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Lekunberri I.,University of Vienna | Sintes E.,University of Vienna | de Corte D.,University of Vienna | Yokokawa T.,Ehime University | And 3 more authors.
FEMS Microbiology Ecology | Year: 2013

The composition of prokaryotic communities was determined in the meso- and bathypelagic waters funneled through the Romanche Fracture Zone (RFZ, 2°7′S, 31°79′W to 0°6′N, 14°33′W) in the tropical Atlantic. Distinct water masses were identified based on their physical and chemical characteristics. The bacterial and archaeal communities were depth-stratified with a total of 116 and 25 operational taxonomic units (OTUs), respectively, distributed among the distinct water masses as revealed by terminal restriction fragment length polymorphism, and cloning and sequencing. The relative abundance of Thaumarchaeota, determined by catalyzed reporter deposition-fluorescence in situ hybridization, was significantly higher in deeper layers (Antarctic Bottom Water, AABW, > 4000 m depth), contributing up to 31% to the total prokaryotic community, than in the mesopelagic and lower euphotic layer. Although the contribution of SAR11 to bacterial abundance did not increase with depth, SAR202, SAR324, SAR406 and Alteromonas did increase with depth. Terminal restriction fragment length polymorphism analysis revealed successional changes in the bacterial and archaeal community composition of the North Atlantic Deep Water (NADW) with a passage time through the RFZ of c. 4 months but not in the under- and overlying water masses. Our results indicate that specific water masses harbor distinct bacterial and archaeal communities and that the prokaryotic community of the NADW undergoes successional changes in this conduit between the western and eastern Atlantic basin. Apparently, in the absence of major input of organic matter to specific deep-water masses, the indigenous prokaryotic community adapts to subtle physical and biogeochemical changes in the water mass within a time frame of weeks, similar to the reported seasonal changes in surface water prokaryotic communities. © 2013 Federation of European Microbiological Societies. Source


Etienne R.S.,Center for Ecological and Evolutionary Studies | Haegeman B.,French Institute for Research in Computer Science and Automation | Stadler T.,ETH Zurich | Aze T.,University of Cardiff | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

The branching times of molecular phylogenies allow us to infer speciation and extinction dynamics even when fossils are absent. Troublingly, phylogenetic approaches usually return estimates of zero extinction, conflicting with fossil evidence. Phylogenies and fossils do agree, however, that there are often limits to diversity. Here, we present a general approach to evaluate the likelihood of a phylogeny under a model that accommodates diversity-dependence and extinction. We find, by likelihood maximization, that extinction is estimated most precisely if the rate of increase in the number of lineages in the phylogeny saturates towards the present or first decreases and then increases. We demonstrate the utility and limits of our approach by applying it to the phylogenies for two cases where a fossil record exists (Cetacea and Cenozoic macroperforate planktonic foraminifera) and to three radiations lacking fossil evidence (Dendroica, Plethodon and Heliconius). We propose that the diversity-dependence model with extinction be used as the standard model for macro-evolutionary dynamics because of its biological realism and flexibility. © 2011 The Royal Society. Source


Van Noordwijk C.G.E.,Radboud University Nijmegen | Van Noordwijk C.G.E.,Ghent University | Verberk W.C.E.P.,Radboud University Nijmegen | Turin H.,Loopkeverstichting SFOC | And 16 more authors.
Ecology | Year: 2015

In the face of ongoing habitat fragmentation, species-area relationships (SARs) have gained renewed interest and are increasingly used to set conservation priorities. An important question is how large habitat areas need to be to optimize biodiversity conservation. The relationship between area and species richness is explained by colonization-extinction dynamics, whereby smaller sites harbor smaller populations, which are more prone to extinction than the larger populations sustained by larger sites. These colonization-extinction dynamics are predicted to vary with trophic rank, habitat affinity, and dispersal ability of the species. However, empirical evidence for the effect of these species characteristics on SARs remains inconclusive. In this study we used carabid beetle data from 58 calcareous grassland sites to investigate how calcareous grassland area affects species richness and activity density for species differing in trophic rank, habitat affinity, and dispersal ability. In addition, we investigated how SARs are affected by the availability of additional calcareous grassland in the surrounding landscape. Beetle species richness and activity density increased with calcareous grassland area for zoophagous species that are specialists for dry grasslands and, to a lesser extent, for zoophagous habitat generalists. Phytophagous species and zoophagous forest and wet-grassland specialists were not affected by calcareous grassland area. The dependence of species on large single sites increased with decreasing dispersal ability for species already vulnerable to calcareous grassland area. Additional calcareous grassland in the landscape had a positive effect on local species richness of both dry-grassland specialists and generalists, but this effect was restricted to a few hundred meters. Our results demonstrate that SARs are affected by trophic rank, habitat affinity, and dispersal ability. These species characteristics do not operate independently, but should be viewed in concert. In addition, species' responses depend on the landscape context. Our study suggests that the impact of habitat area on trophic interactions may be larger than previously anticipated. In small habitat fragments surrounded by a hostile matrix, food chains may be strongly disrupted. This highlights the need to conserve continuous calcareous grassland patches of at least several hectares in size. © 2015 by the Ecological Society of America. Source


Becher M.A.,Martin Luther University of Halle Wittenberg | Hildenbrandt H.,Center for Ecological and Evolutionary Studies | Hemelrijk C.K.,Center for Ecological and Evolutionary Studies | Moritz R.F.A.,Martin Luther University of Halle Wittenberg | Moritz R.F.A.,University of Pretoria
Ecological Modelling | Year: 2010

One of the mechanisms by which honeybees regulate division of labour among their colony members is age polyethism. Here the younger bees perform in-hive tasks such as heating and the older ones carry out tasks outside the hive such as foraging. Recently it has been shown that the higher developmental temperatures of the brood, which occur in the centre of the brood nest, reduce the age at which individuals start to forage once they are adult. It is unknown whether this effect has an impact on the survival of the colony. The aim of this paper is to study the consequences of the temperature gradient on the colony survival in a model on the basis of empirical data. We created a deterministic simulation of a honeybee colony (Apis mellifera) which we tuned to our empirical data. In the model in-hive bees regulate the temperature of the brood nest by their heating activities. These temperatures determine the age of first foraging in the newly emerging bees and thus the number of in-hive bees present in the colony. The results of the model show that variation in the onset of foraging due to the different developmental temperatures has little impact on the population dynamics and on the absolute number of bees heating the nest unless we increase this effect by several times to unrealistic values, where individuals start foraging up to 10 days earlier or later. Rather than on variation in the onset of foraging due to the temperature gradient it appears that the survival of the colony depends on a minimal number of bees available for heating at the beginning of the simulation. © 2009 Elsevier B.V. All rights reserved. Source

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