Abstract
Variation at enzyme loci has been investigated in the endemic Madeiran land snail Heterostoma paupercula (Gastropoda: Helicidae). There is a high degree of differentiation between populations. Part of the variation (about half of the total as measured by F statistics based on three polymorphic loci) is the result of divergence between populations of different islands. There are morphological differences between populations in shell form and the structure of the aperture, and of the genitalia, which have been used to define separate taxa, but these do not show a clear geographical pattern. In the present results, the variation in the genitalia appears to be a polymorphism restricted to a few populations, in which some individuals are euphallic cross-fertilizing hermaphrodites, while others are hemiphallic individuals exhibiting partial selfing. It is suggested that these may in fact be part selfing, part female. This is a breeding pattern which could result in polymorphism.
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Cook, L., Lace, L. Sex and genetic variation in a helicid snail. Heredity 70, 376–384 (1993). https://doi.org/10.1038/hdy.1993.53
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DOI: https://doi.org/10.1038/hdy.1993.53