Dioicous Species Research Articles

A genome assembly for the California endemic liverwort Calasterella californica.

Calasterella californica belongs to a monotypic genus of liverworts endemic to the west coast of North America, primarily distributed in California. This dioicous species occurs in a variety of ecosystems from deserts to redwood forest; little is known about how this species is adapted to live in those seemingly contrasting environments. In this paper, we report the assembly of the nuclear genome of Calasterella californica. As part of the California Conservation Genomics Project (CCGP), we used Pacific Biosciences HiFi long-read sequencing data to produce a de novo assembly that consists of 772 contigs, with a total length of 517 Mbp and a BUSCO complete score of 95%. C. californica is only the sixth species of liverworts - a group with more than 7200 described species - to have a nuclear reference genome. The availability of this reference genome will facilitate the study of the unique features of C. californica and other liverworts, pave the road towards a comparative understanding of liverwort genomes, and add an important starting point for studies of the geographic variation of this species within the CCGP project.

Predicting the Threat Status of Mosses Using Functional Traits.

Mosses are an early lineage of the plant kingdom, with around 13,000 species. Although an important part of biodiversity, providing crucial ecosystem services, many species are threatened with extinction. However, only circa 300 species have so far had their extinction risk evaluated globally for the IUCN Red List. Functional traits are known to help predict the extinction risk of species in other plant groups. In this study, a matrix of 15 functional traits was produced for 723 moss species from around the world to evaluate the potential of such predictability. Binary generalized linear models showed that monoicous species were more likely to be threatened than dioicous species, and the presence of a sporophyte (sexual reproduction), vegetative reproduction and an erect (straight) capsule instead of a pendent (immersed) one lowers the risk of species extinction. A longer capsule, seta and stem length, as well as broader substrate breadth, are indicative of species with a lower risk of extinction. The best-performing models fitted with few traits were able to predict extinction risks of species with good accuracy. These models applied to Data Deficient (DD) species proved how useful they may be to speed up the IUCN Red List assessment process while reducing the number of listed DD species, by selecting species most in need of a full, detailed assessment. Some traits tested in this study are a novelty in conservation research on mosses, opening new possibilities for future studies. The traits studied and the models presented here are a significant contribution to the knowledge of mosses at risk of extinction and will help to improve conservation efforts.

The spatial arrangement of sexes is related to reproductive allocation in mosses: a comparative study of reproductive allocation in three different monoicous sexual systems.

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. 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. 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. 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.

Sporophyte frequency in British dioicous liverworts

ABSTRACT Introduction The extent and causes of variation in sporophyte production among British dioicous liverworts are assessed. Methods Reproductive attributes of dioicous species are taken from Paton’s The Liverwort Flora of the British Isles (1999). The extent to which sporophyte production is potentially restricted by low levels of sex expression, unbalanced phenotypic sex ratios, and probable spatial segregation of the sexes, is quantified. Patterns of variation in sexual reproduction are also characterised for species associated with different biogeographical zones in Europe. Results Of the 188 British liverwort species that are dioicous (62%), sporophytes are unknown in 65, rare in 58, occasional in 50 and frequent in 15. Some species are not or rarely sexually reproductive, but major causes of restricted sexual reproduction are sexual imbalance and probable isolation of the sexes. Among species with skewed sex ratios, female bias is substantially more common than male bias. Sporophyte frequency is relatively high among species widely distributed in temperate and boreal Europe, compared with taxa associated with other climatic zones, including the oceanic fringe. Conclusions Restricted sporophyte production implies that asexual reproduction and clonal longevity are critical for the persistence of many liverworts. Further insights will require field surveys of patterns of sex expression and sporophyte distribution, together with information on reproductive plasticity, genotypic sex ratios, and levels of genetic diversity and structure.

