Phylogenetic relationships between Bryum and supposedly closely related genera

Abstract

The phylogeny of the genus Bryum was studied using cladistic analyses under the maximum parsimony criterion of evolution of anatomical and morphological characters. Three analyses were made with 32 Bryum species plus 20 species from genera supposedly closely related to Bryum, and with Amblyodon dealbatus (Sw. ex Hedw.) Bruch & Schimp., Meesia uliginosa Hedw., and Leptostomum macrocarpum (Hedw.) Bach. Pyl., as outgroups. It is here suggested that under earlier systematic concepts the genus Bryum is paraphyletic. A clade with Bryum billarderi Schwägr., B. capillare Hedw., B. donianum Grev., B. russulum Broth. & Geh., Rhodobryum giganteum (Schwägr.) Paris, and R. keniae (Müll. Hal.) Broth. are circumscribed by spathulate stem leaves that are crowded in the stem apex, suggesting that the rosulate species of Bryum are more closely related to Rhodobryum than to the rest of Bryum. Stem leaf costae without stereids and spores that mature in the winter are synapomorphies for a clade with Anomobryum julaceum (P. Gaertn. et al.) Schimp. and Bryum argenteum (Hedw.). The tropical species B. cellulare Hook. and B. flaccum Wilson ex Mitt. appear in a clade with Plagiobryum zieri (Dicks. ex Hedw.) Lindb. and Synthetodontium pringlei Cardot. In one analysis, B. limbatum Müll. Hal., Epipterygium tozeri (Grev.) Lindb., Leptobryum pyriforme (Hedw.) Wilson, and Roellia roellii (Broth. ex Röll) H.A. Crum came out in a clade with Mniobryum atropurpureum (Wahlenb.) I. Hagen, Mnium hornum Hedw., Pohlia cruda (Hedw.) Lindb., P. longicollis (Hedw.) Lindb., and Pseudopohlia didymodontia (Mitt.) A.L.Andrews. It is here suggested that gametophytic features, such as the orientation and anatomy of the stem leaves and the appearance of vegetative propagules, are important for the internal relationships within the studied ingroup, whereas characters related to the sporophyte, especially those of the peristome, may obscure phylogenetic relationships. Most of the subgenera and the sections of Bryum, as defined by earlier authors, appear to be paraphyletic. However, due to the low stability of most clades it is suggested that analyses including anatomical, morphological, and molecular data are needed.     

The bryophytes of Greece: new records and observations

Abstract

New records of 38 hepatics and 87 mosses are reported from Greece. Leiocolea heterocolpos, Cephaloziella calyculata, Dicranella schreberiana, Hennediella stanfordensis, Weissia levieri, Grimmia alpestris and Grimmia torquata are believed to be new to the country. Claviform propagules formed by the excurrent nerve of the leaf are reported from a collection of Trichostomopsis australasiae.     

A Dote on the habitat of Scorpidium turgescens (T. Jens.) Loeske in Scotland

Abstract

Being a synonym of Bryum nitens Hook., B. cruegeri Hampe is not new to Africa. In addition to tubers, deciduous shoot tips and shoot fragments act as vegetative propagules.     

Seasonal variation in the spore bank of ferns in grasslands on dolomite rock

Composition and seasonal patterns of the fern spore bank were compared to the surface vegetation of grasslands on dolomite rock in Hungary. Viability and potential dormancy of spores were tested through storage experiments. Although Asplenium ruta-muraria L. was the only species found at the study sites, five others, probably originating from air-borne spores from nearby areas, emerged from the soil samples. Considerable seasonal variability was detected in the number of prothallia emerging from soil samples from different sampling dates, with a peak after spore dispersal. The increased number of emerging prothallia after 1 year of storage suggests that a part of the spores stored in the soil samples were presumably dormant. Investigations on the dormancy of fern spores might be of great interest, especially in species adapted to seasonally unfavourable habitats.     

