2023, Fischer, Liliana, Ramesh, Divya, Weidenmüller, Anja

The worldwide decline in pollinating insects is alarming. One of the main anthropogenic drivers is the massive use of pesticides in agriculture. Risk assessment procedures test pesticides for mortality rates of well-fed, parasite free individuals of a few non-target species. Sublethal and synergistic effects of co-occurring stressors are usually not addressed. Here, we present a simple, wildly applicable bio-essay to assess such effects. Using brood thermoregulation in bumblebee microcolonies as readout, we investigate how this collective ability is affected by long-term feeding exposure to the herbicide glyphosate (5 mg/l), the insecticide flupyradifurone (0.4 mg/l) and the combination of both, when co-occurring with the natural stressor of resource limitation. Documenting brood temperature and development in 53 microcolonies we find no significant effect of glyphosate, while flupyradifurone significantly impaired the collective ability to maintain the necessary brood temperatures, resulting in prolonged developmental times and a decrease in colony growth by over 50 %. This reduction in colony growth has the potential to significantly curtail the reproductive chances of colonies in the field. Our findings highlight the potentially devastating consequences of flupyradifurone use in agriculture even at sub-lethal doses and underline the urgent need for improved risk assessment procedures.

2020-01, Razanajatovo, Mialy, Fischer, Liliana, van Kleunen, Mark

Climate change can negatively impact plant–pollinator interactions, and reduce outcross pollination. For reproductive assurance, an increased capacity for autonomous selfing should benefit the persistence of plants under new temperature conditions. Plastic responses of the autonomous selfing capacity to climate change may occur indirectly due to changes in floral traits associated with this capacity. We tested whether the mixed mating plant Mimulus guttatus is capable of plastic changes in floral traits favoring autonomous selfing in response to temperature changes. In seven growth chambers, we grew M. guttatus originating from a large range of latitudes (from 37.89° N to 49.95° N) and thus home temperatures in North America, and experimentally assessed the (autonomous) selfing and outcrossing capacities of the plants. With an increase in the difference between the overall mean daytime and nighttime experimental test temperature and home temperature, flower length and width decreased. The plastic response in flower size suggests that plants may be more successful at autonomous selfing. However, we did not find direct evidence that M. guttatus responded to increased temperature by an increased autonomous selfing capacity. With an increase in temperature difference, the odds of seed production, number of seeds, and individual seed mass decreased. Our results indicate that global warming and the associated increase in extreme temperature events may be detrimental to the reproduction and thus persistence of some plants.