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     

Development of EST-SSR markers from an inner bark cDNA library of Fagus crenata (Fagaceae)

Fagus crenata Blume is widely distributed throughout Japanese cool-temperate deciduous broad-leaved forests, but there are two divergent groups of populations in areas with contrasting winter climates separated by Japan’s Central Mountain Range. To facilitate investigations of adaptive genetic differentiation of the species using potentially functional genes, we have collected Expressed Sequence Tags and developed Simple Sequence Repeat markers using a cDNA library constructed from cambium and surrounding tissues. In total, 270 primer pairs were designed, and 87 of the corresponding loci showed polymorphism in 16 individuals, with 2–21 alleles per locus and expected heterozygosities ranging from 0.06 to 0.97. EST-SSR markers developed in the present study will be useful for genomic analyses of F. crenata populations.     

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.     

Implications of 19th century landscape patterns for the recovery of Fagus crenata forests

Questions: What is the effect of the 19th century (pre‐industrialization) landscape pattern on the recovery of climax forests in cool‐temperate mountain areas dominated by Fagus crenata (Japanese beech)? Location: Secondary forests on Mt. Daisen, western Japan. Methods: Vegetation patterns before and after industrialization were obtained from maps drawn in 1898 and 1979. Tree measurements were made in 12 plots in 1997. Correlation between current Fagus crenata dominance and forest edge in the 19th century was analysed using an S‐shaped regression curve. Fagus juvenile density was counted in the plots, and distances from each plot to the five nearest mother trees were measured to determine the dispersal kernel. Results: Secondary grassland covered a substantial area in 1898, whereas forest covered most of the area in 1997. Fagus was dominant in places in the interior forest 100 years ago, and mature Fagus trees were absent in secondary forests that had been grasslands in 1898. The expected number of juveniles decreased to one individual per 100 m² at 43.5 m from the mother tree. Conclusions: The pre‐industrialization landscape greatly affected recovery of Fagus forest. Forests found on the 1898 vegetation map might have acted as refugia for Fagus. The limited dispersal ability of Fagus suggests that it would take many generations (several hundred years) for Fagus forests to recover at the centre of what had been grasslands in the 19th century.     

Mitochondrial DNA Variation Follows a Geographic Pattern in Japanese Beech Species

The amount and distribution of mitochondrial (mt) DNA restriction fragment length polymorphism was determined among individual tree samples of two Japanese beech species, Fagus crenata and F.japonica. Individual plants were collected from 16 F. crenata populations throughout the range of the species, and from three F. japonica populations. We detected enough variation to characterize eleven and three chondriome types in F. crenata and F.japonica, respectively. The grouping of beech chondriome types based upon the cladistic analysis of mtDNA polymorphism allowed us to recognize the apparent geographical patterns of mtDIMA diversity: the resulting three main groups occupied distinct geographic areas. This geographic differentiation is likely to reflect the history of the Japanese beech forests after the last glacial period of the Pleistocene. In addition, the mtDNA polymorphism encountered within F. crenata encompassed all the variation observed in F.japonica. Our result suggests the need for re-evaluation of their phylogenetic relationships.     

Differences in sapling architecture betweenFagus crenata andFagus japonica

The ecological significance of architectural patterns for saplings ofFagus crenata andFagus japonica co-occurring in a secondary oak forest were evaluated by comparing the size and shape of leaves, trunks and crowns.Fagus japonica saplings were different fromF. crenata saplings in some architectural properties: (i) the leaf area and specific leaf area were larger; (ii) the ratio of sapling height to trunk length was lower, indicating greater leaning of the trunk; and (iii) the projection area of the crown was larger and the leaf area index lower indicating less mutual shading of leaves. These architectural features indicated thatF. japonica saplings were more shade tolerant thanF. crenata andF. crenata saplings were superior toF. japonica for growth in height and could, therefore, utilize sunlight in the upper layer. An erect trunk inF. crenata and a leaning trunk inF. japonica may be important characteristics associated with the regenerations patterns of each species; regeneration from seedlings under canopy gaps in the former and vegetative regeneration by sprouting in the latter.     

