| Epistasis, phenotypic disequilibrium and contrasting associations with climate in the land snail Theba pisana. | |
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MedLine Citation:
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PMID: 21811302 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Hotter conditions favour effectively unbanded (EUB) shells in the snail Theba pisana. T. pisana is also polymorphic for colour of the shell's apex, determined by a pair of alleles at a locus linked to the banding locus. Apex colour is epistatic to shell banding, such that banded snails with a dark apex have darker bands. Annual censuses over 22 years across an ecotone between a sheltered Acacia thicket and open dune vegetation showed a persistent association of both EUB shells and pale apex with the Open habitat. The parallel variation was due partly to strong phenotypic disequilibrium, as the combination of EUB with dark apex was rare. Nevertheless, in fully banded shells the frequency of pale apex was also higher in the Open habitat, confirming independent, parallel associations of the two contributors to paleness. Within the Acacia habitat, temporal variation of the frequencies of banding morphs was much greater than for apex colour, and EUB shells were associated with hotter summers. Consistent with its primary effect only on the very small snails, apex colour did not vary with summer conditions, but instead, higher frequencies of pale apices were associated with sunnier winters. The intensity of selection was lower on apex colour than shell banding, due partly to the constraint of phenotypic disequilibrium. The shell traits in T. pisana are an example of complex responses to climatic variation, in which phenotypic disequilibrium constrains evolution of apex colour, but separate mechanisms of selection are evident.Heredity advance online publication, 3 August 2011; doi:10.1038/hdy.2011.62. |
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Authors:
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M S Johnson |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-8-03 |
Journal Detail:
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Title: Heredity Volume: - ISSN: 1365-2540 ISO Abbreviation: - Publication Date: 2011 Aug |
Date Detail:
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Created Date: 2011-8-3 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0373007 Medline TA: Heredity Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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School of Animal Biology (M092), University of Western Australia, Crawley, Western Australia, Australia. |
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