@article{LambeetsVandegehuchteMaelfaitetal.2008,
  author    = {Lambeets, Kevin and Vandegehuchte, Martijn L. and Maelfait, Jean-Pierre and Bonte, Dries},
  title     = {Understanding the impact of flooding on trait-displacements and shifts in assemblage structure of predatory arthropods on river banks},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-49580},
  year      = {2008},
  abstract  = {1. Species assemblages of naturally disturbed habitats are governed by the prevailing disturbance regime. Consequently, stochastic flood events affect river banks and the inhabiting biota. Predatory arthropods occupy predominantly river banks in relation to specific habitat conditions. Therefore, species sorting and stochastic processes as induced by flooding are supposed to play important roles in structuring riparian arthropod assemblages in relation to their habitat preference and dispersal ability. 2. To ascertain whether assemblages of spiders and carabid beetles from disturbed river banks are structured by stochastic or sorting mechanisms, diversity patterns and assemblage-wide trait-displacements were assessed based on pitfall sampling data. We tested if flooding disturbance within a lowland river reach affects diversity patterns and trait distribution in both groups. 3. Whereas the number of riparian spider species decreased considerably with increased flooding, carabid beetle diversity benefited from intermediate degrees of flooding. Moreover, regression analyses revealed trait-displacements, reflecting sorting mechanisms particularly for spiders. Increased flooding disturbance was associated with assemblage-wide increases of niche breadth, shading and hygrophilic preference and ballooning propensity for spider (sub)families. Trait patterns were comparable for Bembidiini carabids, but were less univocal for Pterostichini species. Body size decreased for lycosid spiders and Bembidiini carabids with increased flooding, but increased in linyphiid spiders and Pterostichini carabids. 4. Our results indicate that mainly riparian species are disfavoured by either too high or too low degrees of disturbance, whereas eurytopic species benefit from increased flooding. Anthropogenic alterations of flooding disturbance constrain the distribution of common hygrophilous species and/or species with high dispersal ability, inducing shifts towards less specialized arthropod assemblages. River banks with divergent degrees of flooding impact should be maintained throughout dynamic lowland river reaches in order to preserve typical riparian arthropod assemblages.},
  subject      = {Flussufer},
  language  = {en}
}
@article{BonteTravisDeClercqetal.2008,
  author    = {Bonte, Dries and Travis, Justin M. J. and De Clercq, Nele and Zwertvaegher, Ingrid and Lens, Luc},
  title     = {Thermal conditions during juvenile development affect adult dispersal in a spider},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48691},
  year      = {2008},
  abstract  = {Abstract: Understanding the causes and consequences of dispersal is a prerequisite for the effective management of natural populations. Rather than treating dispersal as a fixed trait, it should be considered a plastic process that responds to both genetic and environmental conditions. Here, we consider how the ambient temperature experienced by juvenile Erigone atra, a spider inhabiting crop habitat, influences adult dispersal. This species exhibits 2 distinct forms of dispersal, ballooning (long distance) and rappelling (short distance). Using a half-sib design we raised individuals under 4 different temperature regimes and quantified the spiders' propensity to balloon and to rappel. Additionally, as an indicator of investment in settlement, we determined the size of the webs build by the spiders following dispersal. The optimal temperature regimes for reproduction and overall dispersal investment were 20 °C and 25 °C. Propensity to perform short-distance movements was lowest at 15 °C, whereas for long-distance dispersal it was lowest at 30 °C. Plasticity in dispersal was in the direction predicted on the basis of the risks associated with seasonal changes in habitat availability; long-distance ballooning occurred more frequently under cooler, spring-like conditions and short-distance rappelling under warmer, summer-like conditions. Based on these findings, we conclude that thermal conditions during development provide juvenile spiders with information about the environmental conditions they are likely to encounter as adults and that this information influences the spider's dispersal strategy. Climate change may result in suboptimal adult dispersal behavior, with potentially deleterious population level consequences.},
