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Title: What causes geographic variation? : a case study of Anolis oculatus
Author: Malhotra, Anita
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1992
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The lizard Anolis oculatus, endemic to the small Lesser Antillean island of Dominica, was selected as a model to study the causes of geographic variation. Patterns of geographic variation were investigated using a variety of univariate, bivariate and multivariate numerical methods. Patterns were found to be predominately clinal, with some incongruence within and between the character systems (body proportions, scalation, and colour pattern), and included altitudinal, east-west and (on the Caribbean coast) north-south clines. Overall four ecotypic groups were recognisable, and the current subspecies were invalidated. Simultaneous Mantel tests pointed strongly to adaptation to various environmental factors (both biotic and physical) as the cause of variation in most of the characters studied. Canonical correlation analysis was used to study the covariance of character constellations and their relationship to environmental variation. A closely related species from a neighbouring island with an independent evolutionary history, A. marmoratus from Basse Terre (Guadeloupe) showed many parallels, both in patterns of geographic variation and associations with environmental variation, which can be attributed solely to the effect of current ecology. A direct test of the action of natural selection was then provided by a translocation experiment in Dominica, where representative populations of the four ecotypes were translocated into a single habitat. In a very short period, evidence was obtained of strong directional selection acting proportionately to the extent of ecological change experienced by the different ecotypes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available