A century after introduction: variability in Cepaea hortensis (Müller, 1774) in Sibiu, central Romania

Abstract

The polymorphic land snail Cepaea hortensis was introduced to the city of Sibiu, central Romania, in the first decade of the 20th century and has spread widely across the city. A total of 97 locations were examined in 2017 across the city to determine the habitat preferences and variation in shell size, shape, colour and banding polymorphism of C. hortensis, and to relate these to the same features in the likely source population from Mannheim, Germany, and the first established population in Sibiu. We found that C. hortensis was largely restricted to sites with some woody vegetation cover and showed a marked preference for abandoned and overgrown private gardens. Mean adult shell size in present-day populations was almost always smaller than in both the presumed population of origin from Germany and the first recorded population from Sibiu. Populations showed a wide range of variation in frequencies of shell colours and banding morphs. This variation was not related to habitat or cover, and there was no evident geographical structure in the patterns. Comparisons with a smaller-scale sampling in 2004/5 showed that some populations had gone extinct, some remained stable and in some morph frequencies had changed drastically, but in no consistent direction. These results are similar to those obtained for the related species C. nemoralis in comparable circumstances, but differ from those obtained from regions where C. hortensis is long established and where habitats have been stable. The patterns we observed most likely reflect the effect of passive dispersal by humans, genetic drift and founder effects.

Variability of the Phenotypic Composition of Cepaea hortensis (Gastropoda, Helicidae) in Western Ukraine: in Space and Time

“…Th e great uniformity of the phenotypic structure of C. hortensis in Lviv and beyond, noted by us earlier (Gural-Sverlova, Gural, 2021 a) and caused, at least partially, by a common origin, aff ects the low values of the inbreeding coeffi cient, which are considered not typical for relatively recently colonized areas (Cameron et al, 2009;Gheoca et al, 2019). In particular, the Fst value calculated for the frequencies of unbanded shells in the Romanian city of Sibiu, where C. hortensis was introduced more than a century ago, was 0.445 (Gheoca et al, 2019, table 5), which is 2.9-4.4 times higher than similar values calculated for all sites from Lviv in diff erent periods of time (table 5).…”

“…In recent years, a number of publications have appeared trying to relate the level of phenotypic variability in introduced and/or urban populations of land mollusks of the genus Cepaea Held, 1838 with the time of their colonization of the corresponding areas (Cameron et al, 2009(Cameron et al, , 2014Cameron, von Proschwitz, 2020;Gheoca et al, 2019). It has been suggested that a high level of variability, assessed by the inbreeding coeffi cient Fst, is characteristic of recently populated areas, regardless of whether they are within the natural ranges of species or outside them (Cameron et al, 2009).…”

Shell colouration and different introductions of the land snail Cepaea hortensis (Gastropoda: Helicidae) into Western Ukraine

“…Cepaea hortensis (Müller, 1774) is a species of the Central European origin (taylor 1914(taylor , boettGer 1926, the natural range of which also includes apparently many countries of the Northern and Western Europe (Gural-Sverlova & Gural 2021a). This species was also introduced at different times to other European countries (eGorov 2015, Gheoca et al 2019, Gural-Sverlova & Gural 2021a as well as to North America (cocKerell 1890, JohNSoN 1906.…”