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.     

Pollen dispersal patterns and population persistence in a small isolated population of <Emphasis Type="Italic">Fagus crenata</Emphasis>

The potential of long-distance pollen dispersal and the effects of small population size and population isolation on persistence of Fagus crenata populations were investigated in a small, severely isolated population (the Gofuku-ji population) and two other populations located within 7 km of this population (including 87 adult trees in total). Parentage analysis using 13 microsatellite loci showed that 94 of 100 seedlings derived from seeds collected from the Gofuku-ji population had parent pairs within this population, six had one parent within the population, and four of the six seedlings had alleles that were not detected in any of the three populations, indicating that some pollen is dispersed over distances exceeding 7 km. The estimated expected heterozygosity and effective population size were lower in the Gofuku-ji population than in previously examined large continuous populations. Therefore, levels of genetic diversity within the population may have been reduced by strong genetic drift and limitations of pollen- and seed-mediated gene flow associated with the small size and severe isolation. The contemporary mating pattern estimated at the seedling stage was biased toward outbreeding, which may be explained by possible processes: the level of inbreeding in the adult trees is increased; then, inbreeding frequently occurs but is rarely successful, while outbreeding successfully produces offspring. Additionally, high levels of significant linkage disequilibrium and higher numbers of alleles than expected under mutation–drift equilibrium from analyses of the populations’ evolutionary history suggest that the Gofuku-ji population may have experienced admixture before its severe isolation. Therefore, the persistence of the Gofuku-ji population is being adversely affected by the decrease in population size and severe isolation. Further studies of gene flow via pollen in other populations with various degrees of isolation could enhance our understanding of the effects of population isolation and long-distance pollen dispersal in F. crenata and similar species.     

Climatic controls on distribution of Fagus crenata forests in Japan

Abstract. We used classification tree analysis to develop a climate‐based distribution model for Fagus crenata forests in Japan. Four climatic variables judged likely to affect the distribution of the species (summer and winter precipitation, minimum temperature of the coldest month and Kira's warmth index) were chosen as independent variables for the model. Latitudinal and longitudinal information was also used to examine effects of spatial autocorrelation on the model. The climatic factors associated with the distribution of the forests were analysed using a classification tree to devise prediction rules. Predicted areas of high probability for forest occurrence lay mainly on the Sea of Japan side of northern Honshu and southern Hokkaido. This is consistent with actual forest distribution. Some areas with high predicted probabilities of F. crenata forest occurrence were beyond the current natural northern range limits of these forests. Since these areas were widely scattered, it was assumed that the species has been hindered from colonizing them due to dispersal limitations. Deviance‐weighted scores, used to compare magnitudes of the contributions of predictor variables, revealed winter precipitation as the most influential factor, followed by the warmth index, the minimum temperature of the coldest month and summer precipitation. Attempts were made to generate ecological explanations for the effects of the four climatic factors on the distribution of F. crenata forests.     

Natural disturbance and tree species coexistence in an old-growth beech - dwarf bamboo forest,southwestern Japan

