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Investigating novel potential regulators of phosphate stress responses in Arabidopsis thaliana
(2010)
Competition is a key process in plant populations and communities. We thus need, if we are to predict the responses of ecological systems to environmental change, a comprehensive and mechanistic understanding of plant competition. Considering competition, however, only at the population level is not sufficient because plant individuals usually are different, interact locally, and can adapt their behaviour to the current state of themselves and of their biotic and abiotic environment. Therefore, simulation models that are individual-based and spatially explicit are increasingly used for studying competition in plant systems. Many different individual-based modelling approaches exist to represent competition, but it is not clear how good they are in reflecting essential aspects of plant competition. We therefore first summarize current concepts and theories addressing plant competition. Then, we review individual-based approaches for modelling competition among plants. We distinguish between approaches that are used for more than 10 years and more recent ones. We identify three major gaps that need to be addressed more in the future: the effects of plants on their local environment, adaptive behaviour, and below-ground competition. To fill these gaps, the representation of plants and their interactions have to be more mechanistic than most existing approaches. Developing such new approaches is a challenge because they are likely to be more complex and to require more detailed knowledge and data on individual-level processes underlying competition. We thus need a more integrated research strategy for the future, where empirical and theoretical ecologists as well as computer scientists work together on formulating, implementing, parameterization, testing, comparing, and selecting the new approaches. (c) 2008 Rubel Foundation, ETH Zurich. Published by Elsevier GmbH. All rights reserved.
We studied the effects of overgrazing on the foraging behaviour of the lizard Pedioplanis l. lineoocellata (Spotted Sand Lizard), a sit-and-wait forager, in habitats of differing vegetation states to determine the effects of habitat degradation on this species. At high grazing intensity where vegetation cover and diversity is low, the lizard P. lineoocellata moves more frequently, spends more time moving and covers larger distances than in habitats where vegetation cover and diversity is high. These behavioural changes in movement patterns can be explained by less abundant prey in habitats with low vegetation cover and diversity. Although morphology, phylogeny and physiology of P. lineoocellata should constrain the change in foraging behaviour, the species has modified its foraging strategy from sit- and-wait to actively foraging. We assume that this behavioural flexibility of P. lineoocellata is a buffer mechanism enabling the species to use and survive in degraded (unfavourable) habitats.
Exceeding weight gain in childhood is a prevailing issue in industrialised countries, such as in Germany. The aim of this study was to detect a critical age for exceeding weight gain. It is assumed that especially in the early years of life, the years of nursery school age, the individual development of weight is fundamental for the prediction of obesity. The data of 638 children (324 boys and 314 girls) and the data of additional 1390 children of a preceding longitudinal study were analysed. The results show that overweight newborns are not at higher risk of becoming overweight children later, in the first place. But the results identify a high risk of becoming overweight for children 4.5 years old through a BMI rebound. In addition, this comparably earlier BMI rebound is linked with an increasing percentage of body fat. This leads to the assumption, that a comparably early BMI rebound is remarkably atypical for healthy child development. The results are also interrelated with the test person's sex. Endangered girls are of pyknomorphic body type. In contrast, the boys' results are independent of the body type. Obesity of boys therefore is strongly assumed to be caused by environmental factors.
We investigated sex-specific parental care behaviour of lesser spotted woodpeckers Picoides minor in the low mountain range Taunus, Germany. Observed parental care included incubation, nest sanitation as well as brooding and feeding of nestlings. Contributions of the two sexes to parental care changed in progress of the breeding period. During incubation and the first half of the nestling period, parental care was divided equally between partners. However, in the late nestling stage, we found males to feed their nestlings irrespective of brood size while females considerably decreased feeding rate with the number of nestlings. This behaviour culminated in desertion of small broods by females shortly before fledging. The fact that even deserted nests were successful indicates that males were able to compensate for the females' absence. Interestingly, the mating of one female with two males with separate nests could be found in the population, which confirms earlier findings of polyandry in the lesser spotted woodpecker. We conclude that biparental care is not essential in the later stage and one partner can reduce effort and thus costs of parental care, at least in small broods where the mate is able to compensate for that behaviour. Reduced care and desertion appears only in females, which might be caused by a combination of two traits: First, females might suffer higher costs of investment in terms of mortality and secondly, male-biased sex ratio in the population generally leads to higher mating probabilities for females in the following breeding season. The occurrence of polyandry seems to be a result of these conditions.
Ischnopsyllus variabilis (WAGNER, 1898), a model of survival strategy of rare insects? The present paper reports a collection of Ischnopsyllus variabilis in the Schorfheide, a region in the north of Brandenburg (Germany). This bat flea is very rare and the specimens are seldom encountered. The collection of 5 males and 21 females of I. variabilis from summer roosts of the Nathusius`pipistrelle (Pipistrellus nathusii) is a remarkable documentation, since it represents the largest known population of the flea in Europe. Moreover, the data reported here emphasizes for the first time that the Nathusius` pipistrelle is the main host of I. variabilis. The development of the larvae take place in maternity colonies of this bat species. The occurrence of a local concentration of rare specimens may be a vital necessity for the long range survival. Hence, I. variabilis may represent an appropriate model for the understanding of ecology of rare insects, since a local population could be the origin for a scattered distribution over larger areas. The spread of the flea is promoted by the expansive seasonal migrations of the Nathusius`pipistrelle. The exact mechanisms and parameters underlying such an accumulation of specimens in a special maternity colony are still unknown and require further investigations.
In common garden experiments, a number of genotypes are raised in a common environment in order to quantify the genetic component of phenotypic variation. Common gardens are thus ideally suited for disentangling how genetic and environmental factors contribute to the success of invasive species in their new non-native range. Although common garden experiments are increasingly employed in the study of invasive species, there has been little discussion about how these experiments should be designed for greatest utility. We argue that this has delayed progress in developing a general theory of invasion biology. We suggest a minimum optimal design (MOD) for common garden studies that target the ecological and evolutionary processes leading to phenotypic differentiation between native and invasive ranges. This involves four elements: (A) multiple, strategically sited garden locations, involving at the very least four gardens (2 in the native range and 2 in the invaded range); (B) careful consideration of the genetic design of the experiment; (C) standardization of experimental protocols across all gardens; and (D) care to ensure the biosafety of the experiment. Our understanding of the evolutionary ecology of biological invasions will be greatly enhanced by common garden studies, if and only if they are designed in a more systematic fashion, incorporating at the very least the MOD suggested here.
We analyzed relative sensitivities of small- and medium-sized carnivores to livestock husbandry (stocking rates and predator control) in Kalahari, South Africa, rangelands at a regional scale. We monitored small carnivores using track counts on 22 Kalahari farms across a land-use gradient ranging from low to high stocking rates and also interviewed each farm manager to identify farmers" perception of small carnivores as potential predators for livestock. We recorded 12 species of small- and medium-sized carnivores across 22 Kalahari farms. Stocking rate was the most important driving variable for local carnivore abundance. Abundance of all species was lowest on farms where stocking rate was high. Most farm managers perceived medium-sized carnivores, in particular, African wildcat (Felis silvestris lybica), black-backed jackal (Canis mesomelas), and caracal (Caracal caracal), as potential predators of livestock. Multiple regression analysis shows that black-backed jackal, African wildcat, and caracal were negatively affected by predator control measures, whereas bat-eared fox (Otocyon megalotis), cape fox (Vulpes chama), and small-spotted genet (Genetta genetta) were positively affected. Our results show a need for expanding research and conservation activities toward small- and medium-sized carnivores in southern African savannah rangelands. We, therefore, suggest developing a monitoring program combining passive tracking with indigenous knowledge of local Khoisan Bushmen to monitor carnivore populations, and we recommend additional predator removal experiments that manipulate predator densities.
Der Artikel liefert eine Zusammenstellung der aktuellen Ektoparasitenfauna der Fledermäuse (Flöhe, Fledermausfliegen, Wanzen, Zecken und Milben). Die Beziehung zwischen den Fledermäusen und ihren Ektoparasiten eignet sich in besonderem Maße als Modell ökologischer und evolutionärer Prozesse, wie das Überleben seltener Arten, die Kövolution zwischen Wirten und Parasiten, die Übertragung von Parasiten, die Wirtswahl und die Verbreitung von Krankheiten. Der gegenwärtige Stand der ökologischen Forschung auf diesen Gebieten wird zusammengefaßt und die Notwendigkeit und die Ziele weiterer Forschung werden angegeben.