Fire and flood: Soil‐stored seed bank and germination ecology in the endangered Carrington Falls Grevillea (Grevillea rivularis,Proteaceae)

Abstract Seed germination is dependent on the interaction between the dormancy state of a seed and the presence of favourable environmental conditions. Thus, the spectacular pulse of seedling recruitment in many Australian vegetation communities following disturbances such as fire can be attributed to changes in microsite conditions and/or the dormancy‐breaking effect of the disturbance on accumulated seed banks. Grevillea rivularis is a threatened species endemic to the area immediately above Carrington Falls in the NSW Southern Highlands. Most of the population is confined to the riparian vegetation zone in woodland and heath, and is therefore subject to periodic disturbance from fire and flood. For this species, a pulse of seedling recruitment has been recorded after fire, flood and mechanical soil disturbance. The aims of this study were to examine the density and vertical distribution of the soil‐stored seed bank and to investigate the role of heat and scarification as cues for germination of fresh and soil‐stored seed. There was a large seed bank under the canopies of established individuals (194 ± 73 seeds m^?2) and most seeds were found in the 0–2 cm and leaf‐litter layers of the soil profile. The germination response of soil‐stored and fresh seed was examined using a hierarchical series of laboratory experiments. Seeds of G. rivularis showed marked dormancy polymorphism. Thirty‐six percent of soil‐stored seed germinated without treatment, whereas no untreated fresh seeds germinated. Scarification or heating caused significant germination of dormant soil‐stored seed, but only scarification resulted in germination of dormant fresh seeds. These results highlight important differences in the dormancy state of soil‐stored and fresh seed. Thus, being a riparian species in a fire‐prone environment, the dormancy mechanisms in seeds of G. rivularis suit this species to disturbance by both fire and flood.     

A comparison of distribution patterns in British and Irish mosses and liverworts

Abstract

We classified 747 species of British and Irish mosses into 10 clusters, based on their recorded distribution in 10×10 km grid squares (hectads). We generated the clusters in a two-stage process using the CLUSTASPEC program, the method that we had earlier used for British and Irish liverworts and hornworts. The clusters are named after the species with distributions which are most similar to those of the clusters as a whole. Clusters of widespread species (Bryum capillare), southern, lowland species (Rhynchostegium confertum), widespread calcifuges (Pleurozium schreberi), upland species (Blindia acuta), and montane calcifuges (Kiaeria falcata) closely match clusters recognised in the liverworts. The remaining clusters (Tortella flavovirens, Weissia longifolia, Mnium stellare, Encalypta alpina, Mnium lycopodioides) are less similar. The classification of mosses into 15 and 20 clusters generates additional clusters of hyperoceanic and montane mosses which also resemble liverwort clusters. The influence of calcareous bedrock has a more marked effect in determining moss distributions and, unlike the liverworts, the 10 moss clusters include one which is predominantly coastal. Mosses tend to be a less upland group than liverworts; a smaller proportion of their species have northern and western distributions and the lowland clusters are characterised by more extreme environmental conditions. As with the liverworts, geographically restricted clusters of species with predominantly Mediterranean-Atlantic, Arctic-montane and Boreo-arctic Montane world ranges include marked concentrations of threatened species, and species which are not recorded as fruiting in the British Isles.     

Patterns of relationships inTrichostomoideae (Pottiaceae, Musci)

Ribosomal DNA sequences were employed to infer relationships among EuropeanPottiaceae. Intragenic spacer I was sequenced for sixTrichostomoideae (Eucladium verticillatum, Pleurochaete squarrosa, Tortella flavovirens, T. nitida, T. tortuosa, Trichostomum brachydontium) and seven taxa from the other European subfamilies included inPottiaceae (Bryoerythrophyllum recurvirostrum, Didymodon vinealis, Microbryum starkeanum, Tortula muralis, Syntrichia ruralis, Weissia controversa andTimmiella cf.barbuloides). Cladistic analysis of sequence data shows close relationships betweenPleurochaete, Tortella andWeissia. Tortella appears to be paraphyletic, as it includesPleurochaete, Weissia andTrichostomum. Weissia, therefore, seems to be better placed inTrichostomoideae than, as traditionally done, inPottioideae. NeitherMerceyoideae norPottioideae appear to be monophyletic sensu stricto, at least within the limits of the taxa in analysis. Within the latter subfamily,Syntrichia is clearly separated fromTortula. These results would suggest that taxonomy inPottiaceae does not depict the pattern of descent, and therefore is in need of revision.     

