Research Article |
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Corresponding author: Ondřej Korábek ( ondrej.korabek@gmail.com ) Academic editor: Martin Haase
© 2025 Ondřej Korábek, Petr Dolejš, Radovan Coufal, Lucie Juřičková, Kateřina Kubíková, Bernhard Hausdorf.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Korábek O, Dolejš P, Coufal R, Juřičková L, Kubíková K, Hausdorf B (2025) A new distinctive lineage of Helix (Gastropoda, Stylommatophora, Helicidae), with a guide to Helix species from mainland Greece. ZooKeys 1249: 93-135. https://doi.org/10.3897/zookeys.1249.143635
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Greece is home to numerous endemic land snail species, sometimes with highly restricted distributions. Several species of Helix, representing all three subgenera, live there. Although the genus was taxonomically revised in 2014, there remained some open questions and the distribution ranges of individual species are still incompletely known. The discovery of a new, narrowly endemic subspecies, Helix pelagonesica thembones Korábek, Juřičková & Hausdorf, subsp. nov., is reported from the hills bordering the Thessalian Plain in the west. It was previously confused with Helix schlaeflii, but it was found that H. schlaeflii does not occur as far east as previously thought. Notably, the isolated populations from the tip of the Sithonia peninsula (Chalkidiki) that had previously been identified as H. schlaeflii also turned out to be related to H. pelagonesica. Although a divergent mitochondrial lineage was found there, morphological differences limited only to a different shell shape and lack of geographic separation led us to classify these populations as a form of H. pelagonesica pelagonesica. In addition, Helix straminea is reported from Greece for the first time, with a population located near Kalambaka. All the Helix species from mainland Greece are illustrated and accompanied by descriptions to facilitate their recognition and maps of their distribution are provided.
Balkans, distributions, diversity, endemics, land snail, phylogeny, species identification, taxonomy
The distribution of species diversity is uneven as the diversity generally increases towards the equator. Considering the distribution of European land snail diversity (
The south of Europe consists of three peninsulas that differ in diversity and phylogenetic composition of their land snail faunas. The Balkans is the largest and most species-rich, followed by the Iberian Peninsula; the Apennine Peninsula has a relatively low diversity of land snails. In the Balkans, the diversity of land snails concentrates to the mountainous western part of the peninsula, culminating in an area roughly from Montenegro to Greece. Complex topography of the area and abundance of limestones created plenty of opportunities for the diversification of land snails, and the south of the Balkans, in particular Greece, also provided refugia allowing for the survival of relict lineages (as in Phaedusinae;
The diversity in Greece is high and only few groups have been investigated with genetic data. Therefore, there is a need for comprehensive taxonomic revisions employing modern genetic methods in many genera to clarify species limits. There may also still remain undescribed forms, if they have small ranges and/or cryptic lifestyle, and if they occur far from popular holiday destinations.
The diversity of the genus Helix Linnaeus, 1758 appears to be rather well documented. A morphology-based revision of the genus was published more than ten years ago (
A new mitochondrial lineage of Helix, so divergent that it may represent an unknown species, has recently been recognized by sequencing of museum samples previously identified as Helix schlaeflii Mousson, 1859. One individual from western Thessaly yielded a sequence related to Helix pelagonesica (Rolle, 1898) (
Due to this finding of a new lineage and the general scarcity of information on the distribution of Helix species in western Thessaly and the immediately adjacent regions, we decided to revise the eastern-most records of H. schlaeflii as reported by
As a result of the revisions, we describe a new, narrowly distributed subspecies of H. pelagonesica and provide an updated guide to the Helix species of the Greek mainland.
This study is based on material collected in 2023 and stored in the Národní muzeum, Praha, Czechia and on data collected during our previous studies on Helix (e.g.
For phylogenetic analyses we used sequences of fragments of three mitochondrial genes, the cytochrome c oxidase subunit I (cox1), 16S rRNA (rrnL) and 12S rRNA (rrnS). The fragments defined by the primers LCO1490+HCO2198 (cox1; as modified by
Total genomic DNA was extracted from tissue samples following a slightly modified version of the protocol of
In order to illustrate the phylogenetic placement of the analysed individuals, we combined the data generated here with available Helix sequences (
Sequences were aligned with MAFFT 7.520 (
Observations on anatomy of genital system of representatives of the H. pelagonesica clade were done on five individuals from Morfovouni, two individuals from the tip of Sithonia, and three individuals of typical H. pelagonesica from Nikiti (at the base of the Sithonia, Chalkidiki Peninsula).
