Abstract
Cepaea nemoralis is a recently introduced species on Öland. Discounting an early and debateable record, the species has been recorded only in the 21st century, despite intensive earlier faunistic surveys. A recent survey has yielded records from the whole length of the island (137 km), but the majority of known populations are in its southern half, most particularly around the settlements of Mörbylånga, Gräsgård and Färjestaden. Populations are usually in anthropogenic habitats. Most appear small and isolated by less disturbed areas. Nearly all samples are polymorphic for both colour and banding morphs, and the variation among populations is low when compared with similar sets from other places where recent colonisation has occurred. There is no latitudinal variation in morph frequencies, nor is any spatial autocorrelation apparent. While a relatively uniform and rigorous selection regime could account for the patterns seen, a single initial introduction followed by transport of propagules large enough to minimise founder effects is also possible.
Highlights
The polymorphic European land snail Cepaea nemoralis (L.) has become a “model organism” in the study of visible genetic variation within and among populations (Ożgo 2008, 2012, Rosin et al 2011, Cook 2017)
Studies on the shell colour and banding polymorphism of these recently established populations of C. nemoralis have revealed patterns of variation that demonstrate the influence of founder effects or genetic drift, a product of long-distance transport followed by local dispersal, the latter certainly aided by human activity
The populations of C. nemoralis recorded on Öland are of very recent origin, most probably stemming from introduction very late in the 20th century
Summary
The polymorphic European land snail Cepaea nemoralis (L.) has become a “model organism” in the study of visible genetic variation within and among populations (Ożgo 2008, 2012, Rosin et al 2011, Cook 2017). Most samples are polymorphic for both colour and banding morphs, and the variation among populations is low when compared with similar sets from other places where recent colonisation has occurred.
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