Weissia papillosissima Laz. (Pottiaceae,Musci), a species new to the European bryophyte flora

Abstract

Weissia papillosissima Laz. is reported for the first time in Europe at different localities in the Iberian Peninsula. Previously it was known only from Tadhikistan in the former Soviet Union. The. species is described and illustrated and its distribution mapped and discussed.     

Morphological,ecological and molecular studies of the intergrading taxa Bryum neodamense and B. pseudotriquetrum (Bryopsida: Bryaceae)

Abstract

Studies of Bryum neodamense at most of its localities in the British Isles revealed that plants with morphology intermediate with B. pseudotriquetrum var. pseudotriquetrum frequently accompany B. neodamense. A survey of herbarium specimens found that similar intermediates are widespread in continental Europe and also occur in Asia, Alaska and Greenland. Phylogenetic analyses of DNA sequences from three loci imply that B. neodamense and intermediate plants are nested within the rather variable B. pseudotriquetrum. It is therefore concluded that, despite its striking morphological characters, B. neodamense is an inconstant phenotype of B. pseudotriquetrum, which occurs very locally in highly calcareous habitats that are subject to periodic inundation.     

THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON THE DEVELOPMENT OF GEOGRAPHICALLY ISOLATED POPULATIONS OF FUNARIA HYGROMETRICA AND WEISSIA CONTROVERSA

Geographically isolated populations of Funaria hygrometrica Hedw. and Weissia controversa Hedw. were cultured under controlled axenic conditions in the laboratory to determine the developmental variability found between and within two species of widespread distribution. Funaria plants were found to grow more rapidly than those of Weissia; the latter could not be induced to complete the life cycle in culture, and generally had a less broad tolerance to environmental extremes than did Funaria. Optimum temperatures of 30 C for spore germination and 25 C for protonematal growth and gametophore formation were observed in all populations of Funaria. Gametangial formation required cooler temperatures in all populations; however, optimal temperature requirements and sporophytic growth characteristics were population-dependent. The temperature responses of the various stages of the life cycle correlate well with seasonal temperature fluctuations that might be expected in nature. The presence of ecological races in Funaria hygrometrica is demonstrated in the behavior of the reproductive stages of the life cycle.     

Patterns of seed longevity and dormancy in obligate seeding legumes of box‐ironbark forests,south‐eastern Australia

Current fuel loads and distribution suggest that fire events are infrequent and of a low intensity in the regenerated dry sclerophyll forests of the Victorian box‐ironbark ecosystem. However, many box‐ironbark species possess traits consistent with fire‐cued regeneration. It is unclear the degree to which human disturbance may have altered fire regimes in these forests. The infrequent and low‐intensity fire regime suggested by current fuel dynamics may pose a threat to the persistence of fire‐cued species. Obligate seeders such as those of the Fabaceae and Mimosaceae, common in box‐ironbark understoreys, may be particularly vulnerable if inter‐fire intervals exceed seed longevity. This study used seed burial trials to examine seed dormancy and longevity in five legume species to explore their capacity to regenerate under an infrequent, low‐intensity fire regime. All species displayed dormancy and longevity patterns consistent with other south‐east Australian legumes. Before burial, dormancy levels were high for all species (98–100%). After 3 years, storage under in situ and ex situ conditions, dormancy in Pultenaea prostrata remained at pre‐burial levels with virtually no seed becoming non‐dormant. Over time, some Acacia seed became non‐dormant under both in situ and ex situ storage, with the pattern varying among species. Longevity also varied between species. Variation in the dormancy and longevity patterns observed in these obligate seeder legumes suggests two strategies: (i) releasing a portion of soil‐stored seed from dormancy during the inter‐fire period to permit inter‐fire recruitment; and (ii) retaining most soil‐stored seed as dormant during the inter‐fire interval. Both strategies represent potential weaknesses under a long fire interval regime. The first relies on dormancy release translating to successful recruitment and requires ongoing inter‐fire input into the soil seed bank. The second relies on seed longevity exceeding the inter‐fire interval. Whether either is more suitable to coping with long‐term infrequent fire requires long‐term monitoring.     

Observations on periodicity of hatching of eggs of the potato cyst nematode, Heterodera rostochiensis Woll.

