Short and informative DNA products to indirectly measure vascular plant biodiversity

Anthropogenic activities are having a deleterious effect on biodiversity. To understand the magnitude of this issue, and ultimately temper its pace, requires reproducible biodiversity measurements at suitable spatio-temporal scales. Procuring such data solely by existing approaches is unachievable because of the costs, time and the taxonomic expertise required. High-throughput molecular biodiversity analysis shows great promise, increasing the breadth of biota sampled and accelerating the rate of data collection. In this issue of Molecular Ecology, Yoccoz et al. (2012) use short informative DNA product 'meta-barcodes' to provide an insight into above-ground vascular plant diversity from boreal, temperate and tropical environments. Interestingly, their molecular analysis was derived from the soils and not the plants themselves, with the molecular signatures of the soils not only strongly reflecting current diversity, but also traces of crops not sown for up to one hundred years. Importantly, the research examines the complexities associated with deriving biomass estimates from molecular data and the need to consider biomass turnover. The use of soil-derived meta-barcodes extends beyond estimating vascular plant diversity, with the approach being suited to the range of ecological applications, especially scenarios where DNA may be degraded.     

Beta diversity in relation to dispersal ability for vascular plants in North America

Aim To test the hypothesis that plant species with a higher dispersal ability have a lower beta diversity. Location North America north of Mexico. Method Propagules of pteridophytes (ferns and their allies) are more vagile than propagules of spermatophytes (gymnosperms and angiosperms), and thus pteridophytes have a higher dispersal ability than do spermatophytes. The study area was divided into 71 geographical units distributed in five latitudinal zones. Species lists of pteridophytes and spermatophytes were compiled for each geographical unit. Three measures of beta diversity were used: β_sim, which is one minus the Simpson index of similarity, β_slope, which is the slope of the relationship between Simpson index and geographical distance, and β_{0.5‐distance}, which is the distance that halves the similarity from its initial value. Results Average β_sim is higher for spermatophytes than for pteridophytes, regardless of whether the data are analysed for the whole continent or for latitudinal zones. Average β_sim decreases with increasing latitude for both spermatophytes and pteridophytes. The difference in average β_sim between the two plant groups increases with increasing latitude, indicating that beta diversity decreases with increasing latitude faster for pteridophytes than for spermatophytes. When the Simpson index is regressed against geographical distance, the regression slope (β_slope) is steeper for spermatophytes than for pteridophytes, and the slope decreases with increasing latitude for both plant groups. Similarly, β_{0.5‐distance} was shorter for spermatophytes than for pteridophytes in each latitudinal zone and increased with increasing latitude for both plant groups. The results of the analyses using the three different measures of beta diversity are consistent. Main conclusions The fact that beta diversity is lower for pteridophytes with vagile propagules than for spermatophytes with less vagile propagules suggests that beta diversity is negatively related to dispersal ability.     

上海市蕨类植物分布特点及其与环境因子关系分析

在查阅资料和标本基础上,对上海市33个样地蕨类植物进行了野外调查,初步确定了上海市自然分布的蕨类植物23科31属50种,并讨论了归化种与栽培种及曾有记录而可能消亡的种类。采用双向指示种法（TWINSPAN）和典范对应分析（CCA）方法对蕨类植物分布特点及其与环境因子关系进行了分析。结果表明：（1）蕨类分布的样点可分为3组,第1组为市区样点,种数为0～4种;第2组为市郊样点,种数为0～8种;第3组为佘山岛、佘山地区、大金山岛,是上海蕨类最丰富地区,种数达26种以上。（2）影响上海蕨类植物生长的主要环境因子为基质、郁闭度和人为干扰。     

Why are ferns regularly over‐represented on state and provincial rare plant lists?

