Frequency-dependent variation in reproductive success in Narcissus: implications for the maintenance of stigma-height dimorphism. (1/24)

Negative frequency-dependent selection is a major selective force maintaining sexual polymorphisms. However, empirical demonstrations of frequency-dependent reproductive success are rare, particularly in plants. We investigate this problem by manipulating the frequencies of style morphs in a natural population of Narcissus assoanus, a self-incompatible herb with style-length dimorphism and intra-morph compatibility. We predicted that the reproductive success of morphs would vary negatively with their frequency because of the effects of morph-specific differences in sex-organ position on patterns of pollen transfer. This prediction was generally supported. The fruit and seed set of the two morphs did not differ significantly in plots with 1 : 1 morph ratios. However, short-styled plants produced significantly fewer seeds than long-styled plants in monomorphic plots, and significantly more seeds than long-styled plants in plots with 'long-biased' morph ratios. These patterns indicate that in the absence of physiological barriers to intra-morph mating, negative frequency-dependent selection contributes to the maintenance of stylar polymorphism through inter-morph pollen transfer. Our experimental results also provide insights into the mechanisms governing the biased style-morph ratios in populations of Narcissus species.  (+info)

Early detection of apoptosis by staining of acid-treated apoptotic cells with FITC-labeled lectin from Narcissus pseudonarcissus. (2/24)

BACKGROUND: Exposure of anionic phospholipids and modified carbohydrates are main parts of the apoptotic death program. Cells undergoing apoptosis can be identified by various methods, detecting surface changes or modifications of their organelles, respectively. We describe a method for the detection of early apoptosis by staining of cells with fluorescein isothiocyanate (FITC)-labeled lectin from Narcissus pseudonarcissus (NPn). METHODS: Apoptosis in cells or in cell lines was induced by various stimuli. To detect apoptosis the cells were stained with FITC-labeled lectin of NPn. After a short-term acid treatment they were analyzed by flow cytometry. RESULTS: The instability of the cytoplasmic membrane against acid and the binding of NPn were very early features of apoptotic cell death. The NPn lectin staining procedure detected apoptosis with high sensitivity. The staining was stable for at least 12 h. CONCLUSIONS: The method described in this study is suitable for the detection of the very early phases of apoptosis. The NPn lectin staining after short-term acid treatment can, therefore, be added to the list of reliable tools for the research of cell death.  (+info)

Mating patterns and genetic diversity in the wild daffodil Narcissus longispathus (Amaryllidaceae). (3/24)

Despite the importance of Narcissus to ornamental horticulture, there have been no population genetic studies of wild species, many of which have narrow distributions. Here, we measure selfing rates and levels of genetic diversity at allozyme loci in six populations of Narcissus longispathus, a self-compatible daffodil endemic to a few mountain ranges in southeastern Spain. The populations were distributed among four distinct river valleys encompassing two main watersheds in the Sierra de Cazorla mountains. Selfing rates averaged 0.37 (range 0.23-0.46), resulting in significant inbreeding coefficients for the progeny (f = 0.324). In contrast, estimates of inbreeding in parental genotypes were not significantly different from zero (f = 0.001), indicating that few selfed offspring survive to maturity because of inbreeding depression. Species-wide estimates of genetic diversity for the six populations were P(s) = 0.38, H(es) = 0.119 and A(s) = 1.27 with significant genetic differentiation among populations theta = 0.15. The observed patterns of genetic differentiation among populations are likely influenced by the mating system, and a combination of local topography, watershed affinities and gene flow.  (+info)

Daffodil toxicosis in an adult cat. (4/24)

A domestic longhair cat with a 3-day history of lethargy and vomiting after ingesting dried daffodil stems (Narcissus spp.) was severely hypothermic (33.0 degrees C), with bradycardia (78 beats/ min) and hypotension. Treatment with atropine, dexamethasone, fluid therapy, and supportive care resulted in a complete recovery by 6 days after exposure.  (+info)

Herkogamy and mating patterns in the self-compatible daffodil Narcissus longispathus. (5/24)

