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PubMed2003

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.

Genetic Variation↗
PubMed2005

Mating patterns of a subdivided population of the andean oak (Quercus humboldtii Bonpl., Fagaceae).

Mating patterns play a critical role in the maintenance of genetic variation. We analyzed the mating system in a recently fragmented population of the Andean oak (Quercus humboldtii) using four microsatellite loci. Five fragments in northeastern Colombia, South America, were selected consisting of 30.4 trees on average. We sampled about 30 seeds from three target trees in each fragment and genotyped them with four microsatellite loci with a total of 40 alleles across loci. Progenies were analyzed under the mixed mating system model (MLTR program) and the TwoGener pollen pool structure analyses. The number of unshared pollen donors per family (Nu) was estimated using gametotypic counts with the program HAPLOTYPES. Low selfing (3%) is occurring at the population and fragment level. Biparental inbreeding is present (4.9%), but reduced, in the largest fragment. The average pollen neighborhood size (Nep = 5.1 to 6.1) appears comparable to other oak species in sparse landscapes. In contrast, Nu consists of 2 to 4 main donors, although up to 12 are possible, with the mode positively correlated with fragment size. The Andean oak appears to be a resilient species capable of tolerating population subdivision, provided landscapes include large fragments.

Colombia↗
PubMed2006

Mating patterns of black oak Quercus velutina (Fagaceae) in a Missouri oak-hickory forest.

Wind-pollinated forest trees usually have high outcrossing rates, but allogamy does not necessarily translate into high pollen movement. The goal of this study was to determine the outcrossing rates, pollen pool genetic structure, and the size of the effective pollination neighborhood in a population of black oak, Quercus velutina, in a Missouri oak-hickory forest. Based on 6 allozyme loci, 12 maternal trees, and 439 progenies sampled along a transect of 1300 m, we found complete outcrossing (t(m) = 1.000, P < 0.001) and small amounts of biparental inbreeding. Using a TwoGener analysis of the pollen gene pool, we found significant structure across maternal plants (Phi(FT) = 0.078, P < 0.001), which when corrected for adult inbreeding translates into Phi(FT) = 0.066 that corresponds to an effective number of pollen donors of 7.5 individuals. Assuming a bivariate normal distribution and an adult density of 16.25 trees ha(-1), we estimated that the effective pollination neighborhood area had a radius of 41.9 m. Even assuming that our estimates may be conservative, these findings join a growing body of evidence that suggest that the local neighborhood of wind-pollinated forest tree populations may be relatively small creating opportunities for local selection and genetic drift.

Crosses, Genetic↗
PubMed2005

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

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.

DNA, Chloroplast↗
PubMed2000

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.

Journal Article↗
PubMed2000

Post-fire recolonization of dominant epiphytic lichen species on Quercus hypoleucoides (Fagaceae).

Following a forest fire (27 500 ha) in 1994, post-fire recolonization of Quercus hypoeleucoides by epiphytic lichens was documented as changes in lichen cover, number of small thalli, specific factors that affected reestablishment of lichens, and modes of dispersal. Three sites in the Chiricahua Mountains (Arizona, USA) were chosen according to the severity of fire damage-unburned, moderately burned, and severely burned. From 1994 through 1997, the amount of dead lichen cover significantly increased at the moderately burned site. For the same time period, the amount of live lichen cover significantly increased at the severely burned site. Numbers of new thalli increased significantly at the severely burned site each year but only in the last year (1996-1997) for the moderately burned site. Bark texture and proximity to trees with lichens were among the most important physical factors for recolonization. The most important means of dispersal for Flavopunctelia praesignis was fragmentation. For Punctelia hypoleucites, the primary means of dispersal was spores. Increases in live lichen cover and numbers of new thalli occur faster in severely burned areas probably due to the loss of lichens on tree trunks, which provides space and a lack of competition.

Journal Article↗
PubMed2005

Comparison of quantitative trait loci for adaptive traits between oak and chestnut based on an expressed sequence tag consensus map.

