Selection and habitat-specific allozyme variation in the self-fertilizing land snail Cochlicopa lubrica (O.F. Müller)

Allozyme variation of aspartate-aminotransferase locus Aat 1 is analysed in the land snail Cochlicopa lubrica (O. F. Müller, 1774). Two alleles, denoted ‘20’ and ‘80’, have been found in 29 Central European populations investigated. This species reproduces under a high rate of self-fertilization. Only three out of 787 individuals were heterozygous (enzyme pattern Aat 1 ‘20’/‘80’). The homozygous individuals with Aat 1 ‘80’ were frequent in moist and shady habitats. In exposed and open habitats, however, the homozygous individuals with Aat 1 ‘20’ occurred frequently. These results give strong evidence for habitat-specific selection inferred from allozyme variation. Moreover, a tight interlocus correlation of isocitrate-dehydrogenase patterns (Idh 1) and Aat 1 patterns has been observed. Two groups of homozygous genotypes are commonly found: (1) the group Idh 1 ‘145’/Aat 1 ‘80’, and (2) the group Idh 1 ‘155’/Aat 1 ‘20’. The Aat data for Cochlicopa lubrica are complemented by morphometric measurements of the shells. The homozygous types of Aat 1 ‘20’ (common in exposed/open habitats) possessed, on average, slightly smaller shells than the homozygous types with Aat 1 ‘80’ (common in moist/shady habitats). This slight mean difference in shell size might be due to the living conditions in the habitats. In the last part of the study, the allozyme variation of snails was assessed for spatial selection processes, and a compilation of the available papers is shown.