hairs facilitate the adherence of snails to herbaceous plants during feeding when the humidity levels are high. The morphological divergence of T. hispidus and T. sericeus is the result of phenotypic plasticity and selection associated with the habitat, which affect both the shell shape and the hair durability. Since T. hispidus and T. sericeus do to not represent separate biological species and their variability has no genetic basis, they should be considered as ecophenotypes. This and our previous studies suggest that phenotypic plasticity in widely distributed Trochulus species is quite common and may have been of ancestral origin.

Exploring Monacha cantiana (Montagu, 1803) phylogeography: cryptic lineages and new insights into the origin of the English populations (Eupulmonata, Stylommatophora, Hygromiidae)

Molecular analysis of nucleotide sequences of mitochondrial cytochrome oxidase subunit 1 (COI) and 16S ribosomal DNA (16SrDNA) as well as nuclear histone 3 (H3) and internal transcribed spacer 2 of rDNA (ITS2) gene fragments together with morphological analysis of shell and genitalia features showed that English, French and Italian populations usually assigned to Monacha cantiana consist of four distinct lineages (CAN-1, CAN-2, CAN-3, CAN-4). One of these lineages (CAN-1) included most of the UK (five sites) and Italian (five sites) populations examined. Three other lineages represented populations from two sites in northern Italy (CAN-2), three sites in northern Italy and Austria (CAN-3), and two sites in south-eastern France (CAN-4). The taxonomic and nomenclatural setting is only currently available for lineages CAN-1 and CAN-4; a definitive frame for the other two requires much more research. The lineage CAN-1 corresponds to the true M. cantiana (Montagu, 1803) because it is the only one that includes topotypical English populations. The relationships and genetic distances support the hypothesis of the Italian origin of this lineage which was probably introduced to England by the Romans. The lineage CAN-4 is attributed to M. cemenelea (Risso, 1826), for which a neotype has been designated and deposited. Its diagnostic sequences of COI, 16SrDNA, H3 and ITS2 genes have also been deposited in GenBank. Molecular and morphological (shell and genitalia) features showed that M. parumcincta (Rossmässler, 1834) is a distinct taxon from the M. cantiana lineages.

Phenotypic plasticity can explain evolution of sympatric polymorphism in the hairy snail Trochulus hispidus (Linnaeus, 1758)

Morphological variation of snails from the genus Trochulus is so huge that their taxonomy is unclear. The greatest variability concerns forms hispidus and sericeus/plebeius, which are often considered as separate species. To evidence the species barriers, we carried out crossbreeding experiments between these two sympatric morphs. Moreover, we compared the shell morphology of laboratory-bred offspring with their wild parents to test if the variation can be explained by the phenotypic plasticity model. We found that the two Trochulus morphs show no reproductive barriers. The fecundity rates, the mean clutch size, and F₁ viability observed for all crosses were not significantly different. In hybrid crosses (in F₂ generation), we also recorded reproduction compatibility, similar fecundity, and hatching success as in their parents. Accordingly, phylogenetic analyses revealed the significant grouping of sequences from these different morphs and supported no constrains in reproduction between them. Comparison of shell morphology between wild and laboratory samples showed that various characters appeared highly plastic. The average shell shape of the hispidus morph changed significantly from flat with wide umbilicus to elevated with narrower umbilicus such as in the sericeus/plebeius morph. All these findings indicate that the examined morphs do not represent separate biological species and the evolutionary process is not advanced enough to separate their genetic pool. Therefore, phenotypic plasticity has played a significant role in the evolution of Trochulus shell polymorphism. The two morphs can evolve independently in separate phylogenetic lineages under the influence of local environmental conditions.

