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  • Chrysochromulina polylepis bloom  (1)
  • assortative mating  (1)
  • 1
    ISSN: 1573-5117
    Keywords: reproductive isolation ; mating components ; assortative mating ; sexual selection ; fitness estimate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Galician exposed shore populations of the direct developing periwinkle Littorina saxatilis are strikingly polymorphic, with an ornamented and banded upper shore form and a smooth and unbanded lower shore form. Intermediates between the two pure forms occur in a narrow mid shore zone together with the parental forms. We have previously shown that the two pure forms share the same gene pool but that mating between them is non-random. This is due to a non-random microdistribution in the zone of overlap, and also to assortative mating. In this study we present data which show that intermediate (hybrid) females mate less often than pure females in micropatches dominated by either of the pure forms, but not in micropatches in which the two pure forms are equally common. Thus, sexual fitness in intermediate females depends on the frequency of both pure morphs. Furthermore, sexual selection against intermediate females also varies with the densities of snails within each micro patch. The biological mechanisms which may explain this particular reduction of female hybrid fitness are discussed. Assortative mating between the pure morphs is sometimes almost complete, while both morphs do not mate the intermediates assortatively. In the light of this, sexual selection against intermediate females may contribute considerably to restrict gene flow between the pure forms.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: cross water dispersal ; migration ; Chrysochromulina polylepis bloom ; rafting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most marine benthic invertebrate species have planktonic larvae, and in species in which juveniles and adults have low vagility a larva is obviously an efficient way of active dispersal. A minority of benthic invertebrate species develop without any pelagic phase at all. A largely unsolved question is how and at what rate do these species disperse. We have addressed this question using the marine littoral snail Littorina saxatilis (Olivi) as an example of a species that completely lacks larval dispersal. In the Koster archipelago (north part of the Swedish west coast), L. saxatilis occupies rocky island habitats of different sizes, from large islands to small intertidal skerries (islets). In 1988 an extremely dense bloom of a toxin-producing flagellate killed more than 99% of this snail species in this area. Populations of larger islands were reduced, often to less than 1%, but were restored over 2–4 yr. In contrast, populations of small intertidal skerries were completely wiped out and thus could not increase by local recruitment. Four years later, however, four of 33 skerries (12%) were successfully recolonized with relatively dense populations, and another five had received a few founder individuals. These results indicate recruitment through founder individuals, and are rough estimates of dispersal rate in a snail species that lacks a pelagic developmental stage.
    Type of Medium: Electronic Resource
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