Several recent studies have suggested that rare species are not randomly distributed throughout plant taxa. This would appear to apply to North American ferns, which are frequently over-represented on local lists of rare plant species. However, such lists often paint a skewed portrait of the true situation because of our tendency to recognize the rarity of well-known and charismatic species while ignoring that of lesser-known or less-appreciated species. In order to verify if this over-representation of ferns is a real and consistent trend throughout local floras in North America, we used data from what we consider to be the most complete and objective available database: NatureServe Explorer ( http://www.natureserve.org/explorer/ ). We compiled data on total vascular plant species, total fern species, as well as rare vascular plant species and rare fern species for each North American subnational (Canadian province or US state) flora. Rare species were defined as those belonging to one of NatureServe's 'at risk' categories. The null hypothesis that the contribution of rare ferns to total rare species did not differ from their contribution to the total vascular flora was assessed using χ². Out of 64 subnational floras, we obtained significantly higher values than expected in 28 cases, and significantly lower in only one case. Similar trends hold true for individual fern families. These tendencies could be related to several factors of anthropogenic, biological, climatological, evolutionary, and geographical origin. However, we believe that the main reason is related to scale, namely the geopolitical units at which rarity is often studied. Our results illustrate one of the problems of a parochial approach to conservation, where the perceived rarity of an entire taxon is exaggerated because of the scale at which rarity is addressed.     

Lomariopsis ×farrarii: a new hybrid fern between L. japurensis and L. vestita (Lomariopsidaceae) from Costa Rica

A new hybrid,Lomariopsis ×farrarii, is illustrated and described from the La Selva Biological Station, Costa Rica. It is intermediate between its parents,L. japurensis andL. vestita in length and color of the rhizome scales, shape and number of the pinnae, and size and division of the juvenile leaves in a heteroblastic series.     

Nuclear DNA C-values in 30 species double the familial representation in pteridophytes

Nuclear DNA C-values and genome size are important biodiversity characters with fundamental biological significance. Yet C-value data for pteridophytes, a diverse group of vascular plants with approx. 9000 extant species, remain scarce. A recent survey by Bennett and Leitch (2001, Annals of Botany 87: 335-345) found that C-values were reported for only 48 pteridophyte species. To improve phylogenetic representation in this group and to check previously reported estimates, C-values for 30 taxa in 17 families were measured using flow cytometry for all but one species. This technique proved generally applicable, but the ease with which C-value data were generated varied greatly between materials. Comparing the new data with those previously published revealed several large discrepancies. After discounting doubtful data, C-values for 62 pteridophyte species remained acceptable for analysis. The present work has increased the number of such species' C-values by 93 %, and more than doubled the number of families represented (from 10 to 21). Analysis shows that pteridophyte C-values vary approx. 450-fold, from 0-16 pg in Selaginella kraussiana to 72.7 pg in Psilotum nudum var. gasa. Superimposing C-value data onto a robust phylogeny of pteridophytes suggests some possible trends in C-value evolution and highlights areas for future work.     

How much genetic variation in fern populations is stored in the spore banks? A study of Athyrium filix-femina (L.) Roth

The genetic variation within spore banks of Athyrium filix-femina (L.) Roth from three sites in north-eastern Switzerland was investigated. At two sites spore banks were located beneath sporophyte populations. One collection site was 10Om away from a sporophyte population. The gametophytes grown from the soil samples, the dimensions of which were 4 × 4 × 1.5 cm, and sporophytes from each site were analysed electrophoretically for either three or four variable allozyme loci. The spore banks from the different soil samples within and between populations revealed a considerable amount of genetic diversity. The most frequent alleles within the two sporophyte populations were, with a few exceptions, also the most frequent within the spore banks. The influence of single sporophytic individuals on the genetic composition of microsites seems to be considerably reduced by stochastic processes such as soil movement or the action of earthworms, which promote the mixing of spores from different spatial and temporal origins. It was shown that spores remain viable after passing through the gut of earthworms and that spore banks from even small soil samples revealed genetic diversity and could lead to a large number of genetically distinct sporophytes. The results suggest that fertilization seems to be close to random because the sporophyte populations sampled were in Hardy-Weinberg equilibrium and had fixation index ( F _is) close to zero.     

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.