Contrasting patterns of historical colonization in white oaks (Quercus spp.) in California and Europe

Phylogeography allows the inference of evolutionary processes that have shaped the current distribution of genealogical lineages across a landscape. In this perspective, comparative phylogeographical analyses are useful in detecting common historical patterns by either comparing different species within the same area within a continent or by comparing similar species in different areas. Here, we analyse one taxon (the white oak, genus Quercus, subgenus Quercus, section Quercus) that is widespread worldwide, and we evaluate its phylogeographical pattern on two different continents: western North America and Western Europe. The goals of the present study are: (i) to compare the chloroplast genetic diversity found in one California oak species vs. that found in the extensively studied European oak species (in France and the Iberian Peninsula); (ii) to contrast the geographical structure of haplotypes between these two taxa and test for a phylogeographical structure for the California species. For this purpose, we used the same six maternally inherited chloroplast microsatellite markers and a similar sampling strategy. The haplotype diversity within site as well as the differentiation among sites was alike in both taxa, but the Californian species has higher allelic richness with a greater number of haplotypes (39 vs. 11 in the European white oak complex). Furthermore, in California these 39 haplotypes are distributed locally in patches while in the European oaks haplotypes are distributed into lineages partitioned longitudinally. These contrasted patterns could indicate that gene movement in California oak populations have been more stable in response to past climatic and geological events, in contrast to their European counterparts

DNA-based control of oak wood geographic origin in the context of the cooperage industry

International audienceThe recent growth of the French barrel industry, leading to increased importations of oak wood and a general lack of wood origin guarantee, has resulted in the demand for a reliable technique permitting to control the provenance of oak wood. In this study we propose to adapt wood traceability technique using chloroplast DNA markers to this industrial context. The retrieval of DNA and haplotype determination has been tested on different types of wood samples that can be collected in cooperage firms, and a clear effect of wood treatment on DNA degradation has been observed. Despite the poor quantity and quality of DNA retrieved from staves, haplotypes could be determined on a large proportion of the samples, permitting to check the genetic conformity of woods with announced provenances. In several cases, our study proved the existence of unlabeled oak woods originating from eastern Europe and the incorrect use of the names of famous French forests.Contrôle de l'origine géographique des bois de chêne utilisés en tonnellerie. L'importation croissante de bois de chêne et le manque de garantie sur son origine, liés à l'expansion récente de la tonnellerie française, rendent nécessaire la mise au point d'une technique fiable permettant de contrôler l'origine des bois de chêne. Dans cette étude, nous avons cherché à adapter, pour ce secteur industriel, les méthodes moléculaires de traçabilité des bois de chêne utilisant les marqueurs chloroplastiques. La qualité et la quantité de l'ADN extrait et la caractérisation des haplotypes ont alors été évalués sur les différents types d'échantillons de bois rencontrés dans les tonnelleries. Nous avons pu démontrer un effet net des différents traitements du bois sur la dégradation de l'ADN. Cependant, malgré la faible qualité et quantité d'ADN extrait des bois de merrains, les haplotypes ont pu être déterminés sur une large proportion des échantillons, permettant de tester la conformité des bois avec l'origine annoncée. Dans plusieurs cas, nous avons pu mettre en évidence l'existence de bois mal identifiés, provenant de l'est de l'Europe, ainsi que l'utilisation abusive des noms des provenances françaises renommées

