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ARS Home » Pacific West Area » Logan, Utah » Pollinating Insect-Biology, Management, Systematics Research » Research » Research Project #441509

Research Project: Multi-Generational Adaptation of Blue Orchard Bees (Osmia Lignaria) in Response to Climate Change in Orchard Crops

Location: Pollinating Insect-Biology, Management, Systematics Research

Project Number: 2080-21000-019-042-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Dec 1, 2021
End Date: Apr 30, 2024

Blue orchard bees (BOBs) are an important pollinator of fruit and nut crops. However, this species is often wild trapped annually in the mountains of Utah, Washington, and California to pollinate California orchards, rather than having a managed supply readily available for local growers. It is unknown how populations of BOBs are responding to the changing environment when moved to pollinate. Many times, these species are being moved into areas with warmer temperatures than within their natal population range. Bees tend to maintain an optimum temperature within their niche space, where an increase past the optimum temperature leads to an overall decrease in fitness. Bees, due to their ectothermic nature, are strongly tied to temperature changes. In general, warmer temperatures are related to greater performance for a majority of bee species, but for some species such as Osmia, dramatic shifts in warming temperatures outside their natal range can have negative effects. Understanding how adaptable populations are to new and warming environments is critical to understanding how species will respond to an increase in temperature for future generations. The potential for reduced success from warming temperatures for BOBs coupled with the fact that populations of BOBs are often transported outside their range for pollination of orchard crops could lead to a decrease in fitness and pollination productivity. Our main question is to understand if species from different source populations can adapt to new environments (i.e. will BOBs sourced from Utah, Washington, and California adapt to California orchard temperatures over time) through a multi-generation approach. We have identified three objectives to address this question. 1) Is there greater BOB retention in orchards if populations of BOBs are sourced from similar environments? Does this change over time via adaptation? 2) Will reproductive success rates increase for populations that remain in the same environment year after year? 3) How will each of these populations and generations differ under conventional cold storage management verse remaining in California ambient overwintering temperatures during the fall and winter months?

Over a 2.5-year period, field and laboratory methods will be implemented to meet our research objectives. For objective 1 we will obtain bees from three population sources: Utah, Washington, and California. Each of these populations will be deployed in California cherry orchards during season one. Each source population will be in a separate orchard (> 1 mile). The orchards will be matched in locality, age, and management of the stand. Each population source will have three replicates for a total of 9 orchards the first year. The progeny from these orchards will then be redeployed for a subsequent two seasons in the same orchards to test for adaptability to the environment. In addition to the progeny, a new batch of CA, WA & UT bees from the same original source will also be released in nearby orchards, following the same parameters as above, to act as controls of retention for each group. This methodology will be implemented in season two and three for a total of 18 orchards per season. For objective 2, we will monitor the development of the progeny from all treatments: monitoring the number of females, males and the sex ratio produced, mortality of dead larval, prepupa & pupa, parasitism rates and overwintering survival by assessing emergence rates the following year within and between populations. We will assess these metrics for each of the population sources and analyze how these metrics are changing across generations. For objective 3, we will take a subsample of each of the treatments and employ conventional cold storage methods as well have another subsample at California ambient overwintering temperatures to determine the overwintering and adaptation success of our population sources. Based on these treatments we will be able to understand if species can adapt to new and warmer environment through multiple generations.