Sex ratio and sex expression in an urban population of the silver moss,Bryum argenteum Hedw.

ABSTRACT

Introduction. A well-supported pattern among dioicous bryophytes is male rarity. However, few assessments of bryophyte sex ratios have been made across environmental gradients to assess the role of environment in shaping population sex ratios.

Methods. We systematically surveyed 200 shoots from a 20?m² urban population of Bryum argenteum, and regenerated each shoot apex until sex expression occurred (up to 315 days).

Key results. Female shoots outnumbered male shoots 132 to 68, giving a sex ratio of 1.94♀: 1♂. The female bias was found in two transects in higher light environments but not in the third transect, which had a lower light level and an equal sex ratio. Female shoots took longer than male shoots to reach gametangial induction (122 vs. 60 days) and longer to produce 5 inflorescences (120 vs. 80 days). Male shoots produced an average of 10× the total number of inflorescences compared to female shoots (34 vs. 3.5 inflorescences). Despite producing more inflorescences, male plants also produced more regenerant shoots, thus contradicting the prediction that a higher prefertilisation reproductive effort in males trades off with vegetative proliferation. Female plants harboured significantly more associated microbes than male plants.

Conclusions. Our results support the role of light in influencing sex ratios in this species, suggest that trade-offs between reproduction and vegetative growth may not be strong for males, and indicate a potential role of a sex-specific microbiome in influencing sex ratios.     

Iris revoluta Colas., natural hybrid origin species: characterization and preservation problems

Abstract

In order to preserve ex situ rare or vulnerable species, it is necessary to characterise their reproductive mechanisms, and to locate the origin of the interference with their development in their natural habitat. Iris revoluta Colas. is a very rare endemic species of the Salento peninsula (Italy), showing scarce sexual reproduction, but good vegetative propagation through rhizomes, as many other Iris species of natural hybrid origin. For many years this Iris has been cultivated in the Botanical Garden of the Di.S.Te.B.A., University of Lecce, where a detailed study has been initiated to investigate the phenomena that may limit its sexual reproduction.     

Hybridity as a main evolutionary force in the genus Gagea Salisb. (Liliaceae)

Abstract

The important role of hybridity in the evolution of the genus Gagea is becoming clear, through morphological, karyological and molecular evidences. Several species were recently inferred or hypothesized to be of hybrid origin; especially in sect. Didymobulbos, sect. Fistulosae and sect. Gagea. Representative case studies, such as G. luberonensis J.-M. Tison, G. polidorii J.-M. Tison and G. pomeranica Ruthe, are presented and discussed.

Since many Gagea species show very reduced or null sexual reproduction vs. a massive vegetative propagation, there are several problems in distinguishing hybrids from hybridogenous species in this genus. The actual trend is to consider them at specific level because of their ability to stabilize, at least through vegetative propagation by bulblets and/or bulbils.     

Presence of Bacillus coagulans spores and vegetative cells in rat intestine and feces and their physiological effects

ABSTRACT

This study was aimed to investigate the presence of Bacillus coagulans vegetative cells in the intestine and fecal samples in rats fed B. coagulans spores as well as to estimate the ratios of spores and vegetative cells in these samples. A two-step process has been developed to enumerate B. coagulans in different mixed bacterial samples, specifically (1) observation of yellow ring formation on modified GYEA medium upon incubation at 55°C, (2) microscopic examination of spore formation after 7 d of incubation. Our results have demonstrated the presence of vegetative cells in the intestinal and fecal samples in rats fed B. coagulans spores. The ratios of B. coagulans spores and vegetative cells in cecal fluid, colonic content, and feces were approximately 2:8, 2:8, and 4:6, respectively. The existence of B. coagulans vegetative cells improved the intestinal milieu through an elevated short-chain fatty acid concentrations, higher fecal moisture, and lower fecal pH.     

