The U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) and U.S. Fish and Wildlife Service (USFWS) scientists have released a highly detailed map of the rusty patched bumble bee’s genome. This breakthrough is part of the Beenome 100 project, a unique initiative aimed at creating a comprehensive library of genome maps for 100 diverse bee species in the United States. The collaboration involves the ARS and the University of Illinois.
The primary goal of this library is to enable researchers to address crucial questions about bees, such as identifying the genetic variations that make a bee species more susceptible to climate change or pesticide exposure.
The rusty patched bumble bee (Bombus affinis) is a crucial pollinator for various plants, including bergamot, milkweed, cranberries, plums, apples, and alfalfa. However, over the past two decades, its population has declined by approximately 87 percent. In 2017, the species was officially listed as “endangered.” Previously found across the Upper Midwest and Northeast regions in 28 states and 2 Canadian provinces, their range has now shrunk to disconnected areas in 13 states and one Canadian province. The Minneapolis-St. Paul area of Minnesota and Wisconsin are among the few places where they are still commonly observed.
Research entomologist Jonathan B. Uhaud Koch from the ARS Pollinating Insect-Biology, Management, Systematics Research Unit in Logan, Utah, expressed optimism about the potential of the detailed genomic information. He explained that while some factors contributing to the decline of the rusty patched bumble bee are known—such as habitat loss, reduced nectar sources, climate change, pesticide exposure, and increased pathogens and pests—having access to the newly sequenced genome provides an opportunity to find novel strategies to restore their populations.
Koch was surprised by the substantial amount of genetic material from the fungal pathogen Varimorpha bombi found in the bumble bee sample used for genome mapping. The researchers used a small piece of abdominal tissue from a single male collected from a nest in Minnesota. Despite the bee’s endangered status, advanced equipment allowed the resolution of an entire genome consisting of 15,252 genes and 18 chromosomes from this minute sample.
The study revealed that approximately 4.5 percent of the sequenced DNA originated from Microsporidia, the fungal group that includes Varimorpha bombi. Koch emphasized the significance of this finding, highlighting the pathogen’s pervasiveness.
The availability of this high-quality genome will facilitate the identification of genetic differences between thriving and declining populations of rusty patched bumble bees. This knowledge may lead to the discovery of specific genes that enable more adaptable populations to cope with their environment. Additionally, it could enhance understanding of bumble bee behavior, physiology, and adaptation to changing environmental conditions.
Once researchers identify the genes associated with local adaptability, they can use this information to assist in captive breeding programs. By selectively breeding individuals with advantageous genes, populations of rusty patched bumble bees can be bolstered and reintroduced to suitable habitats.