Some butterflies burn bright and fade fast. Heliconius butterflies seem to do the opposite.
A University of Bristol-led study published June 16 in Nature Communications found some Heliconius species live about three times longer than their closest relatives on average, with certain individuals surviving for nearly a year.
The butterflies are found across the rainforests of Central and South America. Researchers said they rank among the longest-lived butterflies ever documented and could become an important model for studying longevity.
Most butterflies live only a few weeks as adults. One of the clearest examples in the study was Heliconius hewitsoni, which reached a maximum lifespan of 348 days. A closely related species, Dione juno, survived only 14 days, a 25-fold difference in maximum lifespan.
Working with scientists at the Smithsonian Tropical Research Institute in Panama, the team also found signs that at least one species, Heliconius hecale, shows little or no measurable physical decline with age.
The researchers used a grip strength test to assess physical performance. Older H. hecale butterflies performed just as well as younger individuals. By comparison, Dryas iulia, a closely related species with a shorter lifespan, showed a clear age-related decline.
To reach the findings, the team combined information from butterfly houses, mark, release and recapture studies, and controlled insectary experiments. Across the Heliconiini tribe, Heliconius butterflies consistently showed longer average and maximum lifespans, lower baseline mortality, and slower rates of aging than related species that do not feed on pollen.
Scientists have long known Heliconius butterflies live unusually long lives, but the reason has been unclear. One leading explanation is their rare ability to feed on pollen as adults, while most butterfly species rely mainly on nectar.
To test that idea, the researchers compared H. hecale with its non-pollen-feeding relative, Dryas iulia. H. hecale maintained its body mass and muscle performance for longer and did not show the age-related physical decline seen in D. iulia.
But pollen alone did not explain the difference. Even when pollen was removed from its diet, H. hecale still lived substantially longer than its relative, suggesting nutrition and evolutionary adaptations both contribute to its extended lifespan.
Dr. Jessica Foley, the study’s lead author from the University of Bristol’s School of Biological Sciences, said: “As the most species-rich animal class, insects are renowned for their extraordinary morphological and ecological diversity. They also exhibit extreme variation in longevity, with maximum lifespans ranging from just a few days in adult mayflies to several decades in the reproductive castes of some ants and termites. This represents a roughly 5,000-fold difference within the class, compared with around a 100-fold difference in lifespan observed in mammals.
“Heliconius butterflies are among the longest-lived butterflies, but what makes them particularly remarkable is that they appear to have evolved not only longer lifespans, but also slower aging. This allows them to live significantly longer than closely related species from which they diverged relatively recently in evolutionary time.
“The exciting implication of this lifespan extension is that it provides a powerful opportunity to identify the mechanisms that underpin longevity. By comparing long-lived Heliconius butterflies with their short-lived relatives, we have a natural evolutionary experiment that can help reveal how lifespan is extended, making them a highly promising new model for research into the biology of aging and longevity.”
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