Review of morphological and biological studies of the carrageenophyte Solieria filiformis (Kützing) Gabrielson (Rhodophyta,Gigartinales)

Abstract

The occurrence of extensive populations of the carrageenophyte Solieria filiformis in the Mar Piccolo of Taranto (Italy, Ionian Sea) has prompted this review of the literature on the subject. S. filiformis is a subtidal alga that inhabits both sheltered and exposed habitats. Interpretation of the literature leads us to classify it as an euryecious species showing high tolerance of a broad range of temperature, irradiance and salinity. S. filiformis grows in both the attached form capable of sexual reproduction and unattached only capable of vegetative propagation. The morphology of both forms as well as of the reproductive organs have been studied in detail. Laboratory and tank cultures are being carried out to estimate growth rates and elucidate its physiological ecology. For the Mediterranean specimens fast-growing strains have been selected and the optimal growth conditions have been established. S. filiformis is a potential candidate for cultivation because of the high quality of its carregeenan and the modest requirements of its thallus.     

The importance of competition,food, habitat,weather and phenotype for the reproduction of Buzzard Buteo buteo

Capsule Variation in reproduction between territories was strongly influenced by intra- and interspecific competition, phenotype, levels of rainfall and human disturbance.

Aims To assess the relative importance of competition, food, habitat quality, weather and phenotype as predictors of variation in reproduction in Buzzard.

Methods Annual breeding data were collected from 1989 to 1996 in a 300-km² study area and related to 35 independent variables through multivariate regression models.

Results Significant predictors of variation in reproduction between territories (78% variance explained) were variables describing intra- and interspecific competition, plumage morph, laying date, precipitation levels and anthropogenic disturbances in the breeding territory. Competition and plumage morph seem to be particularly important, as these variables explained a high level of variation (81%) in the 1996 reproduction of this population.

Conclusion The potential importance of competition, plumage morph and precipitation for reproduction in this Buzzard population is emphasized.     

The role of sexual and vegetative reproduction in the population maintenance of a monocarpic perennial herb,Cardiocrinum cordatum var. glehnii

Because monocarpic perennial plants have only one reproductive opportunity in their entire life, they need to ensure offspring production. Some plants reproduce both sexually and vegetatively, and vegetative reproduction could possibly compensate for seed production. Therefore, the role and significance of these reproductive modes is likely to differ between monocarps and polycarps, which can reproduce many times. Cardiocrinum cordatum var. glehnii is a monocarpic perennial that reproduces both sexually and vegetatively (bulblet formation). Here, we investigated the characteristics and contribution to population maintenance of sexual and vegetative reproduction to reveal the significance of these two reproductive modes in this species. First, we found that bulblet formation occurred in plants after the three‐leaved rosette stage. Second, resource allocation experiments revealed that although resources were mainly invested in fruit maturation after the flowering season, resource allocation was switched from sexual reproduction to vegetative reproduction if seed production was insufficient. Third, the outcrossing rate in this species varied greatly according to the environment surrounding the population. However, reproductive assurance by selfing kept seed production stable even if flowers did not receive sufficient pollen for full seed set via outcross pollination, and moreover, there was no intensive inbreeding depression. Finally, genotypic identification of ramets suggested that daughter ramets derived from vegetative reproduction received the space that the mother flowering ramet had occupied until the previous year.     

Three modes of asexual reproduction in the moss Octoblepharum albidum

Abstract

Populations of Octoblepharum albidum growing in very moist and shaded habitats were found to have three kinds of asexual reproduction. First, the production of foliar gemmae along the upper half of leaf margins. Second, the production of protonema gemmae on protonemata originated from foliar gemmae. Third, the production of buds and new shoots at leaf tips. The formation of new shoots is further repeated at the leaf tips of the new shoots, giving the plant the character of a 'walking moss'.     

Regeneration capacity of oceanic-montane liverworts: implications for community distribution and conservation

Abstract

Scotland’s mountains are home to a rare and unique liverwort community, ‘the oceanic-montane liverwort-rich heath’, but its component species are absent from regions where they could potentially thrive. Many biological characteristics of these species are unknown, making it impossible to explain the reasons for their rarity; however, they have not been observed to produce sporophytes within Britain. We use ex situ cultivation of whole liverworts and fragments, and in situ cultivation of fragments, to assess the growth rate and the potential for vegetative reproduction of several species. Most of the species grew from both fragments and as whole plants, indicating that the rarity of the liverwort heath is not due to poor powers of regeneration. We propose that growth rate and the potential to regenerate from fragments are important factors structuring the liverwort heath community, at least locally. Furthermore, this study demonstrates that there is potential for ex situ conservation of rare liverwort species, in situ enhancement of existing populations, and creation of new ones.     

