Patterns of Clonal Diversity in Dicranopteris linearis on Mauna Loa,Hawaii1

The clonal mat-forming fern, Dicranopteris linearis (N. L. Burm.) Underw., dominates vast areas of rainforests on the windward slopes of Mauna Loa Volcano on the island of Hawai'i. Because clone size has important ecological and evolutionary consequences in such a dominant species, we used isozyme analysis to investigate clone size and other aspects of genetic diversity and reproduction over a broad range of environmental conditions on primary successional sites (pahoehoe lava substrates). Isozyme analysis provided a measure of the upper limit of clonal size in this interdigitating clonal species. Each 0.5-ha primary successional site on Mauna Loa was comprised of a minimum of two to four clones. Genetic diversity in Dicranopteris was low; of 32 putative loci investigated, only 4 were polymorphic, with 2 or 3 alleles/locus. Over the 17 study locations on Mauna Loa and Kilauea Volcanoes, we identified nine multilocus genotypes based on unique combinations of allozymes. Seven of the nine genotypes were heterozygous for at least one locus, evidence of an intergametophytic mating system. Highly dispersible spores, coupled with intergametophytic mating should promote higher genetic diversity. We propose that the following factors contributed to low genetic diversity: founder effects; extreme isolation from mainland gene pools; high potential for mating among different gametophytes produced from the same sporophyte; relatively low numbers of safe sites for gametophyte establishment over space and time; and long-term reliance on vegetative growth. Leaf phenotypes were associated with genotype, but also with environmental conditions. Enough variability within a genotype existed to support the current treatment of Hawaiian Dicranopteris as one species. Vegetative growth was the primary means by which Dicranopteris covered the landscape. Nevertheless, spore production, gametophyte establishment, and sexual reproduction were absolutely essential for colonization of the few favorable microsites available on pahoehoe lava substrates of Mauna Loa following lava eruptions, dieback, and similar landscape-level disturbances.     

SEM studies on vessels in ferns. 9. Dicranopteris (Gleicheniaceae) and vessel patterns in leptosporangiate ferns

Ferns in which vessels have been demonstrated to date are phylogenetically relatively specialized and characteristic of habitats with marked extremes in temperature and water availability. These specifications do not apply to the Gleicheniaceae, which indicates that vessels may occur in a range of more primitive ferns, including those from more nearly mesic habitats. Vessels in Dicranopteris have perforation plates (both lateral and terminal) with morphology similar to that of lateral wall pitting as seen with light microscopy. Scanning electron microscopy (SEM) is therefore necessary to demonstrate presence of perforations. Vessel presence in Dicranopteris is important in forming a picture of vessel presence and specialization in ferns, the phylogenetic and ecological distribution of which may differ from the patterns found in monocotyledons and dicotyledons. We believe that presence of vessels may not be a reliable indicator of phylogenetic position among ferns.     

光里白中的两个新苷类成分

从光里白（Diplopterygium loevissimum）的95％乙醇提取物中分离得到2个新的苷类成分,经波谱手段鉴定了其结构,命名为hymenoside X（1）和hexanoside A（2）。     

内蒙古乌达地区早二叠世晋囊蕨属一新种

Chansitheca (Sphenopteris) wudaensis sp. nov. is described based on the materials collected from the Lower Permian Shansi Formation of Wuda, Nei Mongol, China. The frond is small and at least two times pinnate. The pinnule is sphenopteroid. The sori are borne on the abaxial surface of the pinnule, arranged in two rows parallel to the midvein, elliptic,and composed of 4-10 round sporangia. The indusium is absent. The annulus is transverse and complete, and consists of about 18 thickened cells. The features of the fertile parts, sori, sporangia and annulus and the absence of indusium indicate that the new species belongs to the Gleicheniaceae.     

内蒙古乌达地区早二叠世晋囊蕨属一新种

通过扫描电镜研究,建立了内蒙古中部乌达地区下二叠统山西组晋囊蕨诉一个新种Ｃｈａｎｓｉｔｈｅｃａ ｗｕｄａｅｎｓｉｓ ｓｐ ．ｏｎｖ．。新种的小心片Ｓｐｈｅｎｏｐｔｅｒｉｓ型,囊群椭圆形,由４～１０个孢子囊组成,着生一示羽片背面,位于中脉的两侧。环带横列于孢子囊的上部,完全,单排细胞,细胞数目约为１８个,这些特征表明新种属于里白科。     

里白科植物的系统发育和分歧时间估计——基于叶绿体三个基因序列的证据

里白科(Gleicheniaceae)是古老的真蕨类植物,最早的化石记录可追溯到石炭纪。现存类群的属级分类和系统演化关系一直存在很大的分歧,为了进一步探讨该类群的起源演化,文中运用最大简约法和贝叶斯演绎方法对18种代表现存里白科植物全部6属(包括新测的12种)的叶绿体3个编码基因序列(atpB,rbcL和rps4)进行分析,探讨其主要分类群(属级)的系统演化关系。结果显示,里白科植物为一个单系群,由3个分支构成:里白属(Diplopterygium Nakai)和Gleichenia japonica构成一个分支;芒萁属(Dicranopteris Bernh.)和Gleichenella pec-tinata构成另一个分支;假芒萁属(Sticherus C.Presl)与单种属Stromatopteris Mettenius及Gleichenia dicarpa构成第三个分支。用宽松分子钟方法推测里白科主要类群的起源时间为:现代里白科植物起源于早白垩世(111—140Ma),其主要分支类群随后发生多样性分化,里白属和芒萁属的快速辐射演化均发生在古近纪(40—64Ma,36—50Ma)。起源时间的估算结果暗示化石种三叠里白Diplopterygium triassica不应归入现代里白属,其归属需要重新考虑。     

中国里白科植物小志

在对中国产里白科(Gleicheniaceae)植物分类修订过程中,描述了芒萁属( Dicranopteris )一新变型,即参差大芒萁( Dicranopteris ampla f. irregularis );承认中国里白属( Diplopterygium )植物9种,将红毛里白( Diplopterygium rufopilosum )处理为厚毛里白( D.rufum )的异名,将正里白( Diplopterygium criticum )、海南里白( D.simulans )、灰里白( Hicriopteris reflexa )、假里白( D.glaucoides )、峨眉里白( H.omeiensis )和云南里白( Diplopterygium yunnanense )处理为大里白( D.giganteum )的异名.此外还附有国产里白属植物的分种检索表.     

Chansitheca wudaensis (Gleicheniaceae,fern) from the early Permian Wuda Tuff Flora,Inner Mongolia

A large number of specimens of Chansitheca wudaensis Deng, Sun et Li from the early Permian Wuda Tuff Flora allow an emendation of this species. Characters of the sporangial structure and in situ spores are examined for the first time. Sori are arranged on lateral veins of pinnule lobes, and are 0.61–0.69 mm long and 0.35–0.41 mm wide. Sporangia are sessile and surrounded by an annulus, which is composed of two rows of oblong thick-walled cells. Trilete, smooth in situ spores have diameters of 21.05–26.31 μm. Features of the reproductive organ indicate that this species is similar to Szea Yao et Taylor and some species of Oligocarpia Goeppert and belongs to the Gleicheniaceae. Based on a taphonomical analysis, C. wudaensis was an herbaceous element of the groundcover in the peat-forming coal swamp.