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Background and Aims We examined the relationship between reproductive allocation and vegetative growth in three monoicous sexual systems of bryophytes. The sexual systems show a gradient of increasing distance between the sexes, from gonioautoicous to cladautoicous to rhizautoicous. Here, we investigated the following two hypotheses: (1) reproductive allocation differs between sexes and sexual systems, and male reproductive allocation increases with increasing distance between male and female gametangia; and (2) reproductive allocation is negatively related to vegetative growth. Methods We sampled the three sexual systems, represented by three moss species of the genus Fissidens in the Atlantic Forest of Southeastern Brazil. Ramets were washed in the laboratory; the reproductive structures were detached from the vegetative ramets and sorted regarding sex and individual, dried at 70 °C for 72 h, and weighed in an ultramicrobalance. We calculated the mean reproductive and vegetative mass and reproductive allocation and used generalized linear models to test our predictions. Key Results Reproductive allocation differed between species and sexes. It was higher in the rhizautoicous than in the cladautoicous and gonioautoicous species. Mean reproductive allocation was greater in males than in females of the rhizautoicous species, greater in females than males of the cladautoicous species, and did not differ between the sexes in the gonioautoicous species. Estimates of reproductive and vegetative mass were positively related in females of the rhizautoicous species. Vegetative mass was not related to reproductive allocation in the gonioautoicous species, but negatively related to reproductive allocation in the male and female branchlets of the cladautoicous species and in the female ramets of the rhizautoicous species. Conclusions The reproductive allocation patterns differ between the rhizautoicous species and the ‘truly’ monoicous species, with shorter intersexual distances, which implies that our hypotheses were supported only in part. We suggest that the hypotheses should be reformulated and tested further by comparing ‘truly’ monoicous species with dioicous species and by including other genera.

Background and Aims Plants have evolved an unrivalled diversity of reproductive strategies, including variation in the degree of sexual vs. clonal reproduction. This variation has important effects on the dynamics and genetic structure of populations. We examined the association between large-scale variation in reproductive patterns and intraspecific genetic diversity in two moss species where sex is manifested in the dominant haploid generation and sex expression is irregular. We predicted that in regions with more frequent realized sexual reproduction, populations should display less skewed sex ratios, should more often express sex and should have higher genetic diversity than in regions with largely clonal reproduction. Methods We assessed reproductive status and phenotypic sex in the dioicous long-lived Drepanocladus trifarius and D. turgescens, in 248 and 438 samples across two regions in Scandinavia with frequent or rare realized sexual reproduction, respectively. In subsets of the samples, we analysed genetic diversity using nuclear and plastid sequence information and identified sex with a sex-specific molecular marker in non-reproductive samples. Key Results Contrary to our predictions, sex ratios did not differ between regions; genetic diversity did not differ in D. trifarius and it was higher in the region with rare sexual reproduction in D. turgescens. Supporting our predictions, relatively more samples expressed sex in D. trifarius in the region with frequent sexual reproduction. Overall, samples were mostly female. The degree of sex expression and genetic diversity differed between sexes. Conclusions Sex expression levels, regional sex ratios and genetic diversity were not directly associated with the regional frequency of realized sexual reproduction, and relationships and variation patterns differed between species. We conclude that a combination of species-specific life histories, such as longevity, overall degree of successful sexual reproduction and recruitment, and historical factors are important to explain this variation. Our data on haploid-dominated plants significantly complement plant reproductive biology.

Bryophytes are a diverse group of organisms with unique properties, yet they are severely underrepresented in plant trait databases. Building on the recently published European Red List of bryophytes and previous trait compilations, we present the Bryophytes of Europe Traits (BET) data set, including biological traits such as those related to life history, growth habit, sexual and vegetative reproduction; ecological traits such as indicator values, substrate and habitat; and bioclimatic variables based on the species' European range. The data set includes values for 65 traits and 25 bio-climatic variables, containing more than 135,000 trait values with a completeness of 82.7% on average. The data set will enable future studies in bryophyte biology, ecology and conservation, and may help to answer fundamental questions in bryology. info:eu-repo/semantics/publishedVersion

Introduction. Codonoblepharon forsteri (Dicks.) Goffinet is a rare epiphytic moss characteristically associated with water-filled holes in trees. We reviewed its range and population and assessed effects of climate change. Methods. An inventory of sites from where Codonoblepharon forsteri has been recorded was compiled. Extent of occurrence (EOO) and area of occupancy (AOO) were calculated. Population size was estimated, treating an occupied tree as an ‘individual-equivalent’ of the moss. Climatic conditions of the species’ current distribution were characterised, and an ensemble model of its distribution was generated. The latter was projected onto present and future climatic layers. Key results. Codonoblepharon forsteri has been recorded from 19 countries and 205 sites in Europe, North Africa and Southwest Asia. It has been undergoing an overall decline. Most sites have few occupied trees, and a world population of 1000–10, 000 individual-equivalents is estimated. Model projections suggest that the species will experience a range increase of +0.36–0.65 by 2050 and +0.35–0.68 by 2070, especially in its northwest range, particularly across France and the UK. Range loss is predicted to be between – 0.20 and –0.39 in 2050 and –0.21 and –0.65 in 2070, affecting the driest areas of the current range around the Mediterranean, especially in North Africa. Conclusions. Codonoblepharon forsteri has a relatively large EOO but relatively small AOO, probably due to habitat specialism. A major reason for recent declines appears to be widespread abandonment of traditional ‘pollarding’ of trees. The potential climatic range of the species will shift significantly northwards over the next few decades.

