Maternal environmental effects on fitness, fruit morphology and ballistic seed dispersal distance in an annual forb

Abstract

1. Adaptive phenotypic plasticity enables plant lineages to match trait expression to contemporary environmental conditions, while maternal environmental effects arise in response to environmental factors encountered in the previous generation. Maternal effects on seed dispersal distance in spatially structured habitats could determine the level of microenvironmental variation encountered by a lineage across generations. 2. We conducted a greenhouse experiment that spanned three generations to assess the relationship between variation in maternal phenotype and seed dispersal distance, maternal environmental effects on fitness in response to variation in nutrient availability across generations, fruit morphology, and seed dispersal distance in populations of an invasive annual forb Erodium cicutarium growing on serpentine and non-serpentine soils. Macro- and micronutrient availability is lower on serpentine soils than surrounding non-serpentine soils and result in a significant source of stress for plants growing on serpentine soils. 3. The combined effects of maternal and offspring environment on the fitness of E. cicutarium were substantial. We demonstrated a positive relationship between fruit length and ballistic dispersal distance, and found no evidence for a trade-off between fruit length and seed number in either high- or low-nutrient environments. The maternal environment had a significant effect on the mean ballistic seed dispersal distance such that lineages exposed to consistent nutrient availability across generations disperse their seeds significantly farther than lineages exposed to environmental heterogeneity. Although lineages exposed to different environments across generations on average dispersed their seeds shorter distances, there was a marginally non-significant trend for greater variance in dispersal distance in response to environmental heterogeneity than lineages exposed to consistent environments across generations. On average, lineages from non-serpentine source populations had significantly greater variance in dispersal distance than serpentine lineages. 4. This pattern of maternal effects on mean seed dispersal distance, and the observed trend for maternal effects on the breadth of the dispersal kernel, could be adaptive in the mosaic serpentine soil landscape where E. cicutarium was collected. However, field experiments are needed to rigorously demonstrate the fitness consequences of maternal environmental effects on seed dispersal.