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Big Pine, CA, United States

Burghardt L.T.,Duke University | Metcalf C.J.E.,University of Oxford | Metcalf C.J.E.,Princeton University | Wilczek A.M.,Deep Springs College | And 2 more authors.
American Naturalist | Year: 2015

Organisms develop through multiple life stages that differ in environmental tolerances. The seasonal timing, or phenology, of life-stage transitions determines the environmental conditions to which each life stage is exposed and the length of time required to complete a generation. Both environmental and genetic factors contribute to phenological variation, yet predicting their combined effect on life cycles across a geographic range remains a challenge.We linked submodels of the plasticity of individual life stages to create an integrated model that predicts life-cycle phenology in complex environments. We parameterized the model for Arabidopsis thaliana and simulated life cycles in four locations. We compared multiple “genotypes” by varying two parameters associated with natural genetic variation in phenology: seed dormancy and floral repression. The model predicted variation in life cycles across locations that qualitatively matches observed natural phenology. Seed dormancy had larger effects on life-cycle length than floral repression, and results suggest that a genetic cline in dormancy maintains a life-cycle length of 1 year across the geographic range of this species. By integrating across life stages, this approach demonstrates how genetic variation in one transition can influence subsequent transitions and the geographic distribution of life cycles more generally. © 2015 by The University of Chicago.

Hall J.A.,Oregon State University | Bobe G.,Oregon State University | Hunter J.K.,Oregon State University | Hunter J.K.,Deep Springs College | And 7 more authors.
PLoS ONE | Year: 2013

Selenium (Se) is an essential micronutrient in cattle, and Se-deficiency can affect morbidity and mortality. Calves may have greater Se requirements during periods of stress, such as during the transitional period between weaning and movement to a feedlot. Previously, we showed that feeding Se-fertilized forage increases whole-blood (WB) Se concentrations in mature beef cows. Our current objective was to test whether feeding Se-fertilized forage increases WB-Se concentrations and performance in weaned beef calves. Recently weaned beef calves (n = 60) were blocked by body weight, randomly assigned to 4 groups, and fed an alfalfa hay based diet for 7 wk, which was harvested from fields fertilized with sodium-selenate at a rate of 0, 22.5, 45.0, or 89.9 g Se/ha. Blood samples were collected weekly and analyzed for WB-Se concentrations. Body weight and health status of calves were monitored during the 7-wk feeding trial. Increasing application rates of Se fertilizer resulted in increased alfalfa hay Se content for that cutting of alfalfa (0.07, 0.95, 1.55, 3.26 mg Se/kg dry matter for Se application rates of 0, 22.5, 45.0, or 89.9 g Se/ha, respectively). Feeding Se-fertilized alfalfa hay during the 7-wk preconditioning period increased WB-Se concentrations (PLinear<0.001) and body weights (PLinear = 0.002) depending upon the Se-application rate. Based upon our results we suggest that soil-Se fertilization is a potential management tool to improve Se-status and performance in weaned calves in areas with low soil-Se concentrations. © 2013 Hall et al.

Chew Y