Bei der Untersuchung von Ektoparasiten in verschiedenen Winterqartieren von Fledermäusen im Nordosten Brandenburgs wurde das Artenspektrum an Flöhen, Lausfliegen und Milben erfasst. Die häufigsten Parasiten waren die sogenannten "Winterflöhe", die mit drei Arten (Nycteridopsylla eusarca, N. longiceps und N. pentactena) präsent waren. Bei der Anzahl dieser Flöhe in den Winterquartieren wurden extreme Unterschiede festgestellt. In einzelnen Quartieren kann es zu einem relativ hohen Besatz an Flöhen kommen. Solche Populationszentren könnten für das regionale Überleben der seltenen Ektoparasitenarten eine große Rolle spielen. In diesen Quartieren werden neben den Hauptwirten auch andere überwinternde Fledermausarten als Blutspender genutzt. An den Wasserfledermäusen gab es regelmäßig Funde der Fledermausfliege Nycteribia kolenatii. Im Gegensatz zu den Flöhen und dieser Fledermausfliegenart traten die meisten anderen Parasiten nur sporadisch auf. Bei der Untersuchung wurden drei für Brandenburg neue Ektoparasitenarten festgestellt. Es handelt sich dabei um eine Fledermausfliege: Basilia nana sowie um zwei kleine Milbenarten der Familie Macronyssidae: Macronyssus cyclaspis und Macronyssus ellipticus.
The 2009 British Ecological Society"s Annual Symposium entitled 'Facilitation in Plant Communities' was held at the University of Aberdeen, Scotland, from 20 to 22 April 2009. This was the first ever international meeting dedicated to the rapidly expanding field of facilitation. The aim of the symposium was to assess the current 'state-of- play' by contrasting findings from different systems and by looking outwards in an attempt to integrate this field with other related fields. It was also aimed at understanding how knowledge of facilitation can help understand community dynamics and be applied to ecosystem restoration. The symposium identified several key areas where future work is likely to be most profitable.
Modelling and empirical studies have shown that input from the regional seed pool is essential to maintain local species diversity. However, most of these studies have concentrated on simplified, if not neutral, model systems, and focus on a limited subset of species or on aggregated measures of diversity only (e.g., species richness or Shannon diversity). Thus they ignore more complex species interactions and important differences between species. To gain a better understanding of how seed immigration affects community structure at the local scale in real communities we conducted computer simulation experiments based on plant functional types (PFTs) for a species-rich, fire-prone Mediterranean-type shrubland in Western Australia. We developed a spatially explicit simulation model to explore the community dynamics of 38 PFTs, defined by seven traits - regeneration mode, seed production, seed size, maximum crown diameter, drought tolerance, dispersal mode and seed bank type - representing 78 woody species. Model parameterisation is based on published and unpublished data on the population dynamics of shrub species collected over 18 years. Simulation experiments are based on two contrasting seed immigration scenarios: (1) the 'equal seed input number' scenario, where the number of immigrant seeds is the same for all PFTs, and (2) the 'equal seed input mass' scenario, where the cumulative mass of migrating seeds is the same for all PFTs. Both scenarios were systematically tested and compared for different overall seed input values. Without immigration the local community drifts towards a state with only 13 coexisting PFTs. With increasing immigration rates in terms of overall mass of seeds the simulated number of coexisting PFTs and Shannon diversity quickly approaches values observed in the field. The equal seed mass scenario resulted in a more diverse community than did the seed number scenario. The model successfully approximates the frequency distributions (relative densities) of all individual plant traits except seed size for scenarios associated with equal seed input mass and high immigration rate. However, no scenario satisfactorily approximated the frequency distribution for all traits in combination. Our results show that regional seed input can explain the more aggregated measures of local community structure, and some, but not all, aspects of community composition. This points to the possible importance of other (untested) processes and traits (e.g., dispersal vectors) operating at the local scale. Our modelling framework can readily allow new factors to be systematically investigated, which is a major advantage compared to previous simulation studies, as it allows us to find structurally realistic models, which can address questions pertinent to ecological theory and to conservation management.
The paper presents a simulation and parameter-estimation approach for evaluating stochastic patterns of population growth and spread of an annual forest herb, Melampyrum pratense (Orobanchaceae). The survival of a species during large-scale changes in land use and climate will depend, to a considerable extent, on its dispersal and colonisation abilities. Predictions on species migration need a combination of field studies and modelling efforts. Our study on the ability of M. pratense to disperse into so far unoccupied areas is based on experiments in secondary woodland in NE Germany. Experiments started in 1997 at three sites where the species was not yet present, with 300 seeds sown within 1m2. Population development was then recorded until 2001 by mapping of individuals with a resolution of 5 cm. Additional observations considered density dependence of seed production. We designed a spatially explicit individual-based computer simulation model to explain the spatial patterns of population development and to predict future population spread. Besides primary drop of seeds (barochory) it assumed secondary seed transport by ants (myrmecochory) with an exponentially decreasing dispersal tail. An important feature of population-pattern explanation was the simultaneous estimation of both population-growth and dispersal parameters from consistent spatio-temporal data sets. As the simulation model produced stochastic time series and random spatially discrete distributions of individuals we estimated parameters by minimising the expectation of weighted sum of squares. These sums of squares criteria considered population sizes, radial population distributions around the area of origin and distributions of individuals within squares of 25cm×25 cm, the range of density action. Optimal parameter values, together with the precision of the estimates, were obtained from calculating sum of squares in regular grids of parameter values. Our modelling results showed that transport of fractions of seeds by ants over distances of 1-2m was indispensable for explaining the observed population spread that led to distances of at most 8mfrom population origin within 3 years. Projections of population development over four additional years gave a diffusion-like increase of population area without any "outposts". This prediction generated by the simulation model gave a hypothesis which should be revised by additional field observations. Some structural deviations between observations and model output already indicated that for full understanding of population spread the set of dispersal mechanisms assumed in the model may have to be extended by additional features of plant-animal mutualism.
Predictions on displacement of suitable habitats due to climate change suggest that plant species with poor colonization ability may be unable to move fast enough to match forecasted climate-induced changes in habitat distribution. However, studies on early Holocene plant migration show fast migration of many plant species that are poor colonizers today. We hypothesize that warmer temperatures during the early Holocene yielded higher seed quality, contributing to explaining the fast migration. We studied how the 3 seed quality variables, seed mass, germinability, and requirements for break of seed dormancy, vary for seeds of 11 forest herb species with varying colonization capacity collected along a 1400-km latitudinal gradient. Within species, seed mass showed a positive correlation with latitude, whereas germinability was more positively correlated with temperature (growing degree hours obtained at time of seed collection). Only slow-colonizing species increased germinability with temperature, whereas only fast-colonizing species increased germinability with latitude. These interactions were only detectable when analyzing germinability of the seeds, even though this trait and seed mass were correlated. The requirement for dormancy break did not correlate with latitude or temperature. The results indicate that seed development of slow colonizers may be favoured by a warmer climate, which in turn may be important for their migration capacity.
Aim To investigate the effect of temperature, latitude and local environment on the reproductive traits of widespread perennial forest herbs to better understand the potential impacts of rising temperatures on their population dynamics and colonization capacities. Location Six regions along a latitudinal gradient from France to Sweden. Methods Within each region, we collected data from three to five populations of up to six species. For each species, several variables were recorded in each region (temperature, latitude) and population (local abiotic and biotic environmental variables), and seed production and germination were estimated. Resource investment in reproduction (RIR) was quantified as seed number ¥ seed mass, while germinable seed output (GSO) was expressed as seed number ¥ germination percentage.We performed linear regression and mixed effect models to investigate the effects of temperature (growing degree hours), latitude and local abiotic and biotic environment on RIR and GSO. Results Temperature and latitude explained most of the variation in RIR and GSO for early flowering species with a northerly distribution range edge (Anemone nemorosa, Paris quadrifolia and Oxalis acetosella). Reproduction of the more southerly distributed species (Brachypodium sylvaticum, Circaea lutetiana and Primula elatior), in contrast, was independent of temperature/latitude. In the late summer species, B. sylvaticum and C. lutetiana, variation in RIR and GSO was best explained by local environmental variables, while none of the investigated variables appeared to be related to reproduction in P. elatior. Main conclusions We showed that reproduction of only two early flowering, northerly distributed species was related to temperature. This suggests that the potential reproductive response of forest herbs to climate warming partly depends on their phenology and distribution, but also that the response is to some extent species dependent. These findings should be taken into account when predictions about future shifts in distribution range are made.
