Joint impact of competition, summer precipitation, and maternal effects on survival and reproduction in the perennial Hieracium umbellatum

Abstract

Most studies on consequences of environmental change focus on evolutionary and phenotypic plastic responses, but parental effects represent an additional mechanism by which organisms respond to their local environment. Parental effects can be adaptive if they enhance offsprings ability to cope with environments experienced by their parents, but can also be non-adaptive for instance when offspring from benign environments are just better provisioned and hence perform better than offspring from less benign environments. Parental effects originate from both the abiotic and biotic environmental variation. However, the effects of the parental abiotic and biotic environment are rarely studied together. We make use of an experimental set-up containing plots in a natural heath land, where summer precipitation was manipulated to reflect either ambient or drought conditions. In both plot types, competition from grasses was prevalent. We assessed survival and reproduction of Hieracium umbellatum offspring originating from ambient and drought plots grown in a factorial design with two levels of moisture (control and drought) and two levels of competition (grown with and without a local perennial grass). The maternal environment strongly affected offspring performance. Biomass and reproduction was higher in offspring from ambient plots in agreement with the hypothesis of a better maternal provisioning in the most benign environment. However, adding competition revealed potentially adaptive responses to survival, and altered allocation to reproduction in offspring from maternal drought plots. Under combined competition and drought (mimicking maternal drought plots), survival was only reduced in offspring from ambient plots, and offspring from drought plots survived best. When grown in competition under control watering conditions mimicking maternal ambient plots, offspring from drought plots (growing in an environment different from their maternal one) showed a 25% reduction in reproduction. Potential adaptive responses to the home maternal environment were only revealed when jointly manipulating levels of competition and water availability.