在分子生物学出现以前，基于营养器官特征、花部结构、染色体数目等多方面的证据，许多学者就鹿蹄草亚科内四个属间的系统学关系提出过多种假设。在本论文中，我们扩大取样范围，包括22个实验材料，代表鹿蹄草亚科四个属14个种(Pyrola 10个种，Chimaphila 2个种，Orthilia和Moneses各1个种)以及外类群吊钟花属(Enkianthus)2个种，猕猴桃属(Actinidia)1个种。选取不同遗传背景的基因片段(核基因ITS, 叶绿体基因：atpB-rbcL, trnS-trnG以及trnL-trnF)，运用最大简约法(MP)和贝叶斯方法(BI)先构建最能反映鹿蹄草亚科四属间演化关系的系统树，然后选取16个重要的形态学性状重建它们的演化历史，最终基于分子生物学的结果，确定具有进化意义的分类学性状，讨论该亚科的系统关系。分析结果表明Orthilia位于基部，拥有最多的祖先特征，接下来分出的是Pyrola，Moneses和Chimaphila构成姐妹类群，较为进化。我们的推论同时得到了分子生物学和形态学特征很好的支持。
2. 鹿蹄草属(Pyrola L.)的分子系统学及属下新分类系统的建立
PyrolaL.是鹿蹄草亚科内最大的属，约30余种，广布于整个北温带。从外部形态看，Pyrola是一个一致性很高的类群，仅在叶片质地，花萼、苞片、花药的形状以及花瓣颜色等方面有细微的差别，属内种间关系长期以来不清楚。本论文包括Pyrola 26个种，选取Chimaphila , Moneses , Orthilia , Enkianthus 和Actinidia 作为外类群，基于不同遗传背景的基因片段(核基因ITS, 叶绿体基因：atpB-rbcL, trnS-trnG以及trnL-trnF)，运用最大简约法(MP)和贝叶斯方法(BI)构建系统树。基于分子生物学和形态学的证据，我们重新划分了属内等级。Pyrola被分为sect. Pyrola和sect. Ampliosepala 两个组，其中，P. sect. Pyrola 分为三个系包括P. ser. Pyrola，P. ser. Ellipticae和P. ser. Forrestianae；另一个组P. sect. Ampliosepala 亦包括P. ser. Japonicae，P. ser. Scotophyllae和P. ser. Chloranthae三个系。这是到目前为止Pyrola最为自然的属下分类系统。
3. 喜冬草属(Chimaphila Pursh)的系统学及生物地理学研究
Chimaphila广泛分布于北半球温带及寒温带地区，属内种间在北半球大洲间形成间断分布。本次研究包括Chimaphila全部5个种，其中C. japonica, C. umbellata 包括不同分布点的试验材料。另外我们还包括了鹿蹄草亚科其它三个属的取样：Pyrola(2), Moneses(1), Orthilia (1)，并选取吊钟花属(Enkianthus)和猕猴桃属(Actinidia)作为外类群。属内系统学关系用最大简约法和贝叶斯分析方法进行构建。分异时间用软件PAML/multidivtime进行贝叶斯推导。祖先区域的构建及扩散样式用DIVA软件进行分析。叶绿体片段联合分析构建的系统树显示Chimaphila是一个有很好支持的单系，属内种间关系明晰。从系统树上看，北半球广泛分布的C. umbellata位于基部，最先分出来；接下来是东亚的C. montiocla；再接下来是北美东部的C. maculata；分别采自日本和中国云南的C. japonica聚在一起并和北美西部的C. menziesii构成姐妹类群。我们在综合了分子系统学、分异时间推断、现存物种分布区、北半球地质历史及古气候资料和物种自身的一些生物学特性后，推测如下Chimaphila可能的生物地理历史。Chimaphila可能起源于始新世向渐新世过渡时期(36.94±7.55 mya)的东亚高纬度地区，是北方热带植物区系(boreotropical flora)的组成成分。C. umbellata是本属中最先分出来的物种，它可能经过3次扩散事件形成现在北温带广布的格局，但具体的扩散路线基于我们目前的数据还不能确定，有待于居群水平上的进一步研究。30.14±7.05 到 27.65±6.88 mya期间，北半球正经历一个大范围的降温过程， Chimaphila在东亚内部先完成一次分化，可能沿秦岭一带向南扩散，在今天中国的川西地区形成C. monticola 这个种。 27.65±6.88到 25.69±6.67 mya期间，Chimaphila的一支向西经欧洲越过北大西洋陆桥(NALB)到达北美东部，随着北大西洋陆桥的断裂，构成一次成种事件，在北美东部形成C. maculata 这个种。25.69±6.67到14.04±4.96 mya期间，北半球气温进一步降低，白令陆桥向南移动，该区原来的极夜现象有所减弱，Chimaphila的另外一支向东越过白令陆桥扩散到北美西部。接下来气温急剧下降，Chimaphila在该陆桥附近形成的连续分布区被打断，分别在东亚形成C. japonica, 在北美西部形成C. menziesii。我们通过对Chimaphila开展生物地理的研究，一方面丰富了北温带洲际间断植物起源扩散的类型，另一方面，也使我们充分认识到这种间断分布类型背后植物起源扩散历史的复杂性。在今后的研究中应对北温带植物相关类群开展进一步的研究，以期全面理解北温带植物的起源扩散历史。
|其他摘要||The subfamily Pyroloideae, basal to the Ericaceae, is composed of four genera: Pyrola, Orthilia, Chimaphila and Moneses. Among them both Orthilia and Moneses are monotypic, whereas Chimaphila consists of about five species and Pyrola about 30 species. All the members of the Pyroloideae are native to mainly coniferous and deciduous broad-leaved forests of temperate and cool temperate regions of the Northern Hemisphere. In order to improve our understanding of this very interesting plant groups, our works focused on the following four aspects:
1. Phylogenetic systematics and character evolution in the Pyroloideae (Ericaceae)
Prior to the advent of molecular-based phylogenetic studies, a surprising number of alternative hypotheses have been proposed for the relationships of these few genera based on variation in floral and vegetative structure, in chromosome number and so on. In this study, 22 accessions, representing 4 genera and 14 species of Pyroloideae, were examined. Firstly, we reconstructed phylogenetic relationships of the Pyroloideae based on different genetic background DNA fragments (ITS, atpB-rbcL, trnS-trnG, and trnL-trnF). Then we inferred the evolutionary history of the 16 selected morphological characters in Pyroloideae and identified those morphological characters that are most useful in supporting phylogenetic relationships estimated on the basis of molecular data.
Our final results suggested that Orthilia is basal to the rest of the Pyroloideae, possessing much more plesiomorphic characters, Pyrola is the follwing, the sister group Chimaphila and Moneses is derived. As far as we know, this may be the most natural infrageneric system for Pyrola.
2. A molecular phylogeny and a new classification of Pyrola (Pyroloideae, Ericaceae)
Pyrola is the largest and arguably the most taxonomically complex genus in the subfamily Pyroloideae. The species of Pyrola are a very uniform group possessing only subtle variations in such features as leaf shape, size and form of scape bracts, as well as various floral modification as in sepal shape, anther form and color. For a long time, the infrageneric relationships whthin Pyrola is not clear. In this study, sequence data from the chloroplast DNA atpB-rbcL, trnS-trnG, and trnL-trnF and nuclear ribosomal DNA ITS regions were used to test previous hypotheses of subgeneric relationships. Plants sampled for this study included 26 species of Pyrola, and seven taxa selected from the remaining genera of Pyroloideae (4 species), Enkianthus (2 species), and Actinidia (1 species) were designated as outgroups. In most cases, at least two populations per species were analyzed. Phylogenetic analyses were carried using maximum parsimony and Bayesian methods. Our results strongly support monophyly of Pyrola and demonstrate that the previous infragenera classifications should be reconsidered. A new infrageneral classification based on a phylogenetic approach is proposed here and consists of two sections: P. sect. Pyrola and P. sect. Ampliosepala. P. sect. Pyrola consists of three series: P. ser. Pyrola, P. ser. Ellipticae and P. ser. Forrestianae; P. sect. Ampliosepala is composed of three series: P. ser. Japonicae, P. ser. Scotophyllae and P. ser. Chloranthae.