A comparative genetic and QTL mapping was performed between Quercus robur L. and Castanea sativa Mill., two major forest tree species belonging to the Fagaceae family. Oak EST-derived markers (STSs) were used to align the 12 linkage groups of the two species. Fifty-one and 45 STSs were mapped in oak and chestnut, respectively. These STSs, added to SSR markers previously mapped in both species, provided a total number of 55 orthologous molecular markers for comparative mapping within the Fagaceae family. Homeologous genomic regions identified between oak and chestnut allowed us to compare QTL positions for three important adaptive traits. Colocation of the QTL controlling the timing of bud burst was significant between the two species. However, conservation of QTL for height growth was not supported by statistical tests. No QTL for carbon isotope discrimination was conserved between the two species. Putative candidate genes for bud burst can be identified on the basis of colocations between EST-derived markers and QTL.

Adaptation, Physiological↗
PubMed2003

Female flower and cupule structure in Balanopaceae, an enigmatic rosid family.

The Balanopaceae, whose flowers were poorly known, have, in the past, been variously allocated to the Fagales, Euphorbiaceae, Salicales or other hamamelids and rosids (these groups being in Fagales, Malpighiales and Saxifragales, according to the Angiosperm Phylogeny Group). This paper attempts a clarification based on flower morphology. Female flowers and cupules were studied in Balanops vieillardii, young fruits in B. australiana. The cupules are simple involucres of bracts which are spirally arranged (according to a Fibonacci pattern) on the floral axis preceding the flower. They contrast with the complicated cupules of Fagaceae which consist of a condensed cymose ramification system of axes of several orders around the flower. Flowers appear later than most of the cupular bracts, in contrast to Fagaceae. In addition to a terminal flower there may be several smaller lateral flowers in the axil of cupular bracts, each surrounded by its own small cupule. The female flowers do not have a perianth. They consist of two to three large carpels. At anthesis, the ovary is completely septate; the syncarpous part (ovary and lower style) is completely symplicate. The carpels are free for most of their length, with the free parts once, twice or three times bifurcate, in contrast to simple in Fagales. The stigmatic surface covers the ventral side of each stigmatic branch and at the margins also spreads to the dorsal side. The stigma is wet and secretion appears holocrine. The two ovules per carpel are collateral and axile in early development. However, at anthesis they appear one above the other, because in one ovule the funicle greatly elongates. As the ovary elongates only above the placenta, the ovules appear basal at anthesis. The ovules are (weakly) crassinucellar, bitegmic (not unitegmic), anatropous, and intermediate between apotropous and epitropous (not apotropous). The ovules are mature at anthesis, in contrast to Fagales. In mature ovules the upper part of the nucellus disintegrates, and a weakly differentiated endothelium is present in the inner integument. The morphological results of this study support a position of Balanopaceae in Malpighiales, and not Fagales or other orders, and are thus in accordance with recent molecular results based on chloroplast rbcL sequences data. However, within Malpighiales, as opposed to molecular results, Balanopaceae agree more with Euphorbiaceae s.l. than with Dichapetalaceae/Trigoniaceae and Chrysobalanaceae/Euphroniaceae.

Flowers↗
PubMed1992

Allergenic pollens and pollinosis in Italy: recent advances.

The authors have mapped the occurrence of allergenic pollens throughout Italy and defined their most common clinical symptoms. To obtain an accurate aerobiological and clinical picture of such a geographically complex country as Italy, a detailed investigation was carried out involving 80 data-gathering stations and 40 clinical centers nationwide. Three main pollination periods can be distinguished: winter-pre-spring (January to March) for Betulaceae, Corylaceae, Cupressaceae, Salicaceae and Ulmaceae: spring-summer (April to June) for Gramineae, Urticaceae, Oleaceae, Plantago, Fagaceae, Pinaceae and Polygonaceae, and summer-autumn (August to September) for Urticaceae, Compositae and Chenopodiaceae. Examination of 49,660 patients affected by pollinosis (conjunctivitis, rhinitis, asthma, with positive skin tests or IgE-specific serum determination: RAST, ELISA) throughout Italy revealed sensitivity to Gramineae in 64.6%, to Parietaria in 36.7% to Olea in 15.8%, to Compositae in 13.2%, to Betulaceae-Corylaceae in 7% and to Fagaceae-Cupressaceae-Plantago in 4%-10%; marked regional variations were observed. The patients suffered from rhino-conjunctivitis (55.7%), rhino-conjunctivitis plus asthma (31.6%) and asthma (12.7%). In monosensitised individuals, Parietaria was seen to be the main cause of the asthmatic syndrome (though our preliminary data also implicate Olea) followed by Gramineae.

