Helix (Helix) borealis Mousson, 1859

Helix (Helix) borealis Mousson, 1859 View in CoL

Figs 28 View Figure 28 , 29 View Figure 29

References.

Neubert 2014; Korábek et al. 2021.

Description.

Shell (Fig. 28 View Figure 28 ) mid-sized, globular to slightly conical; aperture rounded and in the more globular populations spacious; umbilicus missing; protoconch small; shell surface rather smooth, with fine growth lines; basal colour ranging from nearly white to pale brown; banding pattern varies from completely reduced bands to well-developed and contrasting; the upper three bands may be separated only on the upper whorls or well separated up to the last whorl; aperture margins and the parietal region brown and much darker than the rest of the shell, the colour ranges from vivid pale brown with orange tones ( Ionian Islands, Epirus) to dark with purple tones (Peloponnese, Evia); mantle margins pale. Animal (Fig. 29 View Figure 29 ) pale grey or pale brown, often but not always with a dark back of the foot.

Distribution and habitat.

Typical Helix borealis is distributed over much of Peloponnese, the east of central Greece (Aetolia, Acarnania, Phocis, Evrytania) and in western Epirus (Fig. 30 View Figure 30 ). It also occurs on the Ionian Islands. The inhabited environments include as disparate types as rocky phrygana, pine forests on sand dunes at the sea level, and open fir forests in the mountains. Geophilous. Besides typical H. borealis , there are two other, rather divergent lineages in Greece. One occurs on northern Evia and Northern Sporades. It is found in rocky habitats on limestones. The second has a small range in the mountains of western Crete.

Remarks.

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. 2 View Figure 2 ), H. borealis appears as possibly polyphyletic. However, the relevant parts of the tree are unresolved, so this is likely just an issue of low phylogenetic signal.