Use of chloroplast microsatellites to differentiate oak populations

International audienceThe possibility to use chloroplast microsatellites (cpSSRs) instead of restriction analysis of PCR-amplified DNA fragments to differentiate oak populations was tested in two economically important tree species: Quercus petraea and Quercus robur. The level and pattern of inter- and intraspecific cpDNA variation were studied over 48 French populations using a total of 24 cpSSR loci. The same pattern of low intrapopulation diversity and high population differentiation was noted with both types of markers, since there was an almost total redundancy of haplotypes identified with both techniques. Overall, our results indicate that chloroplast microsatellites can be used for haplotype discrimination in many contexts including certification or traceability of oak material.Utilisation des microsatellites chloroplastiques pour différencier des populations de chênes. Nous avons cherché à comparer l'efficacité de deux types de marqueurs chloroplastiques, les marqueurs microsatellites (cpSSR) et marqueurs PCR-RFLP (cpRFLP), à différencier des populations de chênes sessiles et pédonculés, deux espèces d'arbres forestiers économiquement importantes. Le niveau et la structuration de la diversité inter et intra-spécifique ont été mesurés au sein de 48 populations françaises au travers de l'analyse de 24 microsatellites chloroplastiques. Une faible diversité intra-population, ainsi qu'une forte différenciation des populations de chênes ont pu être mesurées à l'aide des deux types de marqueurs, du fait d'une redondance quasi-complète des haplotypes identifiés par les deux techniques. Nos résultats indiquent donc que les marqueurs microsatellites chloroplastiques peuvent être utilisés pour la distinction d'haplotypes et de populations de chênes dans le cadre de la certification ou de la traçabilité de matériel forestier (graines, plants, bois)

Contrasting patterns of historical colonization in white oaks (Quercus spp.) in California and Europe

Phylogeography allows the inference of evolutionary processes that have shaped the current distribution of genealogical lineages across a landscape. In this perspective, comparative phylogeographical analyses are useful in detecting common historical patterns by either comparing different species within the same area within a continent or by comparing similar species in different areas. Here, we analyse one taxon (the white oak, genus Quercus , subgenus Quercus , section Quercus ) that is widespread worldwide, and we evaluate its phylogeographical pattern on two different continents: western North America and Western Europe. The goals of the present study are: (i) to compare the chloroplast genetic diversity found in one California oak species vs. that found in the extensively studied European oak species (in France and the Iberian Peninsula); (ii) to contrast the geographical structure of haplotypes between these two taxa and test for a phylogeographical structure for the California species. For this purpose, we used the same six maternally inherited chloroplast microsatellite markers and a similar sampling strategy. The haplotype diversity within site as well as the differentiation among sites was alike in both taxa, but the Californian species has higher allelic richness with a greater number of haplotypes (39 vs. 11 in the European white oak complex). Furthermore, in California these 39 haplotypes are distributed locally in patches while in the European oaks haplotypes are distributed into lineages partitioned longitudinally. These contrasted patterns could indicate that gene movement in California oak populations have been more stable in response to past climatic and geological events, in contrast to their European counterparts

A set of primers for the amplification of chloroplast microsatellites in Quercus

International audienceThe increase in demand for the certification of oak seed lots, as well as control of the geographical origin of oak wood, has led us to develop powerful genetic markers permitting us to discriminate among provenance regions. With the aim of detecting new chloroplast variants, we have identified 17 potential cpSSRs motifs from available oak sequences and tested their variability among French oak populations. Six loci were polymorphic at the intraspecific level in Quercus petraea and Q. robur . Moreover, conservation of the primer pairs was checked on a set of 21 forest tree species and they were all shown to work well on several Quercus species, and even within Fagacaea

A set of primers for the amplification of chloroplast microsatellites in Quercus

International audienceThe increase in demand for the certification of oak seed lots, as well as control of the geographical origin of oak wood, has led us to develop powerful genetic markers permitting us to discriminate among provenance regions. With the aim of detecting new chloroplast variants, we have identified 17 potential cpSSRs motifs from available oak sequences and tested their variability among French oak populations. Six loci were polymorphic at the intraspecific level in Quercus petraea and Q. robur . Moreover, conservation of the primer pairs was checked on a set of 21 forest tree species and they were all shown to work well on several Quercus species, and even within Fagacaea