A major aim in ecology is identifying determinants of invasiveness. We performed a meta-analysis of 117 field or experimental-garden studies that measured pair-wise trait differences of a total of 125 invasive and 196 non-invasive plant species in the invasive range of the invasive species. We tested whether invasiveness is associated with performance-related traits (physiology, leaf-area allocation, shoot allocation, growth rate, size and fitness), and whether such associations depend on type of study and on biogeographical or biological factors. Overall, invasive species had significantly higher values than non-invasive species for all six trait categories. More trait differences were significant for invasive vs. native comparisons than for invasive vs. non-invasive alien comparisons. Moreover, for comparisons between invasive species and native species that themselves are invasive elsewhere, no trait differences were significant. Differences in physiology and growth rate were larger in tropical regions than in temperate regions. Trait differences did not depend on whether the invasive alien species originates from Europe, nor did they depend on the test environment. We conclude that invasive alien species had higher values for those traits related to performance than non-invasive species. This suggests that it might become possible to predict future plant invasions from species traits.
Analysis of organellar genome dynamics and development of methods for organelle transformation
(2010)
Komplexe Systeme reichen von "harten", physikalischen, wie Klimaphysik, Turbulenz in Fluiden oder Plasmen bis zu so genannten "weichen", wie man sie in der Biologie, der Physik weicher Materie, Soziologie oder Ökonomie findet. Die Ausbildung von Verständnis zu einem solchen System beinhaltet eine Beschreibung in Form von Statistiken und schlussendlich mathematischen Gleichungen. Moderne Datenanalyse stellt eine große Menge von Werkzeugen zur Analyse von Komplexität auf verschiedenen Beschreibungsebenen bereit. In diesem Kurs werden statistische Methoden mit einem Schwerpunkt auf dynamischen Systemen diskutiert und eingeübt. Auf der methodischen Seite werden lineare und nichtlineare Ansätze behandelt, inklusive der Standard-Werkzeuge der deskriptiven und schlussfolgernden Statistik, Wavelet Analyse, Nichtparametrische Regression und der Schätzung nichtlinearer Maße wie fraktaler Dimensionen, Entropien und Komplexitätsmaßen. Auf der Modellierungsseite werden deterministische und stochastische Systeme, Chaos, Skalierung und das Entstehen von Komplexität durch Wechselwirkung diskutiert - sowohl für diskrete als auch für ausgedehnte Systeme. Die beiden Ansätze werden durch Systemanalyse jeweils passender Beispiele vereint.
Komplexe Systeme reichen von "harten", physikalischen, wie Klimaphysik, Turbulenz in Fluiden oder Plasmen bis zu so genannten "weichen", wie man sie in der Biologie, der Physik weicher Materie, Soziologie oder Ökonomie findet. Die Ausbildung von Verständnis zu einem solchen System beinhaltet eine Beschreibung in Form von Statistiken und schlussendlich mathematischen Gleichungen. Moderne Datenanalyse stellt eine große Menge von Werkzeugen zur Analyse von Komplexität auf verschiedenen Beschreibungsebenen bereit. In diesem Kurs werden statistische Methoden mit einem Schwerpunkt auf dynamischen Systemen diskutiert und eingeübt. Auf der methodischen Seite werden lineare und nichtlineare Ansätze behandelt, inklusive der Standard-Werkzeuge der deskriptiven und schlussfolgernden Statistik, Wavelet Analyse, Nichtparametrische Regression und der Schätzung nichtlinearer Maße wie fraktaler Dimensionen, Entropien und Komplexitätsmaßen. Auf der Modellierungsseite werden deterministische und stochastische Systeme, Chaos, Skalierung und das Entstehen von Komplexität durch Wechselwirkung diskutiert - sowohl für diskrete als auch für ausgedehnte Systeme. Die beiden Ansätze werden durch Systemanalyse jeweils passender Beispiele vereint.
Secretion in blowfly salivary glands is induced by the neurohormone serotonin and powered by a vacuolar-type H+- ATPase (V-ATPase) located in the apical membrane of the secretory cells. We have established a microfluorometric method for analysing pH changes at the luminal surface of the secretory epithelial cells by using the fluorescent dye 5-N- hexadecanoyl-aminofluorescein (HAF). After injection of HAF into the lumen of the tubular salivary gland, the fatty acyl chain of the dye molecule partitions into the outer leaflet of the plasma membrane and its pH-sensitive fluorescent moiety is exposed at the cell surface. Confocal imaging has confirmed that HAF distributes over the entire apical membrane of the secretory cells and remains restricted to this membrane domain. Ratiometric analysis of HAF fluorescence demonstrates that serotonin leads to a reversible dose-dependent acidification at the luminal surface. Inhibition by concanamycin A confirms that the serotonin-induced acidification at the luminal surface is due to H+ transport across the apical membrane via V-ATPase. Measurements with pH-sensitive microelectrodes corroborate a serotonin-induced luminal acidification and demonstrate that luminal pH decreases by about 0.4 pH units at saturating serotonin concentrations. We conclude that ratiometric measurements of HAF fluorescence provide an elegant method for monitoring V-ATPase-dependent H+ transport in the blowfly salivary gland in vivo and for analysing the spatiotemporal pattern of pH changes at the luminal surface
Komplexe Systeme reichen von "harten", physikalischen, wie Klimaphysik, Turbulenz in Fluiden oder Plasmen bis zu so genannten "weichen", wie man sie in der Biologie, der Physik weicher Materie, Soziologie oder Ökonomie findet. Die Ausbildung von Verständnis zu einem solchen System beinhaltet eine Beschreibung in Form von Statistiken und schlussendlich mathematischen Gleichungen. Moderne Datenanalyse stellt eine große Menge von Werkzeugen zur Analyse von Komplexität auf verschiedenen Beschreibungsebenen bereit. In diesem Kurs werden statistische Methoden mit einem Schwerpunkt auf dynamischen Systemen diskutiert und eingeübt. Auf der methodischen Seite werden lineare und nichtlineare Ansätze behandelt, inklusive der Standard-Werkzeuge der deskriptiven und schlussfolgernden Statistik, Wavelet Analyse, Nichtparametrische Regression und der Schätzung nichtlinearer Maße wie fraktaler Dimensionen, Entropien und Komplexitätsmaßen. Auf der Modellierungsseite werden deterministische und stochastische Systeme, Chaos, Skalierung und das Entstehen von Komplexität durch Wechselwirkung diskutiert - sowohl für diskrete als auch für ausgedehnte Systeme. Die beiden Ansätze werden durch Systemanalyse jeweils passender Beispiele vereint.
Bacterivory by mixotrophic flagellates may contribute to their nutrient supply, providing a competitive advantage in oligotrophic waters. We hypothesized an increase in Dinobryon biomass during the re-oligotrophication process in the large and deep Lake Constance. To estimate whether bacterivory contributed substantially to the flagellates' phosphorus supply, we determined ingestion rates. Dinobryon biomass increased with decreasing total phosphorus concentrations in the lake over a period of 17 years (P = 0.0005). The promotion of Dinobryon biomass during re-oligotrophication may be explained by the increasing light availability due to the decreasing biomass of other phytoplankton yielding a release from competition. The date of the Dinobryon abundance maximum shifted to earlier time points in the year, probably because a smaller phosphorus pool was depleted more quickly. Ingestion rates of Dinobryon ranged between 0.5 and 13 bacteria cell(-1) h(-1) (0.2-5.4 fg C pg C-1 h(-1)), and clearance rates varied between 0.2 and 3.2 nL cell(-1) h(-1) (4-78 pL pg C-1 h(-1)), leading to bacterial losses of up to 30% day(-1) of bacterial standing stock. The ingestion of bacteria covered 77% of the phosphorus need of the flagellate during the period of maximum growth in 1996 (net growth rate 0.34 day(-1)), and it fully covered the need at all other times.
