Genetic variation in phenological and phenotypic traits can be harbored in populations due to the past history of local selection or drift. Plants experience significant environmental heterogeneity across spatial and temporal scales. As an endogenous regulator of biological processes, the circadian clock is an important determinant of fitness; yet significant variation in clock period length exists not only among but also within populations. Few studies have examined the interaction of the environment and the circadian clock within natural populations, explicitly examining the downstream effects on plant growth and development over a growing season. For this project, eleven populations of a local plant species (Boechera stricta) were selected to assess for circadian period and were also measured in situ for phenology and growth. The populations were selected by their location in multiple mountain ranges and occurring along an elevational gradient. Seeds collected were used for leaf movement assays to determine values of circadian period for each B. stricta population.
Results/Conclusions
Across the eleven populations, the mean values for circadian period among the populations ranged from 20.6h to 24.8h. For the populations of B. stricta, variation for growth traits was higher within than among populations. Many phenological traits track with elevation; at higher elevations, reduced variation for flowering and fruiting dates is found, which correlates both with a narrower range of circadian period and lower temperatures with a shorter growing season. This contrasts with higher intrapopulation variation for plant traits from lower elevations. Initiation of flowering is strongly affected by the environment; however, intervals between developmental stages are associated with the plant’s circadian period with no direct association to the environment of origin. Quantitative variation in phenological traits both before and during anthesis is greatly understudied, outside of flowering time itself, and this research demonstrates a correlation between the clock and transitions from flowering to fruiting and subsequent developmental stages. As well, we demonstrate that the interaction of environment and clock relate to plant growth and overall fitness. As the clock is an important determinant of diverse traits, the extent of intrapopulation genetic variation in the clock determines the potential for adaptive evolution within plant populations.