Checking the geographical origin of oak wood: molecular and statistical tools

International audienceNew methods for better identification of timber geographical origin would constitute an important technical element in the forest industry, for phytosanitary certification procedures or in the chain of custody developed for the certification of timber from sustainably managed forests. In the case of the European white oaks, a detailed reference map of chloroplast (cp) DNA variation across the range exists, and we propose here to use the strong geographical structure, characterized by a differentiation of western vs. eastern populations, for the purpose of oak wood traceability. We first developed cpDNA markers permitting the characterization of haplotype on degraded DNA obtained from wood samples. The techniques were subsequently validated by confirming the full correspondence between genotypes obtained from living tissues (buds) and from wood collected from the same individual oak. Finally, a statistical procedure was used to test if the haplotype composition of a lot of wood samples is consistent with its presumed geographical origin. Clearly, the technique cannot permit the unambiguous identification of wood products of unknown origin but can be used to check the conformity of genetic composition of wood samples with the region of alleged origin. This could lead to major applications not only in the forest industry but also in archaeology or in palaeobotany

Allozyme variation of oleaster populations (wild olive tree) (Olea europaea L.) in the Mediterranean Basin

International audienceAs a result of the early domestication and extensive cultivation of the olive tree throughout the Mediterranean Basin, the wild-looking forms of olive (oleasters) presently observed constitute a complex, potentially ranging from wild to feral forms. Allozyme variation was analysed at 10 loci in 31 large and 44 small oleaster populations distributed in various habitats of the Mediterranean Basin and in two populations of the wild subspecies Olea europaea subsp (ssp) guanchica, endemic to the Canary islands and closely related to oleasters. At eight polymorphic loci, 25 alleles were identified. Genetic evidence that nondomesticated oleasters still survive locally was provided by the occurrence of four and one alleles shared exclusively by the eight western and two eastern oleaster populations, respectively, which were collected in forests potentially containing genuinely wild forms according to environmental, historical and demographic criteria. As reported previously from cytoplasmic and RAPDs analysis, substantial genetic differentiation was observed between the eastern oleaster populations genetically close to most olive clones cultivated in the Mediterranean Basin, and the western populations that are related to the wild Canarian populations. In addition, the occurrence of significantly lower heterozygosity in cultivated olive than in oleasters, whatever their origin, suggests that intensive selection involving inbreeding has taken place under cultivation to obtain particular characteristics in the olive cultivars

Chloroplast-DNA variation in cultivated and wild olive (Olea europaea L.)

International audiencePolymorphism in the lengths of restriction fragments of the whole cpDNA molecule was studied in cultivated olive and in oleaster (wild olive) over the whole Mediterranean Basin. Seventy two olive cultivars, 89 very old trees cultivated locally, and 101 oleasters were scored for ten endonucleases. Moreover, maternal inheritance of cpDNA in olive was shown by analysing the progeny of a controlled cross between two parents which di!ered in their cpDNA haplotypes. In the whole species, three site- and three length-mutations were observed, corresponding to "ve distinct chlorotypes. The same chlorotype (I) was predominant in both oleasters and cultivated olive trees, con"rming that these are closely related maternally. Three other chlorotypes (II, III and IV) were observed exclusively in oleaster material and were restricted either to isolated forest populations or to a few individuals growing in mixture with olive trees possessing the majority chlorotype. An additional chlorotype (V) was characterised by three mutations located in distinct parts the cpDNA molecule but which were never observed to occur separately. This chlorotype, more widely distributed than the other three, in both cultivated and wild olive, and occurring even in distant populations, was observed exclusively in male-sterile trees showing the same speci"c pollen anomaly. However, in the present study, no evidence was provided for a direct relationship between the occurrence of the cpDNA mutations and male sterility. It is suggested that the large geographic distribution of chlorotype V may be related to the high fruit production usually observed on male-sterile trees. These may be very attractive for birds which are fond of olive fruit and spread the stones e$ciently. Probably for the same reason, people preserved male-sterile oleasters for long periods and, in several places, used male-sterile cultivars over large areas