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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Weed and Insect Biology Research » Research » Publications at this Location » Publication #425996
Research Project: Conservation and Improved Storage Technologies for Pollinators and Other Insects of Agricultural Importance

Location: Weed and Insect Biology Research

Title: Reproductive senescence in the pollinator, Megachile rotundata

Author
item PITHAN, JACOB - North Dakota State University
item KOHLER, BROOK - North Dakota State University
item Rajamohan, Arun
item GREENLEE, KENDRA - North Dakota State University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2025
Publication Date: 6/10/2025
Citation: Pithan, J.B., Kohler, B., Rajamohan, A., Greenlee, K. 2025. Reproductive senescence in the pollinator, Megachile rotundata. Journal of Insect Science. https://doi.org/10.3390/insects16060612.
DOI: https://doi.org/10.3390/insects16060612

Interpretive Summary: The alfalfa leaf cutter bee (Megachile rotundata) is a farmer-managed solitary pollinator of agricultural crops, especially the fodder crop of alfalfa. The presence of the bee and its pollinating activities has been linked to a significant increase in seed production in crops. However, the bees are not long-lived and only live up to a month, during which time the female bee nests in cavities that are provided by the farmers. This study was conducted to determine whether the reproductive fitness of the bees and their ability to forage for pollen and nectar is affected as they age. However, the study reveals that the older bees are actually more efficient at foraging and producing more offspring. This study proves this not only from the observations on the number of nests built and the survival of the offspring but also by careful observations of the bees’ ovarian development which did not decline with age. The study concludes that the older alfalfa leaf cutter bees contribute to more efficient pollination. This finding has larger implications for pollinator management in addition to providing new insights into the aging process in solitary bees.

Technical Abstract: The disposable soma theory posits that organisms allocate limited resources between reproduction, maintenance, and growth, resulting in trade-offs, particularly as they age. In this study, we examined age-related reproductive senescence in Megachile rotundata, a solitary bee and important agricultural pollinator. We hypothesized that, similar to social bees, aging females would show declines in foraging behavior and reproductive fitness. Contrary to this hypothesis, we found no evidence of reproductive senescence in M. rotundata within the timeframe observed. Instead, older females increased their foraging rate, leading to larger provisions and offspring. We also observed that older bees exhibited improved foraging efficiency, likely due to learning and muscle physiology changes. Furthermore, ovarian development showed no decline with age, indicating that reproductive capacity remains stable throughout the observed lifespan. Our results challenge conventional assumptions about reproductive senescence in solitary bees and suggest that older M. rotundata may contribute to more efficient pollination, with implications for pollinator management. This study provides new insights into the aging process in solitary bees, emphasizing the need for further research into the mechanisms behind age-related behavioral and reproductive changes.