Showing papers by "Karin Johst published in 2008"
TL;DR: In this article, the authors show that in cases where payments for habitat heterogeneity exist, the payment scheme may require overcompensation of the land users, posing a limit to both efficiency and fairness considerations.
48 citations
TL;DR: An individual-based simulation model is used to investigate the effects of three resource partitioning schemes, representing different types of competition, on the form of the R-function and results indicate that all resource partitions can give rise to concave or convex functions depending on the balance between maximum individual birth rate, maintenance cost, and demand for resources.
Abstract: Intra-specific competition defines the relationship between population density and the performance of individual organisms (R-function) Observation of this relationship in nature shows it to be frequently nonlinear, and it has been argued, on intuitive grounds, that this nonlinearity is due to the type of competition (scramble or contest) being expressed Here, we use an individual-based simulation model to investigate the effects of three resource partitioning schemes, representing different types of competition, on the form of the R-function Results indicate that all resource partitioning schemes can give rise to concave or convex functions depending on the balance between maximum individual birth rate, maintenance cost, and demand for resources Given high growth rates and maintenance costs, contest competitors tend to exhibit less concavity than scramblers Therefore, population stability can be strongly affected by the strategy of resource partitioning Life histories and environmental conditions that encourage the homogeneous distribution of resources among individuals lead to complex and unstable dynamics Stable dynamics is fostered by heterogeneous resource distribution, which could result from such things as social hierarchies, individual and environmental variability, and large, indivisible resource packets
38 citations
TL;DR: It is suggested that observation of high biodiversity under spatially correlated disturbances points to a competition–colonisation trade-off, which includes dispersal distances, which opens new possibilities for explaining diversity.
Abstract: In this study, we systematically explore the effects of rate and spatial correlation (level of clumping) of disturbance events on a community of sessile species differing in their life history traits. A spatially explicit individual-based model shows that long-term coexistence is very sensitive to spatial correlation when the trade-off in life history traits includes differences in dispersal distances. Highest biodiversity emerges at highly correlated disturbances of intermediate rates. Diversity peaks shift to larger rates when clumping decreases. Scattered disturbances lead to competitive exclusion. Interestingly, we observed additional peaks in the diversity–disturbance curves at certain levels of clumping. Thus, subject to the differences in life history traits, particular combinations of disturbance rate and spatial correlation may enable subsets of species to coexist, which opens new possibilities for explaining diversity. Our results suggest that observation of high biodiversity under spatially correlated disturbances points to a competition–colonisation trade-off, which includes dispersal distances.
32 citations
TL;DR: An ecological-economic modelling procedure has been developed using the example of protecting Large Blue butterflies to design cost-effective and ecologically effective compensation payments for conservation measures and forms the basis for the decision support tool EcoEcoMod.
Abstract: Compensation payments to farmers who apply species-friendly farming activities are a common instrument to reconcile nature conservation with agriculture in Europe. In order to design cost-effective and ecologically effective compensation payments for conservation measures an ecological-economic modelling procedure has been developed using the example of protecting Large Blue butterflies. The modelling procedure forms the basis for the decision support tool EcoEcoMod. By comparing the effects of different mowing regimes on the butterfly populations for a given budget, the user can identify the cost-effective mowing regime and the corresponding compensation payments for that budget.
21 citations
TL;DR: This study combines hatching asynchrony, provisioning behaviour of parents, jostling behaviour of nestlings and feeding conditions as a network of interacting processes of enormous interest to fully understand the parent-offspring conflict.
Abstract: Using an individual-based simulation model we study how different mechanisms of food division among multiple offspring influence nestling number and quality, as well as parental effort. We consider the combination of different scenarios of food availability (feeding conditions), hatching asynchrony and food division. If parents have full control on how to divide food among offspring, asynchronous broods have higher breeding performance than synchronous ones in a wide range of feeding conditions, giving theoretical support to empirically proved benefits of hatching asynchrony. If parents accept the outcome of sibling competition there is a threshold in feeding conditions below which asynchronous broods produced more fledglings and the reverse was true above the threshold. Interestingly, parents relying on the outcome of nestling competition do not necessarily differ in breeding performance from those which have full control over food allocation. Our study combines hatching asynchrony, provisioning behaviour of parents, jostling behaviour of nestlings and feeding conditions as a network of interacting processes of enormous interest to fully understand the parent-offspring conflict.
11 citations
TL;DR: It is concluded that the strength of dispersal is more important for spatial synchrony than its density dependence, and most important is the mode of intraspecific density regulation.
Abstract: Many theoretical studies support the notion that strong dispersal fosters spatial synchrony. Nonetheless, the effect of conditional vs. unconditional dispersal has remained a matter of controversy. We scrutinize recent findings on a desynchronizing effect of negative density-dependent dispersal based on spatially explicit simulation models. Keeping net emigration rates equivalent, we compared density-independent and density-dependent dispersal for different types of intraspecific density regulation, ranging from under-compensation to over-compensation. In general, density-independent dispersal possessed a slightly higher synchronizing potential but this effect was very small and sensitive compared to the influence of the type of local density regulation. Notably, consistent outcomes for the comparison of conditional dispersal strategies strongly relied on the control of equivalent emigration rates. We conclude that the strength of dispersal is more important for spatial synchrony than its density dependen...
11 citations