Differences in seed dormancy and germination in amphicarpic legumes: manifold bet-hedging in space and time

Abstract

Abstract Aims Dispersal through space or time via dormancy is one of the primary processes whereby organisms can influence the environment they experience. In plants, strong evolutionary correlations are expected between the two kinds of dispersal because both are performed by the seeds and play comparable adaptive roles. In this paper, we investigated these evolutionary correlations using amphicarpic plants, which simultaneously produce aerial seeds with high spatial dispersal propensity and subterranean seeds that do not disperse. Methods We investigated the variation in dormancy and germination in aerial and subterranean seeds of two amphicarpic legumes (Vicia amphicarpa L. and Lathyrus amphicarpos L.) and two closely related homocarpic taxa (Vicia sativa L. and Lathyrus cicera L.) by estimating germination percentages following different combinations of dormancy breaking treatments (i.e. dry after-ripening, cold stratification and physical scarification). Important Findings Our results showed complex interactions between spatial and temporal dispersal. Right after dispersal, aerial seeds were more dormant than their subterranean counterparts, but this trend reversed with after-ripening, as seeds developed physical dormancy. Seeds of homocarpic plants germinated at higher percentages than those of their amphicarpic congeners and lost dormancy homogeneously with after-ripening. Conversely, amphicarpic seeds exhibited varied dormancy strategies modulated by both physiological and physical dormancy. These are expected to increase variation in emergence timing, providing multiple levels of diversifying bet-hedging. This strategy might be adaptive under highly unpredictable conditions by enabling plants to rely on historically favorable sites in good seasons without preventing spatial and temporal migration.