BeeNestABM: An open-source agent-based model of spatiotemporal distribution of bumblebees in nests

Abstract

SummaryThis software features the MATLAB source code for an interactive computational model that can be used to study the localized responses of bumblebees to sublethal exposures to a prevalent class of pesticides called neonicotinoids. The code involves an agent-based stochastic model for the interactions between and movements of individual bees within a nest and the nest-related disruptions that occur due to pesticide exposure. The dynamic states of the bees are stored in a matrix, the default data structure of MATLAB. Agent-based modeling allows for building understanding of the colony scale impacts of multiple interacting factors that affect numerous individuals in close proximity and how those change upon pesticide exposure. The scientific significance is that the model solved in the software focuses on the effects of pesticides that occur in bumblebees over short time scales (hours to days) inside a single nest, which includes a much smaller spatial region with finer resolution than that considered in the state-of-the-art (Thorbek, Campbell, and Thompson 2017). These temporal and spatial scales are appropriate for modeling the effects of neonicotinoid pesticides that account for colony size and interactions between exposed and unexposed individuals. The short and local scales allow the model to explicitly consider neighbor interactions and individual bee interactions with structures inside an isolated environment without confounding external factors. The BeeNestABM model tracks bumblebee activity and motility using empirically estimated probabilities for transitions between active (mobile) and inactive states ( Figure 1A). The location of a bee in relation to the structures such as brood and food pots within the nest influence the transition probabilities and the orientation of bee movement through a combination of random walk and attraction toward the nest structures ( Figure 1B), and the transition probabilities contain a component that considers whether the transition is occuring spontaneously or due to social modulation upon collison with a neighboring bee ( Figure 1C).

Social Buffering of Pesticides in Bumblebees: Agent-Based Modeling of the Effects of Colony Size and Neonicotinoid Exposure on Behavior Within Nests

“…BeeNestABM was parameterized using empirical data (Crall et al, 2018b) and simulates bumblebee activity and interactions within a nest. The code and documentation are available (Ford Versypt et al, 2018). Here, we briefly describe the model.…”

“…Our goal is to elucidate the mechanisms underlying the effects of neonicotinoid exposure on worker behavior within bumblebee nests and how these effects are modulated by colony size. We use our spatially-explicit agent-based model called BeeNestABM (Crall et al, 2018b;Ford Versypt et al, 2018) to test the hypothesis that the effects of exposure on worker behavior within bumblebee nests are reduced in larger colonies. Bumblebee colonies range from a single individual during colony founding by a solitary queen up to several hundred workers (Michener and Laberge, 1954).…”