  language  = {en}
}
@article{GrosHovestadtPoethke2008,
  author    = {Gros, Andreas and Hovestadt, Thomas and Poethke, Hans Joachim},
  title     = {Evolution of sex-biased dispersal : the role of sex-specific dispersal costs, demographic stochasticity, and inbreeding},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48705},
  year      = {2008},
  abstract  = {Abstract: Inbreeding avoidance and asymmetric competition over resources have both been identified as factors favoring the evolution of sex-biased dispersal. It has also been recognized that sex-specific costs of dispersal would select for sex-biased dispersal, but there is little quantitative information on this aspect. In this paper we explore (i) the quantitative relationship between cost-asymmetry and a bias in dispersal, (ii) the influence of demographic stochasticity on this effect, and (iii) how inbreeding and cost-asymmetry interact in their effect on sex-specific dispersal. We adjust an existing analytical model to account for sex-specific costs of dispersal. Based on numerical calculations we predict a severe bias in dispersal already for small differences in dispersal costs. We corroborate these predictions in individual-based simulations, but show that demographic stochasticity generally leads to more balanced dispersal. In combination with inbreeding, cost asymmetries will usually determine which of the two sexes becomes the more dispersive.},
  language  = {en}
}
@article{BonteMaes2008,
  author    = {Bonte, Dries and Maes, Dirk},
  title     = {Trampling affects the distribution of specialised coastal dune arthropods},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48274},
  year      = {2008},
  abstract  = {Abstract: From a conservation point of view, species- tolerances towards disturbance are often generalised and lack reference to spatial scales and underlying processes. In order to investigate how average typical species react to habitat fragmentation and disturbance, we adopted a multi-species approach to address occupancy patterns of five specialised dune arthropods (butterflies Hipparchia semele, Issoria lathonia; grasshopper Oedipoda caerulescens; spiders Alopecosa fabrilis, Xysticus sabulosus) in recently fragmented coastal dune habitats which are subjected to varying levels and modes of local disturbance, i.e. trampling by cattle or people. Occupancy patterns were assessed during two successive years in 133 grey dune fragments of the Flemish coastal dunes (Belgium, France). By treating species as a random factor in our models, emphasis was placed on generalisations rather than documenting species-specific patterns. Our study demonstrates that deteriorating effects of local disturbance on arthropod incidence cannot be interpreted independent of its landscape context, and appear to be more severe when patch area and connectivity decrease. When controlled for patch area and trampling intensity, the probability of species occupancy in poorly connected patches is higher under cattle trampling than under recreation. Incidences additionally decrease with increasing intensity of cattle trampling, but increases with trampling by tourists. This study provides evidence of mode- and landscape-dependent effects of local disturbance on species occupancy patterns. Most importantly, it demonstrates that trampling of sensitive dune fragments will lead to local and metapopulation extinction in landscapes where trampling occurs in a spatially autocorrelated way, but that the outcome (spatial patterns) varies in relation to disturbance mode, indicating that effects of disturbance cannot be generalised.},
  language  = {en}
}
@article{BonteLanckackerWiersmaetal.2008,
