RECONSTRUCTIONS OF ARCHAEOPTERIS,AND FURTHER CONSIDERATION OF ITS PHYLOGENETIC POSITION

Beck , C. B. (U. Michigan, Ann Arbor.) Reconstructions of Archaeopteris, and further consideration of its phylogenetic position. Amer. Jour. Bot. 49(4): 373–382. Illus. 1962.—Two reconstructions, one of a branch bearing the basal part of 3 leaves and the other of the habit, are presented with the evidence upon which they are based. An analysis is made of some features which characterize the ferns. These, and characters of Archaeopteris, are considered in the light of present knowledge of evolutionary trends, and the conclusion is reached that Archaeopteris was neither a primitive fern nor a fern ancestor. Additional evidence is discussed which supports the view that the plant was a progymnosperm.     

黑龙江产十种蕨类植物孢子囊和叶表皮的扫描电镜观察

用扫描电镜对黑龙江产十种不同科属、不同生境的蕨类植物的孢子囊和叶表皮进行了详细观察,结果显示:蕨类植物的孢子囊和叶表皮在扫描电镜下,显示出更为丰富的形态特征,并表现出细致而稳定的异同点,可作为蕨类系统分类的现代手段,能更好的应用于疑难科属的分类研究;十种蕨类植物也都表现出其形态结构与生态生理的高度一致性.     

Genetic and genomic aspects of hybridization in ferns

The morphological and ecological intermediacy of hybrid taxa has long interested and challenged fern biologists, resulting in numerous systematic contributions focused on disentangling relationships within reticulate species complexes. From a genetic perspective, hybrid ferns are especially interesting because they represent the union of divergent parental genomes in unique evolutionary entities. This review summarizes advances in our knowledge of the genetic and genomic aspects of hybridization in ferns from the mid-20th century to the present. The different organismal products of hybridization, evolutionary aspects of additive and non-additive gene expression in allopolyploids, genetic and genomic mechanisms leading to gene silencing and loss, the roles of multiple origins and introgression for imparting genetic variation to hybrid fern taxa and their progenitors, and the utility of allopolyploid ferns to investigate mechanisms of genome evolution in the homosporous ferns are discussed. Comparisons are made to other plant lineages and important future research directions are highlighted, with the goal of stimulating additional research on hybrid ferns.     

蕨类植物的鳞片特征及演化I: 凤尾蕨科

鳞片是蕨类植物体表常见附属物, 是蕨类植物非常显著的分类学特征。凤尾蕨科(Pteridaceae)在蕨类植物系统发育中的位置关系多次发生了变化, 不同学者对该科中包含的类群也有着不同的观点。通过对该科76种植物的鳞片进行取材, 利用解剖镜观察拍照, 对各属鳞片特征进行描述。结果显示, 鳞片特征在不同的属和亚科之间具有明显的形态差异。用GenBank数据库中的rbcL基因序列对所研究物种进行系统发育重建, 并对鳞片的边缘特征和筛孔类型进行祖先性状重建, 结果表明, 全缘型鳞片和均质型鳞片是凤尾蕨科鳞片的祖征性状, 非全缘类型和透明筛孔类型的鳞片是在后期演化过程中形成的特征。此外, 透明和不透明类型的筛孔其形成可能与蕨类植物生活环境中的光照强度有关。     

蕨类植物花青素和原花青素成分及含量分析

以7目14科共44种蕨类植物为材料,对它们的花青素、原花青素和总黄酮含量进行检测。结果显示,44种蕨类植物均含有花青素,较为进化的水龙骨目植物的总花青素平均含量明显高于其它蕨类植物。矢车菊素、飞燕草素和天竺葵素是蕨类植物主要的花青素类型,其中乌毛蕨科植物富含矢车菊素,鳞毛蕨科植物富含飞燕草素。本研究中大部分蕨类含有原花青素,水龙骨目植物的原花青素平均含量高于其它蕨类。研究结果表明,蕨类植物中花青素和原花青素等黄酮类化合物的分布与植物科属相关,推测花青素与蕨类植物的生长发育和抗逆过程相关。     

