Micro- and macrogeographic allozyme variation in Littorina fabalis; do sheltered and exposed forms hybridize?

Citation
A. Tatarenkov et K. Johannesson, Micro- and macrogeographic allozyme variation in Littorina fabalis; do sheltered and exposed forms hybridize?, BIOL J LINN, 67(2), 1999, pp. 199-212
Citations number
39
Categorie Soggetti
Biology
Journal title
BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY
ISSN journal
00244066 → ACNP
Volume
67
Issue
2
Year of publication
1999
Pages
199 - 212
Database
ISI
SICI code
0024-4066(199906)67:2<199:MAMAVI>2.0.ZU;2-D
Abstract
Earlier studies of Swedish populations of the marine snail Littorina fabali s show that snails from different microhabitats (with a greater and lesser exposure to wave action) have almost diagnostic differences in one allozyme locus (arginine kinase, Ark), and differ in adult size. Snails with 'shelt ered' and 'exposed' Ark genotypes occur in sympatry in intermediary exposed sites and here adult sizes remain distinct Approaching the microgeographic differentiation we studied the parts of two populations where the frequenc y of Ark changes dramatically over zones 50-120 m wide. The aim was to test if the transitional zones are best described as areas of mixing of two gen etically separate populations, or if hybridization between the exposed and sheltered groups occurs. Heterozygotes were in deficiency along both dines but were still roughly twice as common as expected from a pure mixing of 's heltered' and 'exposed' groups suggesting hybridization. Hybridization was also supported by the observation that snails homozygous for sheltered and exposed alleles mated at random with each other in both populations. On the macrogeographic scare, we found populations from exposed and sheltered sit es in France and Wales being fixed for the same exposed and sheltered Ark a lleles as found in Sweden. However, variation in three other highly polymor phic loci indicated geographic affinity rather than habitat similarity bein g the main factor of genetic coherence. These observations support a hypoth esis of gene flow between exposed and sheltered populations of L. fabalis. Two Spanish populations were remarkably different with unique alleles at hi gh frequencies in three of four strongly polymorphic loci. (C) 1999 The Lin nean Society of London.