  author    = {Bonte, Dries and Lanckacker, Kjell and Wiersma, Elisabeth and Lens, Luc},
  title     = {Web building flexibility of an orb-web spider in a heterogeneous agricultural landscape},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48262},
  year      = {2008},
  abstract  = {Abstract: Intensification of land-use in agricultural landscapes is responsible for a decline of biodiversity which provide important ecosystem services like pest-control. Changes in landscape composition may also induce behavioural changes of predators in response to variation in the biotic or abiotic environment. By controlling for environmentally confounding factors, we here demonstrate that the orb web spider Araneus diadematus alters its web building behaviour in response to changes in the composition of agricultural landscapes. Thereby, the species increases its foraging efficiency (i.e. investments in silk and web asymmetry) with an increase of agricultural land-use at intermediate spatial scales. This intensification is also related to a decrease in the abundance of larger prey. A negative effect of landscape properties at similar spatial scales on spider fitness was recorded when controlling for relative investments in capture thread length. This study consequently documents the web building flexibility in response to changes in landscape composition, possibly due to changes in prey availability.},
  language  = {en}
}
@article{BonteHovestadtPoethke2008,
  author    = {Bonte, Dries and Hovestadt, Thomas and Poethke, Hans-Joachim},
  title     = {Male-killing endosymbionts: influence of environmental conditions on persistance of host metapopulation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-45344},
  year      = {2008},
  abstract  = {Background: Male killing endosymbionts manipulate their arthropod host reproduction by only allowing female embryos to develop into infected females and killing all male offspring. Because of the reproductive manipulation, we expect them to have an effect on the evolution of host dispersal rates. In addition, male killing endosymbionts are expected to approach fixation when fitness of infected individuals is larger than that of uninfected ones and when transmission from mother to offspring is nearly perfect. They then vanish as the host population crashes. High observed infection rates and among-population variation in natural systems can consequently not be explained if defense mechanisms are absent and when transmission efficiency is perfect. Results: By simulating the host-endosymbiont dynamics in an individual-based metapopulation model we show that male killing endosymbionts increase host dispersal rates. No fitness compensations were built into the model for male killing endosymbionts, but they spread as a group beneficial trait. Host and parasite populations face extinction under panmictic conditions, i.e. conditions that favor the evolution of high dispersal in hosts. On the other hand, deterministic 'curing' (only parasite goes extinct) can occur under conditions of low dispersal, e.g. under low environmental stochasticity and high dispersal mortality. However, high and stable infection rates can be maintained in metapopulations over a considerable spectrum of conditions favoring intermediate levels of dispersal in the host. Conclusion: Male killing endosymbionts without explicit fitness compensation spread as a group selected trait into a metapopulation. Emergent feedbacks through increased evolutionary stable dispersal rates provide an alternative explanation for both, the high male-killing endosymbiont infection rates and the high among-population variation in local infection rates reported for some natural systems.},
  subject      = {Metapopulation},
  language  = {en}
}
@article{PoethkeLiebig2008,
  author    = {Poethke, Hans J. ; and Liebig, J{\"u}rgen},
  title     = {Risk-sensitive foraging and the evolution of cooperative breeding and reproductive skew},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48214},
  year      = {2008},
