Understanding how and why microbial communities change over time is a fundamental goal of microbial ecology (Fierer et al., 2010;Nemergut et al., 2013;Shade et al., 2013). For host-associated microbiomes, the local environment can change dramatically across the host lifespan, influencing their temporal dynamics

The keystone species concept is a useful ecological concept to explain how some species exert a strong force on their community structure; this paper strives to expand the definition to include species that are used in zootherapy, i.e., the use of animals for medicinal purposes. Honey bees (Apis mellifera) can be considered a zootherapy keystone species that exerts a strong impact on other trophic levels through their products that relate to disease resistance. Honey bee products (i.e., honey, propolis, venom, beeswax, bee bread, and royal jelly) confer pathogen/pest resistance. Each of these products have been shown to exhibit antipathogenic properties and to act as a colony-level defense mechanism against disease. The phenomenon of a collective immune defense in social insects, termed social immunity, has evolved for defense against pathogens which spread easily in highly dense eusocial systems, such as that of honey bees. In apitherapy, a type of zootherapy, humans can use honey bee products to improve their health via pathogen resistance. The implication of these phenomena is that honey bees, through their products, can manipulate the microbial community structure both within the hive and outside the hive when these products are used in apitherapy. Because of their importance to human health, zootherapy keystone species should be a top priority in terms of conservation.

Aggression between individuals of the same sex is almost ubiquitous across the animal kingdom. Winners of intrasexual contests often garner considerable fitness benefits, through greater access to mates, food, or social dominance. In females, aggression is often tightly linked to reproduction, with females displaying increases in aggressive behavior when mated, gestating or lactating, or when protecting dependent offspring. In the fruit fly, Drosophila melanogaster, females spend twice as long fighting over food after mating as when they are virgins. However, it is unknown when this increase in aggression begins or whether it is consistent across genotypes. Here we show that aggression in females increases between 2 to 4 hours after mating and remains elevated for at least a week after a single mating. In addition, this increase in aggression 24 hours after mating is consistent across three diverse genotypes, suggesting this may be a universal response to mating in the species. We also report here the first use of automated tracking and classification software to study female aggression in Drosophila and assess its accuracy for this behavior. Dissecting the genetic diversity and temporal patterns of female aggression assists us in better understanding its generality and adaptive function, and will facilitate the identification of its underlying mechanisms.

AbstractAggression between individuals of the same sex is almost ubiquitous across the animal kingdom. Winners of intrasexual contests often garner considerable fitness benefits, through greater access to mates, food, or social dominance. In females, aggression is often tightly linked to reproduction, with females displaying increases in aggressive behavior when mated, gestating or lactating, or when protecting dependent offspring. In the fruit fly, Drosophila melanogaster, females spend twice as long fighting over food after mating as when they are virgins. However, it is unknown when this increase in aggression begins or whether it is consistent across genotypes. Here we show that aggression in females increases between 2 to 4 hours after mating and remains elevated for at least a week after a single mating. In addition, this increase in aggression 24 hours after mating is consistent across three diverse genotypes, suggesting this may be a universal response to mating in the species. We also report here the first use of automated tracking and classification software to study female aggression in Drosophila and assess its accuracy for this behavior. Dissecting the genetic diversity and temporal patterns of female aggression assists us in better understanding its generality and adaptive function, and will facilitate the identification of its underlying mechanisms.

Social insects are ecologically dominant and provide vital ecosystem services. It is critical to understand collective responses of social insects such as bees to ecological perturbations. However, studying behavior of individual insects across entire colonies and across timescales relevant for colony performance (i.e., days or weeks) remains a central challenge. Here, we describe an approach for long-term monitoring of individuals within multiple bumble bee (Bombus spp.) colonies that combines the complementary strengths of multiple existing methods. Specifically, we combine (a) automated monitoring, (b) fiducial tag tracking, and (c) pose estimation to quantify behavior across multiple colonies over a 48 h period. Finally, we demonstrate the benefits of this approach by quantifying an important but subtle behavior (antennal activity) in bumble bee colonies, and how this behavior is impacted by a common environmental stressor (a neonicotinoid pesticide).

How a host’s microbiome changes over its lifespan can influence development and aging. As these temporal patterns have only been described in detail for humans and a handful of other hosts, an important next step is to compare microbiome dynamics across a broader array of host-microbe symbioses, and to investigate how and why they vary. Here we characterize the temporal dynamics and stability of the bumblebee worker gut microbiome. Bumblebees are a useful symbiosis model given their relatively well-understood life history and simple, host-specific gut bacterial communities. Furthermore, microbial dynamics may influence bumblebee health and pollination services. We combined high-temporal-resolution sampling with 16S rRNA gene sequencing, quantitative PCR, and shotgun metagenomics to characterize gut microbiomes over the adult lifespan of Bombus impatiens workers. To understand how hosts may control (or lose control of) the gut microbiome as they age, we also sequenced hindgut transcriptomes. We found that, at the community level, microbiome assembly is highly predictable and similar to patterns of primary succession observed in the human gut. At the same time, partitioning of strain-level bacterial variants among colonies suggests stochastic colonization events similar to those observed in flies and nematodes. We also find strong differences in temporal dynamics among symbiont species, suggesting ecological differences among microbiome members in colonization and persistence. Finally, we show that both the gut microbiome and host transcriptome—including expression of key immunity genes—stabilize, as opposed to senesce, with age. We suggest that in highly social groups such as bumblebees, maintenance of both microbiomes and immunity contribute to the inclusive fitness of workers, and thus remain under selection even in old age. Our findings provide a foundation for exploring the mechanisms and functional outcomes of bee microbiome succession, and for comparative analyses with other host-microbe symbioses.

Social bees are critical for supporting biodiversity, ecosystem function and crop yields globally. Colony size is a key ecological trait predicted to drive sensitivity to environmental stressors and may be especially important for species with annual cycles of sociality, such as bumblebees. However, there is limited empirical evidence assessing the effect of colony size on sensitivity to environmental stressors or the mechanisms underlying these effects. Here, we examine the relationship between colony size and sensitivity to environmental stressors in bumblebees. We exposed colonies at different developmental stages briefly (2 days) to a common neonicotinoid (imidacloprid) and cold stress, while quantifying behaviour of individuals. Combined imidacloprid and cold exposure had stronger effects on both thermoregulatory behaviour and long-term colony growth in small colonies. We find that imidacloprid's effects on behaviour are mediated by body temperature and spatial location within the nest, suggesting that social thermoregulation provides a buffering effect in large colonies. Finally, we demonstrate qualitatively similar effects in size-manipulated microcolonies, suggesting that group size per se , rather than colony age, drives these patterns. Our results provide evidence that colony size is critical in driving sensitivity to stressors and may help elucidate mechanisms underlying the complex and context-specific impacts of pesticide exposure.