Modelling ungulate dependence on higher quality forage under large trees in African savannahs
(2009)
In African savannahs, large trees improve grass quality, particularly in dry and nutrient poor areas. Enhanced below-canopy grass nutrients, such as nitrogen and phosphorus contents should therefore attract and benefit grazers. To predict whether ungulates really need these forage quality islands we focused on four grazer species, i.e., zebra, buffalo, wildebeest, and warthog, differing in body size and digestive system. We confronted literature estimations of their feeding requirements with forage availability and quality, observed in three South African savannah systems, through linear modelling. The model predicted the proportion of below-canopy grass that grazers should include in their diet to meet their nutritional requirements. During the wet season, the model predicted that all animals could satisfy their daily nutrient requirements when feeding on a combination of below- and outside-canopy grasses. However, wildebeest, having relatively high nutrient demands, could meet their nutrient requirements only by feeding almost exclusively below canopies. During the dry season, all animals could gain almost twice as much digestible protein when feeding on below - compared to outside-canopy forage. Nonetheless, only warthogs could satisfy their nutrient requirements - when feeding almost exclusively on below-canopy grasses. The other ungulate species could not meet their phosphorus demands by feeding at either site without exceeding their maximum fibre intake, indicating the unfavourable conditions during the dry season. We conclude that grazing ungulates, particularly warthog, zebra, and buffalo, actually depend on the available below-canopy grass resources. Our model therefore helps to quantify the importance of higher quality forage patches beneath savannah trees. The composition of grazer communities depending on below-canopy grasses can be anticipated if grazer food requirements and the abundance of large trees in savannahs are known. The model suggests that the conservation of large single-standing trees in savannahs is crucial for maintenance of locally grazing herbivores.
Genetic structure and dispersal in a small South African Rodent : is dispersal female-biased?
(2009)
Dispersal greatly determines genetic structure of populations, although it is influenced by landscape heterogeneity, quality of the matrix, resource distribution and local population densities and dynamics. To get insights into some of those processes we analysed the genetic structure of the hairy-footed gerbil Gerbillurus paeba (Rodentia, Murinae, Gerbillinae) in the southern Kalahari (South Africa). Samples were taken from 20 populations covering an area of about 2200 km2. Genetic data were related to landscape characters and population dynamics. We used newly developed microsatellites and found at all loci some indication for the presence of null alleles. However, null alleles seem to have little influence on the general results of our analyses. Altogether we found even nearby populations of G. paeba to be significantly differentiated, although assignment tests revealed 24% of individuals as immigrants. Genetic structure was independent of landscape heterogeneities at all spatial scales. Autocorrelation analyses (range 50-90 km) revealed significant genetic structure within populations on distances <3 km. We found some indication for female-biased dispersal. Our study suggests that dispersing individuals have little influence on the long-term genetic structure and that drift is the major cause of genetic diversity. The observed genetic pattern likely derives from strong population fluctuations of G. paeba. The landscape structure has little influence on the genetic differentiation between populations.
Neben dem Habitatverlust gelten Konsequenzen der Habitatfragmentierung seit den 1990er Jahren als wesentliche Ursache der Gefaehrdung von Pflanzen und stehen damit nun auch im Fokus des botanischen Artenschutzes. Der vorliegende Beitrag gibt einen ueberblick ueber den Stand der populationsbiologischen und genetischen Forschung und versucht abzuschaetzen, welche Bedeutung Habitatfragmentierung und die dadurch entstehenden kleinen, isolierten Populationen auf heimische Pflanzenarten haben koennen. Als wesentliche und offenbar sehr weit verbreitete negative Effekte werden Zufallsereignisse, Randeffekte, Bestaeuberlimitierung, Gendrift und Inzuchtdepression identifiziert. Zusammen mit verringerter Habitatqualitaet durch Eutrophierung, Entwaesserung oder Nutzungsaenderung wirken sie zumeist negativ auf die Fitness der Individuen und Populationen und erhoehen so deren Aussterberisiko. Dieser negative Effekt kleiner Populationen auf die individuelle Fitness wird unabhaengig von der Ursache als Allee-Effekt bezeichnet. Eine durch einen Biotopverbund gefoerderte Metapopulationsdynamik kann das dauerhafte Aussterben von Pflanzenpopulationen verhindern und mindert die negativen genetischen Effekte der Habitatfragmentierung ueber einen erhoehten Genfluss durch Pollen und Samen. Die bisherigen wissenschaftlichen Studien in Mitteleuropa beruhen allerdings in ueberproportionaler Weise auf bestimmten Pflanzenfamilien (Gentianaceae, Primulaceae), Habitaten (Trocken- und Magerrasen, Wirtschaftsgruenland), insekten- und obligat fremdbestaeubten sowie weitgehend auf sexuelle Fortpflanzung angewiesenen Arten, waehrend etwa ueber Grasartige, Ruderalpflanzen, wind- und selbstbestaeubte sowie an vegetative Fortpflanzung angepasste Arten nur wenige Erkenntnisse vorliegen. Gerade diese und Pflanzenarten mit hohem Ausbreitungspotenzial muessen aber nach derzeitigem Wissensstand als weniger sensitiv gegenueber Habitatfragmentierung eingestuft werden. Auf diesen Befunden aufbauend werden fuer die Naturschutzpraxis Biotoptypen hinsichtlich ihrer Sensitivitaet gegenueber Habitatfragmentierung klassifiziert und ein auf biologischen Merkmalen basierender Kriterienkatalog zur Auswahl von Zielarten des Biotopverbunds vorgestellt. Schließlich wird eroertert, was bei Maßnahmen zur Regeneration kleiner bzw. bereits ausgestorbener Populationen zu beachten ist, und es werden allgemeine Folgerungen zur Ausgestaltung eines Biotopverbundskonzepts fuer Pflanzen gezogen.
Besides habitat loss, population-biological and genetic consequences of habitat fragmentation are thought to be a major threat to species since the 1990's and thus are now in the focus of plant species conservation. Using examples, this article gives an overview on the state of the art. It aims to evaluate the relevance habitat fragmentation and the resulting small size and isolation of populations may have for Central European plant populations. Stochasticity, edge effects, pollinator limitation, genetic drift and inbreeding depression are identified as important and very widespread negative effects. Together with changed habitat quality due to eutrophication, drainage or altered land use they negatively affect the fitness of individuals and populations, resulting in an increased risk of extinction. This negative effect of small populations on the fitness of individuals is called the Allee-effect, irrespective of the underlying causes, which can only be identified by scientific experiments. Metapopulation dynamics that are supported by a habitat network may prevent a permanent extinction of plant populations and minimize the negative genetic effects of habitat fragmentation by increasing gene flow via pollen and seeds. However, existing studies from Central Europe mainly concentrated on certain plant families (Gentianaceae, Primulaceae), habitats (species- rich grasslands), insect-pollinated and outcrossing species, and species mainly relying on sexual reproduction. On the other hand, few insights exist about grasses, ruderal plants and weeds, non-indigenous, wind- and self-pollinated species, and species mainly reproducing vegetatively or via apomictic seeds. However, according to the present state of knowledge especially these plant species, and those with a high dispersal potential, have to be considered as less sensitive to habitat fragmentation. Based on these findings, habitat types are classified with regard to their sensitivity to fragmentation, and ecological characters and species traits of sensitive and less sensitive species are compared. Finally, general consequences for conservation practice are presented with regard to target species and habitats for the formation of habitat networks, minimum viable population sizes, genetic rescue of populations, and deploying plants from ex-situ conservation to natural habitats.