  abstract  = {Abstract: Background Group formation and food sharing in animals may reduce variance in resource supply to breeding individuals. For some species it has thus been interpreted as a mechanism of risk avoidance. However, in many groups reproduction is extremely skewed. In such groups resources are not shared equally among the members and inter-individual variance in resource supply may be extreme. The potential consequences of this aspect of group living have not attained much attention in the context of risk sensitive foraging. Results We develop a model of individually foraging animals that share resources for reproduction. The model allows analyzing how mean foraging success, inter-individual variance of foraging success, and the cost of reproduction and offspring raising influence the benefit of group formation and resource sharing. Our model shows that the effects are diametrically opposed in egalitarian groups versus groups with high reproductive skew. For individuals in egalitarian groups the relative benefit of group formation increases under conditions of increasing variance in foraging success and decreasing cost of reproduction. On the other hand individuals in groups with high skew will profit from group formation under conditions of decreasing variance in individual foraging success and increasing cost of reproduction. Conclusion The model clearly demonstrates that reproductive skew qualitatively changes the influence of food sharing on the reproductive output of groups. It shows that the individual benefits of variance reduction in egalitarian groups and variance enhancement in groups with reproductive skew depend critically on ecological and life-history parameters. Our model of risk-sensitive foraging thus allows comparing animal societies as different as spiders and birds in a single framework.},
  language  = {en}
}
@phdthesis{Reichert2008,
  author    = {Reichert, Nina},
  title     = {The Role of LIN9 in Mouse Development},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30889},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {LINC, the human homologue of an evolutionary conserved complex, regulates the transcription of a set of genes essential during the G2/M transition (Osterloh et al., 2007; Schmit et al., 2007). One component of the LINC core module is LIN-9. LIN-9 is essential for the transcriptional activation of LINC target genes and also promotes differentiation in association with pRB (Gagrica et al., 2004). However, nothing is known about its function in vivo. Histological and molecular analysis revealed that Lin9 is ubiquitously expressed throughout embryonic development and in all examined adult organs. Additionally, Lin9 mRNA is expressed in ES cells and blastocysts. Moreover the analogous distribution of the other LINC components suggested that they all function in the same cells and most likely in the same pathway. To deeper investigate the role of LIN9 in cell cycle and differentiation in vivo, a Lin9 gene trap mouse model (GT) was successfully generated and examined. Heterozygouse Lin9GT/+ mice were inconspicuous and develop normally. However, homozygouse knockout embryos were never obtained. The Lin9GT/GT embryos die at peri-implantation, probably due to a defect in the development of the epiblast, which could be shown with in situ hybridization with specific lineage markers. In vitro, the ICM of Lin9-deficient blastocysts did not develop properly. These data suggest that the loss of Lin9 leads to embryonic lethality at peri-implantation, and indicates that LIN9 is required for proper formation of the epiblast. In parallel, the first conditional Lin9 mouse model based on the Cre-loxP technology was generated. The Lin9fl/fl allele can be deleted by Cre-recombinase, in vivo and in vitro. Therefore an inducible system with Lin9fl/fl mice harboring Cre-ERT2 was established. The MEFs generated from these transgenic mice carried a nearly complete knockout upon induction with tamoxifen. Deletion of LIN9 in MEFs had a major impact upon the cell cycle and growth rates. Specifically, they arrested in G2/M phase and stopped to proliferate. Taken together, I was able to generate a lin9 gene trap and a lin9 conditional knockout mouse model. All results obtained so far demonstrate, that Lin9 is an essential gene for embryonic development and cell cycle control. It will be of great interest to further investigate Lin9-deficiency to gain insights into the mechanism of cell cycle control in early embryonic development and cell differentiation.},