Gametophyte development and reproduction of the Asian fern Polystichum polyblepharum (Roem. ex Kunze) C. Presl (Dryopteridaceae,Polypodiopsida)

Abstract

The gametophytic generation of Polystichum polyblepharum (Dryopteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and reproduction strategies, was studied. Spore germination was of the Vittaria model and the developmental pattern was of the Aspidium model. Adult gametophytes were cordate and hairy, with unicellular hairs located at the margins and at the prothallus surface. The marginal ones were secretory. The gametophytes produced archegonia located in the central area between the notch and the rhizoids, but antheridia were never detected. Archegonia were of the normal type described for leptosporangiate ferns. Apogamous sporophytes appeared from a cellular outgrowth developed just under the apical notch. Initially, the outgrowth appeared completely surrounded by glandular hairs and scales, which persisted throughout the subsequent stages of leaf development.     

Differential time allocation of foraging workers in the subterranean termite

Background

Worker reproduction has an important influence on the social cohesion and efficiency of social insect colonies, but its role in the success of invasive ants has been neglected. We used observations of 233 captive colonies, laboratory experiments, and genetic analyses to investigate the conditions for worker reproduction in the invasive Anoplolepis gracilipes (yellow crazy ant) and its potential cost on interspecific defence. We determined the prevalence of worker production of males and whether it is triggered by queen absence; whether physogastric workers with enlarged abdomens are more likely to be reproductive, how normal workers and physogastric workers compare in their contributions to foraging and defence; and whether worker-produced males and males that could have been queen- or worker-produced differ in their size and heterozygosity.

Results

Sixty-six of our 233 captive colonies produced males, and in 25 of these, some males could only have been produced by workers. Colonies with more workers were more likely to produce males, especially for queenless colonies. The average number of days between the first appearance of eggs and adult males in our colonies was 54.1 ± 10.2 (mean ± SD, n = 20). In our laboratory experiment, queen removal triggered an increase in the proportion of physogastric workers. Physogastric workers were more likely to have yolky oocytes (37–54.9%) than normal workers (2–25.6%), which is an indicator of fertile or trophic egg production. Physogastric workers were less aggressive during interspecific aggression tests and foraged less than normal workers. The head width and wing length of worker-produced males were on average 4.0 and 4.3% greater respectively than those of males of undetermined source. Our microsatellite DNA analyses indicate that 5.5% of worker-produced males and 14.3% of males of undetermined source were heterozygous, which suggests the presence of diploid males and/or genetic mosaics in A. gracilipes.

Conclusions

Our experimental work provides crucial information on worker reproduction in A. gracilipes and its potential cost to colony defence. The ability of A. gracilipes workers to produce males in the absence of queens may also contribute to its success as an invasive species if intranidal mating can take place between virgin queens and worker-produced males.

     

Adaptive genetic differentiation in life-history traits between populations of <Emphasis Type="Italic">Mimulus guttatus</Emphasis> with annual and perennial life-cycles

The optimal allocation to sexual and vegetative reproduction as well as the optimal values of other life-history characteristics such as phenology, growth and mating system are likely to depend on the life-cycle of the organism. I tested whether plants of Mimulus guttatus originating from temporarily wet populations where the species has an enforced annual life-cycle have higher allocation to sexual reproduction, lower allocation to vegetative reproduction, more rapid phenology, faster growth, and floral traits associated with a self-fertilizing mating system than plants from permanently wet populations where the species has a perennial life-cycle. I grew a total of 1377 plants originating from three populations with an annual life-cycle and 11 populations with a perennial life-cycle in a greenhouse under permanently and temporarily wet conditions. Plants of M. guttatus in permanently wet conditions had significantly more vegetative reproduction and tended to have a faster growth than plants in the temporarily wet conditions, indicating plasticity in these life-history traits. Plants from populations with an annual life-cycle invested significantly more in sexual reproduction and significantly less in vegetative reproduction than the ones from populations with a perennial life-cycle. Moreover, this study showed that plants originating from populations with an annual life-cycle have a significantly faster development and floral traits associated with autonomous self-fertilization. In conclusion, this study suggests that there has been adaptive evolution of life history traits of M. guttatus in response to natural watering conditions that determine the life span of the species.     

