Found throughout the tropical rainforests of South and Central America, butterflies of the Heliconius tribe are among the longest-lived species ever recorded and could provide a new model for studying the biology of longevity.
While most butterflies survive for only a few weeks, the researchers found that some species of the Heliconius tribe live, on average, around three times longer than their close relatives, with some surviving for almost a year. The most dramatic contrast was between the longest-lived Heliconius species, Heliconius hewitsoni, which reached a maximum lifespan of 348 days, and one of its shortest-lived relatives, Dione juno, which lived for just 14 days, representing a 25-fold difference in maximum lifespan.
The findings suggest that Heliconius butterflies have evolved a unique strategy for extending lifespan, offering fresh insights into how ageing can be delayed in the natural world.
Conducted in collaboration with researchers at the Smithsonian Tropical Research Institute in Panama, the study uncovered another remarkable evolutionary twist. At least one species, Heliconius hecale, appears to show little or no physiological decline with age. Using a grip-strength test as a measure of physical performance, the researchers detected no apparent deterioration in older individuals of H. hecale, while Dryas iulia, a closely-related but shorter-lived butterfly relative, showed an age-related decline. This suggests that Heliconius butterflies may largely escape the age-related decline seen in most animals.
The team made the discovery by combining data from butterfly houses, mark, release and recapture studies, and controlled insectary experiments to compare lifespan and ageing patterns across the Heliconiini tribe.
Overall, Heliconius butterflies exhibited longer median and maximum lifespans, lower baseline mortality and slower rates of ageing than their non-pollen-feeding relatives.
Although Heliconius butterflies are known for their exceptional longevity, the biological basis of their extended lifespan has remained unclear. One leading hypothesis is that their unusual ability to feed on pollen as adults may contribute to their longevity. This is a rare behaviour among butterflies as most species primarily rely on flower nectar.
To investigate, the researchers examined the effects of diet on lifespan in a representative pollen-feeding species, Heliconius hecale, and its non-pollen-feeding relative, Dryas iulia. They found that Heliconius hecale maintained body mass and muscle function for longer and showed no evidence of the age-related physiological decline observed in Dryas iulia. However, Heliconius hecale retained a substantial longevity advantage even when deprived of dietary pollen, suggesting that both nutritional and evolved factors underpin its extended lifespan.
Research into long-lived species across the animal kingdom holds extraordinary potential for uncovering novel mechanisms of healthy ageing. The findings highlight Heliconius butterflies as a potential model for exploring how ecological shifts, such as the evolution of adult pollen‑feeding may contribute to longer life.
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 ageing. 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 ageing and longevity."
Paper
'Evolution of increased longevity and slowed ageing in a genus of tropical butterfly' by Jessica Foley et al. in Nature Communications [open access]