  subject      = {Zellzyklus},
  language  = {en}
}
@phdthesis{Kukat2008,
  author    = {Kukat, Christian},
  title     = {Fusion, Fission und Nucleoids in Megamitochondrien},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30467},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {In rho0-Zellen, die {\"u}ber keine mitochondriale DNA (mtDNA) mehr verf{\"u}gen, entstehen w{\"a}hrend der Kultivierung Megamitochondrien durch endogene Milchs{\"a}ure-Azidifizierung des Kulturmediums. Diese Riesenorganellen bilden sich dabei durch mitochondriale Fusionsereignisse und/oder eine Hemmung der Fission. In Zellen mit mitochondrialem Genom ist es ebenso m{\"o}glich Megamitochondrien durch artifizielles Ans{\"a}uern des Kulturmediums zu induzieren. Diese Erkenntnisse wurden im Rahmen dieser Arbeit als Werkzeug verwendet, um Einblicke in mitochondriale Fusions- und Fissionsereignisse zu erlangen. Zun{\"a}chst wurde die Fusion mitochondrialer Matrixkompartimente mithilfe der photoaktivierbaren Variante des gr{\"u}nen fluoreszierenden Proteins (PA-GFP) untersucht. Hiermit konnte gezeigt werden, dass das Vermischen der Matrixkompartimente nach der Fusion ein sehr schneller Prozess ist. Die Analyse der Bildung und R{\"u}ckbildung der Megamitochondrien erfolgte sowohl konfokal- als auch elektronenmikroskopisch, wobei sich zeigte, dass die Matrix der Riesenorganellen kaum mehr Cristae beinhaltet. Die R{\"u}ckbildung der Megamitochondrien zum normalen Netzwerk ist ein sehr schneller Prozess, bei dem schon nach 15 min keine vergr{\"o}ßerten Organellen mehr sichtbar sind. Dies indiziert, dass der R{\"u}ckbildungsprozess wahrscheinlich durch Ver{\"a}nderungen von verf{\"u}gbaren Proteinen durchgef{\"u}hrt wird, ohne die Induzierung von Proteinneusynthese. Untersuchungen auf ultrastruktureller Ebene zeigten, dass es w{\"a}hrend der R{\"u}ckbildung zur Formation von drei unterschiedlichen Mitochondrientypen kam, die sich in ihrer Morphologie stark unterschieden. Weiterhin wurden vergleichende Studien zur Bildung der Megamitochondrien durchgef{\"u}hrt, bei denen der Einfluss von Atmungsketten-Inhibitoren auf die Bildung von Milchs{\"a}ure-induzierten Riesenorganellen untersucht wurde. Die Resultate deuten f{\"u}r die Megamitochondrieninduktion auf eine Abh{\"a}ngigkeit auf ein intaktes Membranpotential hin. Immunzytochemisch wurde die endogene Lokalisation der mitochondrialen Fusions- und Fissionsproteine Mitofusin 2, hFis1 und Drp1/DNM1L am Modellsystem der Megamitochondrieninduktion aufgekl{\"a}rt. Es zeigte sich, dass diese Proteine punktf{\"o}rmig an der {\"a}ußeren Membran der Riesenorganellen lokalisieren Um das Modellsystem an lebenden Zellen zu nutzen, wurden Vektoren konstruiert, die fluoreszenzmarkierte Proteine der mitochondrialen Fusions- und Fissionsmaschinerie exprimierten. Hiermit konnte einerseits die Lokalisation von Mitofusin 1, Mitofusin 2, hFis1 und Drp1/DNM1L in lebenden Zellen nach Induktion der Megamitochondrien analysiert werden und andererseits der Einfluss der {\"U}berexpression dieser Proteine auf die Bildung der Riesenorganellen dokumentiert werden. Die Ergebnisse machten deutlich, dass nur die {\"U}berepxression von hFis1 die Bildung der Megamitochondrien verhinderte. Ein weiterer Schwerpunkt der vorliegenden Arbeit lag in der Visualisierung und Dynamik mitochondrialer Nucleoids in lebenden Zellen. Nucleoids sind Protein-DNA-Komplexe, in denen mitochondriale Genome organisiert sind. Mit dem Farbstoff PicoGreen gelang es mtDNA in lebenden Zellen zu f{\"a}rben und Dynamikstudien der punktf{\"o}rmigen Strukturen mikroskopisch festzuhalten. W{\"a}hrend sich mtDNA im mitochondrialen Netzwerk nur marginal aufgrund stattfindender Fusions- und Fissionsereignisse bewegte kam es in den Milchs{\"a}ure-induzierten Megamitochondrien zu einer extensiven und extrem schnellen Bewegung von mitochondrialer DNA. In anschließenden Versuchen wurde der mitochondriale Transkriptions- und Verpackungsfaktor TFAM als fluoreszentes Fusionsprotein in Zellen transfiziert und Kolokalisationsstudien zeigten, dass das Fusionsprotein mit