Indication for selfing in geographically separated populations and evidence for Pleistocene survival within the Alps: the case of Cylindrus obtusus (Pulmonata: Helicidae)

Background

Cylindrus obtusus is one of the most prominent endemic snail species of the Eastern Alps. It is restricted to alpine meadows and calcareous rocky habitats above 1500 m. Peculiar intraspecific differences have been observed in its genital tract in the eastern populations the two mucus glands associated with the love dart sac are highly variable, while almost no variation was observed in the western populations. This raises the question whether the mode and success of reproduction of the respective populations are different. To find out whether these anatomical differences reflect genetic differentiation, which might be an indication for distinct glacial refugia, we investigated a 650 bp fragment of the mitochondrial cytochrome oxidase subunit 1 gene (COI) (280 individuals) and 9 microsatellite loci from samples (487 individuals from 29 populations) covering the whole distribution range of the species.

Results

The COI sequences show a geographic differentiation between eastern, central and western populations. The westernmost localities, which were covered under ice sheets during glacial periods, are characterized by extreme low variability. Overall genetic distances among all individuals are small (max. 1.7% p-distance). The microsatellite analysis reveals a high differentiation between populations, implying restriction of gene flow. The highest genetic variability was found in the central populations. Remarkably, nearly all individuals from the eastern populations, which are more variable in their genital morphology, are homozygous in all microsatellite loci, although different alleles were found within populations.

Conclusions

The most peculiar outcome of the study is the strong evidence for selfing in C. obtusus as indicated by the microsatellite data in the easternmost populations. This finding is supported by the deformation of the mucus glands in the same populations. Since mucus glands play an important role in sexual reproduction, it seems plausible that in selfing organisms these structures are reduced. The phylogeographic structure revealed by COI sequences implies that the species has survived the ice ages within the Calcareous Alps. The small genetic distances among all individuals (max. 1.7%) suggest that C. obtusus has experienced severe bottlenecks in the past.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-0977-0) contains supplementary material, which is available to authorized users.

First record of Trochulus clandestinus (Hartmann, 1821) in Austria (Gastropoda: Eupulmonata: Hygromiidae)

The north-west alpine distributed hairy snail Trochulus clandestinus (Hartmann, 1821) was recorded for the first time from Austria. Two living specimens were found in Vorarlberg 11 July 2016. The animals were subjected to genetic barcoding and their genital organs were dissected. The taxonomic situation within north-west alpine species of the genus Trochulus is not unambiguously resolved, but the assignment of the Austrian specimens as T. clandestinus is the most reliable at the current state of knowledge. The habitat of the Austrian location concurs with those of autochthonous populations in Switzerland. Nevertheless, for now it cannot be clearly stated whether the species settled in Vorarlberg directly after the end of the last glaciation or whether the current finding is a result of recent anthropogenic introduction.

Ongoing Speciation and Gene Flow between Taxonomically Challenging Trochulus Species Complex (Gastropoda: Hygromiidae)

Geographical isolation, selection and genetic drift can cause the geographical diversification of populations and lead to speciation. Land snail species in the genus Trochulus show overlaps in geographical ranges as well as in morphology, but genetic data do not always support the species-level taxonomy based on morphological characters. Such a group offers an excellent opportunity to explore the processes involved. We have addressed the problem by determining the status of the restricted endemic T. graminicola within the larger context of Trochulus taxonomy. We used an integrated approach based on morphological features, ecological preferences and two molecular markers: mitochondrial COI sequences and microsatellites. Comparison of these results demonstrated: (i) conchological distinction of T. striolatus and T. sericeus; (ii) anatomical, ecological and genetic differentiation of T. graminicola and (iii) concordance between morphological characters and mtDNA markers in T. striolatus. Moreover, our data showed an intricate evolutionary history within the genus Trochulus, which can be best explained by: (i) recent or ongoing gene flow between taxa or (ii) their large ancestral polymorphism. Both of these hypotheses suggest that diversification within this group of snails has occurred relatively recently. The mismatches between species defined on morphology and on molecular genetics indicate the complexity of the processes involved in the diversification of this genus.

