Disentangling pre- and post-natal maternal age effects on offspring performance in an insect with elaborate maternal care

Maternal effect senescence has attracted much recent scientific interest. However, the age-related effects of pre- and post-natal maternal age are often conflated, as these naturally originate from the same individual. Additionally, many maternal effect senescence studies fail to account for potential biases associated with selective disappearance. Here we use a cross-fostered laboratory population of burying beetle, Nicrophorus vespilloides, to examine both the effects of female pre- and post-natal maternal age on offspring life history traits and the post-care outcomes of mothers while accounting for selective disappearance of post-natal caregivers. Neither pre- nor post-natal maternal age affected offspring longevity or larval weight at hatching, and post-natal age had no effect upon post-care maternal outcomes except to confirm the presence of actuarial senescence. There was weak evidence for concave relationships between two larval traits (dispersal weight and survival) and the age of egg-producers. Selective disappearance of caregivers had no clear effect on any of the measured offspring traits. Contrary to predictions from evolutionary theory, maternal effect senescence and reproductive effort increases do not always manifest, and current theory may be insufficient to account for the true diversity of aging patterns relating to maternal care.