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Iterative changes in Lake Pannon Melanopsis reflect a recurrent theme in gastropod morphological evolution

Published online by Cambridge University Press:  08 April 2016

Dana H. Geary
Affiliation:
Department of Geology and Geophysics, 1215 West Dayton Street, University of Wisconsin, Madison, Wisconsin 53706. E-mail: dana@geology.wisc.edu
Andrew W. Staley
Affiliation:
Department of Geology and Geophysics, 1215 West Dayton Street, University of Wisconsin, Madison, Wisconsin 53706. E-mail: dana@geology.wisc.edu
Pál Müller
Affiliation:
Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary
Imre Magyar
Affiliation:
Department of Geology and Geophysics, 1215 West Dayton Street, University of Wisconsin, Madison, Wisconsin 53706. E-mail: dana@geology.wisc.edu

Abstract

Iterative evolutionary changes are of special interest because they imply that the recurring morphological changes had a cause that also repeated itself and might therefore be possible to uncover. We describe a set of iterative morphological changes in melanopsid gastropods from the ancient, long-lived Lake Pannon. First in the Pannonian Age, and again in the Pontian Age approximately three million years later, a smooth-shelled ancestor gave rise to a shouldered descendant. In both cases, the morphological change was probably coincident with a shift from habitats just outside the lake (e.g., rivers and streams) to habitats within the lake itself. Many other convergent examples exist in which a smooth-shelled river dweller is closely related to a shouldered and/or ribbed lacustrine snail. The frequency of this type of morphological change suggests that it has an adaptive basis; response to differing predators or hydrodynamic conditions seem the most plausible explanations, but the functional nature of these morphological changes remains unknown.

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Copyright
Copyright © The Paleontological Society 

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