Air Pollution↗
PubMed2006

Biogeography, host specificity, and molecular phylogeny of the basidiomycetous yeast Phaffia rhodozyma and its sexual form, Xanthophyllomyces dendrorhous.

Phaffia rhodozyma (sexual form, Xanthophyllomyces dendrorhous) is a basidiomycetous yeast that has been found in tree exudates in the Northern Hemisphere at high altitudes and latitudes. This yeast produces astaxanthin, a carotenoid pigment with biotechnological importance because it is used in aquaculture for fish pigmentation. We isolated X. dendrorhous from the Southern Hemisphere (Patagonia, Argentina), where it was associated with fruiting bodies of Cyttaria hariotii, an ascomycetous parasite of Nothofagus trees. We compared internal transcribed spacer (ITS)-based phylogenies of P. rhodozyma and its tree host (Betulaceae, Corneaceae, Fagaceae, and Nothofagaceae) and found them to be generally concordant, suggesting that different yeast lineages colonize different trees and providing an explanation for the phylogenetic distance observed between the type strains of P. rhodozyma and X. dendrorhous. We hypothesize that the association of Xanthophyllomyces with Cyttaria derives from a previous association of the yeast with Nothofagus, and the sister relationship between Nothofagaceae and Betulaceae plus Fagaceae correlates with the phylogeny of X. dendrorhous strains originating from these three plant families. The two most basal strains of X. dendrorhous are those isolated from Cornus, an ancestral genus in the phylogenetic analysis of the host trees. Thus, we question previous conclusions that P. rhodozyma and X. dendrorhous represent different species since the polymorphisms detected in the ITS and intergenic spacer sequences can be attributed to intraspecific variation associated with host specificity. Our study provides a deeper understanding of Phaffia biogeography, ecology, and molecular phylogeny. Such knowledge is essential for the comprehension of many aspects of the biology of this organism and will facilitate the study of astaxanthin production within an evolutionary and ecological framework.

Base Sequence↗
PubMed2003

Cotyledon storage proteins as markers of the genetic diversity in Castanea sativa Miller.

This study has been to analyse the useful nut globulin proteins as a marker of the genetic diversity in Castanea sativa. The evaluated populations were highly polymorphic for the globulins, being detected up to 35 polymorphic bands with a wide distribution among all the evaluated populations. Taken together for populations from all the chestnut regions, about 39.3% of total allelic variation was distributed among the populations. The estimates of genetic similarity between populations were clearly associated with the collecting site. This method of analysis of the nut storage proteins (globulins) could be a useful tool for the evaluation of genetic diversity in this and other species of the Fagaceae.

Alleles↗
PubMed2003

Comparative mapping between quercus and castanea using simple-sequence repeats (SSRs).

Simple sequence repeat (SSR) markers from Quercus and Castanea were used for comparative mapping between Quercus robur (L.) and Castanea sativa (Mill.). We tested the transferability of SSRs developed in Quercus to Castanea and vice-versa. In total, 47% (25) of the Quercus SSRs and 63% (19) of the Castanea SSRs showed a strong amplification product in the non-source species. From these 44 putative comparative anchor tags, 19 (15 from Quercus and 4 from Castanea) were integrated in two previously established genetic linkage maps for the two genera. SSR loci were sequenced to confirm the orthology of the markers. The combined information from both genetic mapping and sequence analysis were used to determine the homeology between seven linkage groups, aligned on the basis of pairs or triplets of common markers, while two additional groups were matched using a single microsatellite marker. Orthologous loci identified between Q. robur and C. sativa will be useful as anchor loci for comparative mapping studies within the Fagaceae family.