蕨类植物的化感作用及其对生物多样性的影响

植物化感作用是植物通过向环境中释放化学物质从而对同种植株和繁殖体或与其他植物之间产生的直接或间接、有益或有害的作用,它影响植物分布、群落形成与演化、作物间作等,与生物多样性保护以及农林和园艺生产实践关系密切,在国际上受到越来越多的关注。但国内这方面的研究起步相对较晚,研究范围有限,对蕨类植物化感作用的报道更少。本文系统介绍了蕨类植物化感作用的研究进展,包括蕨类植物种内的化感作用(即自毒效应)、常见的蕨类植物种间的化感作用(即孢子体对配子体的化感作用和配子体对配子体的化感作用)及蕨类植物对种子植物的化感作用(蕨类植物可通过化感作用与种子植物争夺更多的资源和生长空间)。还介绍了种子植物对蕨类植物的化感作用(主要表现为抑制作用)以及蕨类植物化感作用与动物侵食、微生物侵染的关系,研究发现昆虫侵食能增强或减弱蕨类植物的化感作用,微生物的活动可能增强某些蕨类植物的化感作用。本文从上述不同角度说明蕨类植物化感作用对生物多样性的影响,希望有助于促进我国学者对该领域的深入研究。     

Complete chloroplast genome sequence of a tree fern Alsophila spinulosa : insights into evolutionary changes in fern chloroplast genomes

Background  

Ferns have generally been neglected in studies of chloroplast genomics. Before this study, only one polypod and two basal ferns had their complete chloroplast (cp) genome reported. Tree ferns represent an ancient fern lineage that first occurred in the Late Triassic. In recent phylogenetic analyses, tree ferns were shown to be the sister group of polypods, the most diverse group of living ferns. Availability of cp genome sequence from a tree fern will facilitate interpretation of the evolutionary changes of fern cp genomes. Here we have sequenced the complete cp genome of a scaly tree fern Alsophila spinulosa (Cyatheaceae).     

TRACHEARY ELEMENTS OF THE FERNS. I. FACTORS WHICH INFLUENCE TRACHEID LENGTH; CORRELATION OF LENGTH WITH EVOLUTIONARY DIVERGENCE

White , R. A. (U. Michigan, Ann Arbor.) Tracheary elements of the ferns. I. Factors which influence tracheid length; correlation of length with evolutionary divergence. Amer. Jour. Bot. 50(5): 447–455. 1963.—To determine the variability of tracheid lengths in ferns, several factors were surveyed which might modify them. On the basis of average lengths based on from 100 to 300 measurements, the following factors were found to affect fern tracheid length significantly: location in the plant, stage of maturation of the plant, length of the internode, ploidy, and habitat. These factors were considered when a statistical analysis was made of the relationship between tracheid length and taxonomic divergence among the species of ferns. A Pearson's correlation coefficient was computed, based on average tracheid lengths from 221 species of ferns, and a divergence index based on 8 characters accepted as indicators of specialization or primitiveness in the ferns. A statistically significant correlation (at the 5% level) between length and divergence was found for root tracheids, but not for rhizome or petiolar tracheids. A better understanding of fern evolution is necessary before a more precise picture of length correlation and divergence in the ferns can be obtained.     

