Intra-annual and within-inflorescence variation in reproductive success of the annual Silene canescens: environmental maternal effect and resource competition

Intra-specific variation in reproductive success is often found among populations but also at the intraindividual level. Differential environmental conditions during flower phenology and the arrangement of flowers within inflorescences may explain large amount of this variation. In annual plants environmental maternal effects are known to be particularly strong, especially concerning variation in seed traits. Here, we studied flowering phenology and female reproductive success in one population of the interdunal annual plant Silene canescens Ten. (Caryophyllaceae). The goal of this study is to determine the effect of maternal environmental conditions and of intra-inflorescence flower position on reproductive success (fruit set, seed set and seed traits), while accounting for the con-specific individual densities and their vegetative functional traits (plant height, root depth and lateral extent, leaf area). This study is part of a two-year lasting project aimed at analyzing the impact of climate change on coastal and marine ecosystems, financed by the University of Pisa. To this end, we selected 10 plots of equal area (80 m2 ) visited three times over one reproductive season in the northern coasts of Tuscany. Each plot was randomly selected to ensure homogeneity and representativeness of the studied population. Within each plot we sampled 5 flowering individuals and annotated environmental characteristics (distance from the sea, altitude, disturbance), total vegetation cover and the total number of S. canescens flowering individuals. Reproductive success at the fruit level (fruit set) was calculated separately in three different parts of similar size within the inflorescence (i.e., bottom, middle, top) on the basis of the total number of flowers within each part. Reproductive success at the seed level was quantified by (a) calculating the seed set (on the basis of the mean number of ovules per fruit) in each inflorescence part, (b) measuring the average seed mass in each inflorescence part, and (c) estimating viability, primary dormancy and germination speed of seeds produced in each inflorescence part. By using mixed regressive models and multivariate approach, we will be able to evaluate covariances and trade-offs between reproductive outputs, vegetative traits and environmental conditions, while considering genetic (individual) and spatial (plot) random effects. Overall, we expect to separate the effects of intrainflorescence (resource allocation) from those of intra-population (maternal environmental conditions) on annual plant reproductive responses.