|其他题名||Leaf cuticular morphology in Castanopsis, Castanea and Chrysolepis with reference to its taxonomic and ecological implications
|摘要||本文对栲属Castanopsis及其邻近属栗属Castanea、金鳞果属Chrysolepis的叶表皮和叶结构、胚胎发育和地理分布进行了分析和研究, 并且结合其它的形态学资料对栲属、栗属、金鳞果属、石栎属Lithocarpus和栎属Quercus等属的共71种进行了分支系统分析, 主要研究结果如下：
选用栲属植物41种, 栗属植物6种和金鳞果属1种, 利用光学显微镜和扫描电镜进行了叶表皮研究。栲属叶的气孔只分布在下表皮, 为环列型, 副卫细胞壁加厚, 染色深；栲属植物绝大多数种的下表皮都分布有薄壁盾状毛。栗属植物的气孔为无规则型或环列型-无规则型之间的过渡类型；金鳞果属中有厚壁的盾状毛, 环列型气孔的副卫细胞壁没有加厚。叶表皮特征比较结果表明金鳞果属与栲属和栗属有明显的不同, 支持把金鳞果属从栲属划分出来独立成属的处理。研究支持分子系统学研究中栲属和栗属姊妹群关系以及栲属-栗属同栎属的亲密关系。叶表皮特征中里, 毛被类型以及毛被分布情况, 气孔类型以及气孔密度具有一定的生态学意义, 同时对于壳斗科叶化石的鉴定都具有重要的意义。
我们对壳斗科栲属及其邻近属的叶结构进行了研究, 并且结合前人对于壳斗科叶结构的研究结果对其分类学意义进行了讨论。叶结构的许多特征对于鉴定壳斗科叶化石的鉴定都具有重要价值。叶结构的许多特征，例如脉序类型, 二级脉的数目, 齿的类型, 三级脉的类型及其排列和小脉分支等特征非常稳定而有明显的区别, 在鉴定壳斗科叶材料中有重要意义。
在栗属中, 二级脉倾向于平行排列, 二级脉和齿分布均匀, 齿的类型为刺状齿或冷琴所说的U3荨麻型齿。而栲属有齿类叶和栗属最大的区别是栲属中齿一般只在叶片2/3以上分布并且往往是不均匀的。金鳞果属的叶片全缘而且常有些反卷, 二级脉有7-9对, 三级脉非常稀疏为极弱贯穿型。由于大量的壳斗科叶化石属于印痕化石, 能够利用的就是叶结构特征, 所以对于壳斗科叶印痕化石鉴定叶结构特征具有重要的价值。野外工作中在壳斗科花和果实材料不可得到的情况下, 叶结构特征对于采集材料的初步鉴定也有帮助。在总结前人对壳斗科叶结构和叶表皮研究和本研究结果基础上列出了属的检索表和70个种的检索表。
对壳斗科植物共71种植物选取了包括叶结构、叶表皮、果实和壳斗等在内的75个特征, 并且以三棱栎Trigonobalanus s.l.为外类群, 构建了邻接树。结果表明, 叶结构特征在不同属之间的一定的镶嵌性, 根据叶结构特征来划分属存在一定的困难, 而叶表皮特征中毛被类型和气孔类型在属间区分中是最为有效的特征。如石栎属特有的指状毛, 金鳞果属的厚壁盾状毛, 栲属的薄壁盾状毛以及副卫细胞加厚的环列型气孔等形状在鉴定化石中对于要把化石鉴定到属的水平最具有重要的价值。根据毛被情况把栲属分为6个群, 群的划分和叶缘/脉序类型有很大的关系。龙州栲和石栎属在分支关系上很接近, 并且受到叶表皮特征的支持。
根据叶结构、叶表皮、果实和壳斗等在内的75个特征所建立的邻接树的分支情况大体上和壳斗科根据花、壳斗特征建立的分类系统基本一致, 但是有存在不一致的情况, 仅仅根据花、壳斗特征建立的分类系统具有一定的不合理性。
以高山栲为研究材料首次报道栲属的胎胚学特征, 并且同壳斗科其它一些类群进行了比较。花药壁基本型有四至五层（宿存的表皮, 具纤维加厚的药室内层、1-2 层中层和一层腺质型绒毡层）。小孢子发生属同时发生型, 四分体排列成四面体。高山栲成熟的花粉为2-细胞型。胚珠为倒生胚珠二层珠被, 厚珠心, 内外珠被共同形成珠孔。雌配子体发育蓼型。胚乳发育先产生核型胚乳。高山栲胚胎和果实发育的特征（例如子房室毛被, 胚珠在子房中的相对体积大小, 败育胚珠的位置）表明栲属和栎属的胚胎发育存在一定的区别。高山栲在子房发育的早期胚珠在子房中占有的体积相对小, 在大孢子母细胞发育前子房中已经有丰富的毛被。栲属和栗属的胚胎发育是最相似的, 这为壳斗科分子系统学中栲属和栗属是姐妹群的结论提供了胚胎学证据。
根据文献资料和标本馆及化石记录, 讨论了壳斗科栲属植物的现代分布和地史分布。现代栲属植物主要分布在东亚及东南亚, 其中印度支那地区是世界栲属植物分布最集中的地区, 有栲属植物82种。中国栲属植物最丰富的地区是滇黔桂地区, 有栲属植物29种。排除金鳞果属后, 栲属的分布类型应属热带亚洲分布。栲属在地质历史上有着比现在更广泛的分布, 最早、最可靠的栲属化石记录发现于始新世地层, 栗亚科化石在古新世就有发现, 化石记录表明栲属起源的时间不晚于古新世。所有的壳斗科及栲属的化石都发现于北半球, 现代分布也主要在北半球, 壳斗科及栲属起源于北半球可以确认。但由于化石证据与现代植物学的研究结果有较大差异以及关键地区化石证据的不足, 具体的起源地尚不能肯定。|
|其他摘要||The leaf cuticle, leaf architecture, comparative embryology and geological distribution of Castanopsis (D. Don) Spach and its related genera（Castanea, Chrysolepis）were comprehensively investigated; Cladistic analysis of morphologic characters, including cuticle, venation, flower and fruit characters were also comprehensively investigated. The results are summarized as follows:
1. Leaf cuticle
In this investigation, the leaf cuticle of 41 Castanopsis species, 6 Castanea species and Chrysolepis chrysophyllum Hjelmq. were examined using both light microscopy (LM) and scanning electron microscopy (SEM). In Castanopsis, all the species possessed the cyclocytic stomata with thickened subsidiary cells; thin-walled peltate trichomes are the most widespread type on the abaxial surface of Castanopsis leaves. In Castanea, the stomata are anomocytic or transitional between cyclocytic and anomocytic stomata; In Chrysolepis, the cyclocytic stomata with non-thickened subsidiary cells and thick-walled peltate trichomes were detected. The comparison of leaf cuticular features indicates obvious differences between Chrysolepis and Castanopsis and, between Chrysolepis and Castanea. The results support taxonomic separation of Chrysolepis from Castanopsis. The results also support the sister group relationship of Castanopsis and Castanea and the close affinity between Castanopsis-Castanea and Quercus. The ecological implications of the morphology of the trichomes and stomata are discussed. The importance of stomatal and trichome types are also discussed with respect to the identification of fagaceous fossil leaves.
2. Leaf architecture
We describe the leaf architecture of Castanopsis and its related genera and discuss the diagnostic value of the characters. Leaf architectural characters such as venation pattern, secondary vein number, tooth type, tertiary vein category and arrangement and veinlets, are usually stable within species and thus of great significance in identifying leaves of Fagaceae.
In Castanea, secondary veins tend to be parallel; secondary veins and tooth are regularly spaced; tooth apex is spinose tooth or modified urticoid type Ⅲ (U3) of Leng (1999). The most remarkable difference of serrate Castanopsis leaves to Castanea is that in Castanopsis the teeth are always irregularly spaced and confined to the one-half to two-thirds superior part of the lamina. Leaf margin of Chrysolepis are entire and often slightly revolute; leaves have seven to nine pairs of secondary veins; tertiary veins are very distantly spaced and very weakly percurrent.