Reiterative growth in the complex adaptive architecture of the Paleozoic (Pennsylvanian) filicalean fern Kaplanopteris clavata

Reiteration is a widespread component of plant growth whose evolutionary importance in ferns is not recognized widely. We introduce and discuss the growth architecture of Kaplanopteris clavata, a fossil filicalean fern from the Pennsylvanian (ca. 305 million yeas old), focusing on types of reiteration exhibited by this species and on the adaptive and phylogenetic significance of reiteration for ferns in general. Kaplanopteris clavata combines two types of reiterative growth where growth modules are borne on fronds: (1) entire fronds derived from primary pinnae, and (2) epiphyllous plantlets. This combination of reiterative pathways, unique among fossil and living ferns, allowed K. clavata to explore ecospace through an opportunistic combination of scrambling, climbing and epiphytic growth. Kaplanopteris clavata underscores the organographic importance of fronds (as opposed to stems) in the adaptive architecture of ferns, emphasizing functional convergences between the different Baupla̋ne of ferns and angiosperms. This unique combination of reiterative pathways is interpreted as a derived condition illustrating the structural and developmental complexity achieved by some filicaleans during the first major evolutionary radiation of leptosporangiate ferns.     

How early ferns became trees

A new anatomically preserved fern, discovered from the basalmost Carboniferous of Australia, shows a unique combination of very primitive anatomical characters (solid centrarch cauline protostele) with the elaboration of an original model of the arborescent habit. This plant possessed a false trunk composed of a repetitive branching system of very small stems, which established it as the oldest tree-fern known to date. The potential of this primitive zygopterid fern to produce such an unusual growth form-without real equivalent among living plants-is related to the possession of two kinds of roots that have complementary functional roles: (i) large roots produced by stems with immediate positive geotropism, strongly adapted to mechanical support and water uptake from the soil; and (ii) small roots borne either on large roots or on petiole bases for absorbing humidity inside the false trunk.     

STUDIES OF PALEOZOIC MARATTIALEANS: NEW SPECIES OF SCOLECOPTERIS (MARATTIALES) FROM THE PENNSYLVANIAN OF NORTH AMERICA

Two new species of the late Paleozoic fern Scolecopteris (Marattiales) are described and their relationships within the genus are discussed. Scolecopteris charma sp.n., from Steubenville, Ohio (Duquesne Coal, Upper Pennsylvanian), is similar to species in the Oliveri group, while S. gnoma sp.n. from Providence, Kentucky (Baker Coal, Middle Pennsylvanian), compares favorably with the Latifolia species group. Scolecopteris gnoma is most similar to S. fragilis but differs in its smaller synangia and spore type. S. charma appears generally similar to S. iowensis because of its large pedicel and histologically undifferentiated walls, but differs in a number of characters such as vasculature and spore type. Despite its occurrence late in the Pennsylvanian, S. charma is thought to possess a number of primitive character states (large trilete spores, vascularized pedicels, flat pinnules with downturned margins). Using the same criteria for the much older S. gnoma, we note a number of relatively apomorphic character states (small monolete spores, unvascularized pedicels, extended pinnule margins). An outgroup analysis of species-level characters of Scolecopteris gives a better concept of primitive versus derived traits in marattialean and other ferns. Genera in the Paleozoic fern orders Filicales (Ankyropteris) and Zygopteridales (Corynepteris, Musatea) were chosen as outgroups, and the comparisons support suggestions for the polarity of several important characters. Some of these agree with previously proposed evolutionary polarities based on the geological occurrence of marattialean ferns.     

A current perspective on apomixis in ferns

This review provides a synopsis of apogamous reproduction in ferns and highlights important progress made in recent studies of fern apomixis. First, a summary of the apomictic fern life cycle is provided, distinguishing between two pathways to diploid spore production that have been documented in apomictic ferns (premeiotic endomitosis and meiotic first division restitution) and briefly discussing the evolutionary implications of each. Next, recent trends in fern apomixis research are discussed, exposing a shift in focus from the observation and characterization of apomixis in ferns to more integrated studies of the evolutionary and ecological implications of this reproductive mode. Peer-reviewed contributions from the past decade are then summarized, spanning the identification of new apomictic lineages through to the developmental, phylogenetic, and population genetic insights that have been made in studies of fern apomixis during that time. Gaps in our understanding are also discussed, including the extent and implications of recombinant apomixis in ferns, the possible reversibility of reproductive mode (from apomictic to sexual) in ferns, and the genomic causes and consequences of apomixis in seed free vascular plants. To conclude, future directions for fern apomixis research are proposed in the context of modern technological advances and recent insights from studies of apomixis in other groups.     

