Genetical Research



Population bottleneck and effective size in Bonamia ostreae-resistant populations of Ostrea edulis as inferred by microsatellite markers


SOPHIE  LAUNEY  a1 c1, MARC  BARRE  a1, ANDRE  GERARD  a1 and YAMAMA  NACIRI-GRAVEN  a1 p1
a1 IFREMER, Laboratoire Génétique et Pathologie (LGP), BP 133 Ronce les Bains, 17390 La Tremblade, France

Abstract

Genetic variability at five microsatellite loci was analysed in three hatchery-propagated populations of the flat oyster, Ostrea edulis. These populations were part of a selection programme for resistance to the protozoan parasite Bonamia ostreae and were produced by mass spawns, without control of the genealogy. Evidence for population bottlenecks and inbreeding was sought. A reduction in the number of alleles, mainly due to the loss of rare alleles, was observed in all selected populations, relative to the natural population from which they were derived. Heterozygote excesses were observed in two populations, and were attributed to substructuring of the population into a small number of families. Pedigree reconstruction showed that these two populations were produced by at most two spawning events involving a limited number of parents. Most individuals within these populations are half or full-sib, as shown by relatedness coefficients. The occurrence of population bottlenecks was supported by estimates of effective number of breeders derived by three methods: temporal variance in allelic frequencies, heterozygote excess, and a new method based on reduction in the number of alleles. The estimates from the different methods were consistent. The evidence for bottleneck and small effective number of breeders are expected to lead to increasing inbreeding, and have important consequences for the future management of the three O. edulis selected populations.

(Received May 12 1999)
(Revised May 17 2000)
(Revised June 22 2001)


Correspondence:
c1 Corresponding author. Laboratoire de Génétique des Poissons, INRA-CRJ, 78352 Jouy-en-Josas, France. Tel: +33 1 34 65 27 57. Fax: +33 1 34 65 23 90. e-mail: launey@jouy.inra.fr
p1 Current address: Conservatoire et Jardin Botaniques, 1, chemin de l'Impératrice, CP 60, 1292 Chambésy, Geneva, Switzerland.


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