Grazing is known as one of the key factors for diversity and community composition in grassland ecosystems, but the response of plant communities towards grazing varies remarkably between sites with different environmental conditions. It is generally accepted that grazing increases plant diversity in productive environments, while it tends to reduce diversity in unproductive habitats (grazing reversal hypothesis). Despite empirical evidence for this pattern the mechanistic link between modes of plant-plant competition and grazing response at the community level still remains poorly understood. Root-competition in particular has rarely been included in theoretical studies, although it has been hypothesized that variations in productivity and grazing regime can alter the relative importance of shoot- and root-competition. We therefore developed an individual-based model based on plant functional traits to investigate the response of a grassland community towards grazing. Models of different complexity, either incorporating only shoot competition or with distinct shoot- and root-competition, were used to study the interactive effects of grazing, resource availability, and the mode of competition (size-symmetric or asymmetric). The pattern predicted by the grazing reversal hypothesis (GRH) can only be explained by our model if shoot- and root-competition are explicitly considered and if size asymmetry of above- and symmetry of below-ground competition is assumed. For this scenario, the model additionally reproduced empirically observed plant trait responses: erect and large plant functional types (PFTs) dominated without grazing, while frequent grazing favoured small PFTs with a rosette growth form. We conclude that interactions between shoot- and root-competition and size symmetry/asymmetry of plant-plant interactions are crucial in order to understand grazing response under different habitat productivities. Our results suggest that future empirical trait surveys in grassland communities should include root traits, which have been largely ignored in previous studies, in order to improve predictions of plants" responses to grazing.
Die in Deutschland gegenwärtig durch Nährstoffeinträge und ausbleibenden Nährstoffentzug stark im Rückgang begriffenen Flechten-Kiefernwälder werden als Biotoptyp wie auch als Lebensraumtyp "Mitteleuropäische Flechten-Kiefernwälder" (Code 91T0) diskutiert. Die bisherige, sehr uneinheitliche Differenzierung von Flechten-Kiefernwäldern auf der Ebene von Biotoptypen wird dargestellt. Auf der Grundlage neuerer vegetationskundlicher übersichten werden Vorschläge für eine einheitliche Abgrenzung des Biotoptyps "Flechten-Kiefernwald" und des Lebensraumtyps 91T0 unterbreitet. Im niedersächsischen Naturwaldreservat "Kaarßer Sandberge" (Niedersachsen) wurde die Anwendung des Konzeptes erfolgreich erprobt. Nicht nur hier, sondern auch deutschlandweit wird der Rückgang der Erdflechten in den Kieferwäldern zugunsten von Drahtschmiele und/ oder pleurokarpen Moosen deutlich. Nach der derzeitigen Definition des Lebensraumtyps 91T0 besteht auf der Grundlage der FFH-Richtlinie nicht für alle Flechten-Kiefernwälder eine Chance der Verbesserung. Der Ausschluss von außerhalb des natürlichen Verbreitungsgebietes der Wald-Kiefer gelegenen sowie von durch Aufforstung angepflanzten Beständen bringt Probleme mit sich, die diskutiert werden. Für den Erhalt und die Wiederherstellung der größtenteils nutzungsbedingt entstandenen Flechten-Kiefernwälder sind praktikable Pflegemaßnahmen notwendig, die im Rahmen von Streunutzungsversuchen erprobt werden müssen.
Vegetation und Standort bodensaurer Buchenwälder am Arealrand : am Beispiel Mittelbrandenburgs
(2008)
Different from NW Germany, the northern part of NE Germany and the "Hohe Flaeming" region, central Brandenburg is considered as being largely devoid of natural beech forests because of its subcontinental, dry climate. In the present study the vegetation ecology of beech forests of the region is comprehensively documented for the first time, and they are compared with NW German stands in Lower Saxony. In the study area beech forests are concentrated in the Berlin-Potsdam region along the Havel river lakes which is characterised by relatively high precipitation and a specific land use history. All belong to the Luzulo-Fagetum growing on acid soils. Four subtypes are distinguished according to nutrient availability and soil moisture. The central Brandenburg Luzulo-Fagetum does not markedly deviate from other beech forests in the northern German lowlands with respect to vegetation structure and edaphic subtypes. However, numerous indicator species for humid or moist conditions are less frequent than under atlantic climate conditions in the lowlands of Lower Saxony, a pattern occurring also in other forest communities. On the other hand, nitrogen and disturbance indicators are more frequent in central Brandenburg. As expected, podzolisation of the soils and humus accumulation is lower in beech forests under subcontinental climate, but surprisingly the soils are more sandy and thus drier. However, beech forests are lacking on south-exposed slopes, and they are notably occurring in northern exposition. A combined analysis of distribution patterns and climatic data, postglacial vegetation history and forest use history, and actual rejuvenation dynamics reveals that the present-day beech forests in central Brandenburg have to be considered as near-natural relics, which are currently spreading. The range of potentially natural beech forests is larger than assumed until now, but further on it is not clearly to define.
Gametophyte and thallus fragments, respectively, may be an important or even the only mode of reproduction for many bryophytes and lichens species. Until now especially birds and mammals have been identifi ed as potential animal dispersal vectors of fragments. This study investigates the dispersal of bryophyte and lichen fragments by red wood ants which build large nest mounds from plant material and are abundant in European coniferous forests. We sampled nest material from 25 nest mounds in fi ve different pine and spruce forest types in Germany and found numerous fragments of 20 bryophyte and ten lichen species. As they occurred on almost all studied mounds and often in large numbers we conclude that collecting cryptogam fragments as nest material is a characteristic feature for the Formica rufa group in coniferous forests. Species number and composition of fragments on mounds coincided with the epigeic vegetation around ant nests to a large extent: Almost all collected species were present in the vegetation, and dominant fragment species occurred in large amounts in the vicinity of ant nests. Lichen fragments were larger than bryophyte fragments. Certain life forms (weft-forming bryophytes, reindeer lichens) were accumulated on mounds, while others (tall turfs, cup-type Cladonia species) were discriminated, refl ecting fragmentation features of species. Collected fragments may regenerate to mature plants if nest mounds are abandoned, and especially if they are lost during transport over several metres. We conclude that dispersal of fragments by red wood ants contributes to maintain epigeic bryophyte and lichen diversity of coniferous forests by supporting colonisation after disturbances, which occur on different spatial and temporal scales.
Ectoparasites of bats in Mongolia (Ischnopsyllidae, Nycteribiidae, Cimicidae and Spinturnicidae)
(2010)
For large parts of the world, the knowledge of bat ectoparasites is still scanty. Regarding Mongolia, only few studies exist to date. This paper analyses results from extensive captures between 2005 -2008, carried out in different sites of Mongolia. Discussed ectoparasites include bat fleas, (Ischnopsyllidae), bat flies (Nycteribiidae), and bat bugs (Cimicidae) and spinturnicid mites (Spinturnicidae). A number of species found in this study were new records for Mongolia, and for many species additional sites were reported. For some bat species, the spectrum and frequency of larger ectoparasites could be determined for the first time.
Die spontane Ausbreitung nicht-einheimischer oder exotischer Arten, unabsichtlich eingeschleppt bzw. absichtlich eingefuehrt, ist heute ein weltweit zu beobachtendes Phaenomen. Arten werden in grossem Umfang zwischen Kontinenten ausgetauscht und innerhalb der Kontinente verfrachtet; in erster Linie eine Folge des weltweiten Handels und Reiseverkehrs. Einige (aber nicht alle) dieser verwilderten Exoten breiten sich rasant aus und ihr Massenvorkommen zieht nachteilige Auswirkungen auf Mensch und Umwelt nach sich. Solche invasive Arten sind heutzutage ein zentrales Thema im internationalen Naturschutz und in der oekologischen Forschung. Die Ausbreitung invasiver Organismen, als biologische Invasionen bezeichnet, gilt mittlerweile neben Lebensraumzerstoerung als die zweitwichtigste Ursache des weltweiten Artenrueckganges. Die Mechanismen, die zu einer biologischen Invasion fuehren koennen, sind sehr vielfaeltig und beruhen auf Eigenschaften der Arten sowie des betreffenden neuen Lebensraumes. Offene Habitate mit geringem Konkurrenzdruck anderer Arten und ohne spezialisierte Frassfeinde und Pathogene zeigen sich als besonders anfaellig fuer die Besiedlung invasiver Arten. Unter invasive Arten fallen auch solche, die in der Land- und Forstwirtschaft Schaeden verursachen oder die Gesundheit des Menschen gefaehrden. In der Schweiz sind ueber 800 exotische Pflanzen-, Tier-, und Pilz-Arten etabliert, von diesen gelten 107 Arten als invasiv. Welche Massnahmen ergriffen werden sollen, richtet sich nach der Haeufigkeit der Art, aber auch nach der Zielsetzung. Die kostenguenstigsten Massnahmen sind praeventive Massnahmen. Die Gruende, wie es zu biologischen Invasionen kommen kann, welche Eigenschaften invasive Arten aufweisen, ob und wie schnell sich verschleppte Arten im neuen Verbreitungsgebiet evolutiv veraendern koennen, und welches die beste Strategie im Umgang mit invasiven Arten ist, ist Gegenstand dieser Schrift.
