Abstract :
[en] When invading new environments, a plant invader may express new phenotypes as a result of different ecological and genetic processes. It includes phenotypic plasticity, local adaptation, environmental maternal effects, and genetic drift. The quantification of each of these factors is crucial in the study of biological invasions.
Ambrosia artemisiifolia L. invasion success is strongly linked to seed characteristics (dispersal by human activities, long-lived soil seed bank, etc.). Known as an opportunist and a colonizer, the species is often limited by the competition from other plants. In the early stages of development, the seedlings can be quickly outcompeted and a rapid growth is therefore a major advantage.
First, this study aims to analyze the seed traits variation, and to detect an impact of these traits on the early development of the seedling (environmental maternal effect). Second, we aimed to quantify the respective role of phenotypic plasticity, environmental maternal effect, local adaptation and genetic drift on seedlings phenotype.
Variability of seeds from 3 geographical zones (Belgium – Centre of France – South of France) was assessed. We measured the seed variation in mass, length, width, circularity, and pigmentation. Seeds were disposed in growth chamber under two temperature treatments. After two months, we compared seedling phenotypic variation in germination time, height, aboveground biomass, belowground biomass, early competitive performance, and the final leaf area.
We found a high variability of seed traits. Seeds were varying significantly among zones, populations, and parents, with more than 30% of the variation attributable to the mother plant identity.
The main sources of seedling phenotypic variation appeared to be phenotypic plasticity and environmental maternal effect. No genetic differentiation was detected in this study. Seed mass was positively correlated to seedling biomass, early competitive performance, and the final leaf area. The relevance of traits reflecting environmental maternal effect is discussed.
Phenotypic plasticity and seed characteristics appear to play a major role in the invasion success.