Soil containing new-generation cysts of Heterodera rostochiensis was taken from the field at monthly intervals during late summer and autumn and kept in various conditions for up to a year. The number of eggs that hatched in the stored cysts was compared each month with the number that hatched in cysts taken directly from the field. Eggs did not hatch readily when stimulated during the late autumn and early winter, although more did so in cysts taken from the field before August than after. A few more eggs hatched in cysts stored in air-dried soil than in cysts stored in moist soil. Some cysts were kept at 15 or 20 °C continuously and others at 5, 15 or 30 °C for 6 weeks followed by 20 °C continuously. Storage at 30 °C caused eggs to hatch sooner, but otherwise the temperature of storage had little effect on hatch at any time of the year. Warmth also increased the hatch of H. cruciferae sooner, and some synthetic hatching agents did so with both of these species. When freed from new cysts, more eggs of H. rostochiensis hatched than in intact cysts and hatch was further increased when the fragments of tanned cyst-wall were left with the freed eggs. Puncturing the cyst-wall of new brown cysts had little effect on the hatch in potato root diffusate. Like eggs in new cysts, those in 1-year-old cysts stored out of doors ceased to hatch during the autumn and winter. The term ‘dormancy’ is inadequate to describe the inability of eggs of H. rostochiensis and other Heterodera spp. to hatch in the appropriate stimulant and the term ‘facultative diapause’, as applied to insects, better fits the phenomenon.     

Post-fire bryophyte dynamics in Mediterranean vegetation

Abstract. Bryophyte dynamics after fire in the Mediterranean macchia of Southern Italy was studied both by diachronic and synchronic approaches. Changes of bryophyte cover and species composition were found in relation to both age and fire intensity. During the first 2 yr after fire, bryophytes dominated the plots which had experienced the highest fire intensity while herbs were dominant in plots affected by lighter fires. Pioneer species, such as Funaria hygrometrica, Barbula convoluta and Bryum dunense, characterized recent intense fires, whereas Bryum torquescens, B. radiculosum and B. ruderale were dominant after less intense burning. Pleurochaete squarrosa, Tortula ruraliformis and Tortella flavovirens dominated intermediate successional stages. Pleurocarpous mosses were dominant only in the older closed stands. Different patterns of regeneration strategies were described: spores dominated early stages of intense fire, while vegetative propagules characterized later successional stages and less severely burned areas. Although bryophytes usually have a low abundance in Mediterranean vegetation, their role in post-fire vegetation dynamics may be locally enhanced according to burning conditions.     

Funaria Rhizoids infected with Pleotrachelus wildermani

Abstract

The recolonisation of bryophytes on soil during 3½ years following fire in a mixed forest in south-west Tasmania is characterised by the presence of Marchantia berteroana, Funaria hygrometrica, Ceratodon purpureus and Polytrichum juniperinum, while limited cover is provided by Campy lop us introjlexus, Tortella calycina and Bryum sauteri. It has been verified that the protonemal growth of the early colonising mosses is more rapid than non-colonising specles. The preference for spores of Funaria hygrometrica, Ceratodon purpureus and Marchantia berteroana to germinate on burnt soil is confirmed. However, it has been shown that burnt substrates do not inhibit the germination of non-colonising species. Therefore, the rapid development of protonemata and gametophytes in the colonising species may be a critical factor for their success.     

Survey of the bryophytes of arable land in Britain and Ireland 1: a classification of arable field assemblages

Abstract

Knowledge of the distribution of arable bryophytes lags behind that of bryophytes of many other habitats, and we have almost no information on their occurrence in relation to crop type and agricultural management regime. A survey of arable fields in Britain and Ireland carried out by members of the British Bryological Society in 2001–05 was designed to provide such baseline data. We surveyed a stratified random sample of 200 fields in the main areas of arable agriculture and a further 620 fields in these areas and in areas where arable fields are less frequent. The species present in each field were listed and their frequency within the field assessed. Data on the crop, the cover of vascular plants, bryophytes, trash and bare soil, and the pH and texture of the soil were recorded for each field. Six species assemblages are described on the basis of a classification of the species recorded in each field and their frequency values. The Tortula truncata–Anthoceros and Dicranella staphylina–Riccia glauca assemblages are the most species-rich and are concentrated on acidic soils in northern and western Britain and in Ireland. By contrast, the Barbula unguiculata–Bryum klinggraeffii and Phascum cuspidatum–Microbryum davallianum assemblages are mainly found on calcareous soils in southern and eastern England. The Bryum dichotomum–Marchantia polymorpha assemblage is characterised by widespread, weedy generalist species and is concentrated in East Anglia. The final assemblage, Brachythecium rutabulum–Fissidens taxifolius, characteristically occurs in late-successional fields and was scattered throughout the area sampled. A comparison of the results from Kent with those of a survey of Kentish fields (using a different methodology) by A.G. Side in 1973–74 suggests that the Bryum dichotomum–Marchantia polymorpha assemblage may possibly have replaced the Dicranella staphylina–Riccia glauca assemblage on acidic soils in the last 30 years. The considerable geographical variation within the arable flora of Britain and Ireland revealed by the survey should be taken into account when assessing the meagre evidence for historic changes in the arable bryophyte flora.     

