Floral traits affecting the transmission of beneficial and pathogenic pollinator-associated microbes

•Several floral traits are associated with pollinator-related microbe transmission.•Beneficial and pathogenic microbes may share some transmission constraints.•Plant and pollinator community context can mediate microbial transmission at flowers.•Future work should clarify the causal role of floral traits in microbe transmission. Flowers provide resources for pollinators, and can also be transmission venues for beneficial or pathogenic pollinator-associated microbes. Floral traits could mediate transmission similarly for beneficial and pathogenic microbes, although some beneficial microbes can grow in flowers while pathogenic microbes may only survive until acquired by a new host. In spite of conceptual similarities, research on beneficial and pathogenic pollinator-associated microbes has progressed mostly independently. Recent advances demonstrate that floral traits are associated with transmission of beneficial and pathogenic microbes, with consequences for pollinator populations and communities. However, there is a near-absence of experimental manipulations of floral traits to determine causal effects on transmission, and a need to understand how floral, microbe and host traits interact to mediate transmission.