mtDNA kolokalisiert. In den Riesenorganellen pr{\"a}sentierten punktf{\"o}rmige TFAM-gef{\"a}rbte Nucleoids ein sehr dynamisches Verhalten mit schneller Bewegung. In rho0-Zellen ohne mitochondriale DNA war die TFAM-Fluoreszenz hingegen gleichm{\"a}ßig verteilt. Ein weiterer Nucleiodbestandteil ist das mitochondriale DNA-Einzelstrangbindeprotein SSBP1, welches in Megamitochondrien ebenso ein sehr dynamisches Verhalten aufwies. Eine mitochondrial-zielgesteuerte und EGFP-markierte Restriktionsendonuklease wies ebenfalls das typische, punktf{\"o}rmige Nucleoidmuster im mitochondrialen Netzwerk auf, was auf eine Interaktion mit der mtDNA schließen l{\"a}sst. In rho0-Zellen ohne mtDNA kam es jedoch zur gleichm{\"a}ßigen Verteilung des Konstruktes in den Mitochondrien. Zusammenfassend wurden in dieser Arbeit sowohl Einblicke in die Biologie der Megamitochondrien gewonnen, als auch Erkenntnisse {\"u}ber die Dynamik mitochondrialer Protein-DNA-Komplexe, wobei der Schwerpunkt hierbei auf einer Analyse mit Hilfe optischer Methoden lag.},
  subject      = {Mitochondrium},
  language  = {de}
}
@phdthesis{Schmitt2008,
  author    = {Schmitt, Johannes},
  title     = {Proteine der Kernh{\"u}lle und deren Rolle bei der Umgestaltung des Zellkerns meiotischer und postmeiotischer Zellen von S{\"a}ugern},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31203},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {W{\"a}hrend der Spermatogenese finden erstaunliche Differenzierungsprozessen statt. Reguliert wird die Spermatogenese sowohl hormonell als auch durch Wechselwirkungen zwischen verschiedenen Zelltypen und der extrazellul{\"a}rer Matrix. Unterteilt wird die Spermatogenese in drei funktionelle Einheiten. Die Proliferationsphase, die Meiose und die Spermiogenese. Im Laufe der Proliferationsphase gehen aus den Spermatogonien, Spermatocyten hervor, die die Meiose durchlaufen. W{\"a}hrend der Prophase I der Meiose kommt es zur Reduktion und Rekombination des genetischen Materials, was mit charakteristischen und h{\"o}chst dynamischen Bewegungsvorg{\"a}ngen der Telomere einhergeht. Auf die Meiose folgt die Spermiogenese, in der das genetische Material in seine „Transportform" {\"u}berf{\"u}hrt wird und aus einer station{\"a}ren, zellverbundenen Einheit ein mobiles autark funktionierendes Vehikel des genetischen Materials wird; das Spermium. Um das Verst{\"a}ndnis dieser Vorg{\"a}nge zu erweitern wurden in dieser Arbeit die Verteilungsmuster einiger Proteine in der Kernh{\"u}lle von Zellen der Spermatogenese, in Hinblick auf ihre dynamische Umverteilung untersucht. Bei diesen Proteinen handelte es sich um die SUN-Dom{\"a}nen Proteine und das meiosespezifische Lamin C2. Die SUN-Dom{\"a}nen Proteine sind Teil des membrandurchspannenden LINC-Komplexes, der Komponenten des Nukleoplasma mit denen des Cytoplasma verbindet. In dieser Arbeit konnte gezeigt werden, dass die SUN-Dom{\"a}nen Proteine, Sun1 und Sun2 w{\"a}hrend der Meiose exprimiert werden, und an den Anheftungsplatten meiotischer Chromosomen lokalisieren und deren dynamisches Verteilungsmuster dem Verteilungsmuster der Telomere w{\"a}hrend der Prophase I der Meiose entsprechen. Dies deutet darauf hin, dass Sun1 und Sun2 eine tragende Rolle, w{\"a}hrend der koordinierten Bewegungsprozessen der Prophase I der Meiose spielen. In der Spermiogenese sind die SUN-Dom{\"a}nen Proteine, Sun1 und Sun3 vertreten. Dabei weist deren unterschiedliche Lokalisation an entgegengesetzten Zellpolen darauf hin, dass Sun1 und Sun3 m{\"o}glicherweise unterschiedliche Funktionen bei der Umgestaltung des Spermienkopfes w{\"a}hrend der Spermiogenese erf{\"u}llen. Ein weiterer Schwerpunkt dieser Arbeit war die Etablierung einer Mauslinie um die Rolle von Lamin C2 in der Meiose untersuchen zu k{\"o}nnen. Hierzu wurde eine Lamin C2 Knock-out Studie begonnen. In ersten Untersuchungen der knock-out Tiere konnte eine Gr{\"o}ßenreduktion der Hoden beobachtet werden. Ebenso konnte ein Abbruch der Meiose vermerkt werden. Die Ergebnisse dieser Arbeit verdeutlichen, dass sowohl die SUN-Dom{\"a}nen Proteine, als auch Lamin C2, wichtige Rollen in dem komplexen Arrangement der Spermatogenese {\"u}bernehmen.},
  subject      = {Meiose},
  language  = {de}
}