Selection drives convergent gene expression changes during transitions to co-sexuality in haploid sexual systems

Co-sexuality has evolved repeatedly from unisexual (dioicous) ancestors across a wide range of taxa. However, the molecular changes underpinning this important transition remain unknown, particularly in organisms with haploid sexual systems such as bryophytes, red algae and brown algae. Here we explore four independent events of emergence of co-sexuality from unisexual ancestors in brown algal clades to examine the nature, evolution and degree of convergence of gene expression changes that accompany the breakdown of dioicy. The amounts of male versus female phenotypic differences in dioicous species were not correlated with the extent of sex-biased gene expression, in stark contrast to what is observed in animals. Although sex-biased genes exhibited a high turnover rate during brown alga diversification, some of their predicted functions were conserved across species. Transitions to co-sexuality consistently involved adaptive gene expression shifts and rapid sequence evolution, particularly for male-biased genes. Gene expression in co-sexual species was more similar to that in females rather than males of related dioicous species, suggesting that co-sexuality may have arisen from ancestral females. Finally, extensive convergent gene expression changes, driven by selection, were associated with the transition to co-sexuality. Together, our observations provide insights on how co-sexual systems arise from ancestral, haploid UV sexual systems.

Bryophytes of Rio Turvo State Park (SP), Brazil: integrating floristics, geographical distribution, reproduction and ecological traits to support the conservation of an Atlantic Forest fragment

Rio Turvo State Park (RTSP) is a Conservation Unit located within the Atlantic Forest biome in the Vale do Ribeira region of the State of São Paulo, Brazil. Considering the lack of knowledge regarding its bryoflora, we performed a floristic inventory of RTSP (following the random-walk method), the results of which we report here including discussion of the geographical distribution (Brazil and worldwide), substrate colonization, life forms and reproduction of the species. We found a total of 414 species, which represents 30 % of all known bryophyte species in Brazil. Dioicous species were predominant over monoicous species, the most colonized substrate was tree trunk (40 % of all species) and the predominant life form was mat (47 %), indicating that the floristic composition is influenced by the environmental conditions of the area (high humidity, dense vegetation and shading). Although anthropogenic intervention is present in RTSP, it harbors huge biodiverse potential, since 22 % of the species are rare. Furthermore, 16 new occurrences were recorded for the State of São Paulo. The information provided by this study exalts the importance of this Conservation Unit in the preservation of bryophytes, as well as all the biodiversity of its included ecosystems.

Differential gene expression patterns during gametophyte development provide insights into sex differentiation in the dioicous kelp Saccharina japonica

BackgroundIn brown algae, dioicy is the prevalent sexual system, and phenotypic differences between male and female gametophytes have been found in many dioicous species. Saccharina japonica show remarkable sexual dimorphism in gametophytes before gametogenesis. A higher level of phenotypic differentiation was also found in female and male gametes after gametogenesis. However, the patterns of differential gene expression throughout gametophyte development and how these changes might relate to sex-specific fitness at the gamete stage in S. japonica are not well known.ResultsIn this study, differences in gene expression between male and female gametophytes in different developmental stages were investigated using comparative transcriptome analysis. Among the 20,151 genes expressed in the haploid gametophyte generation, 37.53% were sex-biased. The abundance of sex-biased genes in mature gametophytes was much higher than that in immature gametophytes, and more male-biased than female-biased genes were observed in the mature stage. The predicted functions of most sex-biased genes were closely related to the sex-specific characteristics of gametes, including cell wall biosynthesis, sperm motility, and sperm and egg recognition. In addition, 51 genes were specifically expressed in males in both stages, showing great potential as candidate male sex-determining region (SDR) genes.ConclusionsThis study describes a thorough investigation into differential gene expression between male and female gametophytes in the dioicous kelp S. japonica. A large number of sex-biased genes in mature gametophytes may be associated with the divergence of phenotypic traits and physiological functions between female gametes (eggs) and male gametes (sperm) during sexual differentiation. These genes may mainly come from new sex-biased genes that have recently evolved in the S. japonica lineage. The duplication of sex-biased genes was detected, which may increase the number of sex-biased genes after gametogenesis in S. japonica to some extent. The excess of male-biased genes over female-biased genes in the mature stage may reflect the different levels of sexual selection across sexes. This study deepens our understanding of the regulation of sex development and differentiation in the dioicous kelp S. japonica.