Komplexe Systeme reichen von "harten", physikalischen, wie Klimaphysik, Turbulenz in Fluiden oder Plasmen bis zu so genannten "weichen", wie man sie in der Biologie, der Physik weicher Materie, Soziologie oder Ökonomie findet. Die Ausbildung von Verständnis zu einem solchen System beinhaltet eine Beschreibung in Form von Statistiken und schlussendlich mathematischen Gleichungen. Moderne Datenanalyse stellt eine große Menge von Werkzeugen zur Analyse von Komplexität auf verschiedenen Beschreibungsebenen bereit. In diesem Kurs werden statistische Methoden mit einem Schwerpunkt auf dynamischen Systemen diskutiert und eingeübt. Auf der methodischen Seite werden lineare und nichtlineare Ansätze behandelt, inklusive der Standard-Werkzeuge der deskriptiven und schlussfolgernden Statistik, Wavelet Analyse, Nichtparametrische Regression und der Schätzung nichtlinearer Maße wie fraktaler Dimensionen, Entropien und Komplexitätsmaßen. Auf der Modellierungsseite werden deterministische und stochastische Systeme, Chaos, Skalierung und das Entstehen von Komplexität durch Wechselwirkung diskutiert - sowohl für diskrete als auch für ausgedehnte Systeme. Die beiden Ansätze werden durch Systemanalyse jeweils passender Beispiele vereint.
The need to implement sustainable resource management regimes for semi-arid and arid rangelands is acute as non- adapted grazing strategies lead to irreversible environmental problems such as desertification and associated loss of economic support to society. In these sensitive ecosystems, traditional sectoral, disciplinary approaches will not work to attain sustainability: achieving a collective vision of how to attain sustainability requires interactive efforts among disciplines in a more integrated approach. Therefore, we developed an integrated ecological-economic approach that consists of an ecological and an economic module and combines relevant processes on either level. Parameters for both modules are adjusted for an arid dwarf shrub savannah in southern Namibia. The economic module is used to analyse decisions of different virtual farmer types on annual stocking rates depending on their knowledge how the ecosystem works and climatic conditions. We used a dynamic linear optimisation model to simulate farm economics and livestock dynamics. The ecological module is used to simulate the impact of the farmers' land-use decision, derived by the economic module, on ecosystem dynamics and resulting carrying capacity of the system for livestock. Vegetation dynamics, based on the concept of State-and-transition models, and forage productivity for both modules is derived by a small- scale and spatially explicit vegetation model. This mechanistic approach guarantees that data collected and processes estimated at smaller scales are included in our application. Simulation results of the ecological module were successfully compared to simulation results of the optimisation model for a time series of 30 years. We revealed that sustainable management of semi-arid and arid rangelands relies strongly on rangeland managers' understanding of ecological processes. Furthermore, our simulation results demonstrate that the projected lower annual rainfall due to climate change adds an additional layer of risk to these ecosystems that are already prone to land degradation.
Plant population modelling has been around since the 1970s, providing a valuable approach to understanding plant ecology from a mechanistic standpoint. It is surprising then that this area of research has not grown in prominence with respect to other approaches employed in modelling plant systems. In this review, we provide an analysis of the development and role of modelling in the field of plant population biology through an exploration of where it has been, where it is now and, in our opinion, where it should be headed. We focus, in particular, on the role plant population modelling could play in ecological forecasting, an urgent need given current rates of regional and global environmental change. We suggest that a critical element limiting the current application of plant population modelling in environmental research is the trade-off between the necessary resolution and detail required to accurately characterize ecological dynamics pitted against the goal of generality, particularly at broad spatial scales. In addition to suggestions how to overcome the current shortcoming of data on the process-level we discuss two emerging strategies that may offer a way to overcome the described limitation: (1) application of a modern approach to spatial scaling from local processes to broader levels of interaction and (2) plant functional-type modelling. Finally we outline what we believe to be needed in developing these approaches towards a 'science of forecasting'.
Aim This study aims to link demographic traits and post-glacial recolonization processes with genetic traits in Himantoglossum hircinum (L.) Spreng (Orchidaceae), and to test the implications of the central-marginal concept (CMC) in Europe. Location Twenty sites covering the entire European distribution range of this species. Methods We employed amplified fragment length polymorphism (AFLP) markers and performed a plastid microsatellite survey to assess genetic variation in 20 populations of H. hircinum located along central-marginal gradients. We measured demographic traits to assess population fitness along geographical gradients and to test for correlations between demographic traits and genetic diversity. We used genetic diversity indices and analyses of molecular variance (AMOVA) to test hypotheses of reduced genetic diversity and increased genetic differentiation and isolation from central to peripheral sites. We used Bayesian simulations to analyse genetic relationships among populations. Results Genetic diversity decreased significantly with increasing latitudinal and longitudinal distance from the distribution centre when excluding outlying populations. The AMOVA revealed significant genetic differentiation among populations (F-ST = 0.146) and an increase in genetic differentiation from the centre of the geographical range to the margins (except for the Atlantic group). Population fitness, expressed as the ratio N-R/N, decreased significantly with increasing latitudinal distance from the distribution centre. Flower production was lower in most eastern peripheral sites. The geographical distribution of microsatellite haplotypes suggests post-glacial range expansion along three major migratory pathways, as also supported by individual membership fractions in six ancestral genetic clusters (C1-C6). No correlations between genetic diversity (e.g. diversity indices, haplotype frequency) and population demographic traits were detected. Main conclusions Reduced genetic diversity and haplotype frequency in H. hircinum at marginal sites reflect historical range expansions. Spatial variation in demographic traits could not explain genetic diversity patterns. For those sites that did not fit into the CMC, the genetic pattern is probably masked by other factors directly affecting either demography or population genetic structure. These include post-glacial recolonization patterns and changes in habitat suitability due to climate change at the northern periphery. Our findings emphasize the importance of distinguishing historical effects from those caused by geographical variation in population demography of species when studying evolutionary and ecological processes at the range margins under global change.
The hypothesis that females of socially monogamous species obtain indirect benefits (good or compatible genes) from extra-pair mating behaviour has received enormous attention but much less generally accepted support. Here we ask whether selection for adult survival and fecundity or sexual selection contribute to indirect selection of the extra- pair mating behaviour in socially monogamous coal tits (Periparus ater). We tracked locally recruited individuals with known paternity status through their lives predicting that the extra-pair offspring (EPO) would outperform the within- pair offspring (WPO). No differences between the WPO and EPO recruits were detected in lifespan or age of first reproduction. However, the male WPO had a higher lifetime number of broods and higher lifetime number of social offspring compared with male EPO recruits, while no such differences were evident for female recruits. Male EPO recruits did not compensate for their lower social reproductive success by higher fertilization success within their social pair bonds. Thus, our results do not support the idea that enhanced adult survival, fecundity or within-pair fertilization success are manifestations of the genetic benefits of extra-pair matings. But we emphasize that a crucial fitness component, the extra-pair fertilization success of male recruits, has yet to be taken into account to fully appreciate the fitness consequences of extra-pair matings.