Studio Del Ritmo Vegetativo Di Olea Europaea L. in Messina Negli Anni 1952–54

Summary

The vegetative growth of the olive tree in Messina is described. The growth period begins at the end of March and prosecutes without interruption as late as November. The secondary wood tissue producted during summer time (from Yuly to August) is abnormal being of a parenchimatoide type. During winter there is a well defined rest period.

The cambium produces secondary wood and bark with an alternate rythm, so that in spring the wood production prevails on the liber and in autumn the opposite condition is realized.

Each phase of production of secondary conducting tissues (wood as well as bark) is followed by a phase of starch storing.

In the stem several false wood rings are produced during one year, while in the young branches each wood ring corresponds to one year.

The longitudinal growth and cork formation on the branches of the year are particularly pronounced during spring (March-May).

Cambium cells swell in a characteristic way before they start dividing and collapse during the resting periods, thickening evidently their walls, so that in winter it is difficult to distinguish a cambial cell from a parenchimatic one.

The behaviour of the vegetative growth of the olive tree in Messina is discussed on the base of the climatic characters of the region.     

Genetic and phenotypic variation,dispersal limitation and reproductive success in the invasive herb Eschscholzia californica along an elevation gradient in central Chile

Background: Reductions of genetic diversity and phenotypic changes in invasive plants are often observed to occur at high elevations. Genetic/phenotypic changes of invasive plants along elevation help to understand mechanisms of the presumed resistance of mountain ecosystems to invasion.

Aims: To assess genetic variability and phenotypic plasticity along an elevation gradient of Eschscholzia californica in the Andes, central Chile.

Methods: Eleven microsatellites were used to describe the genetic structure and the allelic diversity individuals, distributed at three elevations and two sites. We assessed the number of flowers per plant, floral biomass, leaf area, number of leaves, vegetative biomass and plant height of plants at each elevation.

Results: Genetic diversity as genetic structure did not decrease with elevations. Plant height and flower numbers decreased while leaf number and vegetative biomass increased with elevation. The ratio of the number of flowers to vegetative biomass, decreased significantly with elevation.

Conclusions: Strong genetic differences among elevations and similar genetic diversity along elevation do not suggest dispersal limitation to higher elevation. Reduction of reproductive and vegetative traits concomitantly with an increase of the reproductive cost suggests reproductive stress with increasing elevation, reducing the invasiveness of this species to higher elevation.     

Effects of parasitic castration on plant resource allocation

It has been proposed that host castration is a parasite strategy to reallocate host resources from reproductive to vegetative functions to increase parasite fitness. Since resource partitioning between reproduction and vegetative growth can affect host life-history traits, parasite effects on resource allocation can affect both plant fitness and host-parasite coevolution. Field and greenhouse experiments were used to investigate the effects of host castration by the fungus Atkinsonella hypoxylon on the resource allocation and architecture of the grass Danthonia spicata. The results indicate that non-infected D. spicata can reallocate resources from reproduction to vegetative growth when resource allocation to reproduction is prevented. However, I found no evidence that fungal castration causes reallocation of resources from host reproduction to vegetative growth. Instead, infection reduces host biomass and the fungus directly utilizes resources that would have been used for host reproduction for its own reproduction. Received: 25 March 1999 / Accepted: 24 October 1999     

Phenology and life cycle of the annual, <Emphasis Type="Italic">Chamaesyce maculata</Emphasis> (L.) Small (Euphorbiaceae), with multiple overlapping generations in Japan

