Morphology,Anatomy and Histochemistry of Fagus grandifolia Ehrh. (North American Beech) Ectomycorrhizas

Abstract: Five distinct ectomycorrhizal morphotypes were recognized on root systems of Fagus grandifolia collected in a maple-beech woodlot. Three morphotypes showed extensive root branching whereas two had limited root branching. One morphotype, a bright orange, smooth type, was studied in detail anatomically. A compact mantle with few emanating extraradical hyphae covered the root apex of each mycorrhizal lateral. A Hartig net extended around epidermal and hypodermal cells. Roots were mostly diarch and a single-layered endodermis and a biseriate hypodermis with the inner hypodermis having suberized walls were present in all specimens examined. The mantle, and to a lesser extent the Hartig net, stored lipids, polysaccharides and proteins.     

Regional Differentiation in Genetic Components for the American Beech, Fagus grandifolia Ehrh., in Relation to Geological History and Mode of Reproduction

Fagus grandifolia , were investigated throughout its geographical range, using allozyme polymorphisms. A total of 1,131 trees from 21 populations were examined for 32 alleles of 10 polymorphic and two monomorphic loci in eight enzyme systems. The mean expected heterozygosity was 0.186, which indicates a relatively high genetic diversity within the populations. The levels of population differentiation were high, as revealed by genetic parameters, i.e., G _ST =0.168 and F _ST =0.167. The results of principal component analysis on allele frequencies clearly revealed unique regional patterns of differentiation in genetic components among populations “with” and “without” vegetative regeneration by root suckers. The American beech populations consist of two genetically distinct clusters, one from the Gulf-coastal plain, eastern coastal plain, Piedmont Plateau and Ozark Plateau; and the other from the remaining northern glaciated territories. Populations from the Blue Ridge and Great Smoky Mountains turned out to belong to the latter cluster, which is also characterized by extensive regeneration via root suckers. The consequences of regional differentiation in genetic components are discussed in relation to the postglacial spread from refugia to the current geographic distributions and the mode of reproduction. Received 8 August 2000/ Accepted in revised form 29 May 2001     

Demographic genetics of the American beech, Fagus grandifolia. II. Genet substructure of populations for the Blue Ridge, Piedmont and the Great Smoky Mountains

Populations of American beech in Virginia and the Great Smoky Mountain National Park in Tennessee and North Carolina were investigated for demographic genetic substructurings. Two Virginia populations, one on the Blue Ridge (WG1) and the other on the Piedmont (WG2) occur over an elevational gradient of several hundreds meters. One of the Great Smoky Mountain populations (GS1) was in a 'beech gap' and the other (GS2) in a 'cove forest' along a creek. The populations in the Great Smoky Mountain National Park were only separated by a few hundred meters in elevation, but both on the same physiographic province. The populations had two growth forms. Trees produced extensive root suckers at WG1, GS1 and GS2, but WG2 had no root suckers and all individuals had obviously been established from seeds. A total of 1335 shoots were mapped at the four sites, their size measured [diameter at breast height (DBH) or diameter at ground height (DGH)], and genotypes were determined for each locus using allozyme analysis. F_IS among five different size-classes revealed an excess of homozygotes in WG1, GS1 and GS2, and an excess of heterozygotes in WG2. The offshoot formation from root suckers obviously contributed to the abundance of intermediate size-classes in WG1, GS1 and GS2. Exceedingly localized patchiness of different multilocus genotypes reveals genetic clustering of shoots that have obviously originated from root suckers in WG1, GS1 and GS2. The Piedmont population (WG2), on the other hand, showed loose localization of genetically related trees at a scale of 35–40 m in area, suggesting broader ranges of pollen and seed dispersal. The data are discussed in the light of the differences in growth form and mode of reproduction, and also in relation to the post-glacial migration and the current geographic distribution of the species.     