We investigated whether the European near-endemic moss Drepanocladus lycopodioides has declined in its core distribution area in the southern Baltic Sea region and explored potential explanations for this. First, we re-visited sites with documented records from 1854 to 1957 in the Stockholm archipelago and nearby mainland in southern Sweden. Second, we compared the numbers and distributions of Swedish occurrences, their habitats, and substrates up to 1950 (289 herbarium records), and from 1951 onwards (347) using different map layers. Third, we explored whether inter-annual variation in reproductive performance was related to moisture conditions at five sites on an island in the Stockholm archipelago during nine years. We estimated moisture conditions based on precipitation data and dry days during the time when fertilization occurs in the year prior to sporophyte maturation. Drepanocladus lycopodioides has strongly decreased in intensively managed agricultural landscapes but remains frequent in natural or semi-natural habitats on limestone. Sporophyte development varied between years and depended on the weather condition during the fertilization period. Climate forecasts for the study area predict longer dry spells during late spring to late summer, which coincides with the timing of sexual branch initiation and fertilization in the species. We expect that sporophyte production will likely decrease in the future, which will affect the species’ abilities to re-colonize spots where it vanishes during years with poor growth conditions.

Introduction. Half a century since the creation of the International Association of Bryologists, we carried out a review to identify outstanding challenges and future perspectives in bryology. Specifically, we have identified 50 fundamental questions that are critical in advancing the discipline. Methods. We have adapted a deep-rooted methodology of horizon scanning to identify key research foci. An initial pool of 258 questions was prepared by a multidisciplinary and international working group of 32 bryologists. A series of online surveys completed by a broader community of researchers in bryology, followed by quality-control steps implemented by the working group, were used to create a list of top-priority questions. This final list was restricted to 50 questions with a broad conceptual scope and answerable through realistic research approaches. Key results. The top list of 50 fundamental questions was organised into four general topics: Bryophyte Biodiversity and Biogeography; Bryophyte Ecology, Physiology and Reproductive Biology; Bryophyte Conservation and Management; and Bryophyte Evolution and Systematics. These topics included 9, 19, 14 and 8 questions, respectively. Conclusions. Although many of the research challenges identified are not newly conceived, our horizon-scanning exercise has established a significant foundation for future bryological research. We suggest analytical and conceptual strategies and novel developments for potential use in advancing the research agenda for bryology., J. Patiño was funded by the Spanish Ministerio de Ciencia e Innovación (MICINN) through the Ramón y Cajal Program (RYC-2016-20506) and supported by the Fundación BBVA project (PR19_ECO_0046) and the MICINN project (PID2019-110538GA-I00). S. McDaniel was supported by grants from the NSF (DEB 1542609, 1541005, 1541506). J. Martínez-Abaigar was supported by the grant PGC2018-093824-B-C42, funded by MCIN/AEI/10.13039/501100011033 and by the European Regional Development Fund. B. Goffinet was supported by NSF grant DEB-1753811.

Sex ratio variation is common among organisms with separate sexes. In bryophytes, sex chromosome segregation at meiosis suggests a balanced progeny sex ratio. However, most bryophyte populations exhibit female-biased phenotypic sex ratios based on the presence of reproductive structures on gametophytes. Many bryophyte populations do not form sexual organs, and genotypic sex ratio variation in such populations is mostly unknown. We tested sex expression, and phenotypic and genotypic sex ratios against environmental parameters in natural populations of the unisexual wetland moss Drepanocladus lycopodiodes at 11 sites in each of three regions in southern Sweden. We identified sex in 660 individual ramets, based on sexual structures, when present, or with a specifically designed molecular marker, when absent. All regions exhibited a female bias in phenotypic and genotypic sex ratios. Sex ratio biases and sex expression differed between regions. Sex ratios were less female-biased in larger patches. Wetter patches exhibited a stronger female bias in genotypic sex ratio and lower sex expression. This is the first evidence of environmental effects on genotypic sex ratio in mosses. A higher frequency of females in wet patches could be due to higher female resource demands for sporophyte production or higher male sensitivity to wetness. A higher incidence of females than males in moister sites aligns with female flowering plants, but differs from reproductive bryophytes in drier environments. Taken together with previous results, our data indicate that sex ratio variation and its drivers differ among species, their life histories and environments.

In the Baltic area, the long-lived dioicous wetland moss Drepanocladus turgescens (T.Jensen) Broth. produces sporophytes rarely and at irregular intervals. Based on surveys of sporophyte occurrences at 13 sites in two regions in northern Gotland (Sweden) during three to five years, we ask: (1) Is sporophyte formation associated with precipitation and a precipitation index that considers the dry periods during July-August of the preceding year, when gametangia are formed and fertilization occurs? (2) Does the estimated spore output suffice for the species’ long-term persistence of the (Northern) European population species? In one of the study regions, where D. turgescens occurs in depressions, sporophyte formation was associated with the two precipitation parameters. In the other study region, with relatively higher precipitation and exposed occurrences on a slightly sloping bedrock with very little accumulated soil, no such association existed. We suggest that this lack of weather effects results from that the exposed rock habitat requires longer continuously wet periods than the depression habitat to allow for gametangia initiation and development, and fertilisation. Average spore production for six spore capsules, from three Gotland localities was 181,000. Based on the sporophyte counts during the survey years, we estimated the total reproductive output as 411.5 million spores in 2013, and 42.5 million in 2015, in the two respective study regions. Taken together with data on haplotype patterns and considering observations on recent colonisations, we argue that such a relatively low and episodic regional spore production is sufficient to maintain global populations of long-lived species, even if these occur in specialized and geographically restricted habitats.

