The role of selection in the colour polymorphism of Littorina rudis Maton and Littorina arcana Hannaford-Ellis (Prosobranchia: Littorinidae)

Abstract

Acceppled for publication 25 May I982 Forty-one mixed samples of winkles containing the closely related species, Littorina rudis and L. arcana, were collected from different parts of the British Isles. Littorina rudis was the more ubiquitous species, with L. arcana being more-or-less confined to vertical clifi and rocks. The frequencies of different shell d o u r patterns were determined for both species in each sample. Several colour morphs were diagnostic of one or other of the species over large areas, which confirms that these are separate species. The frequencies, in the two species, of the two commonest morphs, brown and fawn, were strongly correlated; in several other morphs their presence and absence in the two species was significantly associated; the levels of phenotypic diversity in the two species were also correlated. These patterns could not have arisen if the variation between shores was the result of genetic drift or founder effects, so some form of selection is implicated. In the brown morph there is some evidence for frequency-dependent selection, and it is suggested that the polymorphism may be maintained by visual predators through apostatic selection.

Ecological Opportunity in Adaptive Radiation of Galápagos Endemic Land Snails

“…Many studies have found a genetic component to morphological variation in gastropods, particularly in the case of discrete characters, such as color and pattern (e.g., Cain et al 1960;Atkinson and Warwick 1983;Palmer 1984Palmer , 1985a. Control of variation in continuous morphological characters, such as shape, is less well understood, although there is evidence for both plastic (Phillips et al 1973;Kemp and Bertness 1984;Boulding and Hay 1993;Gibbs 1993) and genetic (Newkirk and Doyle 1975;Crothers 1980;Palmer 1985b;Johannesson and Johannesson 1996; Parsons 1997) components of variation.…”

The Evolution of Color Polymorphism: Crypticity, Searching Images, and Apostatic Selection

“…It has been studied extensively in pulmonate snails (Cain & Sheppard 1954, Clarke et al 1978, Cook 1998), but it is common among other mollusks as well (e.g., Atkinson & Warwick 1983, Whiteley et al 1997). There are cryptic polymorphic spiders (Bonte & Maelfait 2004, Oxford & Gillespie 1998, crustaceans (Devin et al 2004, Hargeby et al 2004, Merilaita et al 2001, and even vertebrates (Olendorf et al 2006, Wente & Phillips 2003.…”

Maintaining a happy face: stable colour polymorphism in the spider Theiridion grallator (Araneae, Theridiidae)

“…The development of a search image is a common phenomenon in birds (Clarke, 1962;Allen, 1974Allen, , 1976Murdoch and Oaten, 1975;Atkinson and Warwick, 1983;Greenwood, 1984; but see Guilford and Dawkins, 1987). As a result, their foraging intensity in a given area may vary with the frequency and/or abundance of their prey.…”