Calorimetric properties of water and triacylglycerols in fern spores relating to storage at cryogenic temperatures

Storing spores is a promising method to conserve genetic diversity of ferns ex situ. Inappropriate water contents or damaging effects of triacylglycerol (TAG) crystallization may cause initial damage and deterioration with time in spores placed at -15 degrees C or liquid nitrogen temperatures. We used differential scanning calorimetry (DSC) to monitor enthalpy and temperature of water and TAG phase transitions within spores of five fern species: Pteris vittata, Thelypteris palustris, Dryopteris filix-mas, Polystichum aculeatum, Polystichum setiferum. The analyses suggested that these fern spores contained between 26% and 39% TAG, and were comprised of mostly oleic (P. vittata) or linoleic acid (other species) depending on species. The water contents at which water melting events were first observable ranged from 0.06 (P. vittata) to 0.12 (P. setiferum)gH(2)Og(-1)dry weight, and were highly correlated with water affinity parameters. In spores containing more than 0.09 (P. vittata) to 0.25 (P. setiferum)gH(2)Og(-1)dry weight, some water partitioned into a near pure water fraction that melted at about 0 degrees C. These sharp peaks near 0 degrees C were associated with lethal freezing treatments. The enthalpy of water melting transitions was similar in fern spores, pollen and seeds; however, the unfrozen water content was much lower in fern spores compared to other forms of germplasm. Though there is a narrow range of water contents appropriate for low temperature storage of fern spores, water content can be precisely manipulated to avoid both desiccation and freezing damage.     

Major evolutionary events in the origin and diversification of the fern genus Polystichum (Dryopteridaceae)

Recent advances in molecular systematics of the ferns make it possible to address long-standing questions about classification of the major fern genera, such as the worldwide genus Polystichum (Dryopteridaceae), comprising at least 200 species. In this study we examined rbcL sequences and morphological characters from 55 fern taxa: 34 were from Polystichum and 21 were from other genera in the Dryopteridaceae. We found that Phanerophlebia, possibly including Polystichopsis, is the sister group to Polystichum sensu lato (s.l.), including Cyrtomium. Polystichum as commonly recognized is paraphyletic. Our results lead us to suggest recognizing the clade of earliest diverging Polystichum species as a distinct genus (Cyrtomidictyum) and to continue to recognize Cyrtomium as a separate genus, leaving a monophyletic Polystichum sensu stricto (s.s.). We resolved a tropical American clade and an African clade within Polystichum s.s. However, the resemblance between the once-pinnate, bulb-bearing calciphilic species found in Asia and the West Indies appears to be the result of convergent evolution. Optimizing our morphological character transformations onto the combined phylogeny suggests that the common ancestor of Polystichum s.l. and Phanerophlebia had evolved the common features of the alliance, including ciliate petiole-base scales, once-pinnate fronds, ultimate segments with scarious tips, peltate indusia, and microscales.     

The comparative ecology of Polystichum aculeatum, P. braunii, and P. lonchitis in Hordaland, western Norway

The comparative ecology of the three species of Polystichum in Hordaland, western Norway, has been studied. Species frequency data and environmental variables were recorded in 132 sample units from 10 different localities. The numerical methods used to analyse these data are two-way indicator species analysis, detrended correspondence analysis, canonical correspondence analysis, and Gaussian logit regression. The main floristic gradient in the data is closely related to altitude. The second floristic gradient follows patterns in precipitation and soil pH. The ordination and classification results show that P. braunii is primarily a plant of deciduous forests, P. aculeatum occurs in open or woodland habitats near the coast, and P. lonchitis favours open habitats with cool summers at either low or high altitudes. The Gaussian logit regression results suggest that low altitude, short distance from the coast, and high soil pH may be important in influencing the growth of P. aculeatum , whereas P. braunii appears to depend most strongly on high soil depth and humidity and an adequate but not too extensive snow-cover in winter. P. lonchitis is found to favour high soil and air humidity, high light intensity, and not too high summer temperatures. The results contribute to our understanding of the local, national, and European distributions of the three species. In western Norway, conditions appear to be generally favourable for P. braunii and P. lonchitis , but are clearly less favourable for P. aculeatum     

