Theoretical and Applied Genetics

, Volume 92, Issue 7, pp 832-839

First online:

High level of genetic differentiation for allelic richness among populations of the argan tree [Argania spinosa (L.) Skeels] endemic to Morocco

  • A. El MousadikAffiliated withLaboratoire d' Agroforesterie, Faculté des Sciences, Département de Biologie, Université Ibnou Zohr
  • , R. J. PetitAffiliated withLaboratoire de Génétique et Amélioration des Arbres Forestiers, Institut National de la Recherche Agronomique

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Genetic diversity at nine isozyme loci was surveyed in an endangered tree species, the argan tree, endemic to south-western Morocco. The species is highly diverse (3.6 alleles/locus) with populations strongly differentiated from each other (F ST=0.25). This example is used to illustrate a method for standardizing measures of allelic richness in samples of unequal sample sizes, which was developed for the estimation of the number of species and relies on the technique of rarefaction. In addition, it is shown that the measure of subdivision, θ ST, obtained when allelic richness is used in place ofh (Nei's index of diversity), is much larger than the F ST [e.g. θ ST(40)=0.52, where (40) indicates the specified sample used to estimate the allelic richness]. This suggests that rare alleles (which strongly influence measures of allelic richness) have a more scattered distribution than more frequent ones, a result which raises special conservation issues for the argan tree.

Key words

Desertification Genetic diversity Fragmentation Genetic conservation Rarefaction method