Helix (Helix) pelagonesica pelagonesica ( Rolle, 1898 )

Helix (Helix) pelagonesica pelagonesica ( Rolle, 1898) View in CoL

Figs 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9

References.

Neubert 2014; Korábek et al. 2022.

Description.

Shell (Fig. 4 View Figure 4 ) middle-sized, conical with relatively flat base; individual whorls low and tightly coiled; deep suture giving the shell a stepped look; umbilicus fully covered or there is very narrow slit between the shell bottom and the reflected columellar margin of the aperture; protoconch large, making the apex blunt; aperture small and low, with oblique columella; aperture margins and the parietal area dark brown with purple hue; shell surface usually with fine ribs, pale brown, but often corroded even in live individuals; four bands typically present (because 2 + 3 fuse), brown with reddish or purple tones; bands interrupted by fine growth lines and lightly coloured ribs; aperture margins straight, columellar margin thickened, margins and the parietal area dark purple-brown. Animal grey (Fig. 5 View Figure 5 ).

Distribution and habitat.

It has a small range (Fig. 10 View Figure 10 ), within which it occurs sporadically, even though it can be locally abundant. In the north, it was found in the hills on both sides of the valley of Vardar / Axios (Kilkis Regional Unit), e. g. west of Polykastro or near the Dojran Lake. The northernmost record is from northeast of Negotino in North Macedonia. To the south, H. p. pelagonesica is distributed over Chalkidiki, additional populations are known from foothills of Mount Olympus and from Pelion near Volos (in Makrinitsa). The type locality is the island of Kyra Panagia (Pelagonisi) in the Northern Sporades. The characteristic habitat is a loose shrub with Quercus ( Q. coccifera or similar species) and Paliurus spina-christi . It seems to rest relatively frequently on branches of shrubs.

Remarks.

Neubert (2014: fig. 224) figured a shell of a snail from the tip of the Sithonia peninsula, Chalkidiki ( NMBE 524743 ), which was quite similar to the brightly coloured form of H. schlaeflii from Corfu. He discussed this population with the first author in 2011 and back then both eventually identified it as H. schlaeflii , speculating it was possibly an anthropogenic occurrence. Following the examination of new material and phylogenetic analysis (Fig. 1 View Figure 1 ), we currently consider the form living at the tip of Sithonia to be a variety of H. p. pelagonesica . Its globular shell shape is a clear difference to typical H. p. pelagonesica , but this is a question of the height of individual whorls driven probably by the angle of the columella, so a change in a single parameter of the shell geometry is responsible for the difference. In some shells, the columella is not vertical and the difference in shell shape is much weaker (whorls are lower, suture deeper). The colouration of the shell and animal is identical to typical H. p. pelagonesica , whose sample was previously sequenced from a locality on the northern foot of a limestone hill near Porto Koufo (just over a kilometre from where we collected). The strongest argument for a separate taxon for the snails from the tip of Sithonia is the mitochondrial lineage found there, which does not fall within or sister to the clade comprising typical H. p. pelagonesica samples. However, the conchological similarities as well as geographic proximity suggest that there is a gene flow; the divergent mtDNA might be a relic of a period of separation that was then followed by merging back with H. p. pelagonesica . We found this form (Figs 7 View Figure 7 , 8 View Figure 8 ) on the limestone hills on both sides of the Maratia Beach at the southernmost tip of the peninsula. This habitat contrasts with geological conditions on the rest of Sithonia, which is covered by substrates generally unfavourable for snails, in large part by granite and other plutonic rocks ( Christofides et al. 2007). However, a strict dependence on limestone is unlikely, because Neubert (2014) also found a locality of the same form north of the limestone occurrences (17 road km south of Sarti, ~ 39.993°N, 23.959°E; NMBE 524745 ). Typical H. p. pelagonesica tolerates non-limestone substrates.