Diversity of cavity-nesting bees (Hymenoptera: Apoidea) within apple orchards and wild habitats in the Annapolis Valley, Nova Scotia, Canada

Abstract

Abstract-Solitary cavity-nesting bees, especially trap-nesting Megachilidae, have great potential as commercial pollinators. A few species have been developed for crop pollination, but the diversity, abundance, and potential pollination contributions of native cavity-nesting bees within agricultural systems have seldom been assessed. Our objectives were to compare the diversity and fecundity of cavity-nesting bees in Nova Scotia in natural ecosystems with those in apple orchards under three levels of management, using trap nests, and to determine whether any native bees show promise for development as pollinators. Our results show that species richness and numbers of bees reared from trap nests in commercially managed orchards, abandoned orchards, and natural habitats were similar, and species' compositional patterns were not unique to specific habitats. Trap nests can be used to increase and maintain cavity-nesting bee populations within Nova Scotia apple orchards. Osmia tersula Cockerell (Megachilidae), which accounted for almost 45% of all bees captured and was the most abundant species nesting in all habitats evaluated, should be assessed for potential as a commercial pollinator of spring-flowering crops. The influence of natural cavities on bee species richness in trap-nesting surveys is also discussed.Résumé-Les abeilles solitaires qui nichent dans les cavités, particulièrement les Megachilidae qui logent dans les nids-pièges, représentent un important potentiel de pollinisateurs commerciaux. Quelques espèces ont été utilisées pour la pollinisation des cultures, mais on a rarement évalué la diversité, l'abondance et la contribution potentielle à la pollinisation des abeilles qui nichent dans les cavités dans les systèmes agricoles. Notre objectif est de comparer à l'aide de nids-pièges la diversité et la fécondité des abeilles qui nichent dans les cavités dans les écosystè-mes naturels et dans des pommeraies gérées sous trois régimes différents en Nouvelle-Écosse, ainsi que de déterminer s'il y a des abeilles indigènes qui offrent un potentiel pour servir à la pollinisation. Nos résultats montrent que la richesse spécifique et le nombre d'abeilles obtenues dans les nids-pièges sont semblables dans les pommeraies sous gestion commerciale, dans les pommeraies abandonnées et les habitats naturels; de plus, les patrons de composition spécifique ne sont pas propres aux différents habitats. Dans les pommeraies de Nouvelle-Écosse, les nidspièges peuvent servir à augmenter et à maintenir les populations d'abeilles qui nichent dans les cavités. Osmia tersula Cockerell (Megachilidae), qui représente presque 45 % de toutes les abeilles capturées et qui est l'espèce la plus abondante à nicher dans tous les habitats étudiés, devrait être évalué en vue d'une utilisation éventuelle comme pollinisateur des cultures qui fleurissent au printemps. Nous discutons aussi de l'influence des cavités naturelles sur la richesse spécifique des abeilles dans les inventaires faits à l'aide de nids-pièges.

On managing the red mason bee (Osmia bicornis) in apple orchards

“…A likely explanation is that although the amount of pollen provided by the apple orchard is ample enough, the timing of blossom of surrounding fruit trees such as cherry, pear, and red currant extended the provision of pollen to a longer time period. In accordance with this, Sheffield et al (2008) report a greater reproductive success in Osmia lignaria, when additional pollen is supplied by planting lupine in the vicinity (less than 600 m) of orchards. Food availability has also been demonstrated to correlate positively at the landscape scale for bumblebees (Westphal et al 2003;Williams and Kremen 2007) and for O. lignaria (Williams and Kremen 2007) and in caging experiments with Osmia pumilla (Goodell 2003).…”

“…Nevertheless, as this is a field experiment and we have no control site established, we cannot rule out that the increase is also partly because of beneficial effects such as good weather conditions, but given the magnitude of the effect, the limiting effect of nesting opportunities (cf. Sheffield et al 2008;SteffanDewenter and Schiele 2008) for this species could be demonstrated. An important contribution to this increase is probably the fact that due to opening of the bamboo canes, we separated infested and undeveloped cocoons from the healthy ones, which kept the otherwise likely increase of the parasite population under control.…”

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“…Much is known about the biology of many leafcutter bees due to their importance in crop pollination (Hobbs & Lilly 1954;Pengelly 1955;Osgood 1974;Peterson et al 1992;Richards 1993;Raw 2002) and the fact that many species accept trap-nests (Medler 1959(Medler , 1964Fye 1965;Krombein 1967;Frolich & Parker 1983;O'Toole & Raw 1991;Sheffield et al 2008). Most species nest above ground in pre-existing cavities (Figure B) or excavate into pithy stems or decomposing wood (Stephen 1956;Ivanochko 1979).…”

Unusual nesting behavior in <i>Megachile</i> (<i>Eutricharaea</i>) <i>rotundata</i> (Hymenoptera: Megachilidae)

“…Many of the species of Megachile that nest in pre-existing cavities will utilize artificial nesting substrates (e.g., Fye, 1965;Krombein, 1967;Stephen & Every, 1970;Sheffield et al, 2008, MacIvor & Packer, 2015MacIvor, in press), popularly called bee condos or hotels (e.g., Ravoet et al, 2014;MacIvor & Packer, 2015;Fortel et al, 2016), or trap/cavity nests (e.g., Krombein, 1967;O'Neil & O'Neil, 2016;MacIvor, in press). In these artificial nesting sites, the nesting cavities are typically pre-constructed to run horizontally and perpendicular to the nest front surface, though this arrangement may not always be available in natural cavities.…”

“…In these artificial nesting sites, the nesting cavities are typically pre-constructed to run horizontally and perpendicular to the nest front surface, though this arrangement may not always be available in natural cavities. The diameter of the individual tunnels can vary to support occupant diversity (e.g., Tscharntke et al, 1998;Sheffield et al, 2008), and influence sex-ratio for target species (e.g., Stephen & Osgood, 1965).…”