Abstract. The structure and composition of a cool-temperate old-growth beech (Fagus crenata) - dwarf bamboo (Sasa spp.) forest, partially affected by landslide disturbance, in the Daisen Forest Reserve of southwestern Japan, were investigated in relation to forest floor and canopy conditions. All stems ≥ 4 cm DBH were mapped on a 4-ha plot and analyses were made of population structure, spatial distribution and spatial association of major tree species. The dominant species, F. crenata, which had the maximum DBH among the species present, had the highest stem density. However, for other species, larger-sized species had lower stem density with few smaller stems or saplings, while smaller-sized species had higher stem density with many smaller stems or saplings. Canopy trees of F. crenata were distributed randomly in the plot, while its stems in the other layers and all other species were distributed patchily. Small patches represent gap-phase regeneration. Larger patches correlate with landslide disturbance, difference in soil age, or the presence/absence of Sasa. Cluster analysis for spatial associations among species and stems in the different layers revealed that the forest community consists of several groups. One main group was formed on sites not covered with Sasa. This group contained a successional subgroup (from Betula grossa to Acer mono and/or F. crenata) initiated by landslide disturbance and a subgroup of tree species that avoid Sasa. Another group was formed on sites with mature soils covered largely with Sasa. This contained associations of canopy trees of F. crenata and smaller-sized tree species such as Acanthopanax sciadophylloides and Acer japonicum. It is found that the community of this old-growth beech forest is largely organized by natural disturbance and heterogeneous conditions of the forest floor (difference in soil age and presence/absence of Sasa). The existence of these different factors and the different responses of species to them largely contribute to the maintenance of tree species diversity in this forest.; Keywords: Cluster analysis; Fagus crenata; Forest dynamics; Gap; Landslide; Spatial pattern.     

Tree competition and species coexistence in a cool-temperate old-growth forest in southwestern Japan

Abstract. The growth dynamics and mode of competition between adult trees ≥ 4 cm in DBH (stem diameter at breast height 1.3 m) of eight abundant species occupying ca. 90 % of the total basal area were investigated in a 4-ha study plot (200 m × 200 m) of a cool-temperate, old-growth forest on Mount Daisen, southwestern Japan. In the study plot, 30 tree species with individuals ≥ 4.0 cm DBH co-occurred. A bimodal DBH distribution showing upper and lower-canopy layers was found for the most dominant and largest species, Fagus crenata (ca. 78 % of the total basal area), whilst other tree species showed unimodal DBH distributions corresponding mostly to the lower-canopy layer. We developed a model for individual growth incorporating both intra and interspecific competition and the degree of competitive asymmetry. Onesided interspecific competition was detected only from Fagus crenata (upper-canopy species) to Acer japonicum and Acanthopanax sciadophylloides (lower-canopy species) on the scale of the 4-ha study plot. Only Acanthopanax sciadophylloides showed symmetric intraspecific competition. However, a positive (non-competitive) interspecific relationship between adult trees prevailed over a competitive relationship; for example, individual DBH growth rate of Fagus crenata (especially lower-canopy trees) was correlated with the abundance of Acer mono. The positive relationship represented a group of species with similar habitat preference [soil type (mature or immature) caused by landslide disturbance and the presence/absence of Sasa dwarf bamboos in the understorey], where tree densities were not so high as to bring about competition. Competitive interactions between adult trees ≥ 4 cm in DBH occurred only locally between a few specific species and were suggested to be almost irrelevant to the variation in species coexistence on the 4-ha scale of cool-temperate forest. Rather, the coexistence of 30 tree species (species diversity) on this large scale was suggested to be governed by the regeneration pattern of each component species (habitat preference, seedling establishment, sapling competition) with respect to landslide disturbance.     

Dwarf bamboo as an ecological filter for forest regeneration

Quantitative relationships between the aboveground biomass of dwarf bamboo, Sasa nipponica, and the survivorship and emergence of seedlings of Abies homolepis, Fraxinus lanuginosa f. serrata, and Fagus crenata were estimated. We show that dwarf bamboo acts as an ecological filter since the responses of tree species differ according to the biomass of dwarf bamboo. Deer exclusion without management of dwarf bamboo would make it impossible for any tree species to regenerate due to rapid increases in the biomass of dwarf bamboo.     