DNA analysis of molluscs from a museum wet collection: a comparison of different extraction methods

Background

DNA isolation and PCR amplification from molluscan taxa is considered as problematic because polysaccharides in tissue and mucus presumably co-precipitate with the DNA and inhibit the activity of DNA polymerase. In the present study we tested two common extraction methods on specimens from the mollusc collection of the Natural History Museum Vienna (NHMW). We analysed a broad variety of taxa covering a large temporal span (acquisition years 1877 to 1999), which distinguishes our study from previous ones where mostly fresh material was used. We also took other factors into account: effects of sample age, effects of formaldehyde treatment and taxon-specific problems. We used several primer combinations to amplify amplicons of different lengths of two mitochondrial genes: cytochrome c oxidase subunit 1 (COI) and 16S rRNA gene (16S).

Results

Overall PCR success was 43 % in the 576 extractions (including all primer combinations). The smallest amplicon (~240 bp) showed the best results (49 % positive reactions), followed by the 400 bp amplicon (40.5 %). Both short sections yielded significantly better results than the 700 bp long amplicon (27 %). Comparatively, the Gen-ial-First, All-tissue DNA-Kit—extraction method performed significantly better than Promega-Tissue and Hair Extraction Kit. Generally, PCR success is age-dependent. Nonetheless, we were able to obtain the longest amplicon even from 137-year-old material. Importantly, formaldehyde traces did not totally inhibit amplification success, although very high concentrations did.

Conclusions

Museum material has gained importance for DNA analysis in recent years, especially for DNA barcoding projects. In some cases, however, the amplification of the standard barcoding region (partial sequence of the COI) is problematic with old material. Our study clearly shows that the COI barcoding region could be amplified in up to 49 % of PCRs (varying with amplicon length), which is, for museum samples, quite a high percentage. The difference between extraction methods was minimal and we recommend using an established kit for a first attempt because experience and routine in handling might be more important than slight performance differences of the various kits. Finally, we identify fixation, storage, sample conservation and documentation of the specimens’ history rather than the DNA extraction method to be the most crucial factors for PCR success.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2147-7) contains supplementary material, which is available to authorized users.

Differentiation in the Trochulus hispidus complex and related taxa (Pulmonata: Hygromiidae): morphology, ecology and their relation to phylogeography

In this study we investigated the morphology and ecology of representatives of the taxonomically ambiguous genus Trochulus. The main focus was on the T. hispidus complex, which comprises several genetically highly divergent mitochondrial clades, as determined in a parallel molecular genetic study. We analysed shell morphology and anatomical traits and asked whether the clades are differentiated in these characters. In addition, the related species T. oreinos and T. striolatus were investigated and compared with the T. hispidus complex. Finally, we compared the ecological requirements of the taxa. Among the genetic clades of the T. hispidus complex there was no clear morphological differentiation and geographic populations could not be distinguished based on their morphology. The investigated characters of the genital anatomy did not allow discrimination of any of the T. hispidus clades and were not even diagnostic for the group as a whole. The morphotype of T. sericeus is present in all clades and thus cannot be assigned to a genetic group or any specific population. Thus, our morphological data do not provide evidence that any of the mitochondrial T. hispidus clades represent separate species. Concerning interspecific delimitation, the T. hispidus complex was clearly differentiated from T. striolatus and T. oreinos by shell morphological and anatomical characters, e.g. sculpture of shell surface and details of the penis. Finally, the habitat of T. oreinos is different from those of the other two species. In contrast to the lack of correspondence between genetic and morphological differentiation within the T. hispidus complex, related species display intraspecific morphological differentiation corresponding with mitochondrial clades: within T. striolatus there was a slight morphological differentiation between the subspecies T. s. striolatus, T. s. juvavensis and T. s. danubialis. The two subspecies of T. oreinos could be discriminated by a small but consistent difference in the cross-section of the penis. The unequal levels of intraspecific differentiation are caused by different evolutionary histories as a consequence of disparities in ecological demands, dispersal ability and use of glacial refugia: both the T. hispidus complex and T. striolatus are fast-spreading, euryoecious organisms which are able to (re-)colonize habitats and survive under different climate conditions. While the T. hispidus complex probably survived the Pleistocene in several glacial refugia, for T. striolatus one glacial refugium is suggested. Trochulus oreinos differs from the other taxa, as it is a slow disperser with a narrow ecological niche. We suggest that its subspecies spent at least the last glaciation in or close to the presently inhabited areas.