We performed shell measurements to compare the three main lineages within the H. pelagonesica clade (typical H. pelagonesica, the one from Morfovouni and Mouzaki, and the lineage from the tip of Sithonia). With a calliper, we measured the shell diameter and height, the diameter of aperture (from the columellar margin to the insertion) and the diameter of protoconch at 1 whorl as counted by
We performed a principal component analysis (PCA) on the data. We used the shell diameter to normalise the shell height and aperture diameter to size, which would otherwise dominate the first axis. The PCA was done in R 4.4 (stats:prcomp(x, center = TRUE, scale. = TRUE)) and visualised with the package ‘ggbiplot’ (
NMP Národní muzeum, Praha, Czechia.
We could not confirm the presence of H. schlaeflii at any of the sites of its presumed eastern-most occurrences in Thessaly and Western Macedonia we visited (
The specimens from Krionéri in Aetolia-Acarnania (
Phylogenetic analysis of mitochondrial sequences (Fig.
Phylogenetic relationships of the newly analysed Helix samples from Greece (in bold). Maximum likelihood tree based on concatenated mitochondrial nucleotide sequences of partial cox1, rrnL, and rrnS genes. Support values are bootstrap percentages from 500 pseudoreplicates. Branches with bootstrap support <75% are dashed. The tree is rooted with Maltzanella Hesse, 1917; the outgroup is not shown.
The samples from Mouzaki and Morfovouni yielded sequences nearly identical to the previously analysed sample from the latter locality. They form a branch sister to typical H. pelagonesica. This clade is then sister to a new mitochondrial lineage recovered from the sample from the tip of Sithonia.
Of the three lineages, typical H. pelagonesica is characterised by shells with a more triangular outline from the frontal view (Figs
Helix Linnaeus, 1758
Helix pomatia Linnaeus, 1758, by subsequent designation (
Shell (Fig.
It has a small range (Fig.
Genital system of Helix (Helix) p. pelagonesica (Greece, Central Macedonia, Nikiti; 40.2058°N, 23.6975°E; NMP P6M 42932). Abbreviations: ag = albumen gland; bc = bursa copulatrix; dpd = distal pedunculus; ds = dart sac; dv = diverticulum; fl = flagellum; go = genital opening (not visible); hd = hermaphroditic duct; mg = mucous glands; pn+dep = penis + distal epiphallus; pep = proximal epiphallus; ppd = proximal pedunculus; pr = penial retractor muscle; so = spermoviduct; vd = vas deferens.
Genital system of Helix (Helix) p. pelagonesica from the tip of Sithonia (Greece, Central Macedonia, Toroni; 39.9476°N, 23.9321°E; NMP P6M 42933). Abbreviations: ag = albumen gland; bc = bursa copulatrix; dpd = distal pedunculus; ds = dart sac; dv = diverticulum; fl = flagellum; go = genital opening (not visible); hd = hermaphroditic duct; mg = mucous glands; pn+dep = penis + distal epiphallus; pep = proximal epiphallus; ppd = proximal pedunculus; pr = penial retractor muscle; so = spermoviduct; vd = vas deferens.
Approximate distribution of Helix (Helix) p. pelagonesica. Black dots denote populations sampled for molecular analyses. Isolate codes as in the phylogeny in Fig.
Holotype
: (Fig.
Shells of Helix (Helix) pelagonesica thembones. A. Holotype; Greece, Thessaly, Morfovouni; 39.3574°N, 21.7468°E; NMP P6M 44038; B. Greece, Thessaly, Mouzaki; 39.4135°N, 21.6642°E; NMP P6M 42942; C. Greece, Thessaly, between Morfovouni and Ellinopyrgos; 39.3747°N, 21.7318°E; NMP P6M 42944. Photo R. Coufal. Scale bar: 2 cm.
Helix pelagonesica thembones differs from H. p. pelagonesica in the pale brownish shell with inconspicuous bands and paler apertural margins. Helix pelagonesica thembones has globular shells, whereas most populations of H. p. pelagonesica have more conical shells with a relatively smaller aperture.
