Effects of geographic origin and temperature on survival, development, and emergence of the managed pollinator, Osmia lignaria

Authors: SCALICI, MORGAN - Utah State University; McCabe, Lindsie; ALSTON, DIANE - Utah State University; Pitts Singer, Theresa

Submitted to: Frontiers in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2023
Publication Date: 5/5/2023
Citation: Scalici, M.B., McCabe, L.M., Alston, D.G., Pitts Singer, T. 2023. Effects of geographic origin and temperature on survival, development, and emergence of the managed pollinator, Osmia lignaria. Frontiers in Ecology and Evolution. 11. Article 1083448. https://doi.org/10.3389/fevo.2023.1083448.
DOI: https://doi.org/10.3389/fevo.2023.1083448

Interpretive Summary: The blue orchard bee is a widespread North American native pollinator and an important alternative or supplement honey bees for commercial fruit and nut crop production. Some differences in how immature bees development over time have been shown for populations in the western United States, but little is known about how blue orchard bees from various geographic regions with differing climates and conditions (=ecoregions) respond to current recommended management practices or being moved within and between ecoregions. Utah populations have been most widely studied and used as pollinators, but bees trapped in other western states are also being used for crop pollination. In spring 2019, blue orchard bees sourced from Utah and Washington were reared in laboratory incubators under two temperature programs: 1) constant temperatures used to manage bees through development, wintering, and adult emergence, and 2) hourly fluctuating temperatures programmed to mimic the natural daily (24 h) thermal cycles of the nearest cherry orchard growing region. We found that WA bees responded less well compared to UT bees when kept at a constant temperature that was warmer for much of the larval develop time than natural temperatures; the WA bees had a shortened development period and had higher immature mortality at constant 26°C. Our research results support a better understanding of what are the best rearing temperatures for blue orchard bees and the effect of from where the bees are sourced on survival and which immature life stages are affected by source and temperature.

Technical Abstract: The blue orchard bee, Osmia lignaria Say (Hymenoptera: Megachilidae), is a widespread North American native pollinator and an important alternative or supplement to honey bees for commercial fruit and nut crop production. Some differences in developmental phenology between populations in the western United States have been documented, but little is known about how blue orchard bees from various ecoregions respond to current recommended management practices or translocation within and between ecoregions. Utah populations have been most widely studied and employed as pollinators, but bees trapped in other western states are also being used for crop pollination. In spring 2019, blue orchard bees sourced from Utah and Washington were reared in laboratory incubators under two thermal regimens: 1) constant temperatures used to manage bees through development, wintering, and adult emergence, and 2) hourly fluctuating temperatures programmed to mimic the natural daily (24 h) thermal cycles of the nearest cherry orchard growing region. We found that WA bees were more adversely affected by warm rearing temperatures than were UT bees; the WA bees had a shortened development period and had higher immature mortality at constant 26°C, and thermal regimen had also a greater effect on the development period of WA bees than UT bees. Our data support a better understanding of optimal rearing temperatures for blue orchard bees and the effect of bee source and temperature on different life stages and survival variance.