The phylogeny of land plants: A cladistic analysis based on male gametogenesis

A cladistic analysis was carried out to resolve phylogenetic pattern among bryophytes and other land plants. The analysis used 22 taxa of land plants and 90 characters relating to male gametogenesis.Coleochaete orChara/Nitella were the outgroups in various analyses using HENNIG86, PAUP, and MacClade, and the land plant phylogeny was unchanged regardless of outgroup utilized. The most parsimonious cladograms from HENNIG86 (7 trees) have treelengths of 243 (C.I. = 0.58, R.I. = 0.82). Bryophytes are monophyletic as are hornworts, liverworts, and mosses, with hornworts identified as the sister group of a liverwort/moss assemblage. In vascular plants, lycophytes are polyphyletic andSelaginella is close to the bryophytes.Lycopodium is the sister group of the remaining vascular plants (minusSelaginella). Longer treelengths (over 250) are required to produce tree topologies in which either lycophytes are monophyletic or to reconstruct the paraphyletic bryophyte phylogeny of recent authors. This analysis challenges existing concepts of bryophyte phylogeny based on more classical data and interpretations, and provides new insight into land plant evolution.     

Natural soil spore banks — can they be used to retrieve lost ferns?

Some fern species form spore banks — reservoirs in the soil of viable spores which remain dormant while buried but germinate in light if brought to the surface. The recently discovered characteristics of these spore banks are described. Enough is now known to suggest that they might have a role in the conservation of endangered fern species as alternatives toex situ collections of sporophytes, gametophytes and spores, the relative merits of which are also considered. Mature sporophytes of several British species have now been raised from natural spore banks in soil samples; if this proves to be possible also for endangered species, some interesting options become available. The possibilities are discussed of augmenting surviving populations and increasing their genetic diversity, even perhaps of retrieving lost populations, by reintroduction of spore bank-derived plants or by stimulating regeneration from spore banksin situ. Botanic gardens are well placed to provide the further research, the regular monitoring of endangered populations, and the taxonomic and horticultural support required to realise these possiblities.     

A revision of the genusCyathorachis in Japan

Cyathorachis, a genus of Cretaceous tree fern rachises is revised. In addition to the type specimens of the sole species,C. fujiiana Ogura, two specimens collected near the type locality were examined histologically. The histological data being used for the taxonomical comparison were obtained from anatomical studies on the rachises of extant tree ferns. As a result of the study three species are recognized, two of which are new. As a result of this study, it appears that species differentiation of the tree ferns in the late Cretaceous age of Hokkaido was rather high, as it is now in tropical and subtropical regions. Contributions from the Laboratory of Phylogenetic Botany, Chiba University, No. 74.     

Hydrocarbons and fatty acids of ferns

The analysis of hydrocarbons and fatty acids in ten fern species indicate unique differences from plants in a higher phylogenetic order. Significant concentrations of fatty acids above C₂₀ are present. Distributions of hydrocarbons range from C₁₅–C₃₃ with a trend towards two maxima at C₁₇ and C₂₉. Homologous series of n-alkenes are present in all species. Pristane and phytane are large components representing up to 27% of the alkanes. Distinct alkane and fatty acid differences between fern families are observed while species variations within families are slight.     

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.     

Vascular epiphytes in the temperate zones–a review

Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in temperate forests is little appreciated. This review summarises the available information on epiphytism in the temperate zones (> 23.5 latitude), which has not been reviewed omprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum temperate epiphyte communities are generally dominated by ferns and fern-allies. Other temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and diversity (water scarcity or low tempera-tures). are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.     