BACKGROUND AND AIMS: Floral design in self-compatible plants can influence mating patterns. This study investigated Narcissus longispathus, a self-compatible bee-pollinated species with wide variation in anther-stigma separation (herkogamy), to determine the relationship between variation in this floral trait and the relative amounts of cross- and self-fertilization. METHODS: Anther-stigma separation was measured in the field in six populations of N. longispathus from south-eastern Spain. Variation in herkogamy during the life of individual flowers was also quantified. Multilocus outcrossing rates were estimated from plants differing in herkogamy using allozyme markers. KEY RESULTS: Anther-stigma separation varied considerably among flowers within the six populations studied (range = 1-10 mm). This variation was nearly one order of magnitude larger than the slight, statistically non-significant developmental variation during the lifespan of individual flowers. Estimates of multilocus outcrossing rate for different herkogamy classes (t(m) range = 0.49-0.76) failed to reveal a monotonic increase with increasing herkogamy. CONCLUSIONS: It is suggested that the lack of a positive relationship between herkogamy and outcrossing rate, a result that has not been previously documented for other species, could be mostly related to details of the foraging behaviour of pollinators.  (+info)

Mating patterns and demography in the tristylous daffodil Narcissus triandrus. (6/24)

Mating patterns in plant populations are influenced by interactions between reproductive traits and ecological conditions, both factors that are likely to vary geographically. Narcissus triandrus, a wide-ranging heterostylous herb, exhibits populations with either two (dimorphic) or three (trimorphic) style morphs and displays substantial geographical variation in demographic attributes and floral morphology. Here, we investigate this variation to determine if demography, morphology, and mating system differ between the two sexual systems. Our surveys in Portugal and NW Spain indicated that dimorphic populations were less dense, of smaller size, and had larger plants and flowers compared to trimorphic populations. Outcrossing rates estimated using allozyme markers revealed similar outcrossing rates in dimorphic and trimorphic populations (t(m) dimorphic=0.759; t(m) trimorphic=0.710). All populations experienced significant inbreeding in progeny (mean F=0.143). In contrast, parental estimates of inbreeding were not significantly different from zero (mean F=0.062), implying that few inbred offspring survive to reproductive maturity due to inbreeding depression. Although the majority of inbreeding results from selfing, significant levels of biparental inbreeding were also detected in eight of the nine populations (mean s(s)-s(m)=0.081). Density was negatively associated with levels of selfing but positively associated with biparental inbreeding. Population size was positively associated with outcrossing but not biparental inbreeding. There were no consistent differences among the style morphs in outcrossing or biparental inbreeding indicating that the maintenance of trimorphism vs dimorphism is unlikely to be associated with inbreeding of maternal parents.  (+info)

Spatial ecology of mating success in a sexually polymorphic plant. (7/24)

The spatial context of reproduction is of crucial importance to plants because of their sessile habit. Since pollen and seed dispersal is often restricted, mating success is likely to depend on the quantity and quality of mates in local neighbourhoods. Here we use neighbourhood models to investigate the spatial ecology of pollination and mating in Narcissus assoanus, a sexually polymorphic plant with two mating morphs that differ in style length. By mapping individuals in eight populations from southwestern France, we investigated the influence of the density and morph identity of plants at different spatial scales on variation in female fertility. By using inferences on the expected patterns of pollen transfer based on floral morphology, we were able to predict the quantitative relations between local morph ratios and variation in fertility. Our analyses revealed differences in the spatial clustering of morphs and in their response to plant density and morph identity within local neighbourhoods. Mating success in N. assoanus was characterized by both density- and frequency-dependent processes, a condition that may be a general feature of the spatial ecology of plant mating.  (+info)

Radial density distribution and symmetry of a Potexvirus, narcissus mosaic virus. (8/24)

Narcissus mosaic virus is a Potexvirus, a member of the Flexiviridae family of filamentous plant viruses. Fiber diffraction patterns from oriented sols of narcissus mosaic virus have been used to determine the symmetry and structural parameters of the viral helix. The virions have a radius of 55+/-5 A. The viral helix has a pitch of 34.45+/-0.5 A, with 7.8 subunits per turn of the helix. We conclude that all members of the Potexvirus genus have close to 8 subunits per helical turn.  (+info)

• 1
• 2
• 3