The Hellmann Lab at University of Dayton
The Hellmann Lab
The Ohio State University
Exploring the underlying mechanisms of phenotypic plasticity
TRANSGENERATIONAL PLASTICITY
Genetic change via evolution takes many generations, but in a changing environment, it is advantageous for parents to plastically respond to their current environment and produce offspring with phenotypes that match current environmental demands. Transgenerational plasticity (TGP) – when parental environments alter the phenotype of future generations – can program offspring for the environment they are likely to experience. I have several areas of interest under this topic:
1. The specificity of paternal effects
Despite growing evidence for parental effects in response to environmental challenges such as predation risk, the ways in which parental effects prime offspring for specific environmental conditions is largely unknown. On one hand, there may be one conserved pathway by which the parental environment alters offspring phenotypes, such that different, potentially threatening or stressful stimuli experienced by parents (e.g., low food availability, predation) have the same intergenerational consequences (e.g., dispersal, altered stress responses). On the other hand, parental effects may be more fine-tuned, varying across different environmental stimuli or across different populations. If this is the case, transgenerational cues may induce tailored changes in offspring phenotypes that are adaptive for coping with specific environmental challenges or selective pressures. I am exploring how sperm-mediated paternal effects in threespined sticklebacks (Gasterosteus aculeatus) vary with different paternal stimuli (e.g., the type of predator the father encounters), across different populations, and with the length and timing of paternal exposure.
Mothers and fathers may favor different phenotypes in their offspring and the optimal phenotype for sons may be different from the optimal phenotype for daughters. I am examining sex-specific patterns of TGP in response to predation risk in threespined sticklebacks (Gasterosteus aculeatus). I found that maternal and paternal experience with predation risk has distinct effects on offspring, with non-additive interactions between maternal and paternal experiences on some, but not all offspring traits. Further, I found strong phenotypic differences between sons and daughters of predator-exposed parents. These differences emerge well before reproductive maturity and have lineage-specific consequences for the next generation: F2 phenotypes differ depending on whether predation risk is experienced by maternal grandfathers, paternal grandfathers, or both grandfathers. These results provide strong evidence that offspring do not receive a general message about predation risk from their parents, but that mothers and fathers convey different information and parental cues alter different developmental programs in sons and daughters.
Male stickleback in breeding colors
Gravid female stickleback
2. Sex-specific transgenerational plasticity
PHENOTYPIC PLASTICITY INDUCED BY SOCIAL ENVIRONMENTS
1. Male-male cooperation
Although male-male conflict drives sexual selection in most species, new theory suggests that male-male cooperation is an underappreciated mechanism underlying the evolution of sexually-selected traits. I seek to understand how both cooperation and competition among unrelated males affects sexual selection and reproductive behaviors. To do this, I am conducting a series of field experiments with Suzanne Alonzo at UC Santa Cruz and Kelly Stiver at Southern Connecticut State University to understand how outside competition and spawning success influence parenting behavior and cooperation between pairs of unrelated males in the ocellated wrasse (Symphodus ocellatus).
2. Cooperation in group-living species
In nearly all species, social interactions are highly influential in determining an individual’s success within its environment. In humans, positive social interactions are correlated with increased job success, better health, and reduced stress; in other species, social interactions are critical determinants of disease spread, predation avoidance, and learning. In many species, individuals form groups and interact primarily with other group members; however, they also interact with members of other groups.
Most studies quantifying social interactions in group-living species investigate how individuals behave within their group, but do not consider how interactions within their group may change due to the presence of or interactions with other groups. This is problematic, as it is difficult to understand why individuals would cooperate or resolve conflict within their group without understanding the extent to which neighboring groups provide opportunities to leave the group. Similarly, it is difficult to understand the extent to which individuals pursue reproductive opportunities within the group without understanding how neighboring groups offer additional opportunities for current and future reproduction. My dissertation research explores how neighboring groups alter within-group social and reproductive dynamics in Neolamprologus pulcher, a cooperatively breeding cichlid fish native to Lake Tanganyika.