A relict population of Fagus grandifolia var. mexicana at the Acatlan Volcano, Mexico: structure, litterfall, phenology and dendroecology

Aim Fagus grandifolia var. mexicana (Martinez) Little has an extraordinarily restricted distribution in the Mexican montane cloud forests. Isolated Fagus (beech) populations have been recorded in less than 10 small areas (2–40 ha) in the eastern Sierra Madre at altitudes from 1400 to 2000 m. The objectives were to determine tree and seedling age, forest structure, phenology, litterfall patterns and the relationship between mast and climatic variables. Location We report on three Fagus stands at the Acatlan Volcano, Veracruz, Mexico. Methods Changes in forest cover were determined using aerial photographs. Within each stand, basal area, density and tree species composition were determined in a 0.1‐ha band transect. Additionally, litterfall production was quantified and phenophases were recorded monthly over a 3‐year period, and 60 tree cores were collected to determine age distribution and tree‐ring growth. Results The forest was atypical in several respects. Fagus was the only dominant tree species in the crater stand, although in the rim and at the top of the volcano it was codominant with other tree species. Juveniles occurred only on the rim, but there was a seedling bank in the crater. Although forest cover in the area increased between 1968 and 1993, the Fagus stands did not change in size. Leaf production peaked in March and April, and leaf fall occurred from October through February. Litterfall production was the highest in November. During mast years, flowering started in February and between mast events there were no flowers or fruits. Minimum temperatures were highly correlated with Fagus litterfall and leaf fall. Seedlings ranged in age from 2 to 18 years and were 13–60 cm tall. Tree cores ranged from 76 to 120 years, but trees were older than the core samples. Main conclusions Although beech is considered a gap regeneration species that reaches the canopy after alternating periods of release and suppression, the trees in the crater were released when less than 1.5 m tall and have suffered few periods of suppression since. The results indicate that the crater stand was established after a severe disturbance destroyed the existing forest. We conclude that the relict beech population should be able to maintain itself, if not severely disturbed by humans or by climatic changes related to global warming.     

米心水青冈基因组DNA提取及RAPD反应体系优化

采用4种方法对米心水青冈基因组DNA进行提取,通过比较得出改良CTAB法提出的DNA纯度较高,能够达到扩增要求,因此采用此方法用于正式DNA的提取。适合米心水青冈的RAPD反应体系为：反应体积为25 μL,模板DNA40 ng,引物0.8 μmol·L^-1,Taq聚合酶1.25 U,Mg²⁺浓度2.0 mmol·L^-1,dNTP浓度0.16 mmol·L^-1。适合米心水青冈RAPD扩增程序： 94℃预变性3 min,一个循环,94℃变性30 s,37℃退火1 min,72℃延伸2 min,45个循环。     

Chloroplast DNA phylogeography of Fagus crenata (Fagaceae) in Japan

 CpDNA variation in Japanese beech, Fagus crenata (Fagaceae), was studied in 45 populations distributed throughout the species' range. Two cpDNA regions were sequenced: the non-coding region between the trnL (UAA) 5′exon and trnF (GAA), and the trnK region (including matK). Thirteen distinct cpDNA haplotypes were recognized and each haplotype was found to be geographically structured. Two major clades (I and II+III) were revealed in phylogenetic analyses among the haplotypes using F. sylvatica as an outgroup. The haplotypes of Clade I were distributed mainly along the Japan Sea side of the Japanese Archipelago, while those of Clade II+III occurred chiefly along the Pacific Ocean side. Consequently, the distribution of the two major cpDNA clades suggests that there were two migration routes in the history of F. crenata; one along the Japan Sea and the other along the Pacific Ocean side of the Japanese Islands. Received March 19, 2001 Accepted November 22, 2001     

Genetic variation of European beech (Fagus sylvatica L.) along an altitudinal transect at Mount Vogelsberg in Hesse, Germany

Allelic and genotypic variation at 13 different enzyme loci of autochthonous European beech (Fagus sylvatica L.) was investigated in six 110-160-year-old stands growing at elevations between 150 and 660 m above sea level on the western slope of mount Vogelsberg in central Germany. The highest elevated population showed the highest number of effective alleles (Ne), the highest total heterozygosity (He) and the highest population differentiation deltaT. Also, the genotype SKD-A2A3 of shikimate dehydrogenase was significantly more frequent at the two highest elevated stands (P = 11%) than at the three lowest elevated stands (P = 1%). Further differences in genotype frequencies between 11 of 15 stand pairs were elevation independent.     

