UNIQUE BIOLOGY OF BUMBLE BEE QueenS
A single mom caring for her nest. Illustration by Erin Walsh, created in association with an article by Rachael M. Heuer in Conservation Physiology (https://academic.oup.com/conphys/article/8/1/coaa007/582578).
Bumble bees are eusocial insects, where females are divided into the queen and worker castes. The overwhelming majority of bumble bee research has focused on workers, but the queen caste is unique in several ways. Queens live longer (up to more than a year) and go through several life history stages that workers do not, such as an overwintering stage and a solitary nest-founding stage. Queens can mate and produce female offspring, which workers are unable to do. Queen fitness is also a fundamental component of bumble bee population dynamics; the death of a single queen early enough in the season precludes the production of a nest with up to hundreds of workers and new reproductives.
Our work on queen bumble bees falls into two interrelated categories. First, we are examining the underlying drivers of life history transitions in queens, including transitions associated with nest-founding and the entry into diapause. The former is funded by an NSF CAREER grant, focused on identifying what causes queens to change their investment in brood care when they initiate nests and become social. Around this time, queens essentially transition from being solitary, to subsocial, to eusocial, all in the span of a few weeks. This project is coupling experiments that cause changes in brood care with analyses of gene expression in the brain, to identify the molecular basis of brood care in bumble bees. We are also examining how nutritional status influences the preparation for (or entry into) diapause. We have found that queens with more sugar-rich diets appear to enter diapause earlier (Costa et al. 2020). Further, although queens can recuperate their nutrient stores during the pre-diapause period after short-term starvation (Watrous et al., submitted), they are less likely to survive diapause if fully deprived of food at this stage (Woodard et al. 2019). This work is being led by Postdoctoral Researcher Claudinéia Costa.
Our other line of research on queen bumble bees is focused on the consequences of queen reproduction and brood care, for larval development, individual nesting success, and bumble bee population dynamics. Working in collaboration with Guy Bloch (The Hebrew University of Jerusalem), we are exploring social influences on larval development. Thus far, we have found that queens influence larvae such that they ultimately develop into smaller-bodied workers that are more resistant to starvation (Costa et al. 2021). This work is supported by funding from the US-Israel Binational Science Foundation and the US-Israel Binational Agricultural Research and Development Fund. PhD candidate Erica Sarro's research in the lab is focused heavily on queen behavior and reproductive physiology. Her work follows in part from the finding that queen brood-feeding behavior is responsive to social conditions; queens reduce their brood-feeding activity when workers emerge in the nest, and they actively feed brood if workers are absent (Woodard et al. 2013). Erica is using laboratory experiments with the bumble bee B. impatiens to explore how and why queens make decisions about how they spend their time, and has also examined the relationship between ovary development and nesting behavior in wild queens of B. vosnesenskii. In summer 2021, she is visiting the Rocky Mountain Biological Laboratory to study wild queens in this system. Beginning in 2021, we are undertaking an NSF-funded project that couples field studies in the southern Sierra Nevada Mountains with laboratory studies on nest-founding queens, to identify the nutritional drivers of early nesting success in bumblebees. This work is a collaboration with Shalene Jha (UT Austin) and Neal Williams (UC Davis).
Our work on queen bumble bees falls into two interrelated categories. First, we are examining the underlying drivers of life history transitions in queens, including transitions associated with nest-founding and the entry into diapause. The former is funded by an NSF CAREER grant, focused on identifying what causes queens to change their investment in brood care when they initiate nests and become social. Around this time, queens essentially transition from being solitary, to subsocial, to eusocial, all in the span of a few weeks. This project is coupling experiments that cause changes in brood care with analyses of gene expression in the brain, to identify the molecular basis of brood care in bumble bees. We are also examining how nutritional status influences the preparation for (or entry into) diapause. We have found that queens with more sugar-rich diets appear to enter diapause earlier (Costa et al. 2020). Further, although queens can recuperate their nutrient stores during the pre-diapause period after short-term starvation (Watrous et al., submitted), they are less likely to survive diapause if fully deprived of food at this stage (Woodard et al. 2019). This work is being led by Postdoctoral Researcher Claudinéia Costa.
Our other line of research on queen bumble bees is focused on the consequences of queen reproduction and brood care, for larval development, individual nesting success, and bumble bee population dynamics. Working in collaboration with Guy Bloch (The Hebrew University of Jerusalem), we are exploring social influences on larval development. Thus far, we have found that queens influence larvae such that they ultimately develop into smaller-bodied workers that are more resistant to starvation (Costa et al. 2021). This work is supported by funding from the US-Israel Binational Science Foundation and the US-Israel Binational Agricultural Research and Development Fund. PhD candidate Erica Sarro's research in the lab is focused heavily on queen behavior and reproductive physiology. Her work follows in part from the finding that queen brood-feeding behavior is responsive to social conditions; queens reduce their brood-feeding activity when workers emerge in the nest, and they actively feed brood if workers are absent (Woodard et al. 2013). Erica is using laboratory experiments with the bumble bee B. impatiens to explore how and why queens make decisions about how they spend their time, and has also examined the relationship between ovary development and nesting behavior in wild queens of B. vosnesenskii. In summer 2021, she is visiting the Rocky Mountain Biological Laboratory to study wild queens in this system. Beginning in 2021, we are undertaking an NSF-funded project that couples field studies in the southern Sierra Nevada Mountains with laboratory studies on nest-founding queens, to identify the nutritional drivers of early nesting success in bumblebees. This work is a collaboration with Shalene Jha (UT Austin) and Neal Williams (UC Davis).
Taste and nutrition
There is accumulating evidence that bumble bees (like many insects) taste their food and integrate this information into feeding-related (and other) behaviors. However, the molecular basis of this process is almost entirely unknown. PhD candidate Kaleigh Fisher is working in collaboration with Naoki Yamanaka and Anupama Dahanukar (UCR) to examine gustation in bumble bees, focusing on fundamental aspects of how taste operates in this social insect system. This work is supported by USDA-NIFA.
We are also examining the environmental processes that influence bee nutritional states and how these in turn influence foraging behavior. PhD candidate Natalie Fischer is using a metabolomic approach to explore how a primary stressor (neonicotinoid exposure) impacts the bumble bee metabolome, using the laboratory model species B. impatiens. She is also using transcriptomic approaches to examine relationships between the regulation of nutritional pathways and foraging strategies in wild bumble bees (B. bifarius) at the Rocky Mountain Biological Laboratory.
We are also examining the environmental processes that influence bee nutritional states and how these in turn influence foraging behavior. PhD candidate Natalie Fischer is using a metabolomic approach to explore how a primary stressor (neonicotinoid exposure) impacts the bumble bee metabolome, using the laboratory model species B. impatiens. She is also using transcriptomic approaches to examine relationships between the regulation of nutritional pathways and foraging strategies in wild bumble bees (B. bifarius) at the Rocky Mountain Biological Laboratory.