Shrub encroachment linked to heavy grazing has dramatically changed savanna landscapes, and is a major form of rangeland degradation. Our understanding of how shrub encroachment affects arthropod communities is poor, however. Here, we investigate the effects of shrub encroachment on abundance and diversity of ground-dwelling (wingless) arthropods at varying levels of shrub cover in the southern Kalahari. We also ascertain if invertebrate assemblage composition changes with habitat structure and identify which aspects of habitat structure (e.g., grass cover, herbaceous plant cover, shrub density) correlate most strongly with these changes. Ant, scorpion and dung beetle abundance increased with shrub cover, whereas grasshoppers and solifuges declined. Spider and beetle abundance exhibited hump-shaped relationships with shrub cover. RTU richness within orders either mirrored abundances, or exhibited no trend. Shrub density was the habitat component most correlated with similarities between invertebrate assemblages. Ground-dwelling arthropods showed clear shifts in species assemblage composition at a similarity level of 65% according to shrub density. Changes in indicator species showed that within the Tenebrionidae (darkling beetles), certain species respond positively to shrub thickening, replacing other species within the Family. Small-bodied, wingless Scarabaeidae (dung beetles) tended to increase with increased shrub density and three species emerged as significant indicators of more thickened habitats, although this might be a response to greater dung availability, rather than habitat structure itself. We conclude that because ground- dwelling invertebrates showed such clear responses in species assemblage composition, they present excellent candidates for use as indicator species in further studies into bush encroachment.
Scaling up ecohydrological processes : role of surface water flow in water-limited landscapes
(2009)
In this study, we present a stochastic landscape modeling approach that has the power to transfer and integrate existing information on vegetation dynamics and hydrological processes from the small scale to the landscape scale. To include microscale processes like ecohydrological feedback mechanisms and spatial exchange like surface water flow, we derive transition probabilities from a fine-scale simulation model. We applied two versions of the landscape model, one that includes and one that disregards spatial exchange of water to the situation of a sustainably used research farm and communally used and degraded rangeland in semiarid Namibia. Our simulation experiments show that including spatial exchange of overland flow among vegetation patches into our model is a precondition to reproduce vegetation dynamics, composition, and productivity, as well as hydrological processes at the landscape scale. In the model version that includes spatial exchange of water, biomass production at light grazing intensities increases 2.24-fold compared to the model without overland flow. In contrast, overgrazing destabilizes positive feedbacks through vegetation and hydrology and decreases the number of hydrological sinks in the model with overland flow. The buffer capacity of these hydrological sinks disappears and runoff increases. Here, both models predicted runoff losses from the system and artificial droughts occurring even in years with good precipitation. Overall, our study reveals that a thorough understanding of overland flow is an important precondition for improving the management of semiarid and arid rangelands with distinct topography.
The interaction between ecological and hydrological processes is particularly important in arid and semi-arid regions. Often the interaction between these processes is not completely understood and they are studied separately. We developed a grid-based computer model simulating the dynamics of the four most common vegetation types (perennial grass, annuals, dwarf shrubs and shrubs) and related hydrological processes in the region studied. Eco-hydrological interactions gain importance in rangelands with increasing slope, where vegetation cover obstructs run-off and decreases evaporation from the soil. Overgrazing can influence these positive feedback mechanisms. In this study, we first show that model predictions of cover and productivity of the vegetation types are realistic by comparing them with estimates obtained from field surveys. Then, we apply a realistic range in slope angle combined with two land use regimes (light versus heavy grazing intensity). Our simulation results reveal that hydrological processes and associated productivity are strongly affected by slope, whereas the magnitude of this impact depends on overgrazing. Under low stocking rates, undisturbed vegetation is maintained and run-off and evaporation remain low on flat plains and gentle slope. On steep slopes, run-off and evaporation become larger, while water retention potential decreases, which leads to reduced productivity. Overgrazing, however, reduces vegetation cover and biomass production and the landscape"s ability to conserve water decreases even on flat plains and gentle slopes. Generally, the abundance of perennial grasses and shrubs decreases with increasing slope and grazing. Dominance is shifted towards shrubs and annuals. As a management recommendation we suggest that different vegetation growth forms should not only be regarded as forage producers but also as regulators of ecosystem functioning. Particularly on sloping range lands, a high percentage of cover by perennial vegetation insures that water is retained in the system.
SDM performance varied for different range dynamics. Prediction accuracies decreased when abrupt range shifts occurred as species were outpaced by the rate of climate change, and increased again when a new equilibrium situation was realised. When ranges contracted, prediction accuracies increased as the absences were predicted well. Far- dispersing species were faster in tracking climate change, and were predicted more accurately by SDMs than short- dispersing species. BRTs mostly outperformed GLMs. The presence of a predator, and the inclusion of its incidence as an environmental predictor, made BRTs and GLMs perform similarly. Results are discussed in light of other studies dealing with effects of ecological traits and processes on SDM performance. Perspectives are given on further advancements of SDMs and for possible interfaces with more mechanistic approaches in order to improve predictions under environmental change.
Seasonal differences in spatial distribution of small carnivores in fragmented savannah landscapes
(2008)
Assessing the risk of gene flow from genetically modified trees carrying mitigation transgenes
(2008)
Wiederfund von Najas marina L. ssp. marina im Schollener See (Elbe-Havel-Winkel, Sachsen-Anhalt)
(2008)
Oidium pedaliacearum sp. nov. (; O. sesami, nom. inval.) and Podosphaera macrospora comb. et stat. nov. (; Sphaerotheca alpina f. macrospora) are introduced, and the taxonomy and distribution of Erysiphe celosiae is discussed. New host species and new collections of Erysiphe cruciferarum (on Cleome hassleriana), E. flexuosa (on Aesculus hippocastanum), E. hedwigii (on Viburnum carlesii), E. heraclei (on Tinguarra montana), E. cf. macleayae (on Macleaya cordata), E. prunastri (on Prunus cerasifera), E. sedi (on Sedum aff. spectabilis), E. trifolii (on Trigonella caerulea), Golovinomyces cichoracearum (on Argyranthemum pinnatifidum subsp. succulentum), G. cf. hydrophyllacearum (on Nemophila menziesii), G. orontii (on Nolana spp.), G. cf. orontii (on Tiarella cordifolia), Neoerysiphe cumminsiana (on Bidens cf. ferulifolia), Oidium clitoriae (on Clitoria ternatea), O. cf. hortensiae (on Philadelphus coronarius), O. pedilanthi (on Pedilanthus tithymaloides), Oidium (Pseudoidium) sp. (on Utricularia alpina), Podosphaera sp. (on Bergia capensis), Sawadaea bicornis (on Acer platanoides) and S. tulasnei (on Acer ginnala and A. tatarica) are recorded from France, Germany, Greece and Mexico.
The occurrence of two individuals of Zu cristatus at 2 m depth in coastal waters of the Gulf of Castellamare (Tyrrhenian Sea, Italy) together with records of this rare pan-Oceanic mesopelagic species is reported. Analyses of two mitochondrial genes (12 s and 16 s; 936 bp) revealed a 2.6% sequence divergence between Mediterranean and Pacific (Japanese) samples of the species.
In einer Wochenstubengesellschaft der Rauhhautfledermaus (Pipistrellus nathusii), in der Schorfheide im Norden Brandenburgs, wurde ein starkes Vorkommen der Roten Waldameise (Formica rufa) festgestellt. Die Fledermäuse waren offensichtlich durch die Anwesenheit der Ameisen nicht beunruhigt. Der ungewöhnlich enge Kontakt zwischen Ameisen und Fledermäusen führte zur Überlegung, dass es regelmässige Interaktionen zwischen Ameisen und Fledermäusen geben könnte, die beiden Seiten Vorteile bieten. Vergleichbare Beziehungen wurden bisher hauptsächlich bei Vögeln als anting beschrieben. Interaktionen zum gegenseitigen Vorteil sind zwischen Fledermäusen und Ameisen bisher kaum beachtet worden, so dass weitere Untersuchungen notwendig sind.
