Quercus rubra is one of the most important timber and ornamental tree species from eastern North America. It is a widespread species growing under variable ecological conditions. Chloroplast DNA variation was studied by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) in 290 individuals from 66 populations sampled throughout the natural range. A total of 12 haplotypes were detected, with one found in 75% of the trees. Population differentiation is relatively low ( G ST = 0.46), even when similarities between haplotypes are taken into account ( N ST = 0.50), pointing to a weak phylogeographical structure. Furthermore, no spatial structure of genetic diversity could be detected. The genetic differentiation increased northwards, reflecting the postglacial history of Q. rubra . The unusual aspect of this study was the low level of chloroplast DNA genetic differentiation in Q. rubra compared to that typically observed in other oak species. Palynological evidence indicates that during the last glacial maximum, Q. rubra had one major distribution range with populations located relatively far to the north, resulting in only modest movement northwards when climate improved, whereas European white oaks were largely restricted to the southern European peninsulas and experienced extensive movements during the postglacial period. The contrasted geographical features and levels of tree species richness of both continents might further explain why congeneric species sharing similar life history traits have genetic structures that are so different.

Chloroplast DNA variation of Quercus rubra L. in North America and comparison with other Fagaceae

Generally, oaks dominate the broadleaf deciduous forests in Japan. The genetic variation in 6 cpDNA regions (trnT-trnL, trnL-trnF, atpB-rbcL, and trnH-psbA speacers, trnL intron, and matK gene) with regard to the Japanese oak (Quercus mongolica var. crispula) and 3 related species in the section Prinus (Q. serrata, Q. dentata and Q. aliena) was investigated in 598 trees belonging to 44 populations distributed throughout the Japanese archipelago. Additional samples were collected from Korea, China, and Russia (Sakhalin). Thirteen haplotypes (I to XIII) were identified on the bases of 15 nucleotide substitutions and 3 indels. Haplotypes I and II were discovered in northeastern Japan, whereas haplotypes III to IX were distributed in southwestern Japan. The boundary distinguishing these 2 groups was located in central Japan coincident with the Itoigawa-Shzuoka tectonic line. Haplotype I was also found in Sakhalin, whereas haplotypes VI, VII, VIII, X, XI, XII, and XIII were found in Korea and China. Four oak species in the same location shared identical haplotypes, suggesting cpDNA introgression by occasional hybridization. Both the values of total haplotype diversity (HT) and haplotype diversity within populations (HS) in Q. mongolica var. crispula were higher in the southwestern populations than in the northeastern populations. A haplotype network indicated that haplotype VI is the ancestral haplotype. The presence of identical haplotypes in Korea, China, and Japan suggested that the haplotypes diversified on the Eurasian continent before the last glacial period. The difference in genetic structure between the northeastern and southwestern regions indicates a difference in the history of migration and recolonization in Japan during the last glacial period.

Phylogeographic structure and late Quaternary population history of the Japanese oak Quercus mongolica var. crispula and related species revealed by chloroplast DNA variation

Climatic oscillations during the Quaternary strongly affected the distribution of warm-temperate tree species, which experienced local restrictions into ice-free areas and posterior expansions. To evaluate the impact of these range movements on the genetic structure of populations, we performed a phylogeographical analysis of the species Nothofagus obliqua with chloroplast DNA markers. A total of 27 populations covering the whole natural distribution range were analyzed using polymerase chain reaction-restriction fragment length polymorphism. Diversity (h
 T, h
 S), allelic richness (r
 g), and differentiation among populations for unordered (G
 ST) and ordered alleles (N
 ST) were calculated. The relationships among haplotypes were evaluated by the construction of a minimum spanning network. The spatial distribution of the genetic variation was analyzed through a Mantel test and with a nested analysis of molecular variance to differentiate between geographic regions. The screening of 11 non-coding regions allowed the identification of 14 haplotypes. A high genetic differentiation was detected (N
 ST = 0.875 and G
 ST = 0.824) with the existence of phylogeographic structure (p < 0.05). The distribution of the genetic variation was partially explained by the topography of the region when the populations were divided longitudinally into Coastal Mountains, Central Valley, and Andes Mountains (ϕ
 RT = 0.093, p = 0.001). In agreement with pollen records, our results support the hypothesis of Coastal refuges since the region harbors high diversity together with older and private haplotypes. Long-lasting persistence of some Coastal populations without contribution to re-colonization is proposed. Additional refuges are also postulated along the Andes and Longitudinal Valley. Survival in multiple glacial refuges is discussed together with the possible migratory routes.

The effects of Quaternary glaciations in Patagonia as evidenced by chloroplast DNA phylogeography of Southern beech Nothofagus obliqua

Aim We examined the genetic structure of Quercus garryana to infer post-glacial patterns of seed dispersal and pollen flow to test the hypotheses that (1) peripheral populations are genetically distinct from core populations and from one another; (2) genetic diversity declines towards the poleward edge of the species’ range; and (3) genetic diversity in the chloroplast genome, a direct measure of seed dispersal patterns, declines more sharply with increasing latitude than diversity in the nuclear genome. We address our findings in the context of known historical oak distribution from pollen core data derived from previously published research.