Distribución y condición sexual de las Pottiaceae (Bryophyta) en México

Antecedentes y Objetivos: Las briofitas son plantas no vasculares que se reproducen por esporas, yemas o fragmentos de gametofitos (diásporas); de ellos depende su distribución y supervivencia. En esta contribución se evalúa el papel de la condición sexual en la distribución de las especies mexicanas de Pottiaceae, una familia de musgos diversa y frecuente en México. Se propone lo siguiente: a) las especies monoicas deben exhibir una distribución amplia en el país debido a su frecuente producción de esporofitos, b) las especies dioicas que no producen esporofitos, muestran una distribución discontinua o restringida y c) las especies que solo producen yemas deben tener áreas de distribución reducidas. Métodos: Con información bibliográfica y de herbario se elaboraron mapas de distribución de la familia Pottiaceae en México para detectar posibles diferencias en los patrones de distribución de especies dioicas y monoicas. Se agregaron datos de factores ambientales para afinar la agrupación de especies dioicas y monoicas. Resultados clave: Las Pottiaceae dioicas y monoicas difieren en el número de especies. En ambas, sin embargo, se detectaron dos tipos de distribución en México, en grupos que cuentan con un número similar de registros. Los taxa dioicos Plaubelia sprengelii var. sprengelii y Weissia jamaicensis se distribuyen principalmente en el oriente y sureste, mientras que las especies monoicas Syntrichia obtusissima y Timmiella anomala están mejor representadas en las regiones centro y noroeste. Conclusiones: Las Pottiaceae se distribuyen en México sin importar su condición sexual. Las especies que producen yemas no muestran una distribución restringida o limitada, pero las que no tienen esporofitos ni yemas muestran una distribución más reducida.

Different from tracheophytes, liverworts commonly have mixed 35S and 5S arrays.

Unlike other nuclear genes in eukaryotes, rDNA genes (5S and 35S loci) are present in numerous copies per cell and, when stained, can therefore provide basic information about genome organization. In tracheophytes (vascular plants), they are usually located on separate chromosomes, the so-called S-type organization. An analysis of 1791 species of land plants suggested that S-type arrays might be ancestral in land plants, while linked (L-type) organization may be derived. However, no outgroup and only a handful of ferns and bryophytes were included. We analysed genome sizes and the distribution of telomere, 5S and 35S rDNA FISH signals in up to 12 monoicous or dioicous species of liverworts from throughout a phylogeny that includes 287 of the 386 currently recognized genera. We also used the phylogeny to plot chromosome numbers and the occurrence of visibly distinct sex chromosomes. Chromosome numbers are newly reported for the monoicous Lejeunea cavifolia and for females of the dioicous Scapania aequiloba. We detected sex-related differences in the number of rDNA signals in the dioicous Plagiochila asplenioides and Frullania dilatata. In the latter, the presence of two UU chromosomes in females and additional 5S-35S rDNA loci result in a haploid genome 0.2082 pg larger than the male genome; sex-specific genome differences in the other dioicous species were small. Four species have S-type rDNA, while five species have mixed L-S rDNA organization, and transitions may have occurred multiple times, as suggested by rDNA loci not being conserved among closely related species of Pellia. All species shared an Arabidopsis-like telomere motif, and its detection allowed verification of the chromosome number of Radula complanata and chromosome rearrangements in Aneura pinguis and P. asplenioides, the latter also showing sex-specific interstitial telomere repeats. The S and L rDNA arrangements appear to have evolved repeatedly within liverworts, even in the same species. Evidence for differential accumulation of rDNA between the sexes so far is limited.

On the hypothesis of dioicous – monoicous species pairs in the Mniaceae (Bryophyta); morphology, sexual condition and distiribution

AbstractSome early observations seemed to show that, in the Mniaceae, the doubling of the chromo-some set affects a change from dioicous to monoicous condition, larger size of the gametophyte including larger leaf cell size, and to a wider range of the monoicous counterpart. The Mniaceae taxa are divided into four groups based on their sexual condition and morphology. 1. Dioicous – monoicous counterparts which can be distinguished by morphological characters, 2. Dioicous – monoicous taxa which have no morphological, deviating characters, 3. Monoicous species mostly with diploid chromosome number for which no dioicous counterpart is known, and 4. The taxa in Mniaceae with only dioicous plants. Most of the monoicous species of the Mniaceae have wide ranges, but a few of them are endemics in geographically isolated areas. The dioicous species have either a wide holarctic range or a limited range in the forested areas of temperate and meridional North America, Europe and SE Asia, or in subtropical Asia. Some of the monoicous species are evidently autodiploids and a few of them are allopolyploids from cross-sections of two species. Quite recently, several new possible dioicous – monoicous relationships have been discovered.

