Contrasting relationships between the diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

Abstract

Nucleotide diversity was assessed within nine candidate genes (CGs) (in total 4.6 kb) for the time of bud burst in nine sessile oak (Quercus petraea) populations distributed in central and northern Europe. The sampled populations were selected on the basis of their contrasting times of bud burst observed in common garden experiments (provenance tests). The CGs were selected according to their expression profiles during the transition from quiescent to developing buds and/or their functional role in model plants. The overall nucleotide diversity was large (p tot ¼ 6.15 Â 10 À3 ; p silent ¼ 11.2 Â 10 À3 ), but population differentiation was not larger than for microsatellites. No outlier single-nucleotide polymorphism (SNP) departing from neutral expectation was found among the total of 125 SNPs. These results contrasted markedly with the significant associations that were observed between the CGs and bud burst in segregating populations. Quantitative trait loci (QTLs) for bud burst were identified for 13 year * site seasonal observations in a cloned mapping pedigree. Nineteen QTLs were detected, and QTLs located on linkage groups 2, 5 and 9 contributed repeatedly to more than 12% of the phenotypic variation of the trait. Eight genes were polymorphic in the two parents of the pedigree and could be mapped on the existing genetic map. Five of them located within the confidence intervals of QTLs for bud burst. Interestingly, four of them located within the three QTLs exhibiting the largest contributions to bud burst.

A linkage disequilibrium perspective on the genetic mosaic of speciation in two hybridizing Mediterranean white oaks

“…LG2 outliers found in this study colocalize with one of the two most important QTLs for bud flush (Saintagne et al, 2004;Scotti-Saintagne et al, 2004a;Derory et al, 2010), which is maintained in several crosses (Gailing et al, 2005). Bud flush in oaks is an adaptive ecological trait that is entirely correlated with flowering time (Duccousso et al, 1996) and has pleiotropic effects on pre-zygotic reproductive isolation via assortative mating (Savolainen et al, 2006).…”

High genetic diversity at the extreme range edge: nucleotide variation at nuclear loci in Scots pine (Pinus sylvestris L.) in Scotland

“…In fact, genetic variation in Scottish populations seems to be slightly higher than in mainland populations (y sil ¼ 0.011 vs 0.009, respectively) and relative to previous estimates for the species (y sil ¼ 0.005 at 16 loci with some related to timing of bud set and y sil ¼ 0.0089 at 14 cold-tolerance candidate loci (Wachowiak et al, 2009)). Compared with estimates in other forest tree species, overall diversity in Scottish populations (p tot ¼ 0.0078) is only lower than that in broadleaved Populus tremula (0.0111, Ingvarsson, 2005) and is higher than that in Q. crispula, (0.0069, Quang et al, 2008), Q. petraea (0.0062, Derory et al, 2009), P. pinaster (0.0055, Eveno et al, 2008, P. taeda (0.0040, Brown et al, 2004), Picea abies (0.0039, Heuertz et al, 2006) and other conifers . The diversity estimate for Scottish populations is compatible with the patterns of genetic variation observed in previous studies (monoterpenes Forrest, 1980;Forrest, 1982), allozymes Kinloch et al, 1986), chloroplast DNA microsatellite markers Provan et al, 1998).…”

“…Adaptive divergence is, therefore, more likely to result from selection acting on standing variation, which may have arisen in endemic populations that survived last glaciations in Western Europe or the British Isles. Moreover, as differentiation at the trait level in forest trees is likely to result from allelic associations among large numbers of loci, rather than changes in allelic frequencies at individual loci, the signature of selection may be more readily detectable as covariance of allele frequencies at multiple loci (Le Corre and Kremer, 2003;Latta, 2004;Derory et al, 2009). Therefore many more loci, including regulatory regions (to date, generally omitted from analyses of nucleotide variation in conifers), would need to be studied in parallel before the influence of selection could be verified.…”

Evolutionary responses of tree phenology to the combined effects of assortative mating, gene flow and divergent selection

“…Overall, pollen dispersal occurred at a much higher rate than seed dispersal, as indicated by experimental data in many broad-leaved and conifer tree species (Ennos, 1994). Genetic architecture, allelic effects originate from Derory et al (2010), and heritability values stem from Alberto et al (2011). Based on our earlier simulations (Soularue and Kremer, 2012), and in situ and common garden observations (Vitasse et al, 2009a, b), k E was set to 2, meaning that the variance of E values across the landscape is twofold larger than the phenotypic variance of TBB within a given population.…”