Didymella fagi sp. nov. and its anamorphAscochyta fagi, causing the yellow leaf spot disease ofFagus crenata andQuercus mongolica var.grosseserrata in Japan

AnAscochyta fungus was obtained during a survey of leaf spot diseases ofFagus crenata in the mountains of Aomori prefecture in 1995. The pathogenicity of the fungus toF. crenata was confirmed by inoculation. Its teleomorph was first found on artificially infected leaves after the leaves were placed in an incubator at 5°C with a 12-h photoperiod (approximately 500lx, daylight strip lamps) for 4 mo. The fungus was found to be the causal agent of yellow leaf spots ofF. crenata andQuercus mongolica var.grosseserrata in the field. Comparison with similar fungi so far described from Fagaceae indicated that the anamorph isAscochyta fagi and the teleomorph is an undescribed species ofDidymella. The nameDidymella fagi is introduced for the teleomorph. Correlation between the two morphs has been proved by cultural, morphological and pathological studies.     

Two types of matter economy for the wintering of evergreen shrubs in regions of heavy snowfall

Plant adaptation to an environment subject to heavy snowfalls was investigated in four species of evergreen shrubs growing in a Fagus crenata forest in an area of Honshu on the Sea of Japan. These shrubs stored carbohydrates in some organs before the snowy season and were covered with snow for 4–5 months. Aucuba japonica var. borealis, Camellia rusticana, and Ilex crenata var. paludosa maintained a reserve of carbohydrates during the snowy season. In Daphniphyllum macropodum var. humile, the reserve of carbohydrates decreased during winter. The respiration rates in the first three species decreased from autumn to winter, whereas the decrease in D. macropodum was slight. It was found that the first three species could use reserve carbohydrates for the growth of new shoots after the thaw, whereas in the last species the growth of new shoots depends on high photosynthetic activity in late spring. Our findings suggest some types of matter economy in evergreen shrubs for wintering in an environment of heavy snow.     

Gap dynamics in climaxFagus crenata forests

Gap characteristics and gap regeneration were studied in several climaxFagus crenata forests in Japan. 278 gaps were observed. Gaps covered 12% of the total land area of 20.05 ha. Gap density was 13.9 gaps per ha and, mean gap size was 92.0 m². Smaller gaps were much more frequent than larger ones. Gaps larger than 400 m² were rare. Most gaps were created by the death of single trees. Canopy trees died more often standing or with broken trunks than by uprooting, although uprooted trees were relatively abundant in the site with poor soil drainage and in the site on upper slope. Differences of gap regeneration behaviour were recognized among tree species.F. crenata regenerates in gaps from saplings recruited before gap creation and can replace not only its own gaps but also gaps of other species. Most species other thanF. crenata andMagnolia obovata could not regenerate in their own gaps. More successful regeneration ofF. crenata may occur in gaps smaller than 200 m², althought it regenerated in a wide range of gap size. However, increased relative density ofF. crenata in the canopy layer seems to prevent its successful regeneration. Gap regeneration of other species did not clearly depend on a species-specific gap size.     

Synchronized expression of FLOWERING LOCUS T between branches underlies mass flowering in Fagus crenata

Masting is the intermittent and synchronized production of a large amount of flower and seed in plant populations. This population-level phenomenon is caused by individual-level variability in reproduction and its synchrony between individuals. The variability at the individual level is induced by synchronized reproduction between branches within an individual because a tree is an assemblage of branches that are considered as semiautonomous units. However, there have been no empirical studies that quantify the degree of reproductive synchrony at the branch level within the same tree in masting species. Here, we evaluated the reproductive synchrony within individuals by monitoring flowering dynamics and expression level of a flowering-time gene at the branch-level in a typical masting species, Fagus crenata Blume. The 4-year census showed that the branch-level gene expression was highly variable between years and was strongly synchronized between branches. The branch-level synchrony in flowering-time gene expression was followed by coherent flowering cycle at the whole individual. To examine the causal relationship between gene expression and climatic factors, we performed a nonlinear statistical analysis called convergent cross-mapping using the time course data of gene expression and environmental variables. Our results indicated that the observed gene expression pattern was well cross-mapped by temperature or precipitation. However, this cross-mapping skill was lower than that of randomly generated seasonal dynamics, implying a combination of internal and external environmental signals is more likely to regulate gene expression dynamics in F. crenata. Our results provide the first empirical evidence that synchronized expression of a flowering-time gene between branches underlies integrated flowering behavior at the individual level.     

Relationships between vessel element anatomy and physiological as well as morphological traits of leaves in <Emphasis Type="Italic">Fagus crenata</Emphasis> seedlings originating from different provenances

We attempted to observe differences in vessel element anatomy, and physiological and morphological traits of leaves in Fagus crenata seedlings originated from seven different provenances grown under the uniform environmental conditions. We also investigated the relationships between the anatomical characteristics of the vessel elements and physiological plus morphological traits of leaves in Fagus crenata seedlings. To carry out the experiments, Fagus crenata samples were prepared from Chichibu Research Forest of Tokyo University. For anatomical studies of the vessel elements, vessel number per mm², average vessel area, and the percentage of vessel area from the pith to the bark side were measured. We also measured transpiration rate, stomatal conductance, leaf area, leaf thickness, leaf dry mass per unit leaf area and leaf density for foliar studies. The anatomical characteristics of the vessel elements as well as the physiological and morphological traits of leaves were noticeably different among provenances. In addition, we found significant correlations between the foliar characteristics not only with vessel number per mm², but also with vessel area percentage and sum of the (vessel area)², theoretical hydraulic conductivity, from the pith to the bark side. Therefore, we concluded that variations in physiological and morphological traits of leaves in response to provenance variation were in correspondence with vessel number per mm² as a parameter that determines the total vessel area and consequent water hydraulic conductance in Fagus crenata as a diffuse porous hardwood.     

The genus Ponticulomyces (Physalacriaceae, Agaricales) from Japan

Two species of the genus Ponticulomyces collected from Japan for the first time are described and illustrated. Ponticulomyces kedrovayae is characterized by its lamellae staining yellow when bruised and in age, stipe lacking an annulus and a pseudorhiza, scattered pileal hairs, and large amygdaliform basidiospores. It mainly occurs on dead wood of Fagus crenata. Ponticulomyces orientalis is characterized by its scattered pileal hairs and broadly ellipsoid to ellipsoid basidiospores. It was collected mostly on dead wood of Cameria japonica.     

Influence of canopy tree phenology on understorey populations of Fagus crenata

Question: Is light available for subcanopy individuals of Fagus crenata spatiotemporally heterogeneous across patches with closed canopies of different foliage phenologies and gaps? Is local abundance of Sasa influenced by the composition of the canopy layer? If so, does the Sasa layer also affect the amount of light available to small F. crenata saplings? Is variation in F. crenata population structure consistent with the hypothesis that light is important? Location: Mt. Kurikoma, Japan 780 m a.s.l. Methods: Population structure of subcanopy individuals of Fagus crenata and importance of Sasa were examined in five patch types. The patch‐types were Fc (F. crenata only in the crown), Qm (Quercus mongolica var. grosseserrata only in the crown), Mo (Magnolia obovata only in the crown), Fc’ (periphery of F. crenata) and Gap. Seasonal changes in light availability above and below the Sasa layer was examined by using hemispherical photographs and quantum sensors. Results: Subcanopy individuals of F. crenata began unfolding their leaves approximately one month earlier than canopy trees of Q. mongolica var. grosseserrata and M. obovata, but a few days later than those of adult F. crenata. Accumulated photosynthetic photon flux density above the Sasa layer was greatest in Qm and Mo, and lowest in Fc. Importance of Sasa was highest in Gap. Maximum height and the number of subcanopy individuals of F. crenata were greatest in Qm, followed by Mo, and lowest in Fc. Conclusions: Differences in canopy layer composition probably influence the regeneration of F. crenata both directly through their foliage phenologies, and also indirectly by determining the importance of Sasa.