title: Selection during crop diversification involves correlated evolution of the circadian clock and ecophysiological traits in Brassica rapa.
abstract: Crop selection often leads to dramatic morphological diversification, in which allocation to the harvestable component increases. Shifts in allocation are predicted to impact (as well as rely on) physiological traits; yet, little is known about the evolution of gas exchange and related anatomical features during crop diversification. In Brassica rapa, we tested for physiological differentiation among three crop morphotypes (leaf, turnip, and oilseed) and for correlated evolution of circadian, gas exchange, and phenological traits. We also examined internal and surficial leaf anatomical features and biochemical limits to photosynthesis. Crop types differed in gas exchange; oilseed varieties had higher net carbon assimilation and stomatal conductance relative to vegetable types. Phylogenetically independent contrasts indicated correlated evolution between circadian traits and both gas exchange and biomass accumulation; shifts to shorter circadian period (closer to 24 h) between phylogenetic nodes are associated with higher stomatal conductance, lower photosynthetic rate (when CO2 supply is factored out), and lower biomass accumulation. Crop type differences in gas exchange are also associated with stomatal density, epidermal thickness, numbers of palisade layers, and biochemical limits to photosynthesis. Brassica crop diversification involves correlated evolution of circadian and physiological traits, which is potentially relevant to understanding mechanistic targets for crop improvement.
authors.affiliation: Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Yarkhunova
authors.affiliation: Center for Conservation and Sustainable Development, Missouri Botanical Garden, St Louis, MO, 63166, USA.
authors.forename: Christine E
authors.initials: CE
authors.lastname: Edwards
authors.affiliation: Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Brent E
authors.initials: BE
authors.lastname: Ewers
authors.affiliation: Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Baker
authors.affiliation: Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Timothy Llewellyn
authors.initials: TL
authors.lastname: Aston
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 Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Lou
authors.affiliation: Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, 82071, USA.|Department of Molecular Biology, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Weinig
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D018533:Biomass; D029741:Brassica rapa / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D002245:Carbon Dioxide / Q000378:metabolism; D057906:Circadian Clocks; D018548:Cotyledon / Q000502:physiology; D018556:Crops, Agricultural / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D060146:Ecotype; D008027:Light; D010788:Photosynthesis / Q000528:radiation effects; D054046:Plant Stomata / Q000502:physiology / Q000528:radiation effects
chemical_list: D002245:Carbon Dioxide
keywords: Brassica rapa; Farquhar model; circadian rhythms; crop diversification; ecophysiological traits; leaf anatomy