Chromosomal distribution of rRNA genes in the karyotypes of two dioicous liverwort species from the genus Pellia Raddi

Over one hundred years have passed since the first cytogenetic studies were made on the liverwort genus Pellia Raddi. The karyotype of Pellia is characterised by large chromosomes, a varying heterochromatin content and the presence of sex chromosomes in the dioicous species. Most of the Pellia species are diploids with n = 9, but one of them, Pellia borealis Lorb., has been described as an example of allopolyploidy in liverworts. Although the localisation of rRNA genes, which are essential components of the nuclear genome, remains a challenge in bryophytes, data on the number and chromosomal localisation of 35S and 5S rDNA in all of the Pellia species are now available. Previously, fluorescence in situ hybridisation using rDNA probes was performed on the mitotic chromosomes of 2 monoicous species. The aim of this study was to establish the number and chromosomal distribution of rRNA genes in 2 dioicous diploid species—Pellia endiviifolia (Dicks.) Dumort. and Pellia neesiana (Gottsche) Limpr. The relationships between the species within the genus Pellia can now be discussed in the context of the localisation of the rDNA sites and the range in the number of rDNA loci among bryophytes can also be verified.

Sexual Dimorphism, Vegetative Growth and Reproductive Investment in the Rhizautoicous MossFissidens flaccidus(Fissidentaceae, Bryopsida)

Reproduction is one of the most important and expensive processes in the life history of plants. The cost commonly incurred by reproductive investment in plants with separate sexes may result in sexual dimorphism. Among bryophytes, sexual dimorphism has been observed in some sex-expressing dioicous species and in some sex-expressing monoicous species with a rhizautoicous sexual system. In the present study, we have investigated sexual dimorphism in morphological features and relative reproductive investments in sporophytic female, non-sporophytic female, sex-expressing male and non-expressing ramets in a population of the rhizautoicous Fissidens flaccidus. Morphometric analyses confirmed sexual dimorphism; gemmiform male ramets were smaller than the other ramet morphs, and exhibited greater sexual investment. Sexual reproductive investment was approximately 35% in males, 13% in non-sporophytic females and 25% in sporophytic females. Our results indicate trade-offs between reproductive investment and vegetative growth for both sexes in this species.

A New Species of Pylaisia (Hypnaceae) from Peru

Pylaisia afoninae is described from Peru. It is the first known dioicous species in the genus. Additional noteworthy features of the species are its strongly concave, long-acuminate leaves and extensively developed, opaque alar region.

Distribution and Habitat of the Malaysian Species of Lejeunea (Marchantiophyta: Lejeuneaceae), with Description of Lejeunea Tamaspocsii Sp. Nov.

AbstractWe analyze the geographical and elevational ranges and the habitats of 30 species and two varieties of Lejeunea Lib. recorded from Malaysia. The greatest diversity of Lejeunea in Malaysia is found on Mt. Kinabalu with 27 species. The majority of the species are Malesian in distribution with a high number (8) belonging to the West Malesian element. Widely distributed species are often autoicous and produce spores freely; those with narrow distributions are more often dioicous and rarely produce spores. Dispersal of dioicous species seems to be promoted by asexual reproduction, being more common in wide-ranging dioicous species than in narrow-ranging ones. Endemism is 10% with three species being known only from Mt. Kinabalu. Range sizes of species decrease towards higher elevation and endemic species occur exclusively in the mountains. About half of the species occur in the lower montane rainforest belt, which is the elevational zone with the highest diversity of Lejeunea in Malaysia. The majority of the species are epiphytes, either corticolous or ramicolous. One species (L. dimorpha) is an obligate epiphyll. The new species Lejeunea tamaspocsii G. E. Lee is described and two new combinations, L. dipterota (Eifrig) G. E. Lee and L. exilis var. abnormis (Herzog) G. E. Lee, are proposed.

Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants

BackgroundWhether male and female gametes are produced by single or separate individuals shapes plant mating and hence patterns of genetic diversity among and within populations. Haploid-dominant plants (“bryophytes”: liverworts, mosses and hornworts) can have unisexual (dioicous) or bisexual (monoicous) gametophytes, and today, 68% of liverwort species, 57% of moss species, and 40% of hornwort species are dioicous. The transitions between the two sexual systems and possible correlations with other traits have been studied in liverworts and mosses, but not hornworts. Here we use a phylogeny for 98 of the 200 species of hornworts, the sister group to vascular plants, representing roughly equal proportions of all monoicous and all dioicous species, to test whether transitions in sexual systems are predominantly from monoicy to dioicy as might be expected based on studies of mosses. We further investigate possible correlations between sexual system and spore size, antheridium number, ploidy level, and diversification rate, with character selection partly based on findings in mosses and liverworts.ResultsHornworts underwent numerous transitions between monoicy and dioicy. The transition rate from dioicy to monoicy was 2× higher than in the opposite direction, but monoicous groups have higher extinction rates; diversification rates do not correlate with sexual system. A correlation important in mosses, that between monoicy and polyploidy, apparently plays a small role: of 20 species with chromosome counts, only one is polyploid, the monoicous Anthoceros punctatus. A contingency test revealed that transitions to dioicy were more likely in species with small spores, supporting the hypothesis that small but numerous spores may be advantageous for dioicous species that depend on dense carpets of gametophytes for reproductive assurance. However, we found no evidence for increased antheridium-per-chamber numbers in dioicous species.ConclusionsSexual systems in hornworts are labile, and the higher number of extant monoicous species (60%) may be largely due to frequent transitions to monoicy.

Male Dwarfism in the GenusDicranum(Dicranaceae) — A Review

Abstract Understanding of male dwarfism in mosses is reviewed with special reference to the genus Dicranum. Dwarf males occur in about 20% of Dicranum species. Most species seem to be obligately nannadrous; in two species (D. bonjeanii, D. scoparium) male plant size may be normal or dwarfed. Variation in male plant size in Dicranum seems to be environmentally controlled. Male dwarfism in mosses is induced by genetic or environmental factors although the mechanisms leading to male dwarfism are poorly understood. Evidence suggests that male dwarfism increases reproductive success in dioicous species but many questions remain unanswered.

Invited perspective: bryophytes as models for understanding the evolution of sexual systems

One of the first life history characters that students of bryology learn is the bryophyte life cycle. Roughly half of the bryophytes have separate sexes (dioicous) and half are hermaphroditic (monoicous). This variation is important for taxonomic purposes but also has major consequences for nearly every aspect of bryophyte biology. For example, dioicous species generally reproduce less frequently than monoicous species (Longton & Schuster 1983) but harbor more genetic variation than monoicous species (Eppley et al. 2006). More broadly, however, the maintenance of both sexual systems at nearly equal frequencies in the bryophytes is quite unusual among the eukaryotes. This situation makes bryophytes an important model system for studying the evolutionary consequences of changes in sexual system. Bryophytes have a long history as model systems in cytology and genetics. Sex chromosomes in plants were first discovered in the liverwort Sphaerocarpus donnellii (Allen 1917), and the term ‘‘heterochromatin’’ was coined for the dark staining heteromorphic pair of chromosomes in many bryophytes (Heitz 1932). Bryophytes have long served as model genetic systems because the dominant part of the life cycle (i.e., the gametophyte) is haploid, and the phenotype of the plant directly reflects its genotype without the masking of dominance (Allen 1919; Ashton & Cove 1977; Engel 1968; von Wettstein 1924). More recently, efficient gene targeting via homologous recombination was discovered in Physcomitrella patens (Kammerer & Cove 1996; Schaefer & Zryd 1997; Strepp et al. 1998) and Ceratodon purpureus (Brucker et al. 2005; Mittmann et al. 2009; Trouiller et al. 2007). With this tool researchers can construct powerful tests for associations between genes and traits. In addition, the genome of P. patens has now been completely sequenced (Rensing et al. 2008), and sequencing projects for C. purpureus (http://www.jgi.doe.gov/ sequencing/why/ceratodon.html), Phaeoceros laevis (http://ldl.genomics.org.cn/page/searchplant. jsp?speciesname5phaeoceros), and Marchantia polymorpha (http://www.jgi.doe.gov/sequencing/ why/99191.html) are now underway. Together the natural variation in sexual system and the potential for laboratory study make bryophytes ideal for studying the causes and consequences of changes in sexual system. The purpose of this perspective is to highlight areas where interdisciplinary research can provide new insights into the evolution of bryophyte sexual systems. We have structured the perspective around three major evolutionary transitions: 1) the evolution of dioicy; 2) the evolution of sex chromosomes; and 3) the evolution of monoicy. We first provide a brief outline of the evolutionary theory underlying each of these phenomena. Since much of this theory was developed for angiosperms, we suggest how it can be applied to bryophytes. Second, we indicate how 3 Corresponding author’s e-mail: stuartmcdaniel@ufl.edu DOI: 10.1639/0007-2745-115.1.1

