Clinal variation in seed traits influencing life cycle timing in Arabidopsis thaliana.

Early life history transitions are crucial determining lifetime survival and fecundity. Adaptive evolution in early life history traits involves a complex interplay between the developing plant and its current and future environments. We examined the plant’s earliest life history traits, dissecting an integrated suite of pre-germination processes: primary dormancy, thermal induction of secondary dormancy, and seasonal germination response. We examined genetic variation in the three processes, genetic correlations among the processes, and the scaling of germination phenology with the source populations’ climates. A spring annual life-history was associated with genetic propensities toward both strong primary dormancy and heat-induced secondary dormancy, alone or in combination. Lineages with similar winter and spring annual life-history have both weak primary dormancy and weak thermal dormancy induction. A genetic bias to adopt a spring annual strategy mediated by rapid loss of primary d...