Middle-sized globular shell (diameter 32–42 mm, height 33–43 mm) resembling in shape Helix pomatia; no umbilicus; protoconch large (~5–6 mm in diameter at 1 whorl); aperture semicircular; aperture margins and especially columella may be darker than the rest of the shell, with columella often meat-coloured to brown; shell surface relatively smooth, with only fine irregular riblets, pale brownish, sometimes with pinkish hue when alive; bands are inconspicuous, not much darker than the background, but present (2+3 and 4, sometimes weakly also 5, positioned close to the shell axis); apertural margins straight, slightly reflected only towards columella; animal pale brown to greyish brown, mantle margins pale.
Genital system (Fig.
Genital system of Helix (Helix) pelagonesica thembones (paratype; Greece, Thessaly, Morfovouni; 39.3574°N, 21.7468°E; NMP P6M 42943). Abbreviations: ag = albumen gland; bc = bursa copulatrix; dpd = distal pedunculus; ds = dart sac; dv = diverticulum; fl = flagellum; go = genital opening (not visible); hd = hermaphroditic duct; mg = mucous glands; pn+dep = penis + distal epiphallus; pep = proximal epiphallus; ppd = proximal pedunculus; pr = penial retractor muscle; so = spermoviduct; vd = vas deferens.
Named after the opening track of the Alice in Chains’ 1992 album “Dirt” as a little reminder to all in power that they are also “gonna end up a big ol’ pile of them bones”. Noun in apposition.
The species was found on the band of hills that directly adjoin the Plain of Thessaly from the west (Fig.
At the type locality, the greatest concentration of individuals was in an area overgrown by Phlomis fruticosa L. (Fig.
The majority of the Helix pelagonesica populations differ in a conical shell shape from the plesiomorphic more globular shell shape in Helix. This conical shell shape characterises not only the populations in the contiguous main range of the species in Greek Macedonia and North Macedonia, for which the name Helix pelagonesica vardarica Knipper, 1939 has been proposed, but also isolates of the species in Thessalia, for which the name Helix volensis Kobelt, 1906 was proposed, and the population from the island Kyra Panagia (= Pelagonisi) in the Northern Sporades, for which the species name was originally proposed. The populations with conical shell shape are monophyletic in the mitochondrial tree (Fig.
In contrast, the population from the tip of Sithonia came probably in secondary contact with the conical populations when they colonised the rest of Sithonia. We suppose that the globular population from the tip of Sithonia is connected by gene flow with the neighbouring H. pelagonesica populations, which are only about a kilometre apart, and that the differentiated populations are in the process of merging. Therefore, we currently classify this population as H. p. pelagonesica despite the still recognisable difference in shell shape and the deep split between the mitochondrial lineages of these populations (Fig.
We did not find any noteworthy differences between the genital system of H. pelagonesica thembones, typical H. pelagonesica and the form from the tip of Sithonia. The latter might have a somewhat shorter flagellum (35–37 mm, n = 2) compared to H. pelagonesica thembones (38–49 mm, n = 5), but both overlap with the typical H. pelagonesica (35–45 mm, n = 3).
Helix pelagonesica thembones is usually smaller than H. schlaeflii and has a smoother shell surface without the irregular whitish patterns typical for the latter. It differs from individuals of H. borealis with reduced banding in much paler colouration of the aperture margins and a much larger protoconch. Furthermore, the mucous glands in H. borealis are shorter, reaching only to the half of the dart sac, and diverticulum of bursa copulatrix may be much shorter in some individuals. Compared to H. philibinensis, which is usually distinctly banded, H. pelagonesica thembones has a higher aperture.
Shell large, globular to conical; umbilicus sometimes slit-like but usually completely covered; protoconch large; shell surface with irregular ribs; basal colour whitish or very pale brown, more rarely the whole shell is brown; banding often reduced with upper bands 2 and 3 fused or partially fused and the lower two fuzzy and faint, but some populations have well developed, contrasting, reddish brown bands; bands with irregular whitish interruptions; aperture margins straight, only slightly reflected towards the columella; apertural lips and in particular the columellar triangle orange- or meat-brown to violet-brown, but the colouration is sometimes only faint and is missing or only weakly developed in the parietal area; mantle margins pale; animal very pale brown or grey to yellowish.
Common in Epirus and adjacent Western Macedonia (eastern limits uncertain, but apparently west of Kastoria, Neapoli and Grevena); occurs also on Kerkyra (Corfu). The range of the species as currently accepted extends to central Albania and up to the Galičica Mountains between the lakes Ochrid and Prespa (Fig.
