Báo cáo khoa học: Genetic and phenological differentiation between introduced and natural populations of Quercus rubra

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Genetic and phenological differentiation between introduced and natural populations of Quercus rubra...
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Báo cáo khoa học: "Genetic and phenological differentiation between introduced and natural populations of Quercus rubra" Original article Genetic and phenological differentiation between introduced and natural populations of Quercus rubra L JB Daubree A Kremer INRA, laboratoire de génétique et d’amélioration des arbres forestiers, BP 45, 33611 Gazinet, FranceSummary — Gene diversity within populations of Q rubra was compared between 23 introducedstands and 9 geographic regions within the natural range for 4 enzymes encoded by 4 polymorphicloci. Gene diversity within populations was, in general, higher in introduced stands than in geograph-ic regions, due to differences in allelic frequency profiles. For 2 loci, there were directional increasesof frequencies of rare alleles in introduced stands as compared to geographic regions, whereas themean number of alleles was lower in the former populations. Similarly, intraspecific variation among15 introduced stands was compared to geographic variation among 18 origins in the natural rangefor bud flush and leaf coloration in experimental plantations established in France. There was a cli-nal latitudinal variation for both phenological traits in the natural range. The introduced populationsoccupied an intermediate position in the rankings for both phenological traits. A hypothesis of genet-ic differentiation between introduced and natural populations is proposed in light of the results ob-tained.allozymes / bud flush / leaf coloration / genetic differentiation / Quercus rubra LRésumé — Différenciation génétique entre les populations introduites et celles de l’aire natu-relle du chêne rouge d’Amérique (Quercus rubra L). La diversité génétique intrapopulation chezQ rubra L a été étudiée dans 23 peuplements introduits et 9 régions géographiques de l’aire natu-relle avec l’aide de 4 isozymes contrôlés par 4 locus polymorphes. Cette diversité est plus élevéedans les peuplements introduits, à cause des différences de profils des fréquences alléliques, alorsque le nombre moyen d’allèles par population est plus faible en Europe que dans l’aire naturelle.Pour 2 loci, les fréquences d’allèles rares sont systématiquement plus élevées dans les peuple-ments introduits. De la même manière, la variabilité intraspécifique a été étudiée sur un échantillonde 15 populations introduites et 18 populations de l’aire naturelle pour le débourrement et la colora-tion automnale des feuilles. Les populations de l’aire naturelle manifestent une variabilité suivant ungradient latitudinal. Les populations de l’aire introduite se singularisent par leur position intermédiairedans le classement des provenances pour les 2 critères phénologiques. L’hypothèse d’une différen-ciation génétique entre les populations américaines et européennes est émise à la lumière de cesrésultats.allozyme / débourrement/ coloration des feuilles / différenciation Q rubra L génétique /INTRODUCTION Regional genetic variation studies were conducted on allozymes (SchwarzmannNorthern red oak (Q rubra L) was intro- and Gerhold, 1991) and range-wide stud-duced in Europe during the 17th century ies on growth and adaptive traits (Kriebel(Bauer, 1953; Timbal et al, 1993). It was et al, 1976, 1988). Fragmentary data existfirst planted in botanical collections before on intraspecific variation of introduced pop-being planted in forests at the end of the ulations (Krahl-Urban, 1966), but no at-last century. Plantations were established tempt has been made so far to compareall over Europe except in Mediterranean genetic variation among populations be-regions and in Scandinavia. It is currently tween both continents.widely used for afforestation in Francewhere a nationwide tree improvement pro-gram is planned. Stands established in Eu- MATERIALS AND METHODSrope are usually of unknown origin, buthave certainly resulted from successive Genetic variation was assessed by means of al-generations of the original introductions lozymes and phenological traits in populationsrather than from direct importation of from the natural range and populations intro-seeds from the natural range. duced into Europe. The objective of the present contribu-tion was to compare genetic variation be- Allozyme variationtween introduced and natural populationsby means of allozy ...