倒卵叶青冈——广西壳斗科一新记录种

报道了广西壳斗科植物一新记录种——倒卵叶青冈,并对倒卵叶青冈的形态进行了补充描述,同时对该种的生存现状进行评价,为这一物种的保护提供基础资料。     

A phenetic study of the taxonomic delimitation of Quercus acutifolia and Q. conspersa (Fagaceae)

A phenetic study ofQuercus acutifolia andQ. conspersa (Fagaceae) is carried out. The study was based on morphological characters, and included cluster analysis and principal component analysis. The results revealed that the characters employed so far to separateQuercus acutifolia andQ. conspersa seem to be quite unreliable. Nevertheless, both species can still be recognized as taxonomically different entities, although mostly based on characters of leaf margins. We propose that the individuals that have leaves with dentate-aristate margins correspond toQ. acutifolia, whereas those that have leaves with entire and not dentate-aristate margins belong toQ. conspersa.     

Lectotypification of the Linnaean name Fagus castanea (Fagaceae)

The typification of the name Fagus castanea L. (Fagaceae) is discussed. A specimen from the Linnaean Herbarium (no. 1130.1, LINN!) is designated as lectotype.     

Type designation of the oaks Quercus ballota and Q. rotundifolia (Fagaceae)

The names Quercus ballota and Q. rotundifolia (Fagaceae), referring to taxa sometimes considered conspecific with the widely distributed Q. ilex, are discussed and typified. A specimen preserved at MPU is designated as the lectotype of Desfontaines's name Q. ballota. Lamarck's name Q. rotundifolia is neotypified using a specimen preserved at VAL, with several duplicates in other European herbaria.     

栎属青冈亚属（壳斗科）的叶表皮研究

利用光镜和扫描电镜观察了栎属青冈亚属Quercus subgen. Cyclobalanopsis 48种植物的叶表皮,尤以对叶下表皮的毛被特征观察较为仔细。共观察到8种不同类型的叶表皮毛：单列毛、单毛、乳突、星状毛、溶和星状毛、具柄束毛、多出毛和水母状毛。其中乳突在青冈亚属中较常见,而在壳斗科其他属中仅在石栎属 Lithocarpus 少数种类中有报道;水母状毛首次在壳斗科中发现。毛被可能遵循以下的演化规律：乳突→单毛→星状毛;星状毛依照从简单→复杂的演化途径,分化出各种形态各异和结构复杂的毛系。初步讨论了毛被以及叶表皮其他特征(如毛基细胞和表皮细胞的形态、气孔的类型和密度等)的分类和系统学意义。     

Leaf epidermis of Quercus subgen. Cyclobalanopsis (Oerst.) Schneid. (Fagaceae)

