Translator Disclaimer
1 February 2006 ADAPTATION TO A STEEP ENVIRONMENTAL GRADIENT AND AN ASSOCIATED BARRIER TO GENE EXCHANGE IN LITTORINA SAXATILIS
Author Affiliations +
Abstract

Steep environmental gradients offer important opportunities to study the interaction between natural selection and gene flow. Allele frequency clines are expected to form at loci under selection, but unlinked neutral alleles may pass easily across these clines unless a generalized barrier evolves. Here we consider the distribution of forms of the intertidal gastropod Littorina saxatilis, analyzing shell shape and amplified fragment length polymorphism (AFLP) loci on two rocky shores in Britain. On the basis of previous work, the AFLP loci were divided into differentiated and undifferentiated groups. On both shores, we have shown a sharp cline in allele frequencies between the two morphs for differentiated AFLP loci. This is coincident with a habitat transition on the shore where the two habitats (cliff and boulder field) are immediately contiguous. The allele frequency clines coincide with a cline in shell morphology. In the middle of the cline, linkage disequilibrium for the differentiated loci rises in accordance with expectation. The clines are extremely narrow relative to dispersal, probably as a result of both strong selection and habitat choice. An increase in FST for undifferentiated AFLPs between morphs, relative to within-morph comparisons, is consistent with there being a general barrier to gene flow across the contact zone. These features are consistent either with an episode of allopatric divergence followed by secondary contact or with primary, nonallopatric divergence. Further data will be needed to distinguish between these alternatives.

John W. Grahame, Craig S. Wilding, and Roger K. Butlin "ADAPTATION TO A STEEP ENVIRONMENTAL GRADIENT AND AN ASSOCIATED BARRIER TO GENE EXCHANGE IN LITTORINA SAXATILIS," Evolution 60(2), 268-278, (1 February 2006). https://doi.org/10.1554/05-592.1
Received: 20 October 2005; Accepted: 19 December 2005; Published: 1 February 2006
JOURNAL ARTICLE
11 PAGES

This article is only available to subscribers.
It is not available for individual sale.
+ SAVE TO MY LIBRARY

SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top