3. Phylogeny, biogeography and molecular dating of prince's pine (Chimaphila, Pyroloideae, Ericaceae): tracking Tertiary plant migration
Chimaphila exhibits a wide geographical distribution in the boreal and temperate parts of the Northern Hemisphere. This analysis included all five Chimaphila species, of which C. japonica and C. umbellata were each represented by two different populations. We also sampled seven other species, four species from the remaining genera of Pyroloideae, two from Enkianthus and one from Actinidia as outgroups. Phylogenetic relationships were analyzed by maximum parsimony and Bayesian methods; divergence time was estimated by Bayesian molecular dating (PAML/multidivtime); biogeographical scenarios were inferred using dispersal-vicariance analysis (DIVA). Our phylogenetic analysis based on combined cpDNA data shows that Chimaphila is a strongly supported monophyletic group with a clear hierarchic structure. Two accessions of the eastern Asian species C. japonica are sister to the western North America strictly distributed species C. menziesii; their immediate sister is another North America distributed species, C. maculata; followed by another eastern Asian species, C. monticola; a widely distributed species in the Northern Hemisphere, C. umbellata, falls in a basal position within this genus. This kind of topology does not correspond to a simple geographic split between New and Old World groups as species from the same refugial region not being sister to one another. Although there may be other alternatives, by integrating molecular phylogenetic reconstructions, estimated divergence times, extant species geographic distributions and paleontological data of the Northern Hemisphere, we suggest the following biogeographic hypothesis for the widely Northern Hemisphere distribution of Chimaphila. The genus evolved during the transition from Eocene to Oligocene (36.94±7.55 mya) at high latitude of eastern Asia, as an element of the boreotropical flora. According to our analysis, the first split in this genus was the C. umbellata and three dispersal events resulted in its current widely distribution. Unfortunately, using our preliminary data, we could not accurately infer its dispersal routes (NALB or/and BLB), pending for studies based on population level. During the period of 30.14±7.05 to 27.65±6.88 mya, a time at which a series of steps of climate cooling forced large assemblages of warm temperate to subtropical biota to retreat from medium to high latitude circumboreal distributions southward to large refugial regions, one Chimaphila lineage moved southward into the Himalayan region and survived in areas south of the Qinglin Mountains of China, resulting in C. monticola. During the interval 27.65±6.88 to 25.69±6.67 mya, one Chimaphila lineage spread westward across Europe into eastern North America via the North Atlantic Land Bridge (NALB) and the following bridge connection disruption resulted in C. maculata occurrence in eastern North America. During the interval 25.69±6.67 to 14.04±4.96 mya, the other Chimaphila lineage spread eastward to western North America via the Bering Land Bridge (BLB) and the subsequent climatic deteriorating vicariance fragmented it into two lineages: C. japonica in eastern Asia and C. menziesii in western North America. We finally confirm the view that the biogeographic history of the Northern Hemisphere is complex and heterogeneous.
4. A preliminary study on the adaptive mechanisms of Pyroloids in forest and its related ecological effects
Understory vegetation is a critical component in the forest ecosystem. The present paper summaries recently development of the Pyroloids on systematics, population genetics and ecology and explores its mechanism to adapt the understory environment. Finally, we infer that Pyroloides as a key elements in the coniferous and coniferous and broad mixed forest of the Northern hemisphere may firstly change the micro-environment around it then affect the stability, evolution and biodiversity of the whole forest ecosystem.|