The characters of leaf epidermis (mainly epidermal cells, stomata, trichomes) have been examined in 48 species of Quercus subgen. Cyclobalanopsis of the Fagaceae. The adaxial leaf epidermis was investigated under light microscope. The epidermal cells of this surface are of two types in terms of the outline of their anticlinal wall. One type is characterized by having straight wall, and this type has been observed in most of the species studied, while the other is characterized by having sinuate or sinuolate wall, and this type has been found only in eight species, such as Q. blakei and Q. hui. There exist two types of trichome-bases on this surface: in one type the bases are singlecelled, and this type has been found in most of the species studied, such as Q. oxyodon and Q. augustinii; while in the other the bases consist of a group of cells, and this type has been found only in nine species, such as Q. thorelii and Q. chungii. The abaxial leaf epidermis was investigated under light microscope and scanning electron microscope. The epidermal cells and the trichome-bases on this surface under LM are in morphology essentially similar to those on the adaxial surface. The stomata under LM include three types: cyclocytic, subcyclocytic and anomocytic. The stomatal density is of some diagnostic value to distinguish between closely related species, e.g. the stomatal density in Q. glauca is higher than that in Q. schottkyana. Under SEM the stomata are elliptical or roundish. The most noteworthy feature of the adaxial leaf epidermis is the trichomes. Eight types of trichomes have been observed under SEM: simple-uniseriate, solitary, papillae, stellate, fused-stellate, stipitate-fasciculate, multiradiate and jellyfish-like. The first type, i.e. the simple-uniseriate trichome, is glandular, other six types, i.e. the solitary, papillae, stellate, fused-stellate, stipitate-fasciculate and multiradiate trichomes, are non-glandular, and the last one, i.e. the jellyfish-like trichome, may represent an intermediate type in structure between the glandular and the non-glandular trichomes. Papillae are very common in subgen. Cyclobalanopsis although in the Fagaceae they were previously reported only in a few species of Lithocarpus. The jellyfish-like trichome, observed only in Q. sichouensis, is reported in the Fagaceae for the first time. The evolutionary trends of trichomes are discussed. The trichomes seem to evolve toward the direction of increasing complexity in structure. Papillae are considered as the pedomorphism of trichomes. From papillae the solitary trichomes and then the stellate ones have evolved. The complicated trichome types with more arms may be produced from relatively simple ones with fewer arms by means of varions fusion: several stellate trichomes are fused to form the fused-stellate ones by basal fusion, and by the same way the fused-stellate ones to form the stipitate-fasciculate ones; the multiradiate trichomes are formed by the stellate ones, in which the arms emerge in a variety of seemingly random directions from a typically rounded common base. Based on the above results, it is considered that the trichome features are of important significance for a better understanding of the infrageneric division of Quercus and the phylogenetic relationships between this genus and the other genera in the Fagaceae. The very common presence of papillae in Quercus subgen. Cyclobalanopsis and in a few species of Lithocarpus may indicate that subgen. Cyclobalanopsis is a quite natural group on the one hand, and may have close relationship with Lithocarpus on the other hand. The thin-walled, jellyfish-like trichomes found in Q. sichouensis are in structure similar to the “glandular” peltate trichomes in Trigonobalanus, a genus generally regarded as the most primitive in subfam. Quercoideae, indicating that the affinity between subgen. Cyclobalanopsis and Trigonobalanus may becloser than that between subgen. Quercus and Trigonobalanus.     

Epigenetic marks in the mature pollen of Quercus suber L. (Fagaceae)

We have analysed the distribution of epigenetic marks for histone modifications at lysine residues H3 and H4, and DNA methylation, in the nuclei of mature pollen cells of the Angiosperm tree Quercus suber; a monoecious wind pollinated species with a protandrous system, and a long post-pollination period. The ultrasonic treatment developed for the isolation of pollen nuclei proved to be a fast and reliable method, preventing the interference of cell wall autofluorescence in the in situ immunolabelling assays. In contrast with previous studies on herbaceous species with short progamic phases, our results are consistent with a high level of silent (5-mC and H3K9me2) epigenetic marks on chromatin of the generative nucleus, and the prevalence of active marks (H3K9me3 and H4Kac) in the vegetative nucleus. The findings are discussed in terms of the pollination/fertilization timing strategy adopted by this plant species.     

Landscape-level spatial genetic structure in Quercus acutissima (Fagaceae)

Quercus acutissima (Fagaceae), a deciduous broad-leaved tree, is an important forest element in hillsides of South Korea. We used allozyme loci, Wright's F statistics, and multilocus spatial autocorrelation statistics to examine the distribution of genetic diversity within and among three local populations and the spatial genetic structure at a landscape scale (15 ha, 250 × 600 m) on Oenaro Island, South Korea. Levels of genetic diversity in Q. acutissima populations were comparable to mean values for other oak species. A moderate but significant deficit of heterozygotes (mean F(IS) = 0.069) was detected within local populations and low but significant differentiation was observed among populations (F(ST) = 0.010). Spatial autocorrelation analyses revealed little evidence of significant genetic structure at spatial scales of 100-120 m. The failure to detect genetic structure within populations may be due to intraspecific competition or random mortality among saplings, resulting in extensive thinning within maternal half-sib groups. Alternatively, low genetic differentiation at the landscape scale indicates substantial gene flow among local populations. Although wind-borne pollen may be the primary source of gene flow in Q. acutissima, these results suggest that acorn movement by animals may be more extensive than previously anticipated. Comparison of these genetic data for Oenaro Island with a disturbed isolated inland population suggests that population-to-population differences in internal genetic structure may be influenced by local variation in regeneration environment (e.g., disturbance).     

