Cernuella virgata (Da Costa, 1778) (Mollusca: Hygromiidae), commonly known as the “vineyard snail,” is endemic species in Mediterranean and Western Europe including the British Isles, but in the Eastern USA and Australia it represents an introduced invasive species. The present work examines the genetic variability and phylogenetic relationships among the four populations of this land snail sampled along the east Adriatic region of Croatia using mitochondrial markers (partial 16S rDNA and COI gene) in addition to traditional methods of shell’s shape analysis. All the three molecular-phylogenetic approaches (median joining haplotype network analysis and Bayesian analysis, as well as maximum likelihood analysis) revealed two-three major subnetworks for both 16S rDNA and COI, with a clear distinction between south Adriatic haplotypes (Pisak) and north Adriatic haplotypes (Krk and Cres). The population from Karlobag was comprised of both north and south haplotypes, thus representing a putative contact zone between these two groups. The morphometric analysis showed that individuals from Cres island population were statistically significantly wider and higher than individuals from Pisak population. Analysis of the SW/SH ratio and the relationship between shell width and shell height showed no differences in shell growth between the two examined populations, indicating equal shell growth and shape, which gives the possibility that differences in size of individuals between those two populations could be influenced by biotic (physiological) or abiotic (environmental) factors. This study represents the first analysis of genetic variability and relatedness among native populations of C. virgata. 1. Introduction Cernuella virgata (Da Costa, 1778) (Mollusca: Hygromiidae) is a terrestrial mollusks gastropod, commonly known as the “vineyard snail.” Terrestrial gastropods represent a highly diverse group of mollusks. Solem [1] estimated about 24.000 species, of which about 20.500 are pulmonate stylommatophorans, and about 3.650 belong to other groups of terrestrial gastropods. Recent studies report high diversity of this group of animals and emphasize the need for more phylogenetic studies. The molecular techniques have proven useful in cases where morphological features failed to provide unequivocal phylogenetic signal by providing an independent set of characters [2]. Among many different molecular markers, the cytochrome oxidase subunit I (COI gene) has been recently recommended as particularly useful for DNA barcoding of animals [3]. C. virgata is frequent in
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