Visual selection in the land snail Arianta arbustorum

Natural selection on the colour polymorphisms of Trichia hispida (L.)

“…Trichia hispida shows an association morph frequency with background and habitat similar to that found in T striolata (Jones et al, 1974), Cepaea nemoralis (Cain and Sheppard, 1954), C. hortensis (Clarke, 1962), and Arianta arbustorum (Parkin, 1971). That is, darker morphs are more frequent in darker habitats.…”

“…These observations thus provide good evidence that natural selection acts on the colour polymorphisms in T. hispida. The selective agents are not known, although by analogy with Cepaea and Arianta, likely candidates are predatory birds selectively killing those morphs that stand Out against their background (Cain and Sheppard, 1954;Parkin, 1971).…”

Climatic selection in the land snail Arianta arbustorum in Derbyshire, England

“…Because of the change of rainfall along this valley, the area was divided into five approximately equal areas (Parkin, 1971). The relationship was determined between the proportion of Arianta in each sample and its position on the rainfall gradient.…”

“…It has already been shown (Parkin, 1971) that visual selection for crypsis is operative in this area. Higher proportions of yellow shells are found in populations of Arianta from non-woodland localities.…”

“…Visual selection for crypsis by predators has been shown to be of importance in controlling the relative frequencies of the various phenotypes of Cepaea nemoralis (Cain and Sheppard, 1950;Currey, Arnold and Carter, 1964), C. hortensis (Clarke, 1962), Cochlicella acuta (Dr G. A. Lewis, personal communication), Hygromia striolata (B. C. Clarke et al, personal communication), and Arianta arbustorum (Parkin, 1971), among others. Of these, the first two have attracted most attention, partly because of their conspicuous and remarkable polymorphisms.…”