Competitive suppression of Quercus douglasii (Fagaceae) seedling emergence and growth

Reduced recruitment of blue oak (Quercus douglasii) seedlings in California grasslands and woodlands may result from shifts in seasonal soil water availability coincident with replacement of the native perennial herbaceous community by Mediterranean annuals. We used a combination of container and field experiments to examine the interrelationships between soil water potential, herbaceous neighborhood composition, and blue oak seedling shoot emergence and growth. Neighborhoods of exotic annuals depleted soil moisture more rapidly than neighborhoods of a perennial grass or "no-neighbor" controls. Although effects of neighborhood composition on oak seedling root elongation were not statistically significant, seedling shoot emergence was significantly inhibited in the annual neighborhoods where soil water was rapidly depleted. Seedling water status directly reflected soil water potential, which also determined the extent and duration of oak seedling growth during the first year. End-of-season seedling height significantly influenced survival and growth in subsequent years. While growth and survival of blue oak seedlings may be initially constrained by competition with herbaceous species, subsequent competition with adult blue oak trees may further contribute to reduced sapling recruitment.     

Spatial and genetic structure of two sandhills oaks: Quercus laevis and Quercus margaretta (Fagaceae)

Quercus laevis Walt, (turkey oak) and Q. margaretta Ashe (scrubby post oak) are important scrub oaks in the sandhills forest communities of the Coastal Plain of the southeastern United States. We used allozyme loci and Ripley's L-statistics to examine clonal structure and spatial dispersion in these species. Q. laevis greater than 1.5 m in height were randomly dispersed on a scale of 0–40 m; smaller individuals (< 1.5 m) were slightly clustered on a scale of 0–12 m. Larger individuals separated by ≤1 m had 15% probability of being ramets of the same clone. Q. margaretta showed strong clustering on a scale of 0–20 m. Stems separated by ≤ 1 m had a 71% probability of being ramets of the same clone. Clonal offspring were strongly clustered about the presumed clonal parent: 50% fell within 0.50 m of this individual. Simulation modeling and direct comparison of adult and juvenile genotypes indicated that acorns are dispersed on a scale of tens of meters for both species, suggesting animal vectors such as squirrels or blue jays.     

Clonal and genetic structure of two Mexican oaks: Quercus eduardii and Quercus potosina (Fagaceae)

Quercus eduardii and Q. potosina are dominant oak species in Sierra Fría, Aguascalientes, Mexico. These species have been exploited for multiple purposes since the 16th century. Both species produce clonal offspring through root suckering and acorns through sexual reproduction. To understand clonality for the implementation of the most adequate actions for the conservation of these species, we addressed the following questions: (a) what is the spatial clonal structure of both species? (b) How much clonal and genetic diversity is maintained in these species? Random Amplified Polymorphic DNAs (RAPDs) were used as molecular markers for these analyses. Genets of both species have few ramets and these grow close the parent tree. Autocorrelation analyses at the ramet level showed an aggregated distribution at short distances and a random spatial distribution at larger distances. Also, at the genet level the autocorrelation analyses showed a random distribution. Clonal diversity was high in both species (Q. eduardii: D=0.963, G/N=0.60; Q. potosina: D=0.985, G/N=0.65). Genetic diversity was high within populations (Q. eduardii: H _e =0.33±0.11; Q. potosina: H _e =0.35±0.11). Low levels of genetic differentiation among populations were observed (Q. eduardii ? _st =0.19, P < 0.002; Q. potosina ? _st =0.13, P < 0.002). Both species maintain high levels of clonal and genetic diversity, probably due to successful sexual reproduction, which allows gene flow among populations. Conservation and/or reforestation programs must include seed collections and germplasm banks. Due to the small genet size and the high clonal diversity of these species, seeds can be collected in any place in Sierra Fría, Aguascalientes.     

Woodland canopy structure and the light response of juvenile Quercus lobata (Fagaceae)

I investigated competition for light between canopy plants and juvenile valley oaks (Quercus lobata Nee) in a mixed-broadleaf woodland of California's northern Coast Ranges. Canopy effects on understory light supply were separated among the overlying adult valley oak, the adult's woody understory, and neighboring trees and shrubs through a series of light sampling surveys and measurements of the number, size, and spatial distribution of neighboring plants. Light supply in the understory was primarily influenced by neighboring plants, with no detectable effect of the overlying adult valley oak. Light supply in the understory averaged 25% full sun due to a high frequency of canopy gaps and a typically open understory. Seedling response to understory light supply was investigated in an experimental sunfleck gradient (10%, 19%, and 100% full sun). Between 10% and 100% full sun, seedling growth increased by 90% and the shoot:∗∗∗root ratio changed from 1.561 to 0.607. Shade seedlings were also taller and produced fewer, larger, and thinner leaves than seedlings grown in full sun. A field survey of the spatial distribution and crown morphology of saplings and young adults found 1) the distance between young valley oaks and neighboring overstory trees to increase with neighbor size, and 2) crowns of the young oaks to be skewed away from neighbors. Although shading by the canopy was only moderate, canopy effects on understory light supply may restrict juvenile recruitment of valley oak in this woodland.     