附生蕨类植物的克隆性研究进展

石松类及蕨类植物在高等植物中处于比较特殊的进化与系统发育地位, 同时具有孢子植物(孢子)与种子植物(维管束)的双重特征。附生蕨类植物是蕨类植物中占据独特生境的一个大类群, 其生活史策略及进化历史与其附生生长的森林生态系统紧密相关。大部分附生蕨类植物的克隆生长习性及克隆生活史性状在其生态适应中具有重要作用, 但这方面未引起广泛关注。本文主要综述了中国山地森林中附生蕨类植物的根状茎克隆生长、克隆性与生态适应性、不同克隆生长方式与进化等方面, 并展望了蕨类植物克隆性在森林生态系统过程与功能中的作用, 以及今后如何将蕨类植物生态学研究与气候变化、植被恢复、土地利用变化等全球变化的主流方向进行结合。     

蕨类植物配子体发育及其性器官分化的研究进展

作者概述了蕨类植物生活周期中不同发育阶段的特点,并着重介绍了光、植物生长调节物质、水和温度等因素对蕨类植物配子体发育的影响以及成精子囊素、光、钙离子和其它植物生长调节物质在性器官形成和分化过程中的作用。同时作者对蕨类植物性器官分化的不稳定性进行了探讨、并结合目前蕨类植物性器官分化的遗传学和分子生物学研究的最新进展,说明蕨类植物作为研究系统在植物生物学研究领域中的优势。     

蕨类植物配子体育及其性器官分化的研究进展

作者概述了蕨类植物生活周期中不同发育阶段的特点,并着重介绍了不,植物生长调节物质,水和温度等因素对蕨类植物配子体发育的影响以及精子囊素,光,钙离子和其它植物生长调节物质在性器官形成和分化过程中的作用,同时作者对蕨类植物性器官分化的不稳定性进行了探讨,并结合目前蕨类植物性器官分化的遗传学和分子生物学研究的最新进展,说明蕨类植物作为研究系统在植物生物学研究领域中的优势。     

First insights into fern matK phylogeny

MatK, the only maturase gene in the land plant plastid genome, is a very popular phylogenetic marker that has been extensively applied in reconstructing angiosperm phylogeny. However, the use of matK in fern phylogeny is largely unknown, due to difficulties with amplification: ferns have lost the flanking trnK exons, typically the region used for designing stable priming sites. We developed primers that are either universal or lineage-specific that successfully amplify matK across all fern families. To evaluate whether matK is as powerful a phylogenetic marker in ferns as in angiosperms, we compared its sequence characteristics and phylogenetic performance to those of rbcL and atpA. Among these three genes, matK has the highest variability and substitution evenness, yet shows the least homoplasy. Most importantly, applying matK in fern phylogenetics better resolved relationships among families, especially within eupolypods I and II. Here we demonstrate the power of matK for fern phylogenetic reconstruction, as well as provide primers and extensive sequence data that will greatly facilitate future evolutionary studies of ferns.     

Conantiopteris schuchmanii, gen. et sp. nov., and the Role of Fossils in Resolving the Phylogeny of Cyatheaceae s.l.