The hornwort Anthoceros agrestis is emerging as a model system for the study of symbiotic interactions and carbon fixation processes. It is an annual species with a remarkably small and compact genome. Single accessions of the plant have been shown to be related to the cosmopolitan perennial hornwort Anthoceros punctatus. We provide the first detailed insight into the evolutionary history of the two species. Due to the rather conserved nature of organellar loci, we sequenced multiple accessions in the Anthoceros agrestis–A. punctatus complex using three nuclear regions: the ribosomal spacer ITS2, and exon and intron regions from the single-copy coding genes rbcS and phytochrome. We used phylogenetic and dating analyses to uncover the relationships between these two taxa. Our analyses resolve a lineage of genetically near-uniform European A. agrestis accessions and two non-European A. agrestis lineages. In addition, the cosmopolitan species Anthoceros punctatus forms two lineages, one of mostly European accessions, and another from India. All studied European A. agrestis accessions have a single origin, radiated relatively recently (less than 1 million years ago), and are currently strictly associated with agroecosystem habitats.

Land-use changes including agricultural intensification are major drivers of biodiversity loss. As other countries, Switzerland introduced agri-environment schemes (AES) to counteract declining agro-biodiversity. Among numerous bryophytes of the agricultural landscape, arable bryophytes have adapted to recurrent tillage. They are short-lived above-ground, while their diaspores may build up a persistent diaspore bank in the soil. We monitored the field hornwort and the Carolina hornwort, characteristic species of the Central European arable bryophyte flora over a period of almost three decades, and studied effects of Biodiversity Promoting Areas (BPAS), a key element of Swiss AES, on arable bryophyte diversity. Hornwort occurrences strongly declined, and stubble-fields left unprocessed until late autumn, the favourite habitat of arable specialist bryophytes, nearly disappeared from 1991 to 2018. The loss of suitable habitats follows from decreased cereal cultivation and direct post-harvest management. Different BPA-fallows, designed to promote birds, flowering plants, or ecosystem services, harboured arable bryophyte specialists, but their richness decreased with fallow age. Diaspore banks contained arable bryophyte specialists not occurring above-ground and may serve as a reservoir during unsuitable cultivation. Targeted modifications of current AES, aiming to maintain habitats favourable for arable bryophytes, are necessary to safeguard the typical arable bryophytes in the Swiss arable landscape.

The IUCN Red List is recognised as a robust system for assessing the risk of extinction to organisms, but there are difficulties in applying the criteria to bryophytes and other clonal and colonial organisms. Three critical terms are addressed – generation length, mature individual and severe fragmentation – and definitions given in order to facilitate the use of the IUCN Red List criteria for bryophytes. These recommendations provide a pragmatic and effective way of using the IUCN Red List process for bryophytes and may have a wider application to other clonal organisms.

Agricultural intensification represents one of the major drivers for the dramatic loss of biodiversity worldwide. To halt the decline of farmland biodiversity, Switzerland adopted agri-environment schemes (AES) in 1998. Here, we monitored the occurrence, abundance and habitats of two species of arable bryophyte specialists, the Field hornwort (Anthoceros agrestis) and the Carolina hornwort (Phaeoceros carolinianus), in 28 crop fields in the intensively cultivated Swiss Plateau from 1991–2018, to investigate the effects of arable management, AES directives, and weather conditions on their performance. The target species are characteristic of the specialized short-lived arable bryophyte flora of Central Europe that depend on bare substrate in low-intensively cultivated and regularly ploughed fields. Trends in their occurrence thus reflect in many respects the status of the arable bryophytes in cultivated fields. Hornwort occurrence significantly declined between 1991 and 2018. A strong decrease in stubble fields that remain unmanaged after harvest, the favourite habitat for many arable specialists in the study area, largely accounted for the decline. Stubble fields nearly disappeared in the study area because of a gradual reduction in the cultivation area of cereals and the increasing practice of immediate post-harvest tillage. The latter is common in intensive arable farming and was accentuated by AES directives amended in 2005. Hornwort occurrences were positively affected by high air humidity during summer, but weather effects were subordinate to management effects. We propose tailored amendments of AES regulations, that are implemented at selected sites, to maintain the characteristic arable specialist bryophytes in the Swiss Plateau: crop rotation with adequate proportions of cereals that are regularly ploughed but not before the end of October, no post-harvest processing of stubble fields, and optimization of the existing instrument ‘Biodiversity Promoting Areas’, e.g., short-term fallows in crop fields. Late-autumn or overwintering stubbles and short-term fallows will benefit many other organisms that depend on extensively managed open habitats, for example arable wildflowers, farmland breeding birds and specialized arthropods.