Leaf architectural characters are only available characters in a plenty of poorly preserved leaf fossils. Moreover, many leaf cuticular characters are not easily used in the field; in this case, leaf architecture can offer us useful information in identifying leaf material. According to leaf cuticular and architectural characters, we produce a key to help identifying Fagaceae leaves to generic level. Using leaf architectural characters, another key for the identification of 70 Fagaceae species is also presented.
3. Cladistic analysis of morphologic characters
A neighbor-joining tree of 71 Fagaceae species based on 75 leaf cuticle, architecture, fruit and cupule characters was constructed. The result demonstrated that there is a mosaic evolution of these characters in the extant Fagaceae species, which results in some difficulties in generic delimitation. However, trichome types and stomata characters are very useful in the delimitation of genera. The typical appressed parallel tufts of Lithocarpus, thicken-walled peltate trichomes of Chrysolepis, thin-walled peltate trichomes and thickened subsidiary cells of cyclocytic stomata in Castanopsis and anomocytic stomata of Castanea are very helpful in identifying fossil leaves to generic level. Castanopsis species were classified into six groups. The position of C. longzhouica shows its close affinity to Lithocarpus.
According to the neighbor-joining tree on 75 leaf cuticle, architecture, flower and fruit characters, the traditional taxonomic system based only on reproductive characters shows some degree of irrationality.
4. Comparative embryology
The developmental process of flower and fruit production was studied for the first time in Castanopsis delavayi and compared with other taxa of Fagaceae. The anther wall is four layered with a basic type of development (including a persistent epidermis, a fibrous endothecium, one to two ephemeral middle layers and a secretory anther tapetum). Simultaneous cytokinesis during microsporogenesis follows meiosis of the microspore mother cell, thereby forming a tetrahedron. The mature pollen grain is two-celled. Ovules are bitegmic-crassinucellate and anatropous. The inner and outer integuments together form a micropyle. The embryo sac is of Polygonum-type. The development of endosperm is of the nuclear type. Other embryological and fruit characters (trichomes in locule, size of ovules relative to the ovary cavity, and if aborted ovules apical position) reveals some differences between Castanopsis and Quercus. In the early period of ovary development of Castanopsis delavayi, the size of ovules relative to the ovary cavity is small and rich trichomes can be found before the development of the megaspore mother cell. The embryological characters of Castanopsis and Castanea are very similar, thus offer embryological evidence to the sister group relationship previously proposed by molecular study on Fagaceae.
5. Fossil history
Modern and geological distributions of Castanopsis（Fagaceae） are studied based on published data and herbarium specimens as well as fossil records．Modern Castanopsis species are mainly concentrated in Eastern and Southeastern Asia, especially diverse in the floristic region of Indo-China, with 82 species in this area．In china, the floristic region of Dian (Yunnan)-Qian (Guizhou)-Gui (Guangxi) has the highest Castanopsis species diversity, with 29 species found in this region. Excluded genus Chrysolepis, the distribution of Castanopsis is tropical Asia. The earliest and reliable Castanopsis fossil records date back at least to Eocene, and subfamily Castaneoideae fossil records found from Paleocene, it is indicated that appearance of Castanopsis is not later than Paleocene．All fossil records of Fagaceae and Castanopsis report from the Northern Hemisphere and their main distribution regions are in the Northern Hemisphere．It can be concluded that the Northern Hemisphere is the center of origin of Fagaceae and Castanopsis．However, owing to the discrepancy between fossil data and results of modern botany research as well as scarcity of fossil data from key area, precise center of origin of Castanopsis cannot be inferred.|
刘孟奇. 壳斗科栲属及其近邻属的叶表皮、叶结构、胚胎发育和地理分布[D]. 昆明植物研究所. 中国科学院昆明植物研究所,2009.