trié(s) par (Pertinence décroissant(e), Titre croissant(e)) 

Offspring fitness in relation to population size and genetic variation in the rare perennial plant species Gentiana pneumonanthe (Gentianaceae) / ]. Gerard B. Oostermeijer in Oecologia, vol. 97 (Année 1994)

Public [article]  inOecologia > vol. 97 (Année 1994) . - pp. 289-293 Titre : Offspring fitness in relation to population size and genetic variation in the rare perennial plant species Gentiana pneumonanthe (Gentianaceae) Auteurs : ]. Gerard B. Oostermeijer, Auteur ; M.W. van Eijck, Auteur ; J. C. M. den Nijs, Auteur Année de publication : 1994 Article en page(s) : pp. 289-293 Langues : Anglais (eng) Catégories : [Espèces (in biblio)] Gentiana pneumonanthe [Thèmes] Biologie de la conservation [Thèmes] Conservation [Thèmes] Germination des graines [Thèmes] Plante à forte valeur patrimoniale Mots-clés : variation génétique Résumé : "Seeds were sampled from 19 populations of the rare Gentiana pneumonanthe, ranging in size from 5 to more than 50,000 flowering plants. An analysis was made of variation in a number of life-history characters in relation to population size and offspring heterozygosity (based on seven polymorphic isozyme loci). Life-his-tory characters included seed weight, germination rate, proportion of seeds germinating, seedling mortality, seedling weight, adult weight, flower production per plant and proportion of plants flowering per family. Principal component analysis (PCA) reduced the dataset to three main fitness components. The first component was highly correlated with adult weight and flowering performance, the second with germination performance and the third component with seed and seedling weight and seedling mortality. The latter two components were considered as being maternally influenced, since these comprised life-history traits that were significantly correlated with seed weight. Multiple regression analysis showed that variation in the first fitness component was mainly associated with heterozygosity and not with population size, while the third fitness component was only correlated with population size and not with heterozygosity. The latter relationship appeared to be non-linear, which suggests a stronger loss of fitness in the smallest populations. The second (germination) component was neither correlated with population size nor with genetic variation. There was only a weak association between population size, heterozygosity and the population coefficients of variation for each life history character. Most correlation coefficients were negative, however, which suggests that there is more variation among progeny from smaller populations. We conclude that progeny from small populations of Gentiana pneumonanthe show reduced fitness and may be phenotypically more variable. One of the possible causes of the loss of fitness is a combination of unfavourable environmental circumstances for maternal plants in small populations and increased inbreeding. The higher phenotypic variation in small populations may also be a result of inbreeding, which can lead to deviation of individuals from the average phenotype through a loss of developmental stability." (source : auteurs) Type de publication : périodique Référence biblio : Oostermeijer J.-G.-B., van Eijck M.-W., den Nijs J.-C.-M., 1994 - Offspring fitness in relation to population size and genetic variation in the rare perennial plant species Gentiana pneumonanthe (Gentianaceae). Oecologia, 97 : 289-293. ID PMB : 71994 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=71994 [article]

Exemplaires(0)

Disponibilité
aucun exemplaire

Pollination ecology and patch-dependent reproductive success of the rare perennial Gentiana pneumonanthe L. / T. Petanidou in New phytologist, vol. 129 (Année 1995)

Public [article]  inNew phytologist > vol. 129 (Année 1995) . - pp. 155-163 Titre : Pollination ecology and patch-dependent reproductive success of the rare perennial Gentiana pneumonanthe L. Auteurs : T. Petanidou, Auteur ; J. C. M. den Nijs, Auteur ; J. G. B. Oostermeijerand, Auteur ; A.C. Ellis-Adam, Auteur Année de publication : 1995 Article en page(s) : pp. 155-163 Langues : Anglais (eng) Catégories : [Espèces (in biblio)] Gentiana pneumonanthe L. [Thèmes] Pollinisation, pollen, nectar [Thèmes] Reproduction Résumé : "The reproductive behaviour of Gentiana pneumonanthe L., a rare plant species in The Netherlands, was studied in a relatively large wet heathland population during summer 1989. The species co-occurred with the grass Molinia caerulea and co-flowered with Erica tetralix and Calluna vulgaris. The flowering period lasted from July to October, peaking in late August to late September. Flowers are protandrous. The species appeared to be self-compatible, but spontaneous self-pollination was strongly limited. Hand-crossing and hand-selfing resulted in the same amount of seed set as in natural pollination. Reproductive success was dramatically reduced late in the season. Pollination was achieved sternotribically by the species Bombus pascuorum, which visited the flowers for nectar. In the study area, three patch types were distinguished: co-dominated by Erica, by Calluna and Erica, and by Molinia, respectively. Frequency of visits to Gentiana was highest in the Erica-patch. However, this did not result in a higher seed set. In the Molinia-patch seed set was reduced. However, in the Molinia-patch the mean number of ovules was greater than in the others (as high as in plants raised indoors and in cross-pollinated plants). Fruits from the Calluna-patch had less ovules than those from the Erica-patch. We conclude that, in this remnant population, Gentiana is not pollination-limited. However, it is likely that in the Molinia-patch geitonogamy is frequent, which may lead to inbreeding depression. The greater number of ovules observed in Molinia-patches may reflect an excess of nutrients available there, relative to the Calluna-patch where there may be reduced water availability." (source : auteurs) Type de publication : périodique Référence biblio : Petanidou T., den Nijs J.-C.-M., Oostermeijerand J.-G.-B., Ellis-Adam A.-C., 1995 - Pollination ecology and patch-dependent reproductive success of the rare perennial Gentiana pneumonanthe L. New phytologist, 129 : 155-163. ID PMB : 72109 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=72109 [article]

