This week, we are pleased to welcome our own Drew Sauve.
Phenotypic plasticity drives phenological change in a declining Arctic colony of Black Guillemots
The ability of individuals to adjust phenology is predicted to be an important response to adapting to climate change. Changes in phenology could occur either through phenotypic plasticity or microevolutionary change. To date, few studies have investigated these processes in Arctic environments, where temperature is rising at a greater rate than the global mean. The speaker evaluated the contribution of phenotypic plasticity and microevolution to changes in phenology associated with annual variation in snowmelt and female breeding age over a 42-year dataset from an Arctic population of Black Guillemots (Cepphus grylle mandtii). Overall, phenotypic plasticity was the driver of phenological change (egg-laying date) in the Black Guillemots. The speaker used an animal model to decompose the variance observed in laying date and annual fledging success into environmental and genetic components. Bivariate animal models were then used to estimate phenotypic, genetic, and environmental selection on laying date. A regression of the posterior distribution of breeding values for clutch initiation on time was used to determine if microevolutionary change contributed to the shift in egg-laying date. During the study period mean egg-laying date advanced 7.9 days, snowmelt advanced 5.8 days, and the average female breeding experience increased by 4.7 years. Earlier egg-laying was associated with experienced mothers, earlier snowmelt, and increased fitness. Individuals advanced egg-laying at different rates as they aged but responded similarly to variation in snowmelt. Individuals that laid earlier when they were young tended to have an increased annual fitness. Heritability of egg-laying date was low (h2 = 0.07[0.04-0.10]) and there was no evidence of microevolution contributing to the change in phenology. The results suggest that covariation between egg-laying date and fitness is driven by environmental, but not genetic factors. Consequently, phenological change in Black Guillemots is driven by phenotypic plasticity with limited potential for evolutionary change.