Epistasis, phenotypic disequilibrium and contrasting associations with climate in the land snail Theba pisana.

ABSTRACT: Hotter conditions favour effectively unbanded (EUB) shells in the snail Theba pisana. T. pisana is also polymorphic for colour of the shell's apex, determined by a pair of alleles at a locus linked to the banding locus. Apex colour is epistatic to shell banding, such that banded snails with a dark apex have darker bands. Annual censuses over 22 years across an ecotone between a sheltered Acacia thicket and open dune vegetation showed a persistent association of both EUB shells and pale apex with the Open habitat. The parallel variation was due partly to strong phenotypic disequilibrium, as the combination of EUB with dark apex was rare. Nevertheless, in fully banded shells the frequency of pale apex was also higher in the Open habitat, confirming independent, parallel associations of the t

SUBMITTER: Johnson MS 

PROVIDER: S-EPMC3282386 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature