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Biomedical subjects

Frank van den Bosch

Publications and source records attributed to Frank van den Bosch.

5 recordsLinked to original sources
PubMed2006

Coexistence of related pathogen species on arable crops in space and time.

This review considers factors affecting the coexistence of closely related pathogen species on arable crops, with particular reference to data available at Rothamsted for Septoria tritici/Stagonospora nodorum (Mycosphaerella graminicola/Phaeosphaeria nodorum) (septoria leaf blotch diseases on winter wheat), Oculimacula yallundae/O. acuformis (eyespot disease of winter cereals), and Leptosphaeria maculans/L. biglobosa (phoma stem canker on winter oilseed rape). Factors affecting the short-term, medium-term, and long-term coexistence of such related pathogen species are reviewed, and their evolution from common ancestors considered. Small niche differences between the related pathogen species enable them to coexist on the same host. The niche differences result from small differences in their biology/epidemiology, leading to separation in space, time, or resource use. Changes in both natural (e.g., fluctuating temperature) and man-made (e.g., agronomic practices, pollution) factors influence the coexistence. Such factors may result in coexistence between the related species in some parts of the world, whereas in other parts only one species occurs. These principles illustrated with pathogens of arable crops are generic to other host-pathogen systems.

Biological Evolution↗
PubMed2006

Transient population dynamics in periodic matrix models: methodology and effects of cyclic permutations.

Many biological populations are subject to periodically changing environments such as years with or without fire, or rotation of crop types. The dynamics and management options for such populations are frequently investigated using periodic matrix models. However the analysis is usually limited to long-term results (asymptotic population growth rate and its sensitivity to perturbations of vital rates). In non-periodic matrix models it has been shown that long-term results may be misleading as populations are rarely in their stable structure. We therefore develop methods to analyze transient dynamics of periodic matrix models. In particular, we show how to calculate the effects of perturbations on population size within and at the end of environmental cycles. Using a model of a weed population subject to a crop rotation, we show that different cyclic permutations produce different patterns of sensitivity of population size and different population sizes. By examining how the starting environment interacts with the initial conditions, we explain how different patterns arise. Such understanding is critical to developing effective management and monitoring strategies for populations subject to periodically recurring environments.

Daucus carota↗
PubMed2005

Adaptation to the cost of resistance: a model of compensation, recombination, and selection in a haploid organism.

Populations of pathogenic organisms often evolve resistance in response to the use of pesticides or antibiotics. This rise of resistance may be followed by a fall when chemical control is suspended and resistance alleles carry a fitness cost. Another possibility is that mutations at secondary loci compensate for the cost, usually without loss of resistance. This enables resistant types to withstand invasion by the susceptible wild-type; resistance then persists in the population, which reduces the efficacy of future pesticide or antibiotic use. We examined a two-locus model of a haploid organism that adapts to the cost of resistance by a single compensatory mutation. We addressed the question how different combinations of cost and compensation and different levels of recombination affect the consequences of a single pesticide application. Resistance will become fixed in the population when the fraction of the population exposed to pesticide exceeds the cost of resistance. Compensatory mutations reduce the cost of resistance and therefore this threshold level of pesticide use. In the absence of pesticide, recombination promotes stability of equilibria. In the presence of pesticide, recombination accelerates the fixation of resistance and compensating alleles; recombination may also enable the persistence of compensated resistant types after pesticide use.

Adaptation, Biological↗
PubMed2004

Double-Jump migration and diffusive instability.

In order to look into the stability consequences of a particular migration process in which individuals choose to settle, we formulated a continuous-time multi-species multi-patch model in which individuals migrate by one or two instantaneous jumps while making the second jump with a certain probability that possibly depends on the conditions at the end point of the first jump. It turned out that a second jump has some quantitative effects on diffusive instability even when it occurs in the absence of density-dependent mechanisms. When a second jump happens as a natural interspecific response of individuals, and such a response is sufficiently strong, it has crucial effects on diffusive instability: it leads to diffusive instability in the case of competitive interactions, whereas it annihilates diffusive instability in the case of prey-predator interactions. We demonstrated these results in the context of two specific examples.

Animals↗