Reproductive phenology of bryophytes in tropical rain forests: the sexes never sleep

Events of the sexual reproductive cycle of 11 bryophyte species (mosses and liverworts with monoicous and dioicous sexual conditions) were described for two different sites (montane and sea level) of a Brazilian tropical rain forest, during a 15 month-period. The sex expression of many species was continuous over the whole period, irrespective of the seasons and the forest sites. The specific sexual conditions of dioicous species did not change, but synoicous species had strategies to increase the chances of out-crossing, bearing unisexual branches in addition to bisexual ones. The pattern of gametangia and sporophyte development was different among the species, but the same between the sites. There was a seasonal effect on the maturation of gametangia and sporophytes. Male gametangia were mostly mature by the end of the dry season. Fertilization occurred during the wettest months and sporophytes developed during the dry season, dispersal of spores mostly towards the end of the dry season. Female gametangia were receptive over the whole period, with many mature gametangia before the start of the rainy season. Male gametangia, in contrast to female, took longer to develop and aborted in high numbers. Bryophytes in tropical rain forests are favored by wet weather and mild temperatures. Similar reproductive phenological patterns were found in different habitats with minor variations.

Co-variation of life history characters in the family Lophoziaceae: a multivariate analysis

The particular combinations of life history traits that organisms display are a product of trade-offs between conflicting demands on finite energy budgets. Organisms are, therefore, expected to display combinations of co-evolved life history traits, sometimes referred to as tactics or strategies, that overall maximize fitness within the constraints imposed by environmental and/or genetic limitations. This study uses a combination of Principal Component and Cluster analyses to examine patterns of life history co-variation in the family Lophoziaceae, based on data obtained from literature. We also evaluate the relationship between sexuality, reproductive mode and sporophyte/gemma frequency among members of this family. The species studied are resolved into more or less coherent groups that have specific life history trait combinations. No evidence of either phylogenetic constraint or close relationship to habitat parameters could be demonstrated. The results suggest trade-offs between spore frequency and gemma frequency. Dioicous species dominate the family, with about 90% of the species being dioicous. The relationship between sexuality and sporophyte frequency is statistically significant: monoicous species produce sporophytes more frequently than dioicous species. Mode of reproduction and gemmae production were both independent of sexuality. For species that can reproduce both ways, sexuality was independent of diaspore frequency. The data are consistent with the idea of coevolved life history “strategies” as in most others organisms studied.

Diaspore bank of bryophytes in tropical rain forests: the importance of breeding system, phylum and microhabitat

Diaspore banks are crucial for the maintenance and resilience of plant communities, but diaspore banks of bryophytes remain poorly known, especially from tropical ecosystems. This is the first study to focus on the role of diaspore banks of bryophytes in tropical rain forests. Our aim was to test whether microhabitat (substrate type) and species traits (breeding system, phylum) are important in explaining the diaspore bank composition. Using samples cultivated in the laboratory, we assessed the number of species and shoots emerging from bark, decaying wood and soil from two sites of the Atlantic rain forest (montane and sea level) in Brazil by comparing the contribution of species by phylum (mosses, liverworts) and breeding system (monoicous, dioicous). More species emerged from bark (68) and decaying wood (55) than from soil (22). Similar numbers of species were found at both sites. Mosses were more numerous in terms of number of species and shoots, and monoicous species dominated over dioicous species. Substrate pH had only weak effects on shoot emergence. Species commonly producing sporophytes and gemmae had a high contribution to the diaspore banks. These superficial diaspore banks represented the extant vegetation rather well, but held more monoicous species (probably short-lived species) compared to dioicous ones. We propose that diaspore bank dynamics are driven by species traits and microhabitat characteristics, and that short-term diaspore banks of bryophytes in tropical rain forests contribute to fast (re)establishment of species after disturbances and during succession, particularly dioicous mosses investing in asexual reproduction and monoicous mosses investing in sexual reproduction.