Taxonomy of Quercus crassifolia (Fagaceae) and morphologically similar species in Mexico

In this work, ten species morphologically similar to Q. crassifolia are circumscribed based on a phylogenetic species concept. Examination of these species suggests that Q. dysophylla and Q. radiata are of hybrid origin; the putative parents of Q. dysophylla are Q. crassifolia and Q. crassipes, while Q. radiata is likely the result of hybridization between Q. coccolobifolia and Q. conzattii or Q. urbanii. A lectotype of Q. crassifolia is designated here. Dichotomous keys, as well as distribution ranges and photographs, are presented.     

Morphological and molecular diversity among Italian populations of Quercus petraea (Fagaceae)

Quercus petraea (sessile oak) has a scattered distribution in southern and central Italy. The objective of this work was to evaluate the level and distribution of diversity in five Italian populations of Q. petraea by using morphological markers and hypervariable molecular markers such as microsatellites. Forty-eight morphological traits and six nuclear and three plastid loci were scored for each population. Evidence for differentiation in both sets of traits was found, but patterns of differentiation of morphological traits did not coincide with microsatellite differentiation. Morphological variation was correlated with ecological conditions at the site of origin. Analysis of molecular variance revealed significant genetic variation among populations (P < 0.001), both at the nuclear and plastid levels. There was a slight, but significant, correlation between nuclear genetic distance and geographic distance. The relatively high genetic diversity in the populations analysed indicates that the maintenance of their evolutionary potential is possible if population sizes are maintained or increased. Low levels of haplotype diversity found within the small southernmost population (Piano Costantino) indicates that genetic erosion may increase the extinction risk for this population.     

Karyomorphology of the endangered Trigonobalanus doichangensis (A. Camus) Forman (Fagaceae) and its taxonomic and biogeographical implications

Cytological studies were carried out for the first time on five populations of Trigonobalanus doichangensis in China and Thailand. In all populations, the pattern of interphase nuclei was of the simple chromocentre type, the mitotic prophases were of the proximal interstitial type and chromosome numbers were 2 n  = 2 x  = 14. Two B chromosomes were commonly observed at prophase and prophase–metaphase, but rarely at metaphase. Karyotype variation among the populations at the diploid level was limited, but there were some distinguishing cytological characters. Based on the comparison of all the available data on cytology, taxonomy, phytogeography and molecular systematics related to the genus Trigonobalanus , we recommend that the three species of Trigonobalanus comprise the subfamily Trigonobalanoideae and that the genus should not be segregated into three monotypic genera.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 321–330.     

Genetic evidence for hybridization in red oaks (Quercus sect. Lobatae, Fagaceae)

? Premise of the study: Hybridization is pervasive in many plant taxa, with consequences for species taxonomy, local adaptation, and management. Oaks (Quercus spp.) are thought to hybridize readily yet retain distinct traits, drawing into question the biological species concept for such taxa, but the true extent of gene flow is controversial. Genetic data are beginning to shed new light on this issue, but red oaks (section Lobatae), an important component of North American forests, have largely been neglected. Moreover, gene flow estimates may be sensitive to the choice of life stage, marker type, or genetic structure statistic. ? Methods: We coupled genetic structure data with parentage analyses for two mixed-species stands in North Carolina. Genetic structure analyses of adults (including F(ST), R(ST), G'(ST), and structure) reflect long-term patterns of gene flow, while the percentage of seedlings with parents of two different species reflect current levels of gene flow. ? Key results: Genetic structure analyses revealed low differentiation in microsatellite allele frequencies between co-occurring species, suggesting past gene flow. However, methods differed in their sensitivity to differentiation, indicating a need for caution when drawing conclusions from a single method. Parentage analyses identifed >20% of seedlings as potential hybrids. The species examined exhibit distinct morphologies, suggesting selection against intermediate phenotypes. ? Conclusions: Our results suggest that hybridization between co-occurring red oaks occurs, but that selection may limit introgression, especially at functional loci. However, by providing a source of genetic variation, hybridization could influence the response of oaks and other hybridizing taxa to environmental change.