Maternal age effects on fecundity and offspring egg‐to‐adult viability are not affected by mitochondrial haplotype

Abstract

While numerous studies have demonstrated that mitochondrial genetic variation can shape organismal phenotype, the level of contribution the mitochondrial genotype makes to life‐history phenotype across the life course remains unknown. Furthermore, a clear technical bias has emerged in studies of mitochondrial effects on reproduction, with many studies conducted on males, but few on females. Here, we apply a classic prediction of the evolutionary theory of aging to the mitochondrial genome, predicting the declining force of natural selection with age will have facilitated the accumulation of mtDNA mutations that confer late‐life effects on female reproductive performance. This should lead to increased levels of mitochondrial genetic variation on reproduction at later‐life stages. We tested this hypothesis using thirteen strains of Drosophila melanogaster that each possessed a different mitochondrial haplotype in an otherwise standard nuclear genetic background. We measured fecundity and egg‐to‐adult viability of females over five different age classes ranging from early to late life and quantified the survival of females throughout this time period. We found no significant variation across mitochondrial haplotypes for the reproductive traits, and no mitochondrial effect on the slope of decline in these traits with increasing age. However, we observed that flies that died earlier in the experiment experienced steeper declines in the reproductive traits prior to death, and we also identified maternal and grandparental age effects on the measured traits. These results suggest the mitochondrial variation does not make a key contribution to shaping the reproductive performance of females.

Age of Both Parents Influences Reproduction and Egg Dumping Behavior in Drosophila melanogaster

“…We found the egg laying rate in daughters of 2 old parents to resume to normal levels by day 6, however, the egg-to-adult viability remained lowest over all 10 days. Overall, the general pattern of declining egg-to-adult viability over time was observed across all parental age treatments, and is consistent with previous studies (Miller et al 2014; Koch et al 2018). In terms of reproductive fitness, the low fidelity of the day 1 embryos was partially compensated by the egg dumping behavior.…”

“…For example, studies in Drosophila melanogaster have shown increasing female age to be associated with a range of reproductive phenotypes and behaviors including the numbers of eggs laid and egg to adult viability (reviewed in Miller et al 2014). Very little attention has been aimed at understanding trans-generational effects of parental age on offspring fitness traits (but see Koch et al 2018), in spite of a growing body of evidence that trans-generational effects are prevalent throughout model animal study systems (Mousseau and Dingle 1991; Sartorius and Nieschlag 2010; Rando 2012) and can impact human health (D’Onofrio et al 2014; McGrath et al 2014).…”

Life History Effects Linked to an Advantage for wAu Wolbachia in Drosophila

“…This includes a reduction in offspring number when flies were reared on grapes, and a decrease in fecundity, increase in development time, and inconsistent effect of offspring weight in older parents. Female age effects on reproduction have been reported previously (e.g., [40]), and in our case, may reflect an exhaustion of eggs in older females, while the longer development time and weight changes may reflect changes in provisioning of eggs in older females. However, apparent age effects should be treated cautiously because the flies were transferred to new media/fruit, which may have differed from the initial batch used.…”

Inbreeding depression causes reduced fecundity in Golden Retrievers

“…Litter size was calculated as the variable livepup, number of live puppies born, compiled from MAF records. A linear mixed model (coi.with.barcode) was generated with the lmer function (lme4, Bates et al 2015) in R, considering F ROH (coi_with_public), median withers height (median_height), and age in years at the time of litter recording (age_at_visit_year) as fixed effect variables and unique dam ID (barcode) as a random effect variable (as described in Cnaan et al 1997 and implemented in Lüpold et al 2010, Koch et al 2018):coi.with.barcode < - lmer(livepup ~ coi_with_public + age_at_visit_year + median_height + (1|barcode), data = all_data_for_kinship)…”