Geographical variation in shell morphology and isoenzymes of Helix aspersa Mueller, 1774 (Gastropoda, Pulmonata), the edible land snail, from Greece and Cyprus

Geographic variation of shell morphology and isoenzymes of the edible snail Helix aspersa Mueller was studied in 24 different regions of Greece and Cyprus. Principal components analysis and cluster analysis showed a geographical trend in seven variable characters examined jointly. Morphological variation between populations was of a sufficient magnitude to create discriminant functions that were able to classify 100 per cent of the cases correctly in only three populations whereas the classifications of the rest varied from 20 per cent to 60 per cent. For the assessment of the genetic polymorphism 13 enzymic systems with 15 loci and 47 alleles were investigated. Three were monomorphic in all populations. The percentage of polymorphic loci (P) ranged from 33.3 per cent to 66.7 per cent and the mean expected heterozygosity from 0.152 to 0.254. Significant deviations from Hardy-Weinberg equilibrium were found in most loci in most populations. Polymorphism varied greatly from one population to another, but there was not correlation between morphological and genetic variation. Spatial autocorrelation in continental populations tended to decrease significantly with increasing distance for several loci. The results found by correspondence analysis and the dendrogram produced by the UPGMA algorithm using Nei's identity (I) showed that the degree of genetic identity was high among the populations studied, apart from the group of N. W. Greek populations. The pattern of genetic diversity seem to be influenced by different forces in continental and island populations.