Transgenerational and Intergenerational Maternal Age Effects Exhibit Complex, Genotype-Specific Patterns of Inheritance.

AbstractMaternal age effects, in which offspring phenotype is determined by a mother's age at the time of birth, are common and variable among diverse taxa, but relatively little is known about their dynamics across multiple generations. Characterizing patterns of inter- and transgenerational inheritance of maternal age can provide insight into potential molecular and evolutionary mechanisms. In two strains of the rotifer Brachionus manjavacas, we maintained young and old maternal age lineages and tested whether maternal age effects on lifespan and reproduction changed in magnitude or direction across three generations. In the third generation, we initiated switched maternal age cohorts to achieve factorial combinations of maternal and grandmaternal ages to test for the reversibility of maternal age effects. For both strains, maternal age effects on lifetime reproductive output were consistent across generations, with no evidence for the accumulation of either positive or negative effects across old and young lineages. In one strain, offspring with older mothers had reduced lifespan, but the magnitude of this maternal age effect declined across generations. Switched maternal age cohorts revealed that effects were reversible within one generation, but only for certain response metrics and in a strain-dependent manner. Given the noncumulative and often reversible nature of the maternal age effects observed here, we hypothesize that dynamic epigenetic and/or mitochondrial mechanisms are more likely to be involved than are changes to maternal provisioning or mutation accumulation.