Biology subjects

McPherson, J.

Publications and source records attributed to McPherson, J..

3 recordsLinked to original sources

bioRxiv2025

Evolution of increased longevity and slowed ageing in a genus of tropical butterfly

Evolution has given rise to lifespans in extant species ranging from days to centuries. Given that mechanisms of ageing are highly conserved, studying long-lived lineages across the animal kingdom could yield insights relevant for healthy ageing in humans. However, typical models of extended lifespan often live for decades, making them impractical for longitudinal studies. Ideal model systems would be organisms that are naturally long-lived compared to their close relatives, but have lifespans on experimentally tractable scales. Here, we present the Neotropical butterfly genus Heliconius as a novel model system for the evolution of extended longevity. We collate data from 27 species across the Heliconiini tribe to reveal a 25-fold variation in lifespan within the group, with our 348-day maximum for Heliconius hewitsoni longer than any butterfly species previously recorded in the scientific literature. While previous work has attributed this lifespan extension to a plastic response to enhanced nutrition, we conduct detailed survival and functional senescence analyses on two species representative of shorter- and longer-lived clades to show evidence of evolved, heritable mechanisms of slowed ageing in Heliconius. Our results add a new case study to the canon of noteworthy agers, and provide valuable insights into the evolution of increased longevity.

evolutionary biology↗

bioRxiv2023

Pollen-feeding delays reproductive senescence and maintains toxicity of Heliconius butterflies

Dietary shifts may act to ease energetic constraints and allow organisms to optimise life-history traits. Heliconius butterflies differ from other nectar-feeders due to their unique ability to digest pollen, which provides a reliable source of amino acids to adults. Pollen-feeding has been associated with prolonged adult lifespan and increased fertility, yet there is a lack of empirical data demonstrating how pollen consumption influences key fitness traits, including chemical defences and adult body weight, as well as fertility over their elongated lifespan. Here, we investigated the effect of pollen-feeding on fertility, weight and chemical defences, as well as offspring defences, controlling for butterfly age and sex. Recently emerged Heliconius erato butterflies of similar size were fed for 14 or 45 days on one of three diets: sugar solution only, or sugar solution replenished with either amino acid supplement or pollen. At the end of the experiment, oviposition assays were performed to evaluate fertility, and afterwards all butterflies and eggs were weighed and used for quantification of cyanogenic glucosides (CG). We found that there is an age-specific and sex-specific effect of pollen-feeding on butterfly weight, with both the sugar-only and amino-acid supplement diets reducing the weight of old females (45d), but not young females (14d) or males of any age. Females fed only sugar significantly reduced their egg-laying through adulthood, whereas females that had access to pollen maintained their fertility. Diet had a significant effect on the maintenance of the chemical defence of females, but not males. Curiously, even though females that have access to pollen were heavier, more toxic and laid more eggs, this did not translate into improvements in offspring defences, as eggs from butterflies of all ages and diet treatments had similar CG content. Our results emphasise the importance of controlling for age-specific and sex-specific effects in studies of life-history evolution and demonstrate that dietary novelty can relax energetic constraints.

evolutionary biology↗

bioRxiv2022

Effects of temperature on the development of Heliconius erato butterflies

O_LIAnthropogenic climate change is thought to present a significant threat to biodiversity, in particular to tropical ectotherms, and the effects of long-term developmental heat stress on this group have received relatively little research attention. C_LIO_LIHere we study the effects of experimentally raising developmental temperatures in a tropical butterfly. We measured survival, development time, adult body mass, and wing size of a neotropical butterfly, Heliconius erato demophoon, across three temperature treatments. C_LIO_LIEgg survival was lower in the hotter treatments, with 83%, 73%, and 49% of eggs eclosing in the 20-30{degrees}C, 23-33{degrees}C, and 26-36{degrees}C treatments, respectively. Larval survival was five times lower in the 26-36{degrees}C treatment (4%) compared to the 20-30{degrees}C treatment (22%), and we did not detect differences in pupal survival across treatments due to high mortality in earlier stages. C_LIO_LIAdults in the 20-30{degrees}C treatment had a lower body mass and larvae had a lower growth rate compared to the intermediate 23-33{degrees}C treatment, but were heavier than the few surviving adults in the 26-36{degrees}C treatment. Females were heavier and grew faster as larvae than males in the 23-33{degrees}C treatment, but there was no associated increase in wing size. C_LIO_LIIn summary, high developmental temperatures are particularly lethal for eggs and less so for larvae, and also affect adult morphology. This highlights the importance of understanding the effects of temperature variation across ontogeny in tropical ectotherms. C_LI

zoology↗