Sexual dimorphism in excess power index of four North American native bees (Hymenoptera, Andrenidae, Apidae, and Halictidae)

Abstract

A multitude of hymenopteran species exhibit sexual dimorphism for simple traits, such as color, size, or antennal segment number. These differences can reflect selection for specialized biological roles, many of which have not been documented for the majority of bee and wasp species. The excess power index (EPI) is an estimate of insect flight performance that is inferred by the combination of several morphological characteristics. We compared the female and male EPIs in four species of native bees: Agapostemon virescens Fabricius, Andrena carlini Cockerell, Melissodes bimaculata Lepeletier and Xylocopa virginica L.. While females of each species had a significantly larger whole body mass, males had a significantly larger EPI. A larger body mass for females is associated with egg laying abilities and foraging behavior. Male fitness may be dependent on EPI; males that have greater flight capacity can travel further or remain in flight for longer time periods in search of mates.

Observing bees and wasps: Why surveys and monitoring programs are critical and how they can improve our understanding of these beneficial hymenopterans

“…Brown & Paxton (2009) state that the greatest obstacle to advancing pollinator conservation is the dearth of good data on species distributions and abundance. Possibly the most data deficient area is Africa, where very little collecting activity has occurred, in part due to political and infrastructural problems (Eardley et al 2009); however, data are lacking even in North America (Berenbaum et al 2007;Woodard et al 2020;Vigueira et al 2023).…”