Sex ratio variation is commonly observed in natural populations of many organisms with separate sexes and genetic sex determination, including bryophytes. Most bryophyte populations exhibit female-skewed expressed adult sex ratios, generally inferred from counts of sexually mature plants. For the rarely sexually reproducing perennial dioicous moss Drepanocladus lycopodioides, we showed that a female bias also exists in the genetic adult sex ratio, using a specifically designed molecular sex-associated marker. Here, we investigated whether the meiotic spore sex ratio contributes to the observed bias in genetic adult sex ratio in natural populations. Earlier attempts to study meiotic sex ratios have involved commonly cultivated ruderals that rapidly express sex in the laboratory. We established single-spore cultures from field-collected sporophytes from these populations and used the marker to assess the sex of individual sporelings. Spore germinability was (near) complete, and mortality among sporelings was virtually absent. The true meiotic sex ratio did not differ from equality, but strongly differed both from the observed genetic sex ratios in the natural adult populations, and from the European scale genetic sex ratio. We conclude that the biased population sex ratios in this species arise at life cycle stages after spore germination. Sexual dimorphism may selectively favour female proliferation during some phase of gametophyte development. Based on methodological progress, we successfully used a perennial study species with rare sexual reproduction, which significantly broadens the life history spectrum investigated in bryophyte sex ratio studies.

Sex identification before sexual maturity is notoriously difficult in plants with separate sexes, but is crucial to address many life history related issues. To study the performance of the two sexes in the rarely sexually reproducing dioecious moss Drepanocladus turgescens a molecular sex marker is needed. The female-targeting marker previously developed for D. trifarius and D. lycopodioides amplifies for a few D. turgescens males, which can thus not be distinguished from females. In a significant addition to the earlier developed method we sequenced the portion successfully amplified by the primers PT-3f and PT-3r for six females and three males. Differences between males and females were revealed at five sequence positions. Examination of a total of fourteen females and seven marker amplifying males confirm that females and such males differ consistently at these positions. The usefulness of a previous protocol for moss sex identification is thus extended to another dioecious moss by the addition of a step where a portion of the sex-correlated region is sequenced.

Hedenas, L. & Bisang, I. 2019. Are the remains of the Central European population of Drepanocladus turgescens genetically distinct from Scandinavian populations? – Herzogia 32: 209–218.The wetland moss Drepanocladus turgescens occurs in interglacial refugia in both mountains and lowlands of Europe. It is relatively frequent in Scandinavia, but due to habitat deterioration, it has severely declined in Central Europe. We compare haplotype variation based on the nuclear markers ITS (1+2) and gpd, and the plastid rpl16 in 103 samples from both Scandinavia and Central Europe, including the Alps. The Central European population harbours five haplotypes that are unknown in NW Europe. It is genetically similar to southern Scandinavian populations, but differs clearly from the populations in the Scandinavian mountain range and on Svalbard. Despite that D. turgescens has disappeared from many lowland localities in Central Europe, haplotype numbers and diversity do not differ from values in Scandinavia. Central European nucleotide diversity is slightly lower than in Scandinavian populations. The high number of private haplotypes in a limited sample and the still high genetic diversity suggest that conservation measures in Central Europe are motivated. We suggest assessing the spatial and temporal genetic variation in Central Europe, to identify the regions with the highest genetic diversity, and those which genetic diversity has been lost compared to records from the beginning of the 20th Century. This will allow well-targeted and efficient conservation actions.

Different animals play a role as agents for bryophyte dispersal. For example, Splachnaceae have their spores dispersed by flies (Marino et al., 2009), and ants may act as passive vectors for the di...

Patterns of sex expression and sex ratios are key features of the life histories of organisms. Bryophytes are the only haploid-dominant land plants. In contrast with seed plants, more than half of ...

Summary: The evolution of island syndromes has long served as a model to understand the mechanisms accounting for phenotypic differentiation. Combining literature data with actual observations, we determine whether typical syndromes such as the loss of dispersal power and the bias towards self-compatibility (Baker's law) apply to vagile organisms, using bryophytes as a model. The life-history traits (LHTs) observed in oceanic island floras were statistically different from those observed on continents, evidencing the evolution of island syndromes. In contrast, LHTs of continental and continental island floras were similar, pointing to differences in migration intensity between continents, continental islands and oceanic islands. The proportion of bisexual species was significantly higher on oceanic islands than on continents. A significant proportion of species that are unisexual or bisexual on continents shifted towards exclusive bisexuality on oceanic islands, suggesting that Baker's law applies to bryophytes. The underlying mechanisms, however, probably differ from in situ selection for selfing. The proportion of species producing specialized asexual diaspores, which are assumed to play a role in short-distance dispersal (SDD), was higher on oceanic islands than on continents. The proportion of species producing spores, which are involved in long-distance dispersal (LDD), exhibited the reverse trend, suggesting a shift in the prevalent reproductive strategy to favour SDD on oceanic islands. Approximately 50% of the species, however, maintained the ability to produce sporophytes on oceanic islands, and the relative frequency of fertile shoots within collections of four model species was even higher on islands than on continents. Synthesis. Bryophytes exhibit typical island syndromes, indicating that migration rates between oceanic islands and continents are not sufficient to prevent the effects of genetic drift and contradicting the view that the sea does not impede migration in the group. Significant shifts in life-history traits (LHTs) towards increased production of specialized asexual diaspores and decreased sporophyte production on oceanic islands indeed point to a global loss of long-distance dispersal (LDD) ability. The maintenance of traits characteristic for LDD in a large number of species has, however, substantial consequences for our understanding of island plant evolution, and in particular, for our vision of islands as evolutionary dead ends. © 2013 British Ecological Society.

