Scale-specific spatial density-dependence in parasitoids: a multi-factor meta-analysis

1. Within a landscape, the risk of an insect being attacked by a parasitoid varies with the local density of the host species. This relationship should be strongest when observed at medium extents and resolutions with respect to the parasitoids’ foraging range, and turn negative at fine resolutions. The relationship is also hypothesised to depend on certain traits of the host and parasitoid taxa – e.g. being more positive for more specialised hosts or parasitoids and more negative for mobile hosts or gregarious parasitoids. Building on earlier literature reviews, it is now possible to investigate these hypotheses using meta-analysis. 2. We performed a multi-factor meta-analysis on 151 analyses of parasitism rates with respect to host densities at specified scales, from 61 empirical studies published from 1988 to 2012. We explored how the correlation between host density and parasitism rate may be related to the explanatory variables already mentioned, plus parasitoid body-size and various other characteristics of both hosts and parasitoids. 3. Correlations (Pearson’s r) between host density and parasitism rate ranged from –0.88 to 0.98 (mean 0.16, standard deviation 0.39). The correlation was more often negative where the host was exotic or in the orders Lepidoptera or Diptera, where the parasitoid was larger or exotic, or where the study was conducted at a finer grain-size. Hymenoptera and Homoptera were the most likely host orders to reveal positive associations, with Coleoptera and Diptera intermediate. 4. The fact that increased observational grain-size had similar effects to decreased parasitoid body length could be taken as evidence that parasitoids’ foraging ranges increase with their body-length. However, the hypothesis about scale-specific foraging was not supported by studies that compared multiple scales. 5. We conclude that parasitism most commonly produces positive (compensatory) spatial density-dependence, but ecological context is all-important. These findings should help improve the design and interpretation of field experiments on parasitism as well as their application to the modelling of population dynamics and the practice of biological control

Secure Mobile Support of Independent Sales Agencies

Sales agents depend on mobile support systems for their daily work. Independent sales agencies, however, are not able to facilitate this kind of mobile support on their own due to their small size and lack of the necessary funds. Since their processes correlate with confidential information and include the initiation and alteration of legally binding transactions they have a high need for security. In this contribution we first propose an IT-artifact consisting of a service platform that supports multi-vendor sales processes based on previous work. We then analyze use cases of sales representatives of independent sales agencies using this system and derive their security requirements. We then propose a security extension to the IT-artifact and evaluate this extension by comparing it to existing solutions. Our results show that the proposed artifact extension provides a more convenient and secure solution than already existing approaches

Sensitivity analysis of reactive ecological dynamics

Author Posting. © Springer, 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Bulletin of Mathematical Biology 70 (2008): 1634-1659, doi:10.1007/s11538-008-9312-7.Ecological systems with asymptotically stable equilibria may exhibit significant transient dynamics following perturbations. In some cases, these transient dynamics include the possibility of excursions away from the equilibrium before the eventual return; systems that exhibit such amplification of perturbations are called reactive. Reactivity is a common property of ecological systems, and the amplification can be large and long-lasting. The transient response of a reactive ecosystem depends on the parameters of the underlying model. To investigate this dependence, we develop sensitivity analyses for indices of transient dynamics (reactivity, the amplification envelope, and the optimal perturbation) in both continuous- and discrete-time models written in matrix form. The sensitivity calculations require expressions, some of them new, for the derivatives of equilibria, eigenvalues, singular values, and singular vectors, obtained using matrix calculus. Sensitivity analysis provides a quantitative framework for investigating the mechanisms leading to transient growth. We apply the methodology to a predator-prey model and a size-structured food web model. The results suggest predator-driven and prey-driven mechanisms for transient amplification resulting from multispecies interactions.Financial support provided by NSF grant DEB-0343820, NOAA grant NA03-NMF4720491, the Ocean Life Institute of the Woods Hole Oceanographic Institution, and the Academic Programs Office of the MIT-WHOI Joint Program in Oceanography

Professionalism, Golf Coaching and a Master of Science Degree: A commentary

As a point of reference I congratulate Simon Jenkins on tackling the issue of professionalism in coaching. As he points out coaching is not a profession, but this does not mean that coaching would not benefit from going through a professionalization process. As things stand I find that the stimulus article unpacks some critically important issues of professionalism, broadly within the context of golf coaching. However, I am not sure enough is made of understanding what professional (golf) coaching actually is nor how the development of a professional golf coach can be facilitated by a Master of Science Degree (M.Sc.). I will focus my commentary on these two issues

Notas sobre moscas necrófagas (Diptera: Caliptratae) associadas a carcaças de peixe na Amazônia Colombiana

In recent years, there has been an increasing number of studies on carrion fly communities due to their medical importance and as a consequence of the large number of studies on forensic entomology. Surprisingly few studies have adressed with the asynantropic flies of the Amazon, and none were done in Colombia. A faunistic study of asynantropic flies of the families Calliphoridae, Sarcophagidae, Muscidae and Fannidae in three different landscapes of the Colombian Amazon is presented, trapping effectiveness is assessed, and the first record of Mesembrinella batesi (Aldrich, 1922) and Fannia femoralis (Stein, 1897) from Colombia is reported.Apesar de existir uma quantidade considerável de estudos sobre dípteros decompositores devido a sua importância medica e ao avanço da entomologia forense, poucos dizem respeito as moscas asinantrópicas na Amazônia e nada foi feito na Colômbia. No presente trabalho é feito um estudo faunístico sobre moscas, principalmente das famílias Calliphoridae, Sarcophagidae, Muscidae e Fanniidae em três diferentes paisagens da Amazônia Colombiana, além do primeiro registro das espécies Mesembrinella batesi (Aldrich, 1922) e Fannia femoralis (Stein, 1897) para Colômbia e avaliação da amostragem utilizada

Interactions between conventional and organic farming for biocontrol services across the landscape

While the area of organic crop production increases at a global scale, the potential interactions between pest management in organic and conventionally managed systems have so far received little attention. Here, we evaluate the landscape-level co-dependence of insecticide-based and natural enemy-based pest management using a simulation model for parasitoid–host interactions in landscapes consisting of conventionally and organically managed fields. In our simulations conventional management consists of broad-spectrum or selective insecticide application, while organic management involves no insecticides. Simulations indicate that insecticide use can easily result in lose–lose scenarios whereby both organically and conventionally managed fields suffer from increased pest loads as compared to a scenario where no insecticides are used, but that under some conditions insecticide use can be compatible with biocontrol. Simulations also suggest that the pathway to achieve the insecticide reduction without triggering additional pest pressure is not straightforward, because increasing the proportion of organically managed fields or reducing the spray frequency in conventional fields can potentially give rise to dramatic increases in pest load. The disruptive effect of insecticide use, however, can be mitigated by spatially clustering organic fields and using selective insecticides, although the effectiveness of this mitigation depends on the behavioral traits of the biocontrol agents. Poorly dispersing parasitoids and parasitoids with high attack rates required a lower amount of organically managed fields for effective pest suppression. Our findings show that the transition from a landscape dominated by conventionally managed crops to organic management has potential pitfalls; intermediate levels of organic management may lead to higher pest burdens than either low or high adoption of organic management