Characterization of microsatellite markers in Fagus sylvatica L. and Fagus orientalis Lipsky

Using an enrichment procedure, we cloned microsatellite repeats from European beech (Fagus sylvatica L.) and developed primers for the amplification of microsatellite markers. Six polymorphic loci were characterized which produced 3–21 alleles in 70 individuals from one Italian population, with an observed heterozygosity between 0.58 and 0.85. All six loci amplified fragments which were polymorphic in the closely related species, Fagus orientalis, also. Owing to their very high degree of variation, these markers should be very useful in gene flow studies of these species.     

Seasonal Changes of the Antioxidative Systems in Foliar Buds and Leaves of Field-grown Beech Trees (Fagus sylvatica,L.) in a Stressful Climate

The activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate radical reductase, and dehydroascorbate reductase and the contents of ascorbate, chlorophyll and soluble protein were determined in beech (Fagus sylvatica, L.) foliage over two or three seasons. Four important stages of leaf development were distinguished: resting buds, emerging, mature and senescent leaves. Foliar buds in spring, prior to the emergence of new leaves, contained a lower chlorophyll content but a higher protein content and higher activities of ascorbate peroxidase and monodehydroascorbate radical reductase than mature leaves in summer. By contrast, superoxide dismutase and glutathione reductase activities and ascorbate contents were higher in mature leaves than in swollen foliar buds. Dehydroascorbate reductase activity was low in all developmental stages. Resting buds in winter contained activities of superoxide dismutase, ascorbate peroxidase and monodehydroascorbate radical reductase that were similar to those found in mature leaves in summer, whereas the contents of total and reduced ascorbate were 6- and 20-times lower, respectively, in buds than in mature leaves. The low foliar concentration of reduced ascorbate in resting buds, despite high monodehydroascorbate radical reductase activity, suggests that the regeneration of ascorbate might be limited by the availability of reductant. High antioxidative capacity was conferred by mature beech leaves and may be an important protection measure for coping with the large fluctuations in temperature and exposure to elevated ozone concentrations in summer.     

Identification and molecular characterisation of new Mexican isolates of Pochonia chlamydosporia for the management of Meloidogyne spp.

New Mexican isolates of the nematophagous fungus Pochonia chlamydosporia were obtained from nematode infested fields in the vegetable growing area of Tepeaca Valley, Puebla State, Mexico. Based on macro and microscopic morphology, seven ‘putative’ P. chlamydosporia isolates were selected and the DNA extracted for polymerase chain reaction (PCR). Three new isolates of P. chlamydosporia were identified: Pcp2, Pcp21 and Pcp31. The amplification reaction of the internal transcribed spacer (ITS) region revealed a 650 bp amplicon which was used in a maximum likelihood phylogenetic inference analysis. Three groups were recovered in the tree topology, supported by a > 90% bootstrap value. Nucleotide identity values were > 83.6% between the test sequences and the reference sequence. In addition, using specific primers for two existing varieties of P. chlamydosporia, restriction fragment length polymorphism on the ITS products in conjunction with the phylogenetic inferences and the molecular test for detection of P. chlamydosporia vcp1 gene, it was found that all three isolates belong to a new variety which we have named P. chlamydosporia var. mexicana. We compared the chlamydospore production rate, rhizosphere colonisation and egg parasitism percentages of the three native isolates in Meloidogyne spp. with a reference isolate (Pc10). Native isolates produced > 1×10⁶ chlamydospores/50 g of substrate (of which more than 80% were viable), colonised > 80% of the rhizosphere, and parasitised > 60% of Meloidogyne incognita and Meloidogyne arenaria eggs. Meloidogyne hapla egg parasitism was < 60%. Isolates Pcp2 and Pcp21 were identified as potential biological control agents of Meloidogyne spp. to be tested further in greenhouse and field tests.     

生态系统的冗余与营养结构模型

生态系统的冗余与营养结构模型党承林黄瑞复（云南大学生态学与地植物学研究所,昆明６５００９１）ＲｅｄｕｎｄａｎｃｙｉｎＥｃｏｓｙｓｔｅｍｓａｎｄｔｈｅＭｏｄｅｌｆｏｒＴｒｏｐｈｉｃＳｔｒｕｃｔｕｒｅ．ＤａｎｇＣｈｅｎｇｌｉｎ,ＨｕａｎｇＲｕｉｆｕ（Ｉｎ...     

