title: Variation in circadian rhythms is maintained among and within populations in Boechera stricta.
abstract: Circadian clocks have evolved independently in all three domains of life, and fitness benefits of a functional clock have been demonstrated in experimental genotypes in controlled conditions. Still, little is known about genetic variation in the clock and its fitness consequences in natural populations from heterogeneous environments. Using Wyoming populations of the Arabidopsis relative Boechera stricta as our study system, we demonstrate that genetic variation in the clock can occur at multiple levels: means of circadian period among populations sampled at different elevations differed by less than 1 h, but means among families sampled within populations varied by as much as 3.5 h. Growth traits also varied among and within populations. Within the population with the most circadian variation, we observed evidence for a positive correlation between period and growth and a negative correlation between period and root-to-shoot ratio. We then tested whether performance tradeoffs existed among families of this population across simulated seasonal settings. Growth rankings of families were similar across seasonal environments, but for root-to-shoot ratio, genotype × environment interactions contributed significantly to total variation. Therefore, further experiments are needed to identify evolutionary mechanisms that preserve substantial quantitative genetic diversity in the clock in this and other species.
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Matti J
authors.initials: MJ
authors.lastname: Salmela
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Greenham
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Lou
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.
authors.forename: C Robertson
authors.initials: CR
authors.lastname: McClung
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.|Program in Ecology, University of Wyoming.
authors.forename: Brent E
authors.initials: BE
authors.lastname: Ewers
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.|Program in Ecology, University of Wyoming.|Department of Molecular Biology, University of Wyoming.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Weinig
mesh_terms: D019607:Brassicaceae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D014644:Genetic Variation / Q000235:genetics / Q000502:physiology; D011153:Population; D012621:Seasons
keywords: Adaptation; circadian clock; environmental heterogeneity; genetic differentiation; genotype × environment interaction; maintenance of genetic variation