The moss Drepanocladus trifarius (F. Weber & D. Mohr) Broth. ex Paris was used as a model species for a first evaluation of whether male and female haplotype patterns based on a combination of the nuclear molecular markers ITS and gpd, and the chloroplast rpl16 are congruent or not. In 23 female and 23 male shoots from specimens sampled in Northern and Central Europe, sex was determined either by the presence of sexual branches or by a recently developed molecular marker. Analysis of molecular variance (AMOVA) showed that a small (6%) and almost significant (p = 0.066) fraction of the variation within the data is due to differences between the genders and that the haplotype diversity is higher among females than among males. No significant differences in haplotype variation were found among geographical regions. The near significant differences between females and males, despite low variation in ITS and rpl16, in this first study ever of potential differences in haplotype variation between genders of dioecious mosses suggests that further investigations of more specimens and more variable molecular markers should be performed. Such studies could potentially reveal patterns of relevance to understanding, for example, immigration routes and to pin-point refugial areas of different significance to the respective genders.

Premise of research. Maintenance of dioecious and monoecious sexual systems at nearly equal frequencies, infrequent sexual expression, and distinctly female-skewed sex ratios among the dioecious species are reproductive characteristics of bryophytes, which are otherwise unusual among embryophytes. Most sex ratio assessments to date have relied on gametophytes forming sexual organs, and how these reflect genetic genders is largely unresolved.Methodology. For the European wetland moss Drepanocladus lycopodioides, we ask whether the adult expressed sex ratio is more strongly female biased than the “true” population sex ratio based on genetically male and female plants, i.e., whether males exhibit a lower sex expression rate than females (shy males). We assess expressed sex ratio on the basis of sex expression in individually scored herbarium specimens. We directly and on a large geographic scale assess nonexpressed sex ratio, for the second time in a moss, by sexing individual shoots from nonexpressing speci...

The habitat of the pleurocarpous moss Drepanocladus trifarius is commonly described as mineral-rich wet fens. We sampled individual D. trifarius shoots at 214 pre-defined randomly distributed spots in an area of ca 15 km2 in a sloping fen in central–western Sweden. We assessed the habitat variation of the sampling spots in this area by means of a multi-variate analysis (DCA) based on the species identity of the ten shoots adjacent to D. trifarius, and by indicator values for light availability and substrate moisture, acidity, and nutrient availability of the associated species. Both approaches indicated that D. trifarius occurred in well lit and constantly moist, wet or submerged places. Most spots were weakly acid to sub-neutral, but some spots had distinctly acid conditions. Generally the spots were nutrient-poor, but a few were nutrient- rich. DCA revealed gradients from relatively wet, sub-neutral to basic towards drier and more acid habitats, and from nutrient-poor to -richer environments. The species obviously exhibits a broader than expected niche width with respect to substrate acidity and nutrients. We suggest that succession, disturbance, or climatic factors may explain the species’ occurrences in different habitats.

Background: We recently demonstrated that dwarf male plants are much more common among mosses than hitherto thought. Dwarf plants, producing functional male sexual organs occur in 10–20% of the moss species worldwide. Aims: We investigated how an inadvertent omission of dwarf males affects estimates of male sex expression rates and sex ratios. Methods: We recorded frequencies of specimens with female-expressing plants, male-expressing normal-sized and/or dwarf plants, and sporophytes in herbarium material of five model species from Macaronesia. We analysed how frequency estimates of male occurrence and sex ratios were affected by excluding dwarf males. Results: Occurrence of dwarf males was positively associated with sporophyte formation. When dwarf males were excluded, male mate availability was missed in 51–61% of specimens (in 74–76% of sporophyte-containing specimens). Specimen-level sex ratio was balanced in material with sporophytes in the three species exhibiting male dwarfism, but strongly female ...

Dwarf males occur in several animal groups but are unique to mosses among the green land plants. Mosses, with more than 50% unisexual species and common fertilisation distances in the range of a few decimetres, have evolved various means to cope with potential problems to successfully achieve fertilisation and to ensure sporophyte production and sexually produced diaspores. We explore the abundance of different kinds of extreme female-biased sexual size dimorphism in homocostate pleurocarpous mosses. Based on direct observations and literature information, we investigated the large-scale geographical distribution of this phenomenon, and whether male dwarfism was associated with family position. Almost 60% of 1737 species with information about sexuality are dioecious, and males are known in 769 dioecious species. Dwarf males occur in 178 of these (23%), and are considered obligate in 113 species (63% of 178). We thoroughly examined a subset of 162 species. Among these 72 species (44%) form dwarf males, but only 18 species (25% of 72) produce obligate dwarf males. We conclude that especially facultative male dwarfism is much overlooked among dioecious mosses. The distribution of dioecious species and dwarf males among the latter was related to family membership, but showed little correlation with geographic area. Male dwarfism thus appears useful as a taxonomic character to define bryophyte families. We estimate that between roughly one quarter and almost half of dioecious pleurocarpous moss species exhibit male dwarfism, and the majority of these (75%) form dwarf males facultatively. Male dwarfism in mosses is suggested to have evolved as a result of (1) competing selective pressures of the cytoplasmic and nuclear genomes, (2) competition between the sexes, (3) selection for reduced fertilisation distances, or a combination of these. The associated niche shift of the males may also provide these with a suitably humid and nutrient-rich habitat.

