Abstract
General observations of the polymorphic mangrove snail L. pallescens suggest that frequencies of the dark morph are lower in places where it shares its leaf habitat with a congeneric species than where it is present alone. The other species involved resemble the dark morph. This possibility was tested by comparing the composition of samples from two genera of mangrove trees which differ in their likelihood of having the alternative species on the leaves. The results showed the same pattern. This is a systematic effect on morph frequency, possibly selective predation, because the colonies on the different species of trees are drawn from the same larval population.
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Cook, L. Systematic effects on morph frequency in the polymorphic mangrove snail Littoraria pallescens. Heredity 65, 423–427 (1990). https://doi.org/10.1038/hdy.1990.113
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DOI: https://doi.org/10.1038/hdy.1990.113