Emergence of global behaviour in a host–parasitoid model with density-dependent dispersal in a chain of patches

Stability of Rosenzweig-MacArthur models with non-diffusive dispersal on non-regular networks

This paper examines the stability of the Rosenzweig-MacArthur model distributed to identical discrete habitat patches. Migration between patches is assumed to follow the non-diffusive rule that individuals have a fixed rate of leaving their local habitat patch and migrating to another. Under this non-diffusive migration rule, we found that population dispersal on a non-regular and connected habitat network can both stabilize and destabilize the Rosenzweig-MacArthur model. It is also shown that our non-diffusive migration rule apparently becomes diffusive if the habitat network is regular.

Age-structure density-dependent fertility and individuals dispersal in a population model

In this work, we analyze the interplay between general age structured density-dependent fertility functions and age classes dispersal in a patchy environment. As novelties, (i) the fertility function depends on age classes (instead of on the total population size) and (ii) dispersal patterns are also allowed to be different for individuals belonging to different age classes. Our results highlight the interplay between the shape of the age structured density-dependent fertility function and the age classes dispersal patterns. We analyze this interaction from an environmental management point of view by exploring the consequences of connecting patches that can sustain a population (source patch) or cannot (sink patch), as well as its relation to component Allee effects and strong Allee effects. In particular, we have found scenarios such that the metapopulation goes extinct when two isolated source patches are connect due to heterogeneous age classes distribution. On the contrary, there are settings such that heterogeneous age classes distribution enables two isolated sink patches to be sustainable when connected. Besides, we discuss what kind of local interventions are helpful to manage component Allee effect and its impact at the metopopulation level. The source code used to simulations is fully available. The code is presented as a knitr reproducible document in the open source R computing system. Thus, free access and usability of the code are granted.

Plant vigor metrics determine spatio-temporal distribution dynamics of Oulema melanopus (Coleoptera: Chrysomelidae) and its larval parasitoid, Tetrastichus julis (Hymenoptera: Eulophidae)

The cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), is a new invasive insect pest of oat, wheat, and barley in western Canada. Biological control with its principal larval parasitoid, Tetrastichus julis Walker (Hymenoptera: Eulophidae), is the primary management strategy. However, to implement control successfully, a thorough understanding of the spatio-temporal dynamics of the interactions between these two species is important. We examined the nature of spatial associations and distribution dynamics of O. melanopus and T. julis with reference to host plant nutrients and plant vigor traits using Spatial Analysis by Distance Indices. A grid design was used to understand spatial associations between O. melanopus and T. julis. Distributions of O. melanopus and T. julis indicated the presence of significant patches and gaps. Plant nutrient availability and plant vigor varied across the grid in all study years. On a spatial scale, O. melanopus and T. julis represented a tightly coupled system demonstrating the strong density-dependent nature of parasitoid dispersal. Among the factors examined, plant vigor traits significantly influenced field distributions of both O. melanopus and T. julis. Areas across grids with high plant density, greater plant height, and high availability of plant leaves indicated higher establishment of O. melanopus larvae, consequently exhibiting bottom-up effects on T. julis distributions. Maintenance of uniform plant vigor can be a critical aspect in mitigating yield losses from O. melanopus infestation.