(2010). Can the sex-specific molecular marker of Drepanocladus trifarius uncover gender in related species? Journal of Bryology: Vol. 32, No. 4, pp. 305-308.

Dioecious plants, including many bryophytes, rarely exhibit discernible sexual dimorphism before sexual maturity. Because many species and populations of dioecious bryophytes do not express their sex, it remains mostly unresolved whether expressing individuals reflect the ratios of genetically male and female plants. The present study assesses the population sex ratio of the wetland moss Pseudocalliergon trifarium in central and northern Europe. For the first time in a bryophyte, we estimate the sex ratio in a population by assessing directly both expressing and non-expressing plants. Expressed gender ratio was assessed from herbarium specimens. Single shoots from non-expressing specimens were sexed using a recently developed molecular sex marker. On the basis of the female and male frequencies in these two data sets and the overall proportion of expressing specimens, we estimate the European population sex ratio to be 1.93 : 1 (female/male). Expressed, non-expressed, and population sex ratios are not significantly different from each other, suggesting that gender differences in rates of sex expression cannot account for the female bias. Earlier studies of P. trifarium failed to reveal gender-specific growth rates or pre-zygotic reproductive costs. Gender differences at the spore to protonemal stage, in mortality, or niche preferences could potentially explain the uneven sex ratio. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 132–140.

Traditionally managed arable fields host a specialised flora adapted to regular disturbance through tillage. Agricultural intensification during the 20th century resulted in a pronounced biodiversity decline in European agroecosystems. Anthoceros agrestis and Phaeoceros carolinianus, both largely confined to cultivated land in Central Europe and the only representatives of hornworts in northern Switzerland, are examples of species that decreased in Central Europe during the last century. A repeated survey of 28 arable fields in the Swiss Plateau from 1989 to 1995 demonstrated that crop type and associated farming routines were critical in determining hornwort occurrences. During the 10 years following the completion of this survey, agri-environment schemes were introduced aiming at a more environmental-friendly agricultural production. We re-investigated the selected sites in 2005–2007 to examine whether these programmes favoured hornworts. We found a significant decrease of untilled autumn stubble-fields, which accounted for a decline of hornworts. High relative summer air humidity positively affected hornwort occurrence. Gametophytic populations of both taxa regenerated from the persistent diaspore bank after years of unfavourable conditions. To ensure the long-term persistence of hornworts in the Swiss Plateau, we recommend three alternative modifications of current Swiss agri-environment schemes to be implemented in cereal fields with known hornwort occurrences: (1) Tailored conservation headlands, (2) Autumn stubble-fields and (3) Field margin strips sown with arable flora but without crop plants. The proposed practices will promote other typically ephemeral arable bryophytes and seed plants and are likely to be advantageous also for other organisms, such as farmland birds.

Evidence is accumulating that significant amounts of substances can move internally in ectohydric bryophytes, which lack specialized structures for internal water movement. This potential for resource translocation is likely to affect the productivity in individual shoot sections. We tested whether annual growth intervals in the pleurocarpous moss Pseudocalliergon trifarium were performing as independent units by comparing the biomass of annual increments within individual shoots from 13 populations from northern and central Sweden. Pseudocalliergon trifarium has a distinct shoot architecture with discrete annual segments and is therefore well suited to study annual biomass allocation patterns. Mass of the most recent growth interval was directly correlated with segment mass of at least two preceding years. The strength of the relationship between current growth and four consecutively older annual increments decreased linearly with age of the annual segments, suggesting that correlations within shoots were the result of resource translocation rather than of among-year correlations in local environmental factors. Our data suggest that interconnected segments are physiologically integrated, and that size relationships between successive increments are relatively independent of environmental conditions. We conclude that annual growth intervals cannot be considered as independent assimilatory units. Internal resource transfer across annual segments may buffer variation in external availability of or internal demands for resources, and has implications for the understanding of growth patterns and reproductive investments in ectohydric bryophytes.

Background and Aims Roughly half of the species of bryophytes have separate sexes (dioecious) and half are hermaphroditic (monoecious). This variation has major consequences for the ecology and evolution of the different species. In some sexually reproducing dioecious bryophytes, sex ratio has been shown to vary with environmental conditions. This study focuses on the dioecious wetland moss Drepanocladus trifarius, which rarely produces sexual branches or sporophytes and lacks apparent secondary sex characteristics, and examines whether genetic sexes exhibit different habitat preferences, i.e. whether sexual niche partitioning occurs. Methods A total of 277 shoots of D. trifarius were randomly sampled at 214 locations and 12 environmental factors were quantified at each site. Sex was assigned to the individual shoots collected in the natural environments, regardless of their reproductive status, using a specifically designed molecular marker associated with female sex. Key Results Male and female shoots did not differ in shoot biomass, the sexes were randomly distributed with respect to each other, and environmental conditions at male and female sampling locations did not differ. Collectively, this demonstrates a lack of sexual niche segregation. Adult genetic sex ratio was female-biased, with 2·8 females for every male individual. Conclusions The results show that although the sexes of D. trifarius did not differ with regard to annual growth, spatial distribution or habitat requirements, the genetic sex ratio was nevertheless significantly female-biased. This supports the notion that factors other than sex-related differences in reproductive costs and sexual dimorphism can also drive the evolution of biased sex ratios in plants.

