A demographic and evolutionary analysis of maternal effect senescence

Area of Science:

• Evolutionary biology
• Gerontology
• Population ecology

Background:

• Maternal effect senescence, a decline in offspring viability with maternal age, is observed across many species.
• The impact of maternal effect senescence on evolutionary fitness and population dynamics remains incompletely understood.
• Previous studies focused on phenotypic observations, lacking a quantitative framework to assess fitness consequences.

Purpose of the Study:

• To develop and apply matrix population models to quantify the effects of maternal age on fitness and selection.
• To investigate how maternal effect senescence influences population dynamics and evolutionary trajectories.
• To assess the role of maternal age in the evolution of senescence.

Main Methods:

• Development of age- and maternal age-classified matrix population models.
• Fitting models to data from individual-based culture experiments of *Brachionus manjavacas* (rotifers).
• Estimation of selection gradients on survival and fertility across different age and maternal age classes and environments.

Main Results:

• Maternal effect senescence significantly reduces the fitness of *B. manjavacas*, primarily via reduced fertility at advanced maternal ages.
• Selection gradients for survival and fertility decline with increasing individual age and, for later maternal ages, with increasing maternal age.
• The findings suggest maternal effect senescence can evolve similarly to individual senescence, as per Hamilton's theory.

Conclusions:

• Maternal effect senescence poses a significant fitness cost, driven by reduced reproductive output in older mothers.
• The developed modeling approach is broadly applicable for studying maternal effects on fitness across diverse taxa.
• Maternal effect senescence can be a target of natural selection, contributing to the evolution of aging.