Spatiotemporal Patterns of Genets and Ramets in a Population of Clonal Perennial Senecio rivularis : Plant Features and Habitat Effects (original) (raw)
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Population dynamics of the annual plant Senecio vulgaris in ruderal and agricultural habitats
Basic and Applied Ecology, 2001
The annual plant Senecio vulgaris has migrated from ruderal to agricultural habitats resulting in weed populations. The population dynamics of S. vulgaris and its naturally associated rust fungus Puccinia lagenophorae were investigated as a basis for the biological control of S. vulgaris with the rust. A detailed basic study at a single ruderal site and a parallel investigation at each five ruderal and five agricultural sites were conducted from April to November 1997. During the whole period of study the spatial distribution of plants was aggregated and plants showed a relatively large size hierarchy as indicated by mean values of the Gini coefficient higher than 0.5. Seedling establishment appeared to be a major factor influencing the dynamics of S. vulgaris. The importance of seedling establishment, together with the observed short generation time of 5 weeks and the broad range of plant sizes at reproduction classifies S. vulgaris as a ruderal strategist. The population dynamics of S. vulgaris differed between the ruderal and the agricultural habitat. Plants of S. vulgaris at the ruderal habitat survived over winter, resulting in greater population sizes (0.1 to 1 of the maximum) and a majority of plants in flower and seed set (81.9%) in spring. At the agricultural habitat, where only a few S. vulgaris winter due to weed control measures, population sizes in spring were smaller (0 to 0.16 of the maximum) with mainly vegetative plants (66.7%). The limited number of suitable hosts at the agricultural habitat in spring lead to a delay of rust infection until August, in contrast to the ruderal habitat where the rust was already present in April. In both habitats mature plant stages were more susceptible to rust infection than vegetative stages. Manipulating the dynamics of the host over winter may enhance rust epidemics in spring serving as biological control of S. vulgaris.
Heredity, 1986
A comparison between the non-radiate and radiate morphs of Senecio vulgaris for several life history characteristics was made within samples from four geographically separated populations in Britain. For most traits investigated, differences between morph means were common. However, only differences in seed germination behaviour were consistent over all populations. It was also evident that for most characters the non-radiate morph exhibited a similar or greater amount of variation both between and within families than the radiate morph. Possible causes and effects of variation in life history differences between morphs over populations are discussed and considered in relation to the maintenance of the polymorphism for capitulum type and outcrossing rate in natural populations of S. vulgaris.
2020
This paper was a part of studies conducted within an island population of the ragwort Senecio umbrosus (White Mt, southeastern Poland), a vulnerable element of xerothermic grasslands. Special attention was paid to the effects of expansive grass encroachment vs. grassland burning episodes on spatiotemporal patterns and life-stage structure of individuals in the population. The population traits were investigated nine times from 1990 to 2010, within three permanent patches differing in soil properties, initial floristic composition, grassland cover (particularly the cover of Brachypodium pinnatum), ragwort cover and density, shrub/tree cover influencing light intensity (full light–shadow), and grassland burning (zero–six episodes). There was a drastic decline in ragwort abundance within all the study patches accompanied by a decrease in the population clustering coefficient and a gradual equalization of the spatial distribution of ramets. The abundance was negatively correlated (PCA a...
Variability of outcrossing frequency in Senecio vulgaris L
Heredity, 1976
Using a marker gene controlling capitulum type, 30 lines derived from each of a dune and a garden population of Senecio vulgaris L. were tested for their tendency to outcross. Compared with previous estimates of outbreeding in the species a relatively high degree of outcrossing was found in both experimental populations (an overall average of 224 per cent). It was shown that the dune population had a slightly greater mean outcrossing frequency than the garden population but, more importantly, had significantly more heritable variation (between lines) for this trait. In discussion, some reasons are advanced to account for the unexpectedly high level of outcrossing in both populations. It is suggested that the presence of significant genetic variation for outcrossing within the dune population may provide for adaptive flexibility in the native dune habitat where there is much spatial and temporal variation of the environment.
Plant Ecology and Evolution, 2011
Background and aims-A previous study showed that the visitation rate by pollinators and the seed set of the exotic invasive Senecio inaequidens (Asteraceae) were higher compared to the native relative, Jacobaea vulgaris. The first aim of the present study was to assess if these results could be explained by differences in self-fertility, nectar rewards or floral display between the two species. Moreover, in a second step, we examined if the higher visitation rate on S. inaequidens has a negative effect on the reproductive success of J. vulgaris. Methods-Self-fertility was estimated after self-and cross-hand pollinations. Nectar volume, total sugar concentration and sugar composition were analysed on plants cultivated under controlled conditions. In the field, in order to assess the effect of floral display and impact of the invasive on the pollination success of the native, insect behaviour was assessed by comparing visitation rates, number of visitors per 10 min observation and individual censuses. Floral display (density of capitula per unit area) was artificially modified by clipping or grouping inflorescences in both species. Key results-In terms of self-fertility, seed sets were similarly low after self-pollination (11-12%) for both species. S. inaequidens produced lower amounts of nectar with lower sugar concentration compared to J. vulgaris. No influence of floral display was detected on insect visitation rates. The presence of S. inaequidens did not alter pollinator visits and seed set of J. vulgaris. Conclusions-Other traits need to be investigated to explain the different visitation rates and reproductive success between the two species. The higher seed set of S. inaequidens could be due to a higher outcrossing rate, or more frequent pollinator movements between individuals.
Quantitative genetics of life-history and morphology in a rare plant, Senecio integrifolius
Heredity, 1993
A paternal half-sib analysis was performed to estimate the narrow-sense heritability for 35 morphological and life-history characters in two populations of Senecio integrifolius, a rare and threatened plant in Sweden. The two populations differed greatly in size, the small one consisting of separate patches and the large one having a more or less continuous distribution. In addition to significant population differences in the mean of 26 characters, we found slightly higher heritabilities in the small and patchy population (average 0.49) than in the large and continuous population (average 0.43). Overall, the small population displayed significant additive genetic variation for a larger number of characters than the large population (19 vs. 14). Paternal (genetic) effects were consistent in two different environments; the ranking of sire means was similar despite a drastic reduction in light intensity, and few characters had a significant sire Xenvironment interaction. Genetic correlations were also found between different characters measured in the same environment, although most of these were in the 'favourable' direction. Population differences in genetic parameters may reflect contrasting selection regimens at the two sites, although genetic drift may also be important. That more genetic variability was detected in the small population where plants occur in small and isolated patches indicates that the spatial structure has great effects on the retention of heritable variation, and that demographic and environmental factors are more important in the long-term survival of S. integrifolius. This is the first study that relates quantitative genetic variation to population size in a rare and threatened plant.