Dry lands are exposed to a highly variable environment and face a high risk of degradation. The effects of climate change are likely to increase this risk; thus a profound knowledge of the system dynamics is crucial for evaluating management options. This applies particularly for the interactions between water and vegetation, which exhibit strong feedbacks. To evaluate these feedbacks and the effects of climate change on soil moisture dynamics, we developed a generic, process-based, spatially explicit soil moisture model of two soil layers, which can be coupled with vegetation models. A time scale relevant for ecological processes can be simulated without difficulty, and the model avoids complex parameterization with data that are unavailable for most regions of the world. We applied the model to four sites in Israel along a precipitation and soil type gradient and assessed the effects of climate change by comparing possible climatic changes with present climate conditions. The results show that in addition to temperature, the total amount of precipitation and its intra-annual variability are an important driver of soil moisture patterns. This indicates that particularly with regard to climate change, the approach of many ecological models that simulate water dynamics on an annual base is far too simple to make reliable predictions. Thus, the introduced model can serve as a valuable tool to improve present ecological models of dry lands because of its focus on the applicability and transferability.
Recent progress in modelling individual growth has been achieved by combining the principal component analysis and the maximum likelihood principle. This combination models growth even in incomplete sets of data and in data obtained at irregular intervals. We re-analysed late 18th century longitudinal growth of German boys from the boarding school Carlsschule in Stuttgart. The boys aged 6-23 years, were measured at irregular 3-12 monthly intervals during the period 1771-1793. At the age of 18 years, mean height was 1652 mm, but height variation was large. The shortest boy reached 1474 mm, the tallest 1826 mm. Measured height closely paralleled modelled height, with mean difference of 4 mm, SD 7 mm. Seasonal height variation was found. Low growth rates occurred in spring and high growth rates in summer and autumn. The present study demonstrates that combining the principal component analysis and the maximum likelihood principle enables growth modelling in historic height data also.
The new species Erysiphe asclepiadis is described, illustrated and discussed. A new Chinese collection of Erysiphe robiniicola has recently been found that can be used to elucidate and discuss the confused taxonomy and nomenclature of this species and other taxa of Erysiphe s. lat. on Robinia spp. Based on a re-examination of type material in connection with the data given in the protologue, it can be shown that Capnodium lygodesmiae must be reduced to synonymy with Ampelomyces quisqualis. The confusion surrounding the name C. lygodesmiae, caused by the occurrence of the hyperparasite A. quisqualis on a powdery mildew fungus with abundant chasmothecia, is discussed in detail. The new combination, Golovinomyces caulicola (; Spolverinia caulicola), is proposed for the powdery mildew that serves as host of C. lygodesmiae.
The conidial stage and chasmothecia of Golovinomyces orontii have been found in Germany on cultivated Limnanthes douglasii. A powdery mildew anamorph found in the Netherlands on Malva alcea agrees morphologically with the Oidium of the latter species as well. Golovinomyces sp. (anamorph) on Parthenium integrifolium is described and discussed. Erysiphe sp. has been found in Germany on Acer opalus, and E. magnifica is recorded from Germany and Switzerland on Magnolia spp. Oidium passiflorae is new to Switzerland. An Oidium morphologically agreeing with the anamorph of Podosphaera aphanis has recently been collected on Exacum macranthum cultivated in a greenhouse, and conidiophores and conidia of a species of Podosphaera sect. Sphaerotheca subsect. Magnicellulatae (P. fusca complex) on Phlox paniculata and Polemonium caeruleum have been found in Germany.
The introduction of a new powdery mildew disease on Rhus hirta in various parts of Germany (Brandenburg, Rhine- Westphalia, Sachsen-Anhalt and Saxony) is reported. The anamorph found on this host agrees well with the North American Podosphaera pruinosa. Although the teleomorph has not yet been found in Germany and a molecular study has not yet been possible due to the lack of fresh North American material for a comparison, there is little doubt that the European outbreak of the Rhus powdery mildew disease may be referred to as Podosphaera pruinosa. Morphology, taxonomy and distribution of Podosphaera species on Rhus and other hosts of the Anacardiaceae are discussed in detail.
Monitoring animal populations in changing environments is crucial to wildlife conservation and management, but restrictions in resources are a recurring problem for wildlife managers and researchers throughout Africa. Land-use- induced shrub encroachment in Kalahari savannah rangelands has led to fragmentation of the landscape. Mammalian carnivores are particularly vulnerable to local extinction in fragmented landscapes, but their low numbers and their often nocturnal and secretive habits make them difficult to monitor. In this study, we tested the applicability of a passive tracking method and compared two measurement methods and index calculations for monitoring small carnivores across a grazing gradient in the southern Kalahari. During the four years of monitoring in a five-year period, we used the knowledge of indigenous Khoisan Bushmen for the identification of carnivore tracks on 640 sand transects (5 m x 250 m). Our results showed that this simple and inexpensive observation method enabled detailed monitoring of 10 small carnivore species across the grazing gradient. A binary index calculated an index based on presence/absence of a species' tracks on each transect, whereas the track intrusion index used the number of track intrusions to each transect for each species in its calculations. For less common species, the two indices were similar in trend and magnitude, because the number of intrusions to each transect was typically 1 or 0. Usually, the two indices showed relatively strong correlations. However, species with patchy distributions of higher numbers presented difficulties for the binary index to monitor trends, but not for the track intrusion index.
The list contains all the identified fungi collections of the excursion in 1998. In it were also included some records published by OTTO (2001) and few unpublished data of fungi mainly collected by V. Otte after 1998. Unless other information is given, all the fungal collections and their determination were done by the author. Most of the collections are integrated as exsiccata in the herbarium of the author.
Some aspects of the fungal flora in the Bol'Üoj Tha; area (NW-Caucasus) - During an excursion to the Bol'soj Tha; area in north-western Caucasus in the late summer of 1998 a number of mycological observations were made. 111 macrofungi species (30 ascomycetes, 81 basidiomycetes), 16 myxomycetes and 42 phytoparasitic fungi (15 Erysiphales, 27 Uredinales) were registered. The majority of the recorded macromycetes were decomposers of dead stems and logs of different trees and shrubs, especially of the dominating tree species Fagus orientalis and Abies nordmanniana. Bondarzewia montana, Hericium alpestre and Phellinus hartigii are typical colonisers of old Abies trunks and therefore of special interest. They were recorded several times, especially in the primeval forests of the excursion area. Some of the collected taxa like Daldinia petriniae, Hypoxylon cercidicola, H. liviae, Ophiostoma polyporicola, Pezoloma marchantiae, Ramsbottomia macracantha, Symphyosyria angelicae, Auriporia aurulenta, Flagelloscypha pilatii, Hymenochaete carpatica, Marasmius cf. rhododendrorum and Pellidiscus pallidus are discussed in detail. Some of the recorded taxa are probably new for the western Caucasus and in some cases also for Russia.
Analysis of phosphorylation dynamics under nitrogen limitation and nitrate or ammonium resupply
(2009)
The influence of coating polystyrene tissue culture plates with different proteins on murine hybridoma cell growth and antibody production was investigated. Fibronectin, collagen I, bovine serum albumin and laminin were used to coat NUNC and COSTAR cell culture plates. Cell number and antibody concentration in culture fluids were quantified as indicators for cell viability, proliferation and productivity. Adhesive behaviour, morphology, expression of surface receptors of hybridoma cells and the presence of tyrosine-phosphorylated proteins in cell lysates were characterized by cell adhesion experiments, microscopy, flow cytometry and Western Blot analysis. It was shown that coatings with fibronectin (0.2 ;g/ml) lead to a substantial improvement of cell growth by 50-70% and an increase of monoclonal antibody production by 100-120%. Collagen I coatings showed an improvement in cell growth by 30-70% and by 60% for the production of monoclonal antibodies. Coatings with BSA and laminin had minor effects on these parameters. It was found that the hybridoma cell lines used in this study did not express the ;2-chain of the ;2;1-integrin, which is responsible for binding to collagen and laminin. However, the presence of ;1- integrin on the cell surface was shown, which should enable hybridoma cells to bind fibronectin. We propose, therefore, that fibronectin adsorption to cell culture materials may be a promising approach to enhance the production of monoclonal antibodies by cultivated hybridoma cells.