Leaf foraging sources of leafcutter bees in a tropical environment: implications for conservation

Abstract

Leafcutter bees collect leaf discs to encase brood cells. However, our understanding of their use of plants as nesting resources, which is critical for their conservation, is poor. We followed plants and observed bees cutting leaves to understand the leaf and plant traits of the leaf forage plants of Megachile spp. We studied whether the leaf size explains the cut size and the number of cuts in the leaves. The bees collected leaves from 59 species, 49 genera and 25 families of plants of various habits. Plant habit, leaf morphotype and leaf size did not influence leaf choice by the bees. Of the plants surveyed, 45.22% had the distinguishable cutting marks. About 63% and 98% of the plants the bees used are native to the region and to the tropical southern hemisphere, respectively. Bees selected leaves over an extreme size range, and the leaf size predicted the number of cuts on a leaf. Comparing our results with other studies, we conclude that the leafcutter bees' selection of plants is adapted to the local environment.

Foraging preferences of leafcutter bees in three contrasting geographical zones

“…Only three studies to date (our own in India [Kambli et al., ] and Arizona (present study), and MacIvor, ) have generated a comprehensive list of plants used by leafcutter bees. However, other researchers, while studying the nesting biology of a given bee species or as part of other investigations connected to leafcutter bee ecology, have reported plant use, and we have included these data in our analyses where appropriate.…”

“…Most of the data we use here on leaf selection by leafcutter bees were drawn from the published literature (Table ). To these, we added data from our own studies in India (Kambli et al., ) and south‐eastern Arizona (presented here). Broadly speaking, we compared data from three geographical regions: South Asia, Nearctic Canada and the Nearctic United States.…”

“…Kambli et al. () and MacIvor () provide descriptions of their study sites. The US study took place on the University of Arizona (UA) campus ((3 sq.…”

“…A brood cell contains leaf discs of variable size and shape (Alqarni, Hannan, Gonzalez, & Engel, ; Sabino & Antonini, ). In cases where the leaves are very small, the bees bring to their nest entire leaves rather than pieces cut from them (Kambli et al., ). Individuals of most leafcutter bee species use leaves of only one plant species to make the inner layer of the roll.…”

“…Surprisingly, information on which species of plants leafcutter bees choose and why is almost entirely lacking (but see, MacIvor, ; Kambli et al., ). We do not know whether the leafcutter bees have preference for leaves of certain plant clades, or leaves with certain physical characteristics.…”