An ISSR‐based Approach for the Molecular Detection and Diagnosis of Dwarf Bunt of Wheat,Caused by Tilletia controversa Kühn

Dwarf bunt of wheat, caused by Tilletia controversa Kühn, is an important international quarantine disease in many countries. The objective of this investigation was to develop a diagnostic molecular marker generated from intersimple sequence repeat (ISSR) for rapid identification of T. controversa. A total of 60 primers were tested by ISSR to detect DNA polymorphisms between T. controversa and related species. The primer ISSR818 generated a polymorphic pattern displaying a 952‐ bp DNA fragment specific for T. controversa. The marker was converted into a sequence characterized amplified region (SCAR), and specific primers (TCKSF2/TCKSR2) were designed for use in a PCR detection assay. Its detection limit was 1 ng of DNA, which could be yielded by 1.1 μg of teliospores in a 25‐ μl PCR. Conclusively, a method to distinguish T. controversa from similar pathogenic fungi has been successfully developed based on the use of a SCAR marker.     

Ecological longevity of Polaskia chende (Cactaceae) seeds in the soil seed bank,seedling emergence and survival

• Soil seed banks are essential elements of plant population dynamics, enabling species to maintain genetic variability, withstand periods of adversity and persist over time, including for cactus species. However knowledge of the soil seed bank in cacti is scanty. In this study, over a 5‐year period we studied the seed bank dynamics, seedling emergence and nurse plant facilitation of Polaskia chende, an endemic columnar cactus of central Mexico.
• P. chende seeds were collected for a wild population in Puebla, Mexico. Freshly collected seeds were sown at 25 °C and 12‐h photoperiod under white light, far‐red light and darkness. The collected seeds were divided in two lots, the first was stored in the laboratory and the second was use to bury seeds in open areas and beneath a shrub canopy. Seeds were exhumed periodically over 5 years. At the same time seeds were sown in open areas and beneath shrub canopies; seedling emergence and survival were recorded over different periods of time for 5 years.
• The species forms long‐term persistent soil seed banks. The timing of seedling emergence via germination in the field was regulated by interaction between light, temperature and soil moisture. Seeds entered secondary dormancy at specific times according to the expression of environmental factors, demonstrating irregular dormancy cycling.
• Seedling survival of P. chende was improved under Acacia constricta nurse plants. Finally, plant facilitation affected the soil seed bank dynamics as it promoted the formation of a soil seed bank, but not its persistence.

     

The influence of crop rotation and soil fumigation on a mycorrhizal fungal community associated with soybean

Population densities of mycorrhizal fungal propagules in a western Kentucky field highly productive for soybean were measured by bioassay throughout a soybean production season. The primary experimental variables were crop rotation (soybeans in 1985, then 2 years in corn, milo, fescue, or soybean, then soybean in 1988 on all plots when populations of propagules were determined) and soil fumigation with 67% methyl bromide/33% chloropicrin. Of the 20 species in three genera found, Glomus predominated both in terms of number of species and population densities. Most species of Glomus occurred at higher population densities in rotated plots than in continuous soybean plots. In continuous soybean plots, species of Gigaspora made up a much higher proportion of the mycorrhizal fungal community than in rotated crops. Species richness and diversity were lower, and dominance and equitability higher, in nonfumigated continuous soybean plots than in rotated plots early in the season, but the differences were not present at the end of the season. Soil fumigation killed most propagules in the upper 15 cm of soil, but after production of a crop of soybeans, populations of total propagules and most Glomus spp. recovered to prefumigation densities. However, Gigaspora margarita and Gigaspora gigantea did not recover similarly. Fumigation reduced species richness and diversity and increased dominance, but the effects were ameliorated by the end of the season. Colonization of roots was low during vegetative growth but increased rapidly after the onset of soybean reproduction. There was no evidence for mutualism during the early half of the season, perhaps due to high soil P and low dependency of soybean. Fumigation increased soybean yields. A stable mycorrhizal fungal community appeared to become established with continuous soybean production, and both crop rotation and soil fumigation disrupted the community.     