Base Sequence↗
PubMed2004

Pollen-tube growth and fertilization mode in Gymnostoma (Casuarinaceae): their characteristics and evolution.

A unique mode of fertilization called "chalazogamy", whereby the pollen tube passes through the chalaza instead of the micropyle, is known in several species of derived genera in Casuarinaceae. In this paper we report the occurrence of chalazogamy in Gymnostoma ( G. poissonianum), the most primitive genus in the family. We also show that the pollen tube grows discontinuously from the stigma to ovules in about 3 months. At the time of pollination, the ovules have not yet formed in the ovary, and require a long time to develop. The pollen tube(s) lie in a zigzag line and are branched in the upper region of the style, and their growth is arrested there until the ovary develops further. Studies of the relevant literature further revealed discontinuous pollen-tube growth in relation to a prolonged period between pollination and fertilization, as well as chalazogamy, in Betulaceae, Juglandaceae and/or Fagaceae that are closely related to Casuarinaceae. This feature may have derived early in the evolution of Fagales.

Betulaceae↗
PubMed2006

Molecular evidence for an Asian origin and a unique westward migration of species in the genus Castanea via Europe to North America.

The genus Castanea (Fagaceae) is widely distributed in the deciduous forests of the Northern Hemisphere. The striking similarity between the floras of eastern Asia and those of eastern North America and the difference in chestnut blight resistance among species has been of interest to botanists for a century. To infer the biogeographical history of the genus, the phylogeny of Castanea was estimated using DNA sequence data from different regions of the chloroplast genome. Sequencing results support the genus Castanea as a monophyletic group with Castanea crenata as basal. The three Chinese species form a strongly supported sister clade to the North American and European clade. A unique westward expansion of extant Castanea species is hypothesized with Castanea originating in eastern Asia, an initial diversification within Asia during the Eocene followed by intercontinental dispersion and divergence between the Chinese and the European/North American species during the middle Eocene and a split between the European and the North American species in the late Eocene. The differentiation within North America and China might have occurred in early or late Miocene. The North America species are supported as a clade with C. pumila var. ozarkensis, the Ozark chinkapin, as the basal lineage, sister to the group comprising C. pumila var. pumila, the Allegheny chinkapin, and Castanea dentata, the American chestnut. Morphological evolution of one nut per bur in the genus may have occurred independently on two continents.

Base Sequence↗
PubMed2001

The potential role of orbicules as a vector of allergens.

BACKGROUND: In the locules of anthers of flowering plants, tiny (1.5-2 microm) granules of sporopollenin may occur next to the pollen grains. Those granules, called orbicules, mostly occur on the radial and innermost tangential wall of secretory tapetum cells. METHODS: We have investigated the presence of orbicules in 15 important European allergenic species with scanning electron microscopy (SEM). RESULTS: Orbicules were present in all species investigated of the families Betulaceae, Chenopodiaceae, Fagaceae, Poaceae, Polygonaceae, and Urticaceae. However, in the Asteraceae and Oleaceae species studied, orbicules were lacking. In all Chenopodiaceae, Poaceae, and Urticaceae species, orbicules were attached to the pollen exine. These observations indicate the possibility of the dispersal of orbicules into the atmosphere during anthesis. CONCLUSIONS: The hypothesis of the potential role of orbicules as possible important vectors of allergens is put forward, based on the comparison of our results with recent literature about the evidence of allergenic activity in the smaller micronic atmospheric aerosol fraction. Our results provide evidence that an in-depth investigation of the sites of allergens across the whole anther is required. We suggest that allergen researchers apply immunoelectron microscopy on whole anthers to determine whether orbicules possess allergens.

Allergens↗
PubMed2002

Spatial pattern of chloroplast DNA variation of Cyclobalanopsis glauca in Taiwan and East Asia.