We studied infraspecific morphological variation within European Dicranum majus Sm. A principal components analysis based on six leaf characters scored in 82 specimens revealed two distinct plant types. Plants with bistratose submarginal upper leaf lamina cells, numerous spine-like dorsal lamina projections, a costa that is dorsally rough far down and has two layers of guide cells in its basal part, and falcate or strongly falcate, long leaves are mainly of a relatively southern origin. Specimens with a unistratose, smooth upper leaf lamina, a costa that is dorsally rough only above and has one layer of guide cells, and with slightly curved to straight, short leaves were only collected in northern Europe. Even if most authors do not formally recognize variation within D. majus, our results suggest that the two kinds of plants should be recognized at least at the variety level. In view of the confusing nomenclature in Dicranum it is beyond the scope of this paper to find a name for the northern pla...

A fundamental assumption in life-history theory is that reproduction is costly. Higher reproductive investment for fruits than for flowers may result in larger costs of reproduction in females than in males, which is often used to explain male-skewed sex ratios in unisexual seed plants. In contrast, bryophytes have predominantly female-biased sex ratios, suggested to be a product of a higher average cost of sexual reproduction in males. Empirical evidence to support this notion is largely lacking. We investigated sex-specific reproductive effort and costs in the unisexual moss Pseudocalliergon trifarium that has a female-dominated expressed sex ratio and rarely produces sporophytes. Annual vegetative segment mass did not differ among male, female, and non-expressing individuals, indicating that there was no threshold-size for sex expression. Mean and annual mass of sexual branches were higher in females than in males, but branch number per segment did not differ between sexes. Prefertilization reproductive effort for females was significantly greater (11.2%) than for males (8.6%). No cost for sexual branch production in terms of reduced relative vegetative growth or decreased investment in reproductive structures in consecutive years was detected. A higher realized reproductive cost in males cannot explain the unbalanced sex ratio in the study species.

Based on a literature survey and our own investigations of selected species, we present a compilation of expressed sex ratios in 103 taxa of dioicous bryophytes, including 56 mosses and 47 liverworts. We grouped the approaches used to determine sex into two categories: (1) sex assessment per herbarium specimen or per patch in the field; (2) sex assessment by examination of individual shoots or thalli, usually in the field. Eighty-eight per cent of the taxa studied by the former methods, and 68% of those included in the latter, exhibited a female-biased sex ratio. The F : M values varied by a factor of 46 among species, excluding cases with only one sex expressing. There was also within-species variation of sex expression and ratio related to geographical area, altitude, year, substratum, plant maturity, and compared with cultivation conditions, and between the two method categories. Across taxa, proportions of non-expressing and sporophytic samples were negatively related to each other; however, t...

Habitat preferences and habitat differentiation were studied among species of Acroporium (Sematophyllaceae) and related taxa between 140–2,000 m a.s.l. in Peninsular Malaysia (02.92°–04.87°N, 100.80°–101.83°E). Canonical Correspondence Analysis was used to reveal how species data were related to 16 environmental factors that represent geographical, physical environmental, chemical, and substrate type components. We found some geographical variation, but this explained little of the species distribution patterns. A minimum model based on automatic forward selection suggested that elevation, the substrate peaty soil, and pH explain 57% of the variation in the species data, and variation partitioning suggests that much of the variation in the latter is explained by several factors in combination. Light availability and the substrate mineral soil were of moderate importance in explaining species data distribution, whereas other variables influenced the variation less and mainly along the third and fo...

We tested whether mate availability in the pleurocarpous dioicous mosses Rhytidiadelphus triquetrus and Abietinella abietina affects fertilization success by transplanting individual male shoots into non-sporophytic female colonies. Fertilization success in both species was limited by the availability of mates and distance-dependent, and the number of sporophytes produced was higher in R. triquetrus than in A. abietina. Our estimate of a maximum fertilization distance of 34 cm in R. triquetrus is an order of magnitude larger than previous estimates that have been based on non-manipulative approaches. In R. triquetrus the number of female reproductive branches and plot inclination (horizontal vs sloping) had significant effects on the number of sporophytes produced. In A. abietina, the number of female reproductive branches per plot did not affect sporophyte production. Within sloping experimental plots, sporophyte number was significantly higher, and the distance of sporophytes from the spermatozoid source was larger below the male transplants than above. We conclude that mate availability may be important for reproductive success in sessile dioecious organisms, and that the spatial structure at various scales is essential to understand their dynamics.

A new, resource-efficient, herbarium-based method for estimating temporal frequency changes in species, especially of non-vascular plants and fungi, is presented. It is based on a reference data set for the temporal distribution of general collecting activity for the organism group and geographical area of interest. The reference data set includes the collecting year of 650–1000 randomly selected herbarium specimens. The technique relies on the assumption that the temporal distribution of herbarium collections reflects the collecting activity in a region. The temporal distribution of collections of example species is compared with that of the reference data set to correct for the collecting intensity. Thus, cases that are explained by changes in general collecting frequency can be separated from those where other causes are likely. Species of the latter category need to be examined individually in order to assess whether the actual causes for the detected frequency variations are due to environmental changes or other factors. The present method provides a tool to assess actual increases and decreases of moderately frequent to common taxa, to aid in tracing predicted or unpredicted changes in nature.

