Biology subjects

Drake, E. D.

Publications and source records attributed to Drake, E. D..

3 recordsLinked to original sources

bioRxiv2026

No evidence sex-specific senescence varies with resource competition in Soay sheep

Demographic senescence, the age-related decline in survival and reproduction, is widespread. Older individuals, and particularly males in polygynous systems, are expected to be disproportionately vulnerable to environmental stressors due to physiological decline and high reproductive costs. However, studies testing if harsh conditions exacerbate senescence, and whether this effect is sex-dependent, remain limited in wild populations. Using 40 years of data from wild Soay sheep (Ovis aries) on St Kilda, Scotland, we tested whether increased resource competition (indexed by population density) accelerates demographic senescence, and if late-life environmental sensitivity is male-biased. High densities consistently suppressed overall adult performance, making individuals less likely to survive, breed, or rear high-quality offspring under more intense competition. Although survival and reproductive traits exhibited clear senescence, increased population density did not accelerate late-life declines in any trait. Rates of decline with age were unaffected by density and did not differ between the sexes. Our results challenge the assumption that older individuals and males are inherently more vulnerable to harsh conditions, suggesting physiological or behavioural buffering may maintain late-life resilience against resource limitation in some systems.

evolutionary biology↗

bioRxiv2024

Sex-specific effects of early-life adversity on adult fitness in a wild mammal

Early-life adversity influences adult fitness across a range of vertebrates. In polygynous systems with intense intrasexual competition, males may be more sensitive to conditions experienced during growth and development. However, the relative importance of different aspects of the early environment and how their effects differ between the sexes remain poorly understood. Here, we used a long-term study of wild Soay sheep to characterise the early-life environment in terms of weather, infection, resource competition and maternal investment, and test the hypothesis that males are more vulnerable to early adversity than females. Birth weight positively predicted lifetime breeding success in both sexes, suggesting a classic silver spoon effect, though the effects were stronger in males. Males experiencing high population densities in their first year had lower lifetime breeding success suggesting lasting negative consequences of nutritional stress, but there was no association in females. In contrast, challenging weather in the first winter of life appeared to act as a selective filter, with males surviving these harsh conditions having higher adult fitness. Our findings further evidence the important long-term fitness consequences of early-life adversity in wild vertebrates, highlighting that different aspects of the early environment may shape later fitness in different and sex-specific ways.

evolutionary biology↗

bioRxiv2023

Stochasticity explains non-genetic inheritance of lifespan and apparent trade-offs between reproduction and ageing

Stochastic effects are central to the biology and demography of ageing. Genetically identical individuals do not all die at the exact same time but show a distribution of lifespan. Although such effects are appreciated, any cascading effects from stochastic effects of ageing are underappreciated. We show here that genetically identical female flies (Drosophila melanogaster) that live long, produce longer lived daughters. In line with previous work, we also find that daughters born to older mothers are shorter lived, also termed the Lansing effect. We further show that longer-lived flies produce less offspring, suggesting an apparent trade-off due to stochastic effects alone. We explain these effects using an extension of the reliability theory of ageing by dichotomising ageing physiology in reproduction and lifespan supporting units. These simple models reproduce non-genetic inheritance of lifespan, the Lansing effect and trade-offs between reproduction and lifespan. Our work implies that if non-genetic inheritance of lifespan is widespread it explains the generally low heritability of this trait. Furthermore, trade-offs between performance, e.g. reproduction, and lifespan may be less widespread than predicted by evolutionary biology of ageing, stemming from stochasticity rather than differential investment. Anti-ageing treatments therefore come without any unintended costs to other physiology, a perceived risk that limits translation of these treatments to humans.

evolutionary biology↗