Demographic genetics of the American beech (Fagus grandifolia Ehrh.) III. Genetic substructuring of coastal plain population in Maryland

Spatiotemporal genetic substructurings were investigated in the American beech population of the east-central coastal plain in Maryland. All trees including seedlings, various sizes of juveniles, and mature trees within the study site (10 × 100 m) were mapped, diameters measured, and leaves collected for allozyme analyses. Eleven polymorphic loci in eight enzyme systems were examined: 6Pgdh2, 6Pgdh3, Acp2, Adh1, Adh2, Fum, Got1, Got3, Lap, Pgi, and Pgm2. A total of 1945 trees were analyzed and 595 multilocus genotypes were detected. Six size-classes and 10 spatial blocks were discriminated for spatiotemporal analyses. Parameters for genetic variations (heterozygosity, Simpson's index, Shannon-Weaver's index, and inbreeding coefficient) decreased in larger size-classes. These genetic parameters fluctuated in spatial blocks of 10 m intervals, in which certain alleles were characteristic of specific blocks. The spatial autocorrelation by Moran's I and coancestry revealed the ranges of genetic relatedness to be only 20–30 m. Multilocus genotype analyses showed that higher genetic variations occur in larger size-classes and at gap openings where seed shadows for mother trees are overlapped. The relationships among reproductive trees, seedlings and juveniles suggested that the seed dispersal range of the American beech is normally in the range of 30–40 m. The mechanisms of a remarkably high genetic polymorphism maintained in this once artificially disturbed and grazed forest are discussed as related to conservation biology.     

Confirmation of clonal reproduction of Fagus crenata Blume from Sado Island,Niigata Prefecture

While clonal growth is important in the East Asian Fagus subgenus Engleriana and the North American Fagus grandifolia (subgenus Fagus), for other subgenus Fagus species the vast majority of regeneration involves sexual reproduction with clonal growth only rarely observed. Here we aim to confirm using nuclear microsatellite markers whether clonal growth occurs in the Japanese endemic species Fagus crenata (subgenus Fagus) by investigating the origin of multi-stemmed clumps found within a high-elevation dwarf beech forest on Sado Island, Niigata Prefecture. We found that all stems collected from three separate clumps belonged to the same clump-specific multi-locus genotypes. The maximum size of clones was 3–4 m in diameter, comparable in size to those seen in the predominantly asexually regenerating Japanese species Fagus japonica (subgenus Engleriana). The species capacity for clonal growth is likely to underlie its ability to persist at high-elevation exposed sites at the limits of its ecological range.     

Development and polymorphism of microsatellite markers for Fagus crenata and the closely related species, F. japonica

 We have developed microsatellite markers (SSRs) applicable to Fagus crenata using the RAHM method and investigated their polymorphisms. We also applied the SSRs in an analysis of a closely related species, F. japonica. Here we describe the isolation and characterization of nine polymorphic microsatellite markers, of which eight are applicable to both species. Among 30 individuals of each of F. crenata and F. japonica we detected a total of 79 and 77 alleles, respectively, with an average of 9.9 and 8.6 alleles per locus. The mean expected heterozygosity (He) was 0.615 (range: 0.216–0.925) in F. crenata and 0.660 in F. japonica (range: 0.259–0.827). The He values were considerably higher than those previously found for isozymes. Paternity exclusion probabilities for multiple loci, calculated over all loci, were extremely high (0.999 and 0.998 in F. crenata and F. japonica, respectively): sufficiently high to study pollen flow in both species. Received: 5 December 1998 / Accepted: 28 December 1998     

Genetic diversity of Mexican brook lamprey <Emphasis Type="Italic">Lampetra (Tetrapleurodon) geminis</Emphasis> (Alvarez del Villar, 1966)