Evidence for natural selection in a fern hybrid zone

Morphological characters, chloroplast DNA, and allozymes were used to analyze the distribution of individuals within a hybrid population of the ferns Polystichum munitum and P. imbricans in northwestern California. Microsites within the population were characterized according to soil moisture and light levels reaching the plants. In sites with low soil moisture and high light levels, all of the ferns were genetically and morphologically like P. imbricans. In contrast, ferns with the genetic and morphological identity of P. munitum predominated in moist shady sites. Intermediate sites supported very few P.munitum, a wide variety of hybrid recombinants, and a majority of ferns with P. imbricans characteristics. The pattern of variation within the population is noteworthy because of the close proximity of the habitat extremes and the long-range dispersal of fern spores. We conclude that natural selection along environmental gradients must be a major factor in determining the ecological and genetic associations within the hybrid zone. The results of this study are evaluated in the context of the fern life cycle and compared to the assumptions of models explaining the establishment and maintenance of hybrid zones, which vary in the role attributed to environmentally mediated natural selection.     

Population biology of two rare fern species: long life and long-lasting stability

? Premise of the study: This study describes the population dynamics of two rare fern species and evaluates the prospects of their survival. This is the first detailed demography study of ferns using transition matrix models. The study species, Asplenium adulterinum and A. cuneifolium, are restricted to serpentine rocks and differ in ploidy level and partly in habitat requirements. Both species are of interest in nature conservation. ? Methods: Single life-history traits were evaluated and transition matrix models were used to describe the dynamics of the populations. Population growth rates, elasticity values, and life-table response experiments were used to compare the dynamics between species, years, and different habitat types. Predicted population performance based on models was compared with real data on population growth. ? Key Results: All populations of both species are growing. Stable stage distribution based on stochastic simulation corresponds to current stage distribution. The most critical phase of the life cycle is stasis of large adult plants. Reproduction is of low importance. Extinction probability of small populations is low. Mean life span of individuals of both species is 30-50 yr. When compared with real data, the model successfully predicted population performance over 10 yr. ? Conclusion: Populations in the study region are not endangered, and current population dynamics are stable. Differences in life-history traits between species, probability of extinction between species and habitat, and different ploidy-and, thus, probably different dispersal ability-suggest the existence of metapopulation dynamics.     

Gene Flow among Populations of Two Rare Co-Occurring Fern Species Differing in Ploidy Level

Differences in ploidy levels among different fern species have a vast influence on their mating system, their colonization ability and on the gene flow among populations. Differences in the colonization abilities of species with different ploidy levels are well known: tetraploids, in contrast to diploids, are able to undergo intra-gametophytic selfing. Because fertilization is a post-dispersal process in ferns, selfing results in better colonization abilities in tetraploids because of single spore colonization. Considerably less is known about the gene flow among populations of different ploidy levels. The present study examines two rare fern species that differ in ploidy. While it has already been confirmed that tetraploid species are better at colonizing, the present study focuses on the gene flow among existing populations. We analyzed the genetic structure of a set of populations in a 10×10 km study region using isoenzymes. Genetic variation in tetraploid species is distributed mainly among populations; the genetic distance between populations is correlated with the geographical distance, and larger populations host more genetic diversity than smaller populations. In the diploid species, most variability is partitioned within populations; the genetic distance is not related to geographic distance, and the genetic diversity of populations is not related to the population size. This suggests that in tetraploid species, which undergo selfing, gene flow is limited. In contrast, in the diploid species, which experience outcrossing, gene flow is extensive and the whole system behaves as one large population. Our results suggest that in ferns, the ability to colonize new habitats and the gene flow among existing populations are affected by the mating system.     