The phenology of germination, vegetative growth and sexual reproduction in the annual Chamaesyce maculata (L.) Small (Euphorbiaceae) were investigated in a natural population in western Japan. Seedlings emerged from mid-June to early October, with three peaks: mid-June, late July and late August. Plants that emerged in June commenced sexual reproduction from late July, and thereafter both vegetative growth and sexual reproduction occurred together until early November, the plants showing no switching from vegetative growth to sexual reproduction. Seedlings that emerged in June and July suffered high mortality, but most seedlings that emerged from August onward survived until the reproductive stage. The minimum size for reproduction was largest for plants that emerged early in the season, and it decreased with a delay in seedling emergence. The late emergence of seedlings that resulted in low reproductive output may be to some extent compensated for by the increased probability of survival in the seedling stage. A transplant experiment clarified that C. maculata can repeat a maximum of three overlapping generations within a year. Multiple generations per year were attained by non-dormant seeds produced in the first and second generations and clearly resulted in an increased reproductive output per year. The life cycle with multiple overlapping generations may have been acquired in habitats where unpredictable disturbance results in temporally unsuitable conditions for germination, vegetative growth and sexual reproduction of annual plants, but where suitable conditions frequently continue over a period longer than the single generation time of annual plants.     

Don't pull the plug! the Drosophila mating plug preserves fertility

ABSTRACT

Mating plugs are hardened structures—typically a coagulation of seminal fluid components—that are transferred to, or formed within, the female reproductive tract of numerous animal species (both mammals and insects). Analysis of the role(s) of the mating plug in reproduction has been conducted in a wide array of diverse species. These structures have been proposed to have a multitude of functions, which include altering female re-mating rate, acting as a barrier to re-mating and being required for sperm storage or sperm movement to occur in mated females. A recent analysis of the Drosophila melanogaster mating plug has shown that proper formation of the structure is required for optimal fertility in flies: the Drosophila mating plug is required to retain the ejaculate within the female reproductive tract once mating has terminated. Here, we discuss the possible implications of the Drosophila mating plug in the fertility of this species in light of these new results.     

Notes on Shetland lichens: I

ABSTRACT

Background: According to modern coexistence theory, ecologically similar species can coexist if fitness differences between them are small, or niche differences between them are large. However, these predictions have not been tested extensively in real systems and are difficult to examine in traits-based studies.

Aims: The aim of our study was, by using the carnivorous pitcher plant genus Nepenthes as a model system, to examine (1) species growth ranks as a proxy for fitness; (2) modern coexistence theory at a geographical scale; (3) evidence for pitcher trait-mediated resource partitioning between sympatric Nepenthes species.

Methods: We used growth ranks, obtained from a survey of experienced Nepenthes nursery owners, as a proxy for fitness. Multivariate pitcher-, vegetative- or combined-trait distances, computed from morphometric-trait data from the literature were used as proxies for niche differences. Data on global Nepenthes species-pair sympatry was modelled against these fitness and niche differences.

Results: Niche and growth rate differences were positively and negatively correlated with sympatry, respectively, as expected from theory.

Conclusion: Our results agree with theory and suggest that fitness differences can be approximated from average species growth. Prey- and microhabitat-resource partitioning, operating through divergent pitcher and vegetative traits respectively, are likely mechanisms that stabilise the coexistence of sympatric Nepenthes species.     

Il genere Allium L. in Italia. IV. Studio citofotometrico sul granulo pollinico di Allium Chamaemoly L.

Abstract

The genus Allium L. in Italy. IV. A DNA cytophotometric study on the pollen grain of Allium chamaemoly L. — A cytophotometric analysis of DNA contents in pollen generative and vegetative nuclei of Allium chamaemoly L. was carried out. DNA synthesis in both nuclei was confirmed and a lightly higher DNA amount than 2C in the vegetative nucleus was pointed out. An analysis of the Fast-green stainable histones in the generative and vegetative nuclei was also accomplished. While the generative nucleus had a very high content of Fast-green stainable histone, the vegetative one have nearly no stainable histone. The occurrence of DNA synthesis and the very low histone content suggest the vegetative nucleus is functional and biochemically activ. The higher than 2C DNA content supports the possibility of a DNA amplification process including probably the amplification of ribosomal cistrons in the pollen vegetative nucleus.