Differences to H. thessalica and H. borealis are described under the respective species. Helix schlaeflii differs from H. straminea in globular shape with an expanded last whorl and a larger aperture; the Greek populations often differ in a pale colouration, because H. straminea has typically more vivid colours. Helix straminea also lacks the whitish pattern on the bands characteristic for H. schlaeflii and often has a darker, brown foot.
Helix schlaeflii is not monophyletic in the mitochondrial tree (Fig.
Shell (Fig.
Helix straminea occurs in the northwest of North Macedonia and in central Albania (Fig.
Helix straminea was in the Balkans found in different habitats, from beech forests to shrubs. There is no clear species boundary to the closely related H. vladika in the north (northern Albania to central Serbia).
Shell (Fig.
In Greece it lives in higher altitudes. It is relatively broadly distributed in the Rhodopes (Fig.
The most similar species in Greece is H. schlaeflii. In Helix thessalica, the shell is in most cases much more darkly coloured with a distinctly developed periostracum. Greek populations lack any brown colour on the columella, which in turn is characteristic for H. schlaeflii. Helix thessalica has a dark grey penis, epiphallus and vagina. The description as provided fits the Greek populations, but in other parts of the range the species may be distinctively banded, with brown apertural margins and darker foot.
Shell (Fig.
Distributed from Lake Prespa (northwestern Greece) to the island of Thasos (northeastern Greece) (Fig.
Shell (Fig.
Typical Helix borealis is distributed over much of Peloponnese, the east of central Greece (Aetolia, Acarnania, Phocis, Evrytania) and in western Epirus (Fig.
Some H. borealis populations have a globular shell with shape resembling that of H. figulina, but with a smoother, not regularly ribbed surface. There is also always some brown colouration of the apertural margins. In colour, H. borealis is often very similar to H. pelagonesica, but the two differ in shell shape and in the small protoconch of H. borealis. The globular-shelled form of H. pelagonesica from the tip of Sithonia (see below) is similar to H. borealis also in the shell shape but has a larger protoconch. In Epirus, H. borealis occurs syntopically with H. schlaeflii. Although the colouration may be similar there, H. schlaeflii is much larger and has a large protoconch.
In the mitochondrial phylogeny (Fig.
ICZN 2002;
Shell (Fig.
Found commonly in northern Greece except for west of the Pindos Mts. (Fig.
Helix lucorum is very variably coloured and also details of the shell and aperture shape vary. The forms present in mainland Greece are typically very darkly coloured, with a white band on the periphery. The animal is also rather darkly coloured. It has a similar shell shape as H. straminea and H. pelagonesica, but besides the colour it differs in smooth shell surface and presence of strong transverse banding, visible at least at the bottom of the shell. We found H. lucorum syntopic with H. figulina, H. thessalica and H. philibinensis.
Helix (Helicogena) pelasgica Kobelt 1904 = Helix figulina Rossmässler, 1839, by subsequent designation (
Shell (Fig.
Very common species distributed over large part of mainland Greece and the Peloponnese (Fig.
Helix figulina is easily recognisable due to small size, a very small protoconch, globular shell shape with large aperture, rounded columella smoothly transitioning to the bottom of the previous whorl, completely white aperture margins, and regularly ribbed surface. It may be found syntopically or nearly so with H. lucorum, H. borealis, H. philibinensis and H. pelagonesica. Helix philibinensis is the most similar species overlapping in size, but it has a blunter apex, smoother shell surface, smaller aperture which usually has at least partially coloured margins.
Several other Helix species occur on the islands in the Aegean Sea; we provide here only a brief overview. Majority of them appears to be non-native, indicating a substantial transport of these edible snails in the past.
An endemic, divergent lineage of H. borealis lives in western Crete (sample BR21A in Fig.
