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ABSTRACT Differences in dominance are frequently invoked to explain the outcomes of competition. Yet, what it means to be dominant, and which traits underlie dominance, are poorly understood. Here, we sought to determine the relationships between multiple aspects of dominance, the potential for trade‐offs with discovery ability, and the traits associated with these patterns within a high elevation community of five ant taxa. We examined several common dominance metrics—behavioral dominance (winning aggressive encounters at both the individual and colony levels), numerical dominance (abundance and activity in baits and pitfall traps), and ecological dominance (high relative frequency in baits)—and found that individual‐ and colony‐level behavioral dominance was positively correlated, as were ecological and numerical dominance. However, colony‐level behavioral and numerical dominance were negatively correlated, and no other dominance metrics were associated. There was a dominance‐discovery trade‐off, as increased behavioral (but not numerical or ecological) dominance was associated with slower resource discovery. This trade‐off was likely driven by behaviorally dominant ants having larger body sizes and recruiting a greater biomass of workers to baits. In contrast, fast discoverers were more abundant in the environment (i.e., numerically dominant). Complementing our empirical study, a meta‐analysis of 54 responses from 21 studies showed that the association between dominance and discovery ability depended on the dominance metric. Whereas discovery ability was positively correlated with numerical dominance, its relationships with behavioral and ecological dominance were highly variable and not significantly different from zero. Overall, our empirical findings, in combination with the synthesis of past studies, demonstrate that different aspects of ant dominance are not equivalent. Yet, regardless of dominance type, there is little evidence that dominance‐discovery trade‐offs occur in most ant communities. 

Abstract Stressors can shift the microbiome into an altered, “dysbiotic” state that reduces host fitness. While well-studied in humans and laboratory models, the prevalence, predictability, and drivers of dysbiosis in nature remain unclear. We addressed these questions by monitoring gut microbiomes of a wild bumble bee (Bombus vosnesenskii) population in Southern California. We found that dysbiosis is highly pervasive: more than a third of all bees were dysbiotic, when defined as a >50% replacement of host-specialized core bacteria by environmental bacteria. This replacement covaried with increased alpha and beta diversity, an enrichment of oxygen-tolerant taxa, and pathogens—all common hallmarks of dysbiosis in other hosts. Given that dysbiosis may be harmful, and that bumble bees are in decline globally, there is a clear need for monitoring and experiments to determine if dysbiosis elevates bumble bee extinction risk. Surprisingly, dysbiosis was not associated with a morphological indicator of stress nor with a variety of potential stressors. It instead appears to be intrinsic to the host life cycle. In the first year of sampling, dysbiosis emerged only late in the season, when bumble bee colonies normally reproduce and then senesce. But following historic rainfall and a sustained resource base,B. vosnesenskiilife history shifted, and dysbiosis was entrenched throughout the season. These findings show how dysbiosis may be regulated by the host life cycle, yet also change unpredictably due to life history plasticity. As the climate becomes more extreme and erratic, so too may host life cycles and microbiome dynamics, with uncertain consequences. 

Plant secondary metabolites are key mechanistic drivers of species interactions. These metabolites have primarily been studied for their role in defense, but they can also have complex consequences for mutualisms, including seed dispersal. Although the primary function of fleshy fruits is to attract seed-dispersing animals, fruits often contain complex mixtures of toxic or deterrent secondary metabolites that can reduce the quantity or quality of seed dispersal mutualisms. Furthermore, because seeds are often dispersed across multiple stages by several dispersers, the net consequences of fruit secondary metabolites for the effectiveness of seed dispersal and ultimately plant fitness are poorly understood. Here, we tested the effects of amides, nitrogen-based defensive compounds common in fruits of the neotropical plant genus Piper (Piperaceae), on seed dispersal effectiveness (SDE) by ants, which are common secondary seed dispersers. We experimentally added amide extracts to Piper fruits both in the field and lab, finding that amides reduced the quantity of secondary seed dispersal by reducing ant recruitment (87%) and fruit removal rates (58% and 66% in the field and lab, respectively). Moreover, amides not only reduced dispersal quantity but also altered seed dispersal quality by shifting the community composition of recruiting ants (notably by reducing the recruitment of the most effective disperser by 90% but having no detectable effect on the recruitment of a cheater species that removes fruit pulp without dispersing seeds). Although amides did not affect the distance ants initially carried seeds, they altered the quality of seed dispersal by reducing the likelihood of ants cleaning seeds (67%) and increasing their likelihood of redispersing seeds outside of the nest (200%). Overall, these results demonstrate that secondary metabolites can alter the effectiveness of plant mutualisms, by both reducing mutualism quantity and altering mutualism quality through multiple mechanisms. These findings present a critical step in understanding the factors mediating the outcomes of seed dispersal and, more broadly, demonstrate the importance of considering how defensive secondary metabolites influence the outcomes of mutualisms surrounding plants.