Phylogeography of the Southeast Asian stone oaks (Lithocarpus)

Abstract Aim To describe current geographical patterns of genetic diversity and infer the historical population dynamics of the stone oaks (Lithocarpus) in Southeast Asia. Location We sampled three populations in Indochina: (1) Yunnan province, China; (2) Pyin Oo Lwin area, Myanmar and (3) north‐western Vietnam; two in western Borneo: (1) South‐western Sarawak and (2) West Kalimantan, Indonesia; two in central Borneo: (1) north coastal Sarawak and (2) north‐eastern Sarawak, Malaysia; and two in northern Borneo: (1) Central Sabah and (2) Northern Sabah, Malaysia. Methods A phylogenetic reconstruction of chloroplast DNA sequence variation from numerous individuals of multiple species was used to determine geographical distribution of genetic diversity. A resampling scheme was used to determine the significance of these patterns at different hierarchical levels of the phylogeny. Results were compared with a previously published set of nuclear DNA sequence data. Results A high level of chloroplast sequence variation was found, which was divided equally between two major clades separated by four non‐homoplasious changes. One clade was confined to the island of Borneo, while the other was widespread. Strong geographical structure was observed in the chloroplast sequence variation. The Indo‐chinese populations were much more closely related than expected, comparable with the highly endemic and isolated population on the western coast of Borneo. Conversely, individuals from the Kelabit Highlands were found to be more distantly related than expected. The highest levels of genetic endemism were observed in western Borneo. More geographical structure was observed in the Bornean clade than in the Widespread clade, because of limited genetic diversity in the Widespread clade. Relatively weak geographical structure was found in the nuclear sequence variation: only populations in southern China and central Sabah were significantly related. Conclusions The high levels of chloroplast genetic diversity and the persistence of an ancestral haplotype that is a single step away from a haplotype found in Castanopsis indicates the continuous presence of tropical rain forest in Southeast Asia throughout the evolutionary history of the genus (c. 40 Myr). This conclusion is supported by the high frequency of numerous endemic types observed in every population and the relatively few number of ‘missing’ haplotypes. This situation suggests both limited migration and limited extinction. In contrast, the nuclear genetic diversity contained less geographical structure, indicating that our taxonomic sampling among populations was unbiased and that gene flow mediated through pollen is less geographically restricted and contains less geographical structure than purely seed‐mediated (chloroplast) gene flow. The most likely scenario suggested by the evidence involves four major patterns: (1) the widespread presence of an ancestral haplotype; (2) the large degree of separation (four non‐homoplasious base pairs) between the types found in the two major clades; (3) the concentration of derived types from both major clades found in central and northern Borneo; and (4) the molecular endemism found in each location. These patterns suggest four primary things about the population dynamics of Lithocarpus since the late Eocene: (1) populations have either spanned the entire region throughout much of the evolutionary history of the genus or substantial populations have persisted in both Indochina and Borneo with limited migration between them; (2) significant fragmentation has occurred subsequently between the Asian mainland and the Melasian island archipelago, leading to independent genetic diversification in both regions; (3) several locations possessing significant independent histories, have experienced little migration and have never gone completely extinct; and (4) that the central highlands of Borneo have been re‐invaded from the north and the west. The timing of these events is difficult to ascertain but probably predate the Quaternary Period, suggesting that although the recent ice ages might have affected the overall distribution of rain forest in Southeast Asia, it managed to persist in most regions even through the most dramatic drying events.     

Aerobiology of Fagaceae pollen in Trieste (NE Italy)

The aerobiological behaviour of Fagaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen grains of Castanea, Fagus and Quercus were collected from 1990 to 2003 using a Hirst type spore trap. The main pollen season (MPS) takes place in April and May for Quercus and Fagus, in June and July for Castanea. The highest values occur in year 1993 for Quercus, in 1998 for Castanea and in 1992 for Fagus. The Fagaceae content of the air is mainly due to Quercus and Castanea pollen, Fagus usually having a scarce pollen shedding in Trieste. The highest counts of Fagaceae pollen grains are found from late April to mid May and are mainly due to the pollen shedding of oaks. The cumulative counts vary over the years, with a mean value of 2.719 pollen grains, a lowest total of 1.341 in 2002 and a highest total of 4.704 in 1993. No positive nor negative long-term trends in pollen shedding are found. No cyclic variations were observed. Spearman’s correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data. Daily pollen concentrations present sometimes positive correlation with temperature, negative with rainfall and wind speed, and no correlation with humidity. Fagus and Quercus start dates result positively correlated between themselves. Significant correlations are found between the start of MPS and the mean and maximum temperature in March for Fagus and Quercus, and May for Castanea.     