Helix (Helix) pronuba Westerlund, 1879 is more widely distributed in the south of Crete. It is a species with dark brown apertural margins. Its small shells have a granulated upper surface and are often conspicuously banded. The shell is rounded, with a large last whorl and relatively spacious aperture. Besides Crete, H. pronuba was also reported from Chalki (
The taxonomically problematic group of Helix (Helix) cincta is represented on eastern Aegean islands by a lineage known as Helix valentini Kobelt, 1891 as well as by typical Helix cincta Müller, 1774. The group originates from northern Levant (
Helix (Helix) fathallae Nägele, 1901 lives in Greece only on Rhodos. It is most similar in shell shape and colour to H. philibinensis, having a larger protoconch and darker apertural margins than H. cincta. Furthermore, the columellar triangle is differently shaped, not depressed as in H. cincta. It is also a non-native species with problematic taxonomy, but the sample from Rhodos analysed by
Helix (Helix) asemnis Bourguignat, 1860 is a middle-sized to large species with whitish shells. Banding pattern varies, but the brown or reddish bands are often not very dark and the three upper bands typically fuse. Aperture margins are purely white and the foot is greyish pink to purely pink in adults. It lives on the islands of Megisti (
Southeastern Aegean islands are inhabited by Helix (Pelasga) nucula Mousson, 1854, whose distribution limits are marked by Lesvos in the north and Kasos in the west (
Helix (Aegaeohelix) godetiana Kobelt, 1878 (Fig.
Eight of the ~38 currently accepted Helix species (MolluscaBase eds 2024) live in continental Greece, which includes species from two (Helix, Pelasga) of its three subgenera (the third, Aegaeohelix, is endemic to the Greek islands) and from all three major clades within the nominotypic subgenus (
When revising the eastern distribution limits of H. schlaeflii, we discovered two new mitochondrial lineages that form a clade with H. pelagonesica. Both have a limited distribution: one is found only on the tip of the Sithonia peninsula, the other lives along a strip of hills that is no more than 50 km in length. The latter lineage is described here as a new subspecies, Helix pelagonesica thembones. We decided to introduce a new taxon for four reasons: a) this mitochondrial lineage is distinctive, sister to the lineage found in typical H. pelagonesica across its distribution range, b) populations sharing this lineage are characterised by shell shape different from typical H. pelagonesica and c) their shell colouration is unique, and d) this lineage and the corresponding morphotype occur in a small area that is geographically isolated from the rest of H. pelagonesica’s distribution range. Only a) and b) applies also for the lineage from the tip of Sithonia. These snails are, except for a different shell shape, very similar to typical H. pelagonesica, and there is currently no geographic isolation from H. pelagonesica. Although the lineage from the tip of Sithonia is more distantly related to typical H. pelagonesica in the mitochondrial tree than is the one described here as a new subspecies, we decided not to formally describe it as a new taxon. In H. pelagonesica thembones the difference in appearance is more pronounced and the geographic isolation means that the lineage is evolving independently. In contrast, the mitochondrial lineage from the tip of Sithonia could be a remnant of a previously isolated lineage whose nuclear genome now largely merged back with H. pelagonesica. Genome-wide data from a detailed sampling of H. pelagonesica would be needed to resolve the issue definitely.
The new subspecies appears to have a very restricted distribution range. We speculate that the species may be limited by geological conditions, occurring basically only in a narrow strip of limestones squeezed between flysch to the west and the Thessalian plain to the east (
We thank Eike Neubert, Estée Bochud (both
The authors have declared that no competing interests exist.
No ethical statement was reported.
No use of AI was reported.
This work has been supported by the Ministry of Culture of the Czech Republic (DKRVO 2024–2028/6.II.b, National Museum of the Czech Republic, 00023272) and by the Charles University Research Centre program No. UNCE/24/SCI/006.
Conceptualization: OK. Data curation: OK. Formal analysis: OK. Funding acquisition: PD, BH. Investigation: KK, PD, OK, RC, LJ. Methodology: BH, OK. Resources: BH, LJ. Visualization: OK, RC. Writing – original draft: OK. Writing – review and editing: OK, RC, KK, LJ, BH, PD.
Ondřej Korábek https://orcid.org/0000-0002-2522-9165
Petr Dolejš https://orcid.org/0000-0001-9360-7247
Radovan Coufal https://orcid.org/0000-0002-5870-5041
Lucie Juřičková https://orcid.org/0000-0001-5163-1222
Kateřina Kubíková https://orcid.org/0009-0003-7328-0146
Bernhard Hausdorf https://orcid.org/0000-0002-1604-1689
Nucleotide sequences were deposited in the NCBI Nucleotide database; accession numbers are listed in the Supplementary Information.
List of samples used in the phylogenetic analysis with locality and voucher information and GenBank accession numbers
Data type: ods