POPULATION STRUCTURE AND ESTIMATES OF GENE FLOW IN THE HOMOSPOROUS FERN POLYSTICHUM MUNITUM

Levels and distribution of genetic variation were investigated in the homosporous fern, Polystichum munitum. Homosporous ferns differ from higher vascular plants in that they possess potentially bisexual gametophytes which can produce a completely homozygous sporophyte in a single generation. Because of this, it has long been maintained that ferns possess an inbreeding mating system, resulting in low levels of genetic variation and high levels of homozygosity within populations. The four populations sampled maintain high levels of genetic variation (P? = 0.542; H? = 0.111; ā = 2.23), comparable to that maintained by populations of outcrossing seed plants. The mean fixation index, F, for the four populations was 0.052, indicating no significant deviations from Hardy-Weinberg genotypic expectations. Polystichum munitum distributes most of its genetic variation within rather than among populations. Population-genetic structure was assessed by subdividing each of two large populations into 10 × 10-m subpopulations. Comparisons of genetic variation within and among subpopulations indicated little genetic substructure within either of the artificially subdivided populations. Estimates of interpopulational gene flow (Nm) are extremely high, comparable to those reported for gymnosperms. Statistical estimates of intragametophytic selling are very low, ranging from 0 to 3%. This study suggests that Polystichum munitum is an outcrossing species. Evidence from this and other investigations indicates that fern species do not typically self-fertilize and that mating systems in ferns vary as they do among species of seed plants.     

Origin of Hawaiian Polystichum (Dryopteridaceae) in the context of a world phylogeny

A genus-wide molecular phylogeny for Polystichum and allied genera (Dryopteridaceae) was reconstructed to address the biogeographic origin and evolution of the three Hawaiian Polystichum species, all endemic there. The analysis was based on the cpDNA sequences rbcL and the trnL-F spacer from a taxonomically and geographically diverse sample. Parsimony and Bayesian phylogenetic analyses of the combined data support a monophyletic Polystichum and corroborate recent hypotheses as to membership and sequence of origin of the major groups within the genus. The Hawaiian Polystichum species are polyphyletic; two separate lineages appear to have arrived independently from the Old World. The provenance of the diploid Polystichum hillebrandii is continental eastern Asia, while the source of the polyploid lineage comprising tetraploid P. haleakalense and octoploid P. bonseyi is likely continental Asia. From our results, the origin of the Hawaiian species of Polystichum, like many Hawaiian fern genera with several species, is the result of multiple migrations to the islands, rather than single migrations yielding nearly all the local diversity as in the angiosperms. This emerging pattern provides a modern test of the premise that propagule vagility has a central role in determining pattern of evolution.     

Fern-associated arbuscular mycorrhizal fungi are represented by multiple Glomus spp.: do environmental factors influence partner identity?

Symbioses involving arbuscular mycorrhizal fungi (AMF) are among the most important ecological associations for many plant species. The diversity of AMF associated with ferns, however, remains poorly studied. Using recently designed Glomus-specific primers, we surveyed the AMF community associated with ferns from deciduous, broad-leaved second-growth forest habitats at the eastern edge of the piedmont region of central Virginia, USA. Results indicate that this molecular approach may be a useful tool for detecting AMF in ferns compared to traditional techniques based on morphology. Over 30 potential fungal ribotypes were identified from eight fern species using denaturing gradient gel electrophoresis. Fungal ribotypes were found to differ widely in terms of (1) the number of fern partners with which they interact and (2) their relative frequency within each fern. Sequence analysis of fungal isolates from three species of fern indicated that the primers were generally highly specific for Glomus species but some non-target DNA was also amplified. Cloned polymerase chain reaction (PCR) products from Polystichum acrostichoides and Osmunda regalis revealed several phylogenetically distinct Glomus species. A single Glomus species was identified in the cloned PCR products from Botrychium virginianum. These findings challenge the hypothesis that the extent or degree of fern–fungal symbiosis is somehow tied to root complexity. Environmental factors appear to influence the suite of AMF that form partnerships with ferns. Some species of fern from similar habitats associated with dissimilar fungal partners (e.g., P. acrostichoides and Athyrium filix-femina var. asplenioides), whereas others harbored uniform fungal communities (e.g., Asplenium platyneuron). The significance of these data in terms of ecological and evolutionary dynamics of the AMF–fern symbiosis is discussed. Brittany West, Jessica Brandt, and Kay Holstien contributed equally to this work.     