Some Mediterranean plant species (Lavandula spp. and Thymus satureioides) act as potential ‘plant nurses’ for the early growth of Cupressus atlantica

The mycorrhizal status of several representative shrub species (Lavandula spp. and Thymus satureioides) in Moroccan semiarid ecosystems, was evaluated as well as their contribution to the mycorrhizal potential of the soil. Furthermore, the rhizosphere soils collected under these target species were tested for their influence on the growth of Cupressus atlantica, a tree species whose natural stands has declined in this area. Soil samples were collected from the rhizosphere of L. stoechas, L. dentata and of C. atlantica existing in the experimental area. Control samples were randomly collected from bare soil sites, away from plant influence.All the target species formed AM symbiosis and the extent of AM fungal colonization was not significantly different between plant species. No significant difference was detected between the total number of AM fungal spores of the bare soil and those recorded in the root zones of target species and C. atlantica. Three genera of AM fungi (Scutellospora, Glomus and Acaulospora) were present in the rhizospheres of the plant species and in the bare soil.The number of mycorrhizal propagules in soil originating from around the four target plant species was significantly higher than the one in the bare soil (Figure 1). The most probable number (MPN) of mycorrhizal propagules per 100 g of dry soil ranged from 7.82 (bare soil) to 179.7 (L. dentata and C. atlantica) and 244.5 (L. stoechas and T. satureioides). As the total number of spores was not different for the soil of different origins, the increase of the mycorrhizal soil infectivity (MSI) mainly resulted from larger AM mycelial networks that constituted the main source of AM fungal inoculum. In addition, this MSI enhancement was linked with changes in the functioning of soil microbial communities. In a glasshouse experiment, the growth of C. atlantica seedlings was significantly higher in the C. atlantica and in the shrub species soils than in the bare soil. Although the AM inoculum potential is not sufficient to ensure the development of forest trees in Mediterranean ecosystems, the use of plant nurses such as T. satureioides or Lavandula spp. could be of great interest to restore a self-sustaining vegetation cover to act against desertification.     

东北草地异质生境芦苇种群根茎芽年龄结构及输出规律

为明确异质生境条件下芦苇种群根茎芽年龄结构及输出规律,揭示芦苇种群的营养繁殖特性,采用单位土体挖掘取样,分别计数各龄级根茎芽的调查与统计方法,对东北草甸草原草甸土和盐碱土两个生境单优群落芦苇种群根茎芽动态进行比较分析。结果表明,两个生境芦苇种群根茎芽库主要均由6个龄级组成;草甸土生境在6—10月均为增长型年龄结构;盐碱土生境6—7月份为衰退型年龄结构,8月份为稳定型年龄结构,9—10月份为增长型年龄结构。根茎芽数量1—4a普遍以草甸土生境高于盐碱土生境,5—6a普遍以盐碱土生境高于草甸土生境,各龄级根茎芽数量与月份之间均符合y=a+bx直线关系(P0.05)。随着龄级的增加,休眠芽比率呈逐渐下降趋势,而萌发芽比率则呈逐渐上升趋势,5个生育期的休眠芽比率和萌发芽比率与龄级之间均符合y=a+bx直线关系(P0.01)。各龄级根茎的休眠芽具有一个相对稳定的萌发输出过程,草甸土生境根茎休眠芽按每年11%的比率萌发输出,而盐碱土生境根茎休眠芽按每年7%的比率萌发输出。虽然芦苇种群根茎芽年龄结构及年龄谱在异质生境中存在显著差异,但却有着相同的季节变化规律,均以不断形成新根茎的芽来维持着种群的营养繁殖更新。