Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki

Postcopulatory processes can influence male reproductive success in several animal species. Females can use different mechanisms to bias male paternity after copulation. One of such mechanisms consists in expelling all or part of the ejaculate after copulation. Euxesta bilimeki is an Ulidiid fly whose females not only frequently expel ejaculates after mating but also consume the ejaculate after expulsion. In order to understand the significance of these behaviors we examined video recordings of courtship, copulatory, and postcopulatory behaviours. The presence of sperm in female storage organs was confirmed after mating with males of different sizes and was correlated with duration of courtship, copulation, and the period from the end of copulation to ejaculate expulsion. The effect of ejaculate consumption on female fitness (fecundity and longevity) was compared among females held under different dietary treatments: a rich diet consisting of protein, sugar and water, an intermediate diet composed of sugar and water, a poor diet of only water and females that were completely deprived of food and water. All of the observed females expelled ejaculates after mating. The probability of storing sperm in the two spermathecae and the ventral receptacle was correlated with interactions between the duration of all behaviours examined and male size. Except for starved females, who lived longer when allowed to consume ejaculates, ejaculate consumption had no effect on fitness. Results suggest that females can bias sperm storage according to male mating effort, while the consumed ejaculate had some nutritional value only evident when females were completely starved.     

Trinkwasserschutzgebiete

Conflict are frequently observed when drinking water protection areas are to be defined and when many variants of how to protect these area are to be found. Using ten potential scenarios, a method is presented here which shows how such conflicts concerning these variants may be handled in a systematic manner. The technique is derived from the use of partially ordered sets and their visualization by Hasse diagrams. The first step is to define rankings of different variants according to each aim of protection. A further step is to define an appropriate relationship of order. It is then possible to visualize the extent of consensus and of dissension through the use of a Hasse diagram. The final step is to quantify the importance of each protection aim and the initialization of an iteration. Should a complete consensus be found, this would result in a chain of (connected) variants. Should a complete dissension be found on the other hand, an antichain would then result (i.e. where all variants are isolated).     

Production and fate of copepod fecal pellets across the Southern Indian Ocean

The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore, the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 μg C m⁻³ day⁻¹. At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical export of fecal pellets was low (<0.02 mg m⁻² day⁻¹).     

Models of fish school size in relation to environmental productivity

A simple energy-balance model, relating energetic requirements of fish schools to food production, was used to predict shoal sizes. Lower limits to school size are unlikely to be set by food but rather by predation. Upper limits depend on both food and school behavior, being greater for schools that break up to feed than for schools that remain continuously cohesive. Faced with a decreasing food supply, a school could either break into smaller schools or change behavior, increasing the area available for foraging. The models suggest that environmental productivity needs to be considered when examining fishery statistics such as (catch per unit effort), where maximum catch may be limited by maximum school size.     

Ozon in Waldökosystemen aus atmosphärenchemischer und pflanzenphysiologischer Sicht

The trend of rising ozone concentrations in forest ecosystems and the phytotoxicity of ozone demand a realistic risk assessment according to an internationally accepted and flux-based quality standard. Ozone fluxes within the canopy are influenced by chemical gas-phase reactions with nitrogen oxide and biogenic hydrocarbons and by surface deposition processes. Therefore, a differentiation of the ozone flux within the canopy is needed between stomatal uptake and other transport pathways. The Eddy Covariance technique is the method of choice for the determination of trace gas fluxes relevant for ozone chemistry. This method is also used for stomatal conductance measurements based on evapotranspiration fluxes and for emission measurements of biogenic hydrocarbons by PTR-MS. Although considerably research efforts were directed to canopy measurements in recent years, the underlying processes are not fully understood yet. Thus, major differences occur in the ratios of stomatal ozone uptake, non-stomatal deposition and gas-phase chemistry between different studies. Furthermore, the vertical concentration gradients within the canopy measured at several forest sites are rather inconsistent and the existing deposition models do rarely account for chemical transformation and detoxification processes. Only a simultaneous measurement of all photochemically relevant trace gases, plant physiological parameters at different sites and forest species over entire vegetation periods, and model parameterization according to the measurement results from the experimental sites will contribute to the clarification of the canopy processes and will ensure realistic risk assessments.     

Determining patterns of variability in ecological communities: time lag analysis revisited

All ecological communities experience change over time. One method to quantify temporal variation in the patterns of relative abundance of communities is time lag analysis (TLA). It uses a distance-based approach to study temporal community dynamics by regressing community dissimilarity over increasing time lags (one-unit lags, two-unit lags, three-unit lags). Here, we suggest some modifications to the method and revaluate its potential for detecting patterns of community change. We apply Hellinger distance based TLA to artificial data simulating communities with different levels of directional and stochastic dynamics and analyse their effects on the slope and its statistical significance. We conclude that statistical significance of the TLA slope (obtained by a Monte Carlo permutation procedure) is a valid criterion to discriminate between (i) communities with directional change in species composition, regardless whether it is caused by directional abundance change of the species or by stochastic change according to a Markov process, and (ii) communities that are composed of species with population sizes oscillating around a constant mean or communities whose species abundances are governed by a white noise process. TLA slopes range between 0.02 and 0.25, depending on the proportions of species with different dynamics; higher proportions of species with constant means imply shallower slopes; and higher proportions of species with stochastic dynamics or directional change imply steeper slopes. These values are broadly in line with TLA slopes from real world data. Caution must be exercised when TLA is used for the comparison of community time series with different lengths since the slope depends on time series length and tends to decrease non-linearly with it.