Exploring the evolution of humus collecting leaves in drynarioid ferns (Polypodiaceae, Polypodiidae) based on phylogenetic evidence

Most species of the paleotropic fern genera Aglaomorpha and Drynaria, together constituting a monophyletic clade (drynarioid ferns), possess humus-collecting structures as an adaptation to their epiphytic life form. Humus-collectors are either present as a specialized foliar structure (external leaf dimorphism) or as a specialized leaf part (internal dimorphism). Apart from these basic patterns there are several forms of reduction and an internal fertile – sterile dimorphism in Aglaomorpha. We present a phylogeny of drynarioid ferns based on morphological and molecular (cpDNA) markers. The genus Aglaomorpha was found to be monophyletic, whereas Drynaria is likely to be a paraphyletic assemblage including a grade of Himalayan to Southern Chinese taxa basal to Aglaomorpha. The evolution of humus-collectors is reconstructed by plotting their character state changes onto the obtained phylogeny. Despite the complex morphological pattern across species, evolution of drynarioid humus-collecting structures can be reconstructed postulating a simple sequence of character state changes based on only a few elementary processes.     

Gymnogrammitis dareiformis is a polygrammoid fern (Polypodiaceae) – Resolving an apparent conflict between morphological and molecular data

 Maximum parsimony and maximum likelihood analyses of the combined data sets of two chloroplast genes, rbcL and rps4, demonstrate that nk;the monotypic genus Gymnogrammitis is part of the polygrammoid clade (Polypodiaceae + Grammitidaceae), and not the Davalliaceae as proposed in most studies. The genus forms a clade together with two Asiatic genera of the Polypodiaceae, Arthromeris and Selliguea. These last two genera have either simple or once-pinnate leaves, whereas Gymnogrammitis has highly divided (3- to 4-pinnate) blades. Two characters of this genus, the basic chromosome number of x=36 and the absence of indusia, support a relationship with the Polypodiaceae. Neither feature is found within Davalliaceae. Three morphological characters support the placement of Gymnogrammitis within the selligueoid lineage of Polypodiaceae: spores with a thick perine extending in microspines, sclerenchymatous strands in the rhizome, and non-clathrate rhizome scales. These results demonstrate that molecular and morphological data are phylogenetically congruent with the exception of blade dissection. Our study clearly shows the pitfalls of classifications based on single characters, and illustrates the importance of phylogenetic assessment of all taxonomic conclusions. Received November 22, 2001; accepted May 21, 2002 Published online: November 14, 2002 Addresses of the authors: Harald Schneider (e-mail: hschneid@duke.edu), Department of Biology, Duke University, Durham, North Carolina, 27708, USA; Current address: Albrecht-von-Haller Institut für Pflanzenwissenschaften der Universit?t G?ttingen, Abteilung Systematische Botanik, Untere Karspüle 2, D-37073 G?ttingen, Germany. Alan R. Smith, Ray Cranfill, University Herbarium, University of California, Berkeley, California 94720-2465, USA. Christopher H. Haufler, Terri Hildebrand, Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA. Tom A. Ranker, University Museum and Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, Colorado 80309, USA.     

Sex allocation in aquatic ferns: The role of body size

Patterns of resource allocation reflect the plastic strategies that result from different selective pressures imposed by the environment. However, biomass allocation can be limited by architectural restrictions that change with the plant size. Our knowledge about sex allocation in heterosporous aquatic ferns remains scarce and studies on the reproductive strategies of these plants may yield valuable information regarding the evolutionary history of heterospory. Here, we investigate resources allocation, both in number and in biomass, to produce megasporangia and microsporangia among three species of Salvinia with different body sizes. Salvinia oblongifolia, S. auriculata and S. minima were collected in temporary ponds on the floodplain of the Pandeiros River in Brazil. We counted megasporangia and microsporangia, and measured their dry mass in each ramet. We also measured the total vegetative biomass and total reproductive biomass of each ramet in each species. Resource allocation to megasporangia production is associated with the specific body size of each species. However, the allocation for microsporangia production was higher in the species with intermediate size, which probably may be related to the drought event. The total reproductive biomass of each species was not dependent on the total vegetative biomass, but despite a similar reproductive effort, species differ on which sex is prioritized in the allocation process. Our results provide the first data about the processes underlying the sex allocation of Salvinia in the floodplains. The production of sori is size dependent in each Salvinia species and is shaped by drought, an intense selective pressure in temporary wet habitats.