The Past Is Never Dead, It Isn't Even Past: Maternal Environment Affects Multiple Generations of Offspring via Hormone Provisioning

An animal’s phenotype may be shaped by its genes, but also reflects its own environment and often that of its parents. Nongenetic parental effects are often mediated by steroid hormones, and operate between parents and offspring through mechanisms that are well described in vertebrate and non-vertebrate model systems. However, less is understood about the strength and frequency of hormone mediated nongenetic parental effects across more than one generation of descendants, and in nonmodel systems. In Chapter 2, I report that variation in the ecdysteroid hormones (ESH) provided by female house crickets (Acheta domesticus) to their eggs can be robustly, replicably measured using an Enzyme Immunoassay technique. In Chapter 3, I show that variation in the ESH that female A. domesticus deposit into their eggs determines the early development rates of their offspring. I also show that variation in the active forms of ESH provided by a female house cricket to her eggs derives primarily from the quality of nutrition available to her mother and maternal grandmother, regardless of genetic background, age at oviposition, or any contribution of ESH by her mate. In Chapter 4, I uncover a potential mechanism of generating delayed density dependence by showing that female A. domesticus alter their ESH provisioning strategy in response to social density. In Chapter 5, I demonstrate that these effects are not limited to lab-raised species, but are relevant to and present in at least two species of wild Gryllid (Gryllus veletis and G. pennsylvanicus). In sum, work reported here demonstrates the power of variable hormone provisioning by mothers to their offspring. These findings highlight the importance of distinguishing between phenotypic plasticity and genetic effects in observing field and laboratory organisms across time and space.PHDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/143928/1/crockerk_1.pd