We investigated the cost of sporophyte production in the moss Dicranum polysetum both by examining patterns of growth and reproduction in unmanipulated shoots and by experimentally manipulating sexual reproduction. The estimated proportion of total carbon investment allocated to sexual reproduction in sporophyte-producing shoots over the study period was 74.8%. Unmanipulated shoots that aborted all sporophytes had a significantly higher growth in the top shoots than shoots that produced sporophytes. In sporophyte-producing shoots, total apical growth decreased proportionately with the number of sporophytes. Experimental prevention of sporophyte development resulted in significantly higher total apical growth of the gametophytes. Shoots where current perichaetia were lacking when marked had a mass increase in the top shoots similar to manipulated sporophytic shoots whereas sporophytic control shoots grew significantly less than these two categories. The difference between control shoots and manipulated shoots in the mass of vegetative apical growth was mainly because of different length increments whereas mass per unit length was similar between groups. The probability to reproduce sexually in the year after the manipulation, and the biomass allocated to this reproduction, were not affected by the experimental treatment.

Infraspecific genetic diversity is generally underestimated in biodiversity assessments. We use haplotype patterns based on the nuclear gpd and plastid rpl16 to examine whether genetic diversity is related to geography, gender, habitat and/or frequency of sexual reproduction in Drepanocladus lycopodioides. This moss is restricted to western Eurasian semi-natural and natural habitats and decreases in frequency in many parts of Europe. Haplotype diversity differs among three regional populations (Öland, Gotland, Stockholm archipelago) in its South Swedish Baltic core distribution area and is positively affected by patch size. The regional populations differ from each other genetically and haplotype variation is unequally partitioned between the genders, most likely a result of immigration history and limited equalizing effects of sexual reproduction. In a Holocene context, the regional populations of Öland and Gotland display evidence of a decrease or bottleneck, and immigration into both regions. We suggest that higher haplotype diversity in Gotland and Öland and lack of migration to the Stockholm archipelago may be an effect of longer colonization history of the former, and niche pre-emption in the natural habitats of the latter. The Baltic population is representative for the genetically relatively homogeneous European population, and D. lycopodioides displays low ITS variation compared with other European mosses. In a conservation context it is relevant that the three regional populations are not interchangeable. It is of concern that three populations within the species’ core distribution are vulnerable. Our results strongly suggest that infraspecific genetic diversity must be considered in the management of the species at the continental level.

This study investigates the status of endangered bryophytes in Switzerland, as an example of the situation in large parts of Central Europe. The decline in species and populations is quantified by examination of 522 selected literature or herbarium records. They belong to taxa classified in the Red Data List of Swiss byrophytes as endangered (E) or rare (R). In a field survey, 31% of 195 populations proved to be still present. The proportion of confirmed populations differed widely between the three main natural regions of Switzerland—50 out of 109 within the Alps, six out of 39 in the Jura mountains and only four out of 46 in the densely populated lowland area of the Mittelland. Recommendations are made for practical conservation measures for each of the populations recently confirmed or discovered.

Maps of the distribution of Anthoceros punctatus L. var. cavernosus auct. and Phaeoceros laevis (L.) Prosk. ssp. carolinianus (Michx.) Prosk. in Switzerland are presented. They are based on herbarium specimens and field studies and distinguish between records before and since 1960. According to bibliographical data from the beginning of this century, both taxa were widespread throughout Central Europe, A. punctatus being more common than P. laevis. This view is not supported by herbarium collections. Detailed field research from 1981 to 1989 in the vicinity of Berne showed that the occurrence of hornworts depends largely on the type and treatment of cultivation. P. laevis seems to be more sensitive to changes in habitat conditions caused by modern agricultural practice (mechanical stress, increase in fertilizer input and use of pesticides) than A. punctatus. In conclusion, P. laevis is classified as endangered in Switzerland.

Most dioecious plants do not exhibit discernible sexual dimorphism before sexual maturity. Therefore, it is impossible to address any sex-related questions during the prereproductive phase unless a genetic sex marker is available for gender determination. The aim of the present study was to develop a genetic sex marker for the moss Pseudocalliergon trifarium to allow gender and sex ratio determination at any stage in the life cycle. A high proportion of P. trifarium populations do not express sex. The screening of genomic DNA with inter simple sequence repeat (ISSR) primers was used to discover sex-specific polymerase chain reaction (PCR) amplification products. A presumably female-specific band was found, excised from the gel, cloned, and sequenced. A sequence-walking method was used to characterize the same region in males. A primer pair was designed to allow the amplification of a 159-bp portion of the female-specific DNA region. All tested material, up to 16-year-old herbarium specimens, provided unambiguous amplification products. This study successfully provides, for the first time in a moss, a sex-specific DNA marker. It allows reliable determination of gender and sex ratios. The short length of the amplification product is an advantage as satisfactory PCR products are more likely when the targeted sequence is short. The amount of variation in the DNA region shared by both sexes was relatively high. If the male sequence can be better characterized, the sex-specific regions could possibly be used to evaluate sex-specific phylogeographic patterns.