Genetic Variation and Differentiation Within a Natural Community of Five Oak Species (Quercus spp.)

Abstract

Chloroplast DNA and two categories of nuclear markers - isozymes and microsatellites - were used to examine a very rich natural community of oaks (Quercus spp.) situated in west-central Romania. The community consists of five oak species: Q. robur, Q. petraea, Q. pubescens, and Q. frainetto - that are closely related -, and Q. cerris. A total of five chloroplast haplotypes was identified. Q. cerris was fixed for a single haplotype. The other four species shared the two most common haplotypes. One haplotype was confined to Q. robur and a very rare one was restricted to Q. petraea. Both types of nuclear markers revealed a larger genetic variation for Q. pubescens and Q. petraea than for Q. frainetto and Q. robur, although the differences between species are in most cases not significant. At the nuclear level, Q. cerris could be clearly separated from the other four oak species confirming the taxonomic classification. Regardless of the estimate used, the levels of polymorphism revealed by microsatellites were much higher than those based on isozymes. For the four closely related species the overall genetic differentiation was significant at both categories of nuclear markers. Several loci, such as Acp-C for isozymes, and ssrQpZAG36 and ssrQrZAG96 for microsatellites were very useful to discriminate among species. However, the level of differentiation varied markedly between pairs of species. The genetic affinities among the species may reflect different phylogenetic distances and/or different rates of recurrent gene flow at this site.

Genetic Diversity and Structure of Natural Quercus variabilis Population in China as Revealed by Microsatellites Markers

“…P values were adjusted by using a Bonferroni correction. Private alleles were calculated by using the GenAlEx software [38,39]. Gene flow (N m ) was calculated using the formula: [40].…”

Interspecific gene flow and maintenance of species integrity in oaks

“…Genetic markers with increased interspecifi c divergence were found between neighboring populations of different taxonomic groups of interfertile oak species among AFLPs , Mariette et al 2002, isozymes (Finkeldey 2001), gSSRs (Scotti- Saintagne et al 2004b, gene-based EST-SSRs (Sullivan et al 2013) and Single Nucleotide Polymorphism (SNP) markers . For example, interspecifi c differentiation between Q. petraea and Q. robur at outlier locus ssrQrZAG96 was 22.3% (Muir & Schlötterer 2005) and 30.8% (Curtu et al 2007b) compared to an average genomic differentiation of less than 3% at nuclear markers (Mariette et al 2002). High genetic differentiation at these "outlier loci" was interpreted as result of divergent selection acting on these gene markers or linked makers since divergence was substantially greater than expected under a null hypothesis of neutrality (Scotti-Saintagne et al 2004b).…”

High genetic diversity promotes a common-garden trial of Quercus robur as a potential seed source

“…Oak populations usually exhibit high levels of genetic diversity as assessed based on nuclear microsatellites (Streiff et al, 1998;Degen et al, 1999;Mariette et al, 2002;Cottrell et al, 2003;Curtu et al, 2007;Dering & Chybicki, 2012). However, natural regeneration of oak stands or establishing plantations based on seeds originating from a single stand do not guarantee the increase or even the maintenance of genetic diversity levels in offspring generations (Dering & Chybicki, 2012).…”