Population genetics of Norway spruce (Picea abiesKarst.) at regional scale: sensitivity of different microsatellite motif classes in detecting differentiation

Abstract

-Four populations of Norway spruce (Picea abies Karst.) were screened using nine nuclear microsatellite markers (three trinucleotides and six dinucleotides) and four chloroplast markers (all mononucleotides). Marker classes were compared for their variability, mutation rate and ability to detect differentiation between stands. Dinucleotide markers proved to be the most variable group and chloroplast stretches the least variable, with differences in mutation rate between the former and the latter spanning over two orders of magnitude. Variability correlated to the number of repeats but not to the absolute length of the microsatellite region. The different marker classes were combined with two different measures of genetic distance in order to investigate the performance of markers and evolutionary models for the study of genetic variation in natural populations of Norway spruce. Weir and Cockeram's F ST generally performed better in this clear-cut, four-population model study. Chloroplast haplotypes turned out to be the most sensitive marker system, being able to differentiate populations and to detect differences in genetic variability between sub-regions.conifers / SSR / divergence / statistical testing / genetic distance Résumé -Génétique des populations d'épicéa (Picea abies Karst.) à l'échelle régionale : sensibilité de différent motifs microsatellites dans la détection de la différenciation. Quatre populations d'épicéa (Picea abies Karst.) ont été analysées avec neuf marqueurs microsatellite nucléaires (trois trinucléotidiques et six dinucléotidiques) et quatre marqueurs chloroplastiques (tous mononucléotidiques). La variabilité, le taux de mutation et la performance dans la détection de la différentiation entre sites de ces classes de marqueurs ont été comparées. Les marqueurs dinucléotidiques ont montré la plus forte variabilité, et les marqueurs chloroplastiques la plus faible, avec une différence en taux de mutation d'un facteur cent entre les deux classes. La variabilité est corrélé avec le nombre de répétions mais n'est pas corrélé avec la taille de la répétition. Les différentes classes des marqueurs ont été combinées avec deux mesures de distance génétique pour analyser les effets du choix du marqueur et du model évolutif sur l'étude de la variabilité génétique des populations naturelles d'épicéa. Le F ST de Weir et Cockeram a produit en général les meilleurs résultats dans cette simple étude sur quatre populations. Les haplotypes chloroplastiques ont montré la plus grande efficacité, permettant de distinguer les régions et les populations à l'intérieur des régions.conifères / SSR / divergence / test statistique / distance génétique

Combined analysis of nuclear and mitochondrial markers provide new insight into the genetic structure of North European Picea abies

“…The heterozygote deficiency that we detected in the Norway spruce stands seems to be in accordance with studies from other parts of its distribution range, both at isozyme loci (Lagercrantz and Ryman, 1990) and at different sets of microsatellite loci (Maghuly et al, 2006;Scotti et al, 2006;Meloni et al, 2007). Deviation from HW proportions was found within stands, frequently at loci largely unaffected by null alleles (Table 1, Appendix A).…”

What sampling is needed for reliable estimations of genetic diversity in Fraxinus excelsior L. (Oleaceae)?

“…Clearly, if emphasis is put on allele richness the use of other genetic markers may lead to different conclusions. In fact, marker choice certainly complicates matters as shown in a recent analysis (Scotti et al, 2006) on Norway spruce (Picea abies) where population differentiation estimates are not only correlated to sample size but to marker choice (di and tri nucleotide nuclear SSR and mononucleotide chloroplast SSR). In the case of allozyme markers in ash or other species, with many fewer alleles than microsatellites, sample sizes will necessarily be smaller than those suggested here (300).…”

Genetic aspects of age dynamics of a natural Picea abies (L.) Karst. population in the Białowieża Primeval Forest, Poland

“…Because of its widespread use in forestry and its importance in the ecosystem, there is much interest in its ecological requirements and its genetic structure at the population level (Ravazzi 2001). The genetic structure of populations of P. abies has been investigated in a number of studies (Lagercrantz and Ryman 1990;Maghuly et al 2006;Scotti et al 2006;Vendramin et al 2000); however, most of those studies were conducted in plantation forests. Also, little is known about the differentiation of the genetic structure of spruce populations at various stages of development (Leonardi et al 1996;Prus-Głowacki and Godzik 1995).…”