Conantiopteris schuchmanii gen. et sp. nov. The specimen, 23.2 cm long and 11.7 cm wide, shows helically arranged persistent frond bases embedded in adventitious roots, and is clothed by multicellular trichomes. A parenchymatous pith with mucilaginous cells and sclerotic nests is surrounded by an amphiphloic distyostele, parenchymatous inner cortex, and outer sclerenchymatous cortex. Sclerenchyma also surrounds the cauline vasculature and leaf traces. Medullary and cortical bundles are absent. Phloem contains both axially elongated and tangential sieve elements. Frond bases are oval in outline with three vascular bundles, including an undulating abaxial arc and an adaxial pair. Protoxylem of the stipe is endarch and is associated with cavity parenchyma. These characters are indicative of tree fern affinities. A cladistic analysis using trunk characters of both living and fossil tree ferns was conducted to help establish relationships of the new species and other fossil ferns, and to test hypotheses of general tree fern relationships. Additional analyses of living taxa only were also performed. Results from the analysis using both living and fossil taxa compare favorably with those that included only living species when either morphological characters or molecular sequences of the chloroplast gene rbcL are utilized. Although there are variations in the topologies of the various trees, results indicate that the new genus is nested among a paraphyletic assemblage of dicksoniaceous, lophosoriaceous, and metaxyaceous species that subtend a monophyletic Cyatheaceae s.s. Received 26 April 1999/ Accepted in revised form 15 July 1999     

Recurrent genome duplication events likely contributed to both the ancient and recent rise of ferns

Ferns, the second largest group of vascular plants, originated ～400 mil ion years ago(Mya). They became dominant in the ancient Earth landscape before the angiosperms and are stil important in current ecosystems.Many ferns have exceptional y high chromosome numbers,possibly resulting from whole-genome duplications(WGDs).However, WGDs have not been investigated molecularly across fern diversity. Here we detected and dated fern WGDs using a phylogenomic approach and by calculating synonymous substitution rates(Ks). We also investigated a possible correlation between proposed WGDs and shifts in species diversification rates. We identified 19 WGDs: three ancient events along the fern phylogenetic backbone that are shared by 66%–97% of extant ferns, with additional lineage-specific WGDs for eight orders, providing strongevidence for recurring genome duplications across fern evolutionary history. We also observed similar Ks peak values for more than half of these WGDs, with multiple WGDs occurring close to the Cretaceous(～145–66 Mya). Despite the repeated WGD events, the biodiversity of ferns declined during the Cretaceous, implying that other factors probably contributed to the floristic turnover from ferns to angiosperms. This study provides molecular evidence for recurring WGDs in ferns and offers important clues to the genomic evolutionary history of ferns.     

Edaphic heterogeneity and the evolutionary trajectory of Amazonian plant communities

We investigated how the phylogenetic structure of Amazonian plant communities varies along an edaphic gradient within the non‐inundated forests. Forty localities were sampled on three terrain types representing two kinds of soil: clayey soils of a high base cation concentration derived from the Solimões formation, and loamy soils with lower base cation concentration derived from the Içá formation and alluvial terraces. Phylogenetic community metrics were calculated for each locality for ferns and palms both with ferns as one group and for each of three fern clades with a crown group age comparable to that of palms. Palm and fern communities showed significant and contrasting phylogenetic signals along the soil gradient. Fern species richness increased but standard effect size of mean pairwise distance (SES.MPD) and variation of pairwise distances (VPD) decreased with increasing soil base cation concentration. In contrast, palm communities were more species rich on less cation‐rich soils and their SES.MPD increased with soil base cation concentration. Species turnover between the communities reflected the soil gradient slightly better when based on species occurrences than when phylogenetic distances between the species were considered. Each of the three fern subclades behaved differently from each other and from the entire fern clade. The fern clade whose phylogenetic patterns were most similar to those of palms also resembled palms in being most species‐rich on cation‐poor soils. The phylogenetic structuring of local plant communities varies along a soil base cation concentration gradient within non‐inundated Amazonian rain forests. Lineages can show either similar or different phylogenetic community structure patterns and evolutionary trajectories, and we suggest this to be linked to their environmental adaptations. Consequently, geological heterogeneity can be expected to translate into a potentially highly diverse set of evolutionarily distinct community assembly pathways in Amazonia and elsewhere.