Resource dependence in a new ecosystem: A host plant and its colonizing community

Pesticide resistance in arthropods: Ecology matters too

Pesticide resistance development is an example of rapid contemporary evolution that poses immense challenges for agriculture. It typically evolves due to the strong directional selection that pesticide treatments exert on herbivorous arthropods. However, recent research suggests that some species are more prone to evolve pesticide resistance than others due to their evolutionary history and standing genetic variation. Generalist species might develop pesticide resistance especially rapidly due to pre‐adaptation to handle a wide array of plant allelochemicals. Moreover, research has shown that adaptation to novel host plants could lead to increased pesticide resistance. Exploring such cross‐resistance between host plant range evolution and pesticide resistance development from an ecological perspective is needed to understand its causes and consequences better. Much research has, however, been devoted to the molecular mechanisms underlying pesticide resistance while both the ecological contexts that could facilitate resistance evolution and the ecological consequences of cross‐resistance have been under‐studied. Here, we take an eco‐evolutionary approach and discuss circumstances that may facilitate cross‐resistance in arthropods and the consequences cross‐resistance may have for plant–arthropod interactions in both target and non‐target species and species interactions. Furthermore, we suggest future research avenues and practical implications of an increased ecological understanding of pesticide resistance evolution.

Disturbance induced dynamics of a tritrophic novel ecosystem

Novel ecosystems formed by invasive plants provide a good opportunity to get insight into early dynamics and pattern formation of these ecosystems. The invasive black locust as host plant, Bruchophagus robiniae as host-specific seed predator and its parasitoids were the components of the studied tritrophic system. To investigate disturbance-driven dynamics of this system we created seed-vacated host plant patches in a field experiment. We removed all pods from selected patches of black locust resulting in an induced local extinction of seed predators and their parasitoids. We hypothesized that disturbance enhances top-down control by parasitoids; this enhanced top-down control decreases seed predation, facilitating the host plant's spread. We found that disturbance modified only parasitism after controlling with year effect: in vacated patches median parasitism was higher than in control patches. Seed predation exceeded its initial level in vacated patches in the third year after the disturbance, but in the fourth year it dropped again presumably due to the strong top-down control. Our findings also suggested that the seed predator was also affected by the bottom-up control of its host plant's density. We found that in the studied new ecosystem the top-down control was strengthened by the disturbance. Since the host plant of the tritrophic system is an invasive species, partial habitat disturbance of such species may increase the severity of parasitoid top-down control, which may reduce seed predation by the herbivores.