Abstract
Eusocial insect colonies are defined by extreme variation in reproductive activity among castes, but the ancestral conditions from which this variation arose are unknown. Investigating the factors that contribute to variation in reproductive physiology among solitary insects that are closely related to social species can help to fill this gap. We experimentally tested the role of nutrition, juvenile hormone (JH), and social cues on reproductive maturation in solitary alkali bees (Halictidae: Nomia melanderi). We find that alkali bee females emerge from overwintering with undeveloped ovaries and Dufour’s glands. Initial activation of these reproductive structures does not depend on pollen consumption, though dietary protein or lipids may be necessary for long-term reproductive activity. JH is likely to be a limiting factor in alkali bee reproductive activation, as only those females treated with JH developed mature oocytes and Dufour’s glands. These females reached reproductive maturity without access to mates or nesting opportunities. Unlike for related social bees, the effects of JH were not suppressed by the presence of older, reproductive females. These results provide important insight into the factors that influence reproductive activity in an important native pollinator, and those that may have been particularly important in the evolution of reproductive castes.