Location  Oak–savanna ecosystems from southern Oregon, USA (core populations/non-glaciated range) northward to Vancouver Island, British Columbia, Canada (peripheral populations/glaciated range).



Methods  We genotyped 378 trees from 22 sites with five chloroplast and seven nuclear microsatellite loci. For both sets of markers, we estimated genetic diversity and differentiation using an analysis of molecular variance and generated Mantel correlograms to detect genetic and geographical distance correlations. For the nuclear markers, we also used a Bayesian approach to infer population substructure.



Results  There was a large degree of population differentiation revealed by six chloroplast haplotypes, with little (≤ 3) or no haplotype diversity within sites. Peripheral island locations shared the same, maternally inherited chloroplast haplotype, whereas locations in mainland Washington had greater haplotype diversity. In contrast, genetic diversity of the nuclear markers was high at all locations sampled. Populations clustered into two groups and were significantly positively correlated over large spatial scales (≤ 200 km), although allele richness decreased significantly with latitude. Population substructure was observed between core and peripheral populations because rare alleles were absent in peripheral localities and common allele frequencies differed.



Main conclusions  The observed pattern of chloroplast haplotype loss at the northern periphery suggests restricted seed dispersal events from mainland sites to peripheral islands. This pattern was unexpected, however, as refugial oak populations remained near the current post-glacial range even during the Last Glacial Maximum. Using nuclear markers, we found high within-population diversity and population differentiation only over large spatial scales, suggesting that pollen flow is relatively high among populations.

/pdf/patterns-of-seed-dispersal-and-pollen-flow-in-quercus-4u3qnzuyjw.pdf

Patterns of seed dispersal and pollen flow in Quercus garryana (Fagaceae) following post-glacial climatic changes

Hardwood tree species in forest, plantation, and urban environments (temperate regions of the world) are important biological resources that play a significant role in the economy and the ecology of terrestrial ecosystems, and they have aesthetic and spiritual value. Because of these many values of hardwood tree species, preserving forest tree biodiversity through the use of biotechnological approaches should be an integral component in any forestry program in addition to large-scale ecologically sustainable forest management and preservation of the urban forest environment. Biotechnological tools are available for conserving tree species as well as genetic characterization that will be needed for deployment of germplasm through restoration activities. This review concentrates on the biotechnological tools available for conserving, characterizing, evaluating, and enhancing hardwood forest tree biodiversity. We focus mainly on species grown for lumber and wood products, not species grown mainly for fiber (pulp and paper production). We also present a brief summary of the importance of non-wood forest products from temperate hardwood tree species (a research area that needs further development using biotechnological techniques) and a few case studies for preserving forest tree biodiversity.

https://www.nrs.fs.fed.us/pubs/jrnl/2011/nrs_2011_pijut_001.pdf

Biotechnological efforts for preserving and enhancing temperate hardwood tree biodiversity, health, and productivity

Chloroplast DNA (cpDNA) variation was examined in 48 northern red oaks at 14 sites representing contrasting glacial histories and age structures within the state of Indiana in the United States. PCR-RFLP of three intergenic regions revealed five haplotypes. Haplotype I was common to seven sites and was the most frequent (17 trees). Haplotype II was common to five sites and was nearly as frequent as haplotype I (16 trees). Haplotypes III, IV and V were equally infrequent and did not occur together. Genetic diversity resided among rather than within populations (GST = 0.73 ± 0.14). This preliminary survey shows that cpDNA diversity will be a useful tool for the investigation of ancient seed dispersal patterns in northern red oak.

Chloroplast DNA variation of northern red oak (Quercus rubra L.) in Indiana

We mapped the biogeographical distribution of chloroplast haplotypes in northern red oak (Quercus rubra L.) to test the hypotheses that the founder effects during postglacial migration will result in a latitudinal gradient of haplotype diversity with exhaustion of haplotype richness at the extreme northern edge of the range. PCR-RFLP markers for 23 populations of Q. rubra in old growth and minimally disturbed forests across 13,000 km2 of the contemporary range revealed only four of the five haplotypes detected previously at 12 sites in Indiana. The four northernmost populations were fixed for either haplotype I or haplotype II, the two most common haplotypes. Haplotype richness declined poleward, but the biogeographical pattern of 829 haplotypes across the 35 sites did not clearly indicate postglacial migration routes along latitudinal gradients from the southern edges of the study area. Although Q. rubra and the European white oak Q. robur L. are both early successional species that recolonized ...

Yi Feng

Papers

Chloroplast DNA variation of northern red oak (Quercus rubra L.) in Indiana

Biogeographical Distribution of Chloroplast Diversity in Northern Red Oak (Quercus rubra L.)