The status of general reproductive-strategy theories, illustrated in winkles.

Populations of the rough winkle, Littorina rudis from two spatially-adjacent but distinct habitats have been compared in terms of reproductive effort, size at maturity and embryo size and number. In each case, the basis for the comparison has been examined critically. The suites of characteristics exhibited by the two populations do not fit the conventional 'r-K' scheme which has come to dominate life-history theory.Specifically, individuals in a 'boulders' population make a smaller reproductive effort, delay maturity longer and produce more numerous, smaller young than individuals in a 'crevice' population.The effects in the two populations of various environmental factors on shell thickness, animal size and these three life-history traits are examined and discussed. These factors adequately explain the characteristics exhibited by the populations. It is argued that the conventional scheme is inadequate in that it fails to take such specific effects into account.