Ecological and phylogenetic approaches for diversification of apogamous ferns in Japan

It has long been argued that related asexual and sexual taxa have different distribution patterns. In general, apomictic angiosperms are believed to occur preferentially at higher latitudes and elevations compared to their sexual relatives. It is thus expected that the frequency of apomixis increases with latitude or from warmer to colder climatic regions. However, despite the significant role played by apogamy in fern evolution and diversification, the distribution pattern of apogamous ferns and lycophytes has received little attention. To clarify the ecological diversity pattern and evolutional diversification of apogamous ferns, we analysed a variety of apogamous fern species with reference to latitude, elevation and climatic factors, and reconstructed the ancestral state and estimated the divergence time of Japanese apogamous ferns. Our results on the distribution of apogamous ferns along these two gradients suggest a decline in the proportion of apogamous ferns towards high latitudes and elevations. Temperature was correlated with the proportion of apogamous ferns along both gradients, and the seasonality of precipitation was correlated with the proportion of apogamous ferns along latitude. Reconstruction of ancestral state and estimates of divergence time showed that the crown groups of apogamous ferns diversified less than 15 Ma. The results of our ecological and phylogenetic approaches reinforce the hypothesis based on previously reported phylogenetic results in which the apogamous ferns appears to be correlated with strongly seasonal climates such as the Asia monsoon.     

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。     

湖南丹霞地貌区蕨类植物多样性

丹霞地貌是有别于石灰岩地貌和花岗岩地貌的特殊地貌类型,发育着较为独特的植被类型和植物区系。我们于2007-2010年间对湖南新宁崀山、茶陵浣溪、平江石牛寨、资兴程江口、浏阳达浒、通道万佛山、沅陵五强溪夸父山、溆浦思蒙等地丹霞地貌的蕨类植物进行了广泛调查,报道了湖南丹霞地貌区蕨类植物31科66属183种的详细名录。其中,无腺姬蕨(Hypolepis polypodioides)、隐囊蕨(Notholaena hirsuta)、仙霞铁线蕨(Adiantum juxtapo-situm)、百山祖短肠蕨(Allantodia baishanzuensis)、肉质短肠蕨(A.succulenta)、骨碎补铁角蕨(Asplenium ritoense)、钝齿耳蕨(Polystichum deltodon var.henryi)、无盖耳蕨(P.gymnocarpium)、单羽耳蕨(P.simplicipinnum)、二型肋毛蕨(Ctenitis dingnanensis)等9种为湖南新记录种。湖南丹霞地貌的蕨类植物种类组成主要有鳞毛蕨科、蹄盖蕨科、水龙骨科、金星蕨科、卷柏科、铁角蕨科等较大科及鳞毛蕨属(Dryopteris)、卷柏属(Selaginella)、铁角蕨属(Asplenium)、短肠蕨属(Allantodia)和凤尾蕨属(Pteris)等较大属。生态适应特点分析表明丹霞地貌既有喜钙质土的种类,也有喜酸性土的种类,仙霞铁线蕨和无盖耳蕨可能是丹霞地貌的特有植物,因而具有石灰岩地貌蕨类植物区系和花岗岩地貌蕨类植物区系之间的过渡性特点。建议将垫状卷柏(Selaginella pulvinata)、福建观音座莲(Angiopterisfokiensis)、仙霞铁线蕨、骨碎补铁角蕨、鞭叶蕨(Cyrtomidictyum lepidocaulon)、无盖耳蕨等种类列为丹霞地貌蕨类植物中的优先保护种类,将通道万佛山三十六湾、湖南沅陵夸父山列为丹霞地貌蕨类植物的优先保护地区。     

Diverse spore rains and limited local exchange shape fern genetic diversity in a recently created habitat colonized by long-distance dispersal

Background and Aims

Populations established by long-distance colonization are expected to show low levels of genetic variation per population, but strong genetic differentiation among populations. Whether isolated populations indeed show this genetic signature of isolation depends on the amount and diversity of diaspores arriving by long-distance dispersal, and time since colonization. For ferns, however, reliable estimates of long-distance dispersal rates remain largely unknown, and previous studies on fern population genetics often sampled older or non-isolated populations. Young populations in recent, disjunct habitats form a useful study system to improve our understanding of the genetic impact of long-distance dispersal.

