Genotype accounts for intraspecific variation in the timing and duration of multiple, sequential life-cycle events in a willow species

PremisePhenological variation among individuals within populations is common and has a variety of ecological and evolutionary consequences, including forming the basis for population-level responses to environmental change. Although the timing of life-cycle events has genetic underpinnings, whether intraspecific variation in the duration of life-cycle events reflects genetic differences among individuals is poorly understood. MethodsWe used a common garden experiment with 10 genotypes of Salix hookeriana (coastal willow) from northern California, United States to investigate the extent to which genetic variation explains intraspecific variation in the timing and duration of multiple, sequential life-cycle events: flowering, leaf budbreak, leaf expansion, fruiting, and fall leaf coloration. We used seven clones of each genotype, for a total of 70 individual trees. ResultsGenotype affected each sequential life-cycle event independently and explained on average 62% of the variation in the timing and duration of vegetative and reproductive life-cycle events. All events were significantly heritable. A single genotype tended to be early or late across life-cycle events, but for event durations, there was no consistent response within genotypes. ConclusionsThis research demonstrates that genetic variation can be a major component underlying intraspecific variation in the timing and duration of life-cycle events. It is often assumed that the environment affects durations, but we show that genetic factors also play a role. Because the timing and duration of events are independent of one another, our results suggest that the effects of environmental change on one event will not necessarily cascade to subsequent events.

Automated summary

Phenological variation within populations has ecological and evolutionary consequences, but the genetic basis of intraspecific variation in the duration of life-cycle events is poorly understood. This study demonstrates that genetic factors explain a significant proportion of the variation in the timing and duration of multiple life-cycle events in Salix hookeriana.