Triterpene hexahydroxydiphenoyl esters and a quinic acid purpurogallin carbonyl ester from the leaves of Castanopsis fissa

Triterpene hexahydroxydiphenoyl (HHDP) esters have only been isolated from Castanopsis species, and the distribution of these esters in nature is of chemotaxonomical interest. In this study, the chemical constituents of the leaves of Castanopsis fissa were examined in detail to identify and isolate potential HHDP esters. Together with 53 known compounds, 3,4-di-O-galloyl-1-O-purpurogallin carbonyl quinic acid (1) and 3,24-(S)-HHDP-2α,3β,23,24-tetrahydroxytaraxastan-28,20β-olide (2) were isolated and their structures were elucidated by spectroscopic and chemical methods. The polyphenols of the leaves were mainly composed of galloyl quinic acids, triterpenes HHDP esters, ellagitannins and flavonol glycosides. In particular, the isolation yields of 1,3,4-trigalloyl quinic acid and compound 2 were 1.53% and 0.27%, respectively, from the fresh leaves. The presence of lipid soluble HHDP esters of oleanane-type triterpenes as one of the major metabolites is an important chemotaxonomical discovery. Lipase inhibition activities and ORAC values of the major constituents were compared. The triterpene HHDP ester showed moderate lipase inhibition activity and myricitrin gave the largest ORAC value.     

中国水青冈属（壳斗科）叶结构及分类学意义

叶结构对壳斗科（Fagaeeae）现存植物和化石的鉴定具有重要意义。通过对水青冈属5种植物叶结构特征进行细致的研究,结果发现水青冈属植物叶脉有羽状弓形脉、羽状半达缘脉两种类型;三级脉有波状对生贯穿、互生贯穿及混合贯穿三种类型：小脉缺失、简单无分支或一次分支：脉间区发育良好,网眼有三边形、四边形和五边形三种类型,排列规则;具齿种类叶齿由齿主脉和齿侧脉构成,齿侧脉环状。研究结果表明水青冈属二级脉与更高级脉序形成的结构稳定且存在种问差异．具重要分类学价值。基于水青冈属叶结构特征观察结果,本次研究编制了水青冈属植物的分种检索表：参照已有研究结果并结合重要外部形态学特征,编制了壳斗科相关类群分属检索表。     

中国壳斗科植物属的分布区定量研究

通过植物专业网站及发表的论文论著,收集每一种壳斗科植物在中国的具体分布地点（县）,并采用地理信息系统技术,以县为空间数据的基本单元,以壳斗科植物为研究对象,制作属的空间分布图,从图中定量地提取斑块的数目、面积、周长,计算形状指数、最大斑块指数,以及属的Shannon均匀度指数、Simpson均匀度指数,分析中国壳斗科植物属的空间分布及其特点,为植物区系空间分布定量研究提供依据。结果表明：（1）中国壳斗科植物属的空间分布呈现连续分布或间断分布,间断分布有星散分布、主次分布区、主分布区3种类型,以图形和定量的方式体现出属在空间上的分布差异。（2）中国壳斗科植物属的分布区或最大斑块的分布区在中国亚热带,能连续分布到热带,但在温带斑块分散,面积小,由此推断中国亚热带植物区系应划分为古热带植物区。（3）根据三棱栎属、锥属、柯属在世界和中国的分布,推断它们均为热带亚洲和热带美洲洲际间断分布。     

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.     

福建壳斗科部分植物染色体计数及核型分析

采用去壁低渗法处理根尖细胞,得到了壳斗科13种植物分散较好的细胞中期分裂相,并分析了其中9种植物的染色体数目、随体数目和位置、核型公式、核型类型、臂比、相对长度、着丝点指数、核型不对称系数等内容。结果表明:除东南石栎属1B型外,其他均属2B型,K(2n)=24,在植物界属小染色体类型。