Methods

Microsatellite markers were used to analyse the amount and distribution of genetic diversity in young populations of four widespread calcicole ferns (Asplenium scolopendrium, diploid; Asplenium trichomanes subsp. quadrivalens, tetraploid; Polystichum setiferum, diploid; and Polystichum aculeatum, tetraploid), which are rare in The Netherlands but established multiple populations in a forest (the Kuinderbos) on recently reclaimed Dutch polder land following long-distance dispersal. Reference samples from populations throughout Europe were used to assess how much of the existing variation was already present in the Kuinderbos.

Key Results

A large part of the Dutch and European genetic diversity in all four species was already found in the Kuinderbos. This diversity was strongly partitioned among populations. Most populations showed low genetic variation and high inbreeding coefficients, and were assigned to single, unique gene pools in cluster analyses. Evidence for interpopulational gene flow was low, except for the most abundant species.

Conclusions

The results show that all four species, diploids as well as polyploids, were capable of frequent long-distance colonization via single-spore establishment. This indicates that even isolated habitats receive dense and diverse spore rains, including genotypes capable of self-fertilization. Limited gene flow may conserve the genetic signature of multiple long-distance colonization events for several decades.     

Evolution of genome space occupation in ferns: linking genome diversity and species richness

Background and AimsThe dynamics of genome evolution caused by whole genome duplications and other processes are hypothesized to shape the diversification of plants and thus contribute to the astonishing variation in species richness among the main lineages of land plants. Ferns, the second most species-rich lineage of land plants, are highly suitable to test this hypothesis because of several unique features that distinguish fern genomes from those of seed plants. In this study, we tested the hypothesis that genome diversity and disparity shape fern species diversity by recording several parameters related to genome size and chromosome number.MethodsWe conducted de novo measurement of DNA C-values across the fern phylogeny to reconstruct the phylogenetic history of the genome space occupation in ferns by integrating genomic parameters such as genome size, chromosome number and average DNA amount per chromosome into a time-scaled phylogenetic framework. Using phylogenetic generalized least square methods, we determined correlations between chromosome number and genome size, species diversity and evolutionary rates of their transformation.Key ResultsThe measurements of DNA C-values for 233 species more than doubled the taxon coverage from ~2.2 % in previous studies to 5.3 % of extant diversity. The dataset not only documented substantial differences in the accumulation of genomic diversity and disparity among the major lineages of ferns but also supported the predicted correlation between species diversity and the dynamics of genome evolution.ConclusionsOur results demonstrated substantial genome disparity among different groups of ferns and supported the prediction that alterations of reproductive modes alter trends of genome evolution. Finally, we recovered evidence for a close link between the dynamics of genome evolution and species diversity in ferns for the first time.     

Contrasting Predictors of Fern versus Angiosperm Decomposition in a Common Garden

