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Ellison Abstract- 1998 Merkt and Ellison

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Merkt, R. E. & A. M. Ellison. 1998. Geographic and habitat-specific morphological variation of Littoraria (Littorinopsis) angulifera (Lamarck, 1822). Malacologia 40: 279-295.


Recent, detailed examination of the morphology of the Littorinidae inhabiting Indo-West Pacific mangrove forests led Reid (1986) to identify 20 species of Littoraria, all of which had previously been assigned to only three species within the pantropical "Littorina scabra." No similar study has been done on the neotropical Littoraria angulifera (Lamarck), which occurs in mangrove forests on both sides of the Atlantic Ocean. We quantified variability in shell and genital morphology of L. angulifera throughout its range in the tropical Atlantic using material from both museum collections and new, field collections. We tested two hypotheses regarding variation in shell shape and sculpture, and frequency of color morphs in populations of L. angulifera: (1) observed variation is associated with the five major current regimes that could restrict its dispersal throughout the tropical Atlantic; or (2) observed variation is associated with habitat characteristics that can influence shell thermal properties. Strong geographical variation in shell shape and sculptural characteristics suggested initial support for the dispersal hypothesis. Absence of geographical variation in genital morphology, however, led to the rejection of the dispersal hypothesis. Parallel associations of habitat with geography suggests that L. angulifera is a single species throughout the tropical Atlantic, and observed variability results primarily from responses to local environmental conditions. However, this conclusion can be tested only with additional genetic analysis of disparate populations of L. angulifera.

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