Exemplaires(0)

Disponibilité
aucun exemplaire

Population biology and management of the marsh gentian (Gentiana pneumonanthe L.), a rare species in The Netherlands / ]. Gerard B. Oostermeijer in Botanical Journal of the Linnean Society, vol. 108, n°2 (Année 1992)

Public [article]  inBotanical Journal of the Linnean Society > vol. 108, n°2 (Année 1992) . - pp. 117-130 Titre : Population biology and management of the marsh gentian (Gentiana pneumonanthe L.), a rare species in The Netherlands Auteurs : ]. Gerard B. Oostermeijer, Auteur ; J. C. M. den Nijs, Auteur ; Leon E. L. Raijmann, Auteur Année de publication : 1992 Article en page(s) : pp. 117-130 Langues : Anglais (eng) Catégories : [Espèces (in biblio)] Gentiana pneumonanthe [Thèmes] Conservation [Thèmes] Pays basque [Thèmes] Plante à forte valeur patrimoniale Mots-clés : gestion  suivi  biologie des populations Résumé : "A broad study into the population biology of the marsh gentian has revealed so far that in The Netherlands there are two types of populations, characterized by a different demographic behaviour, viz. 'dynamic' populations, with high seedling turnover and low percentage of adult flowering plants, and 'static' or 'senile' populations, consisting mostly of flowering individuals and with hardly any seedlings. Also, populations encounter problems due to increasing isolation and decreasing numbers of individuals. Important parameters, such as seedling recruitment, seedling growth potential, seed production, rates of outcrossing and gene flow and the degree of genetic variation, all appear to be reduced in small populations. An evaluation of the effects of different management strategies, based on population ecological studies, is discussed as well." (source : auteurs) Type de publication : périodique Référence biblio : Oostermeijer ].-G., den Nijs J.-C.-M., Raijmann L.-L., 1992 - Population biology and management of the marsh gentian (Gentiana pneumonanthe L.), a rare species in The Netherlands. Botanical Journal of the Linnean Society, 108 (2) : 117-130. ID PMB : 71996 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=71996 [article]

Exemplaires(0)

Disponibilité
aucun exemplaire

Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands / ]. Gerard B. Oostermeijer in Journal of Applied Ecology, vol. 31 (Année 1994)

Public [article]  inJournal of Applied Ecology > vol. 31 (Année 1994) . - pp. 428-438 Titre : Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands Auteurs : ]. Gerard B. Oostermeijer, Auteur ; R. van 't Veer, Auteur ; J. C. M. den Nijs, Auteur Année de publication : 1994 Article en page(s) : pp. 428-438 Langues : Anglais (eng) Catégories : [ZG] Pays-Bas [Espèces (in biblio)] Gentiana pneumonanthe [Thèmes] Conservation [Thèmes] Plante à forte valeur patrimoniale Mots-clés : suivi Résumé : "1. After analysis of population age-state spectra of Gentiana pneumonanthe in a variety of vegetation types, three different population types could be distinguished: (a) `invasive' or `dynamic' populations, characterized by high densities of seedlings and juveniles relative to the adult age states, (b) `normal' or `stable' populations with adult age states prevailing, but with low densities of seedlings and juveniles, and (c) `regressive' or `senile' populations, consisting only of adult flowering and adult vegetative individuals. 2. The structure of the surrounding vegetation appears to be very important in determining the population structure of the marsh gentian. In particular the percentage of bare soil surface and the cover of the litter layer explain most of the variation in the density and proportion of different age states in the populations. The area of bare soil surface in the vegetation increases the percentage of seedlings and juveniles in the population and, consequently, decreases the proportion of generative adults, while the reverse is true for the cover of the litter layer. 3. In heathlands, a clear trend can be observed in the age state structure from `invasive' populations in young successional stages, via `normal' populations in relatively stable situations, to `regressive' populations in late successional stages or unmanaged areas dominated by grasses or shrubs. In hay meadows, `normal' populations are usually observed, except where mowing has been stopped or where a combination of early mowing and acidification exists. This leads to closure of the community by grasses or bryophytes, respectively, and therefore to a `regressive' population structure. 4. Individuals in heathland and grassland populations seem to have a different lifestrategy because of the differences in vegetation dynamics between these two habitat types. Ecotypic differentiation in life-history characteristics may therefore be expected. 5. It is argued that, as a basis for conservation and management, monitoring the age state structure of populations of rare perennial plant species is far more effective than counting only the flowering individuals, as is mostly done." (source : auteurs) Type de publication : périodique Référence biblio : Oostermeijer J.-G.-B., van 't Veer R., den Nijs J.-C.-M., 1994 - Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands. Journal of Applied Ecology, 31 : 428-438. ID PMB : 71995 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=71995 [article]

Exemplaires(0)

Disponibilité
aucun exemplaire

---

1 (1 - 4 / 4) Par page : 25 50 100 200