We evaluated differences in the rates and correlates of decomposition among 32 fern and angiosperm litter types collected in Hawai'i. Leptosporangiate ferns were separated into groups based on phylogeny: 'polypod' ferns, a monophyletic clade of ferns that diversified in the Cretaceous, and all other ('non-polypod') ferns that diversified earlier. We measured initial litter chemistry (nutrients and carbon chemistry), and mass loss and nitrogen (N), phosphorus (P), and calcium (Ca) of litter tissue during a 1-yr incubation in a common garden. Nutrient concentrations and carbon (C) chemistry differed significantly among litter types, and litter turnover ( k -values) ranged from 0.29 to 8.31. Decomposition rates were more closely correlated with nutrient concentration than is typically observed. Lignin:N was the best predictor of decomposition across all litter types combined; however, among plant groups different predictors of decomposition were important. Nitrogen and P concentrations best predicted fern decomposition, whereas C chemistry, particularly lignin concentration, was more important for angiosperm (monocot and dicot) decomposition. Among native plants, non-polypod ferns decomposed significantly more slowly than both polypod ferns and angiosperms. Contrary to our hypothesis, fern litter did not decompose more slowly than angiosperm litter overall. Nutrient dynamics in litter were affected by initial litter concentration more than phylogeny; low-nutrient litter immobilized more nutrients than high-nutrient litter. Systematic differences in rates of decomposition, and the importance of nutrients in predicting fern decomposition, imply that changes in species composition within ferns and between ferns and angiosperms could influence the functioning of ecosystems where ferns are important forest components.     

Impacts of predator-mediated interactions along a climatic gradient on the population dynamics of an alpine bird

According to classic theory, species'' population dynamics and distributions are less influenced by species interactions under harsh climatic conditions compared to under more benign climatic conditions. In alpine and boreal ecosystems in Fennoscandia, the cyclic dynamics of rodents strongly affect many other species, including ground-nesting birds such as ptarmigan. According to the ‘alternative prey hypothesis’ (APH), the densities of ground-nesting birds and rodents are positively associated due to predator–prey dynamics and prey-switching. However, it remains unclear how the strength of these predator-mediated interactions change along a climatic harshness gradient in comparison with the effects of climatic variation. We built a hierarchical Bayesian model to estimate the sensitivity of ptarmigan populations to interannual variation in climate and rodent occurrence across Norway during 2007–2017. Ptarmigan abundance was positively linked with rodent occurrence, consistent with the APH. Moreover, we found that the link between ptarmigan abundance and rodent dynamics was strongest in colder regions. Our study highlights how species interactions play an important role in population dynamics of species at high latitudes and suggests that they can become even more important in the most climatically harsh regions.     

Phenology and wintering capacity of sporophytes and gametophytes of ferns native to northern Japan

Summary To investigate life history adaptations to cold climates, the leaf development, sporulation period, growing stage of gametophytes, and the frost and drought resistance of sporophytes and gametophytes of 67 fern species native to Kokkaido were studied. Most ferns common in Hokkaido are summer-green with leaves developing during late May to June and decaying during October. Most of the ferns in Hokkaido sporulate during August to early September. Spores dispersed from June to September germinate before winter begins, forming vegetative prothallia. Gametophytes mature only in the following summer. Thus in Hokkaido the gametophytes as well as perennial sporophytes are exposed to severe winter conditions. In order to correlate the life cycles of temperate ferns with winter cold stress, frost resistance of gametophytes, rhizomes, and leaves of sporophytes were determined. Maximal frost resistance of rhizomes reflects the stress conditions of their habitats: rhizomes of forest understory ferns are damaged at-5°to -17.5°C, epiphytic ferns and ferns of habitats exposed to severe frost sustained temperatures of -20° to-40°C. The leaves of winter-green and evergreen ferns resist frost ranging from -25° to -40°C. The leaves of summer-green ferns are killed by late frost below -5°C. With some exceptions, gametophytes of ferns growing on the forest floor resist frost to -40°C and are much hardier than sporophytes. These results suggest the possible restrictive effects of cold climate on the life span of leaves as well as on the sporulation period. If winter cold is one of the decisive factors for seasonality expression and habitat distribution of ferns, the sensitive generation must be the sporophyte rather than the gametophyte. The hardier gametophyte is therefore able to colonize habitats in which the sporophyte is excluded by frost if mechanisms of vegetative propagation are evolved.Contribution No. 2451 from The Institute of Low Temperature Science     

Host‐Plant Choice Behavior at Multiple Life‐Cycle Stages: The Roles of Mobility and Early Growth in Decision‐Making