Lampreys are the only surviving representatives of the oldest known vertebrates. The Mexican lamprey L. geminis (nonparasitic), is particularly interesting, because it is an endemic, biogeographical relict, and a threatened species. RAPD markers were used to describe genetic diversity in L. geminis A total of 77 specimens were collected from five populations, three in the R'o Grande de Morelia-Cuitzeo basin and two in the R'o Duero-Lerma-Chapala basin, Mexico. Eighty-eight RAPD markers were obtained from eight primers. Genetic diversity within each population was estimated using Shannon's index (S), heterozygosity (H) and gene diversity (h). These estimates revealed significant variation within populations, although a variance homogeneity test (HOMOVA) showed no significant differences among populations or between basins. Nei genetic distance values indicate a low genetic differentiation among populations. Analysis of molecular variance (AMOVA) indicates that most of the genetic diversity occurs within populations (91.4%), but that a statistically significant amount is found among populations (P0.001). Principal coordinates and cluster analyses of RAPD phenotypes show that specimens are not grouped by geographical origin. The genetic diversity found within L. geminispopulations may be explained by its breeding system and an overlapping of generations. The scarce genetic differentiation among populations is likely to the low rate of DNA change that characterizes the lamprey group.     

Quantity over quality: light intensity,but not red/far‐red ratio,affects extrafloral nectar production in Senna mexicana var. chapmanii

Extrafloral nectar (EFN) mediates food‐for‐protection mutualisms between plants and insects and provides plants with a form of indirect defense against herbivory. Understanding sources of variation in EFN production is important because such variations affect the number and identity of insect visitors and the effectiveness of plant defense. Light represents a potentially crucial tool for regulating resource allocation to defense, as it not only contributes energy but may help plants to anticipate future conditions. Low red/far‐red (R/FR) light ratios can act as a signal of the proximity of competing plants. Exposure to such light ratios has been shown to promote competitive behaviors that coincide with reduced resource allocation to direct chemical defenses. Little is known, however, about how such informational light signals might affect indirect defenses such as EFN, and the interactions that they mediate. Through controlled glasshouse experiments, we investigated the effects of light intensity, and R/FR light ratios, on EFN production in Senna mexicana var. chapmanii. Plants in light‐limited conditions produced significantly less EFN, and leaf damage elicited increased EFN production regardless of light conditions. Ratios of R/FR light, however, did not appear to affect EFN production in either damaged or undamaged plants. Understanding the effects of light on indirect defenses is of particular importance for plants in the threatened pine rockland habitats of south Florida, where light conditions are changing in predictable ways following extensive fragmentation and subsequent mismanagement. Around 27% of species in these habitats produce EFN and may rely on insect communities for defense.     

Same parental species, but different taxa: molecular evidence for hybrid origins of the rare endemics Saxifraga opdalensis and S. svalbardensis (Saxifragaceae)

Saxifraga opdolensis was described from Oppdal in southern Norway and hypothesized to have originated as the hybrid S. cernua × rivularis or to have been derived from a S . cernua-like progenitor. We tested these alternative hypotheses using uni- and biparentally inherited molecular markers observed in S. opdalensis and its putative parental species at the type locality: PCR-RFLPs (restriction fragment length polymorphisms in amplified fragments of chloroplast DNA; cpDNA), sequences of the cpDNA intron trnL and the spacer tmL-tmF , and RAPDs (random amplified polymorphic DNAs). The data provided unambiguous support for the hybrid hypothesis. The cpDNA analyses distinguished two well-differentiated chloroplast genomes, one in S. opdalensis and S. rivularis , and another in S. cernua . The majority of the RAPD markers showed distinct additivity in S. opdalensis relative to its postulated parental species. Thus, S. opdalensis has probably originated from a hybrid with S. rivularis as the maternal parent and S. cernua as the paternal parent. We also included S. svalbaardnsis in the present study because previous molecular analyses of Svalbard material have shown that this species had probably also originated as a hybrid between S. cernua and S. rivularis . The chloroplast genome of S. svalbaardnsis was identical to that of S. opdalensis , but the two species differed in many RAF'D markers. Although these two endemics probably have been derived from the same hybrid combination, they are morphologically and genetically distinct and should be referred to separate species. Differences between such independently originated hybrid taxa may result from intraspecific variation in their parental taxa. Saxufraga cernua comprises, for example, several highly divergent evolutionary lineages.