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The effect of herbivores on genotypic diversity in a clonal aquatic plant
No full textIn clonal plants, vegetative parts may outcompete seeds in the absence of disturbance, limiting the build-up of genotypic diversity through repeated seedling recruitment (RSR). Herbivory may provide disturbance and trigger establishment of strong colonizers (seeds) at the expense of strong competitors (clonal propagules). In the clonal aquatic fennel pondweed (Potamogeton pectinatus), two distinct herbivore guilds may modify the dynamics of propagation. In winter, Bewick's swans may deplete patches of tubers, promoting seedling establishment in spring. In summer, seed consumption by waterfowl can reduce the density of viable seeds but grazing may also reduce tuber production and hence facilitate seedling establishment. This study is among the first to experimentally test herbivore impact on plant genotypic diversity. We assess the separate and combined effects of both herbivore guilds on genotypic diversity and structure of fennel pondweed beds. Using microsatellites, we genotyped P. pectinatus from an exclosure experiment and assessed the contribution of herbivory, dispersal, and sexual reproduction to the population genetic structure. Despite the predominance of clonal propagation in P. pectinatus, we found considerable genotypic diversity. Within the experimental blocks, kinship among genets decreased with geographic distance, clearly identifying a role for RSR in the maintenance of genotypic diversity within the fennel pondweed beds. However, over a period of 5 years, none of the herbivory treatments affected genotypic diversity. Hence, sexual reproduction on a local scale is important in this putatively clonal plant and possibly sufficient to ensure a relatively high genotypic diversity even in the absence of herbivores. Although we cannot preclude a role of herbivory in shaping genotypic diversity of a clonal plant, after 5 years of exclusion of the two investigated herbivore guilds no measurable effect on genotypic diversity was detected
Formate oxidation driven calcium carbonate precipitation by Methylocystis parvus OBBP
No full textMicrobially Induced Carbonate Precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented in this study to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4 ± 1.6 % of the initial calcium was precipitated in the methane amended cultures compared to 35.1 ± 11.9 % when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A
maximum 0.67 ± 0.03 g CaCO3 g Ca(CHOOH)2-1 calcium carbonate precipitate yield was obtained when 109 cells mL-1 and 5 g L-1 of calcium formate were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry.
‘Met de Grondwetpad op pad. Acht belangrijke herzieningen van de Nederlandse Grondwet (1815-1983) uitgelegd voor iedereen tussen 6 en 106 jaar.’ Tekstbijdragen voor de Grondwetarena in het kader van de viering ‘Tweehonderd jaar Koninkrijk’
No full textIdentifying the African wintering grounds of hybrid flycatchers using a multi–isotope (δ2H, δ13C, δ15N) assignment approach
No full textMigratory routes and wintering grounds can have important fitness consequences, which can lead to divergent selection on populations or taxa differing in their migratory itinerary. Collared (Ficedula albicollis) and pied (F. hypoleuca) flycatchers breeding in Europe and wintering in different sub-Saharan regions have distinct migratory routes on the eastern and western sides of the Sahara desert, respectively. In an earlier paper, we showed that hybrids of the two species did not incur reduced winter survival, which would be expected if their migration strategy had been a mix of the parent species' strategies potentially resulting in an intermediate route crossing the Sahara desert to different wintering grounds. Previously, we compared isotope ratios and found no significant difference in stable-nitrogen isotope ratios (δ15N) in winter-grown feathers between the parental species and hybrids, but stable-carbon isotope ratios (δ13C) in hybrids significantly clustered only with those of pied flycatchers. We followed up on these findings and additionally analyzed the same feathers for stable-hydrogen isotope ratios (δ2H) and conducted spatially explicit multi-isotope assignment analyses. The assignment results overlapped with presumed wintering ranges of the two species, highlighting the efficacy of the method. In contrast to earlier findings, hybrids clustered with both parental species, though most strongly with pied flycatcher.
Numériser les lettres de Belle de Zuylen: Un regard plus précis sur les rapports familiaux
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Olympische Winterspelen 2014
No full textTijdens de Olympische Winterspelen in Sotsji presteerden de Nederlandse sporters boven verwachting goed met 8 gouden, 7 zilveren en 9 bronzen medailles. TeamNL eindigde daarmee op de 5de plaats in het medailleklassement achter Rusland, Noorwegen, Canada en de Verenigde Staten, maar voor Olympische wintergrootmachten als Duitsland en Oostenrijk. Maar hoe goed was de Nederlandse prestatie als we rekening houden met verschillen tussen landen in bevolkingsomvang en welvaart?