The choice of food plants often assumes critical importance for a herbivore. Although many studies have investigated host‐plant choice behavior, few have examined preferences (vs. growth and survival) at multiple stages of the life cycle, notwithstanding the importance of identifying the critical stage(s) in an animal’s life history. Fern moths Herpetogramma theseusalis (Lepidoptera: Crambidae) provide an excellent opportunity to test host‐plant choice at several stages. Fern moth larvae feed on distantly related ferns, sensitive Onoclea sensibilis and marsh fern Thelypteris palustris, and adults oviposit on both species. We examined newly hatched larvae, overwintered larvae and ovipositing females to test hypotheses predicting when host‐plant choice takes place (overwintering and mobility hypotheses: overwintering stage determines choice of substrate vs. most mobile stage chooses) and the basis for choice (optimal oviposition and enemy‐free space hypotheses: resource producing highest fecundity vs. lowest losses to enemies). We also evaluated the hypothesis that host‐associated fitness trade‐offs explain host specialization. Only ovipositing females, the most mobile stage, exhibited a clear preference (for marsh fern), consistent with the mobility hypothesis. However, their preference for marsh fern fits neither the optimal oviposition hypothesis nor the enemy‐free space hypothesis; although some larvae initially grew faster on marsh fern, adults reared from the two ferns did not differ significantly in mass and experienced marginally lower parasitism on sensitive fern. Thus, we found no host‐associated fitness trade‐offs. Overwintering losses in marsh fern plots exceeded those in sensitive fern, and mixed plots supported the most overwintered larvae. Preference for marsh fern suggests that early success drives host‐plant choice, an advantage that later disappears. Temporal variability may prevent closer fits to the hypotheses, because both ferns provide the moths with acceptable resources throughout their life cycles.     

Ferns in the present-day periglacial zone of the Central Altai

This article presents data on the species composition and distribution of ferns in the present-day periglacial zone of the Aktru, Karagemskiy, Akkem, Sofiiskiy, Gebler, and Taldurinskiy glaciers in the Central Altai. Sixteen fern species have been found and confirmed by herbarium specimens. Botrychium lunaria (L.) Sw., Cystopteris dickieana R. Sim, C. fragilis (L.) Bernh., and Polystichum lonchitis (L.) Roth were the most tolerant to the severe conditions of high mountains. The distribution of ferns in the centers of the present-day glaciation was related mostly to the occurrence of rocks. Colonization of the periglacial zone by ferns occurred only by means of spores, initially by their introduction from habitats located far from the periglacial zone. The further colonization and migration of species, following the retreating glaciers, was possible by means of spores produced by sporophytes growing in the periglacial zone. Germination of spores and development of gametophytes and sporophytes under severe conditions of the periglacial zone generally occurred in local microlandscapes providing protection in the cold season and a sufficient amount of moisture in the warm season.     

观赏蕨类引种栽培及其物候期的观察

对中华水韭、福建观音座莲、华南紫萁、西南凤尾蕨、剑叶铁角蕨、翅轴蹄盖蕨、东方荚果蕨、同形鳞毛蕨、圆顶耳蕨等30种蕨类进行了引种栽培和物候期观察.结果表明:(1)引种成活率高;(2)管理粗放;(3)多数种类四季常青,形态优美,具有较高的观赏价值,能够在怀化市安全越冬,值得在亚热带地区开发利用;(4)华南紫萁、小黑桫椤、光蹄盖蕨、长江蹄盖蕨、翅轴蹄盖蕨、三相蕨、同形鳞毛蕨、圆顶耳蕨、镰羽贯众等9种蕨类在展叶时,同时长出孢子囊;(5)多数蕨类的孢子囊在长出后1个月左右发育成熟;(6)在叶开始萌动时引种栽培的蕨类,当年的营养叶萌发期和展叶期都推迟半个月左右,但孢子囊群的出现期和成熟期不受影响;(7)不同蕨类的孢子囊群形成期具有差异性,同种蕨类的孢子囊群形成期具有相对稳定性,因此,可以作为鉴别物种的依据之一。建议在编写、修订《中国植物志》和地方植物志时增加蕨类孢子囊群形成期的描述。