This study examined the spatial pattern of chloroplast DNA (cpDNA) variation in Cyclobalanopsis glauca (Thunb. ex Murray) Oerst. (Fagaceae) in 140 trees from Taiwan (25 populations), Japan (three), Ryukyus (two), Hong Kong (one) and Mainland China (one). By sequencing three cpDNA intergenic spacer fragments using universal primers (trnT-trnL, trnV-trnM, including the trnV intron, and petG-trnP), we found a total of 1,980 bp and 15 polymorphic sites. Among them, 12 sites were caused by point mutation, and three resulted from insertion. This gives rise to a total of 13 cpDNA haplotypes. The level of differentiation among the populations studied is relatively high (GST = 0.612). Two ancestral haplotypes (A and B) are distributed widely in East Asia. Interestingly, all the derived cpDNA variations are found only in Taiwan but not in other areas. The Central Mountain Ridge (CMR) of Taiwan creates an unsurpassed barrier to the east-west gene flow of C. glauca. Among the populations on the west of CMR, only three separated populations, Yangmingshan, Wushe and Chinshuiying, have high haplotype diversity, each consisting of sister haplotypes all mutated from the same ancestral haplotype. Thus, they have probably originated from de novo mutation after the last glaciation. This inference agrees with the observation that no spatial autocorrelation existed on the west side. Two unrelated dominant lineages on the east of the CMR (haplotypes D and F) showed significant spatial genetic structure. Estimate of NST - GST was -0.090 and differed significantly from zero. Thus at the local scale, the phylogeographical component of the genetic structure is significant on the east of the CMR. Accompanied by published palynological records of the last glaciation, this study suggests the possibility that these two types were colonized northward from the southeastern part of Taiwan. 'Star-like' genealogy is characterized, with all the haplotypes coalescing rapidly and as a general outcome of population expansion (Page & Holmes 1998). A neutrality test also suggested a demographic expansion recovered from a bottleneck. We therefore inferred that the southeastern part of Taiwan might be a potential refugium for C. glauca.

DNA, Chloroplast↗
PubMed2002

Spatial arrangement of branches in relation to slope and neighbourhood competition.

To gain a better understanding of the effects of spatial structure on patterns of neighbourhood competition among hardwood trees, the three-dimensional extension of primary branches was surveyed for ten community-grown Castanea crenata (Fagaceae) trees with respect to the positioning of neighbouring branches and the slope of the forest floor. There were significantly more branches extending towards the lower side of the slope than towards the upper side, but structural properties such as branch length and vertical angle were not affected by slope. When horizontal extension of a branch towards its neighbour was compared for a C. crenata branch and a neighbouring heterospecific, the former was significantly narrower than the latter when the inter-branch distance (horizontal distance between the base positions of two neighbouring branches) was short (< approx. 5 m). Castanea crenata branches tended to extend in a direction avoiding neighbouring branches of heterospecifics when the inter-branch distance was short. Furthermore, for an inter-branch distance <3 m, the horizontal extension of a C. crenata branch was less when it was neighbouring a heterospecific branch than when neighbouring a conspecific branch. These results suggest that horizontal extension of C. crenata branches is more prone to spatial invasion by nearby neighbouring branches of heterospecifics, and that the invasion can be lessened when C. crenata trees are spatially aggregated. The reason why such an arrangement occurs is discussed in relation to the later leaf-flush of C. crenata compared with that of other species in the forest.

Computer Simulation↗
PubMed2006

Shoot life span in relation to successional status in deciduous broad-leaved tree species in a temperate forest.

In trees, leaf life span is closely related to successional status. Although leaves are attached to shoots, shoot life span has been insufficiently studied in the context of ecological systems. Interspecific variation in shoot survivorship was investigated over 27 months in 15 temperate hardwood tree species. Relationships between shoot architecture and shoot survival were also investigated. Shoot life span was shortest in early successional species, and longest in late successional species, in each of the families Betulaceae and Fagaceae. In Salicaceae, all of which were early successional species, shoot life span was longer in mountainous than in riparian species. Early successional or riparian species distributed longer shoots densely, even in proximal positions on mother shoots, resulting in mutual shading and consequent early and massive shoot shedding. By contrast, late successional or mountainous species concentrated shoots in distal positions, allowing shoots to receive equally favorable light, resulting in a longer life span. These results reveal close relationships between shoot life span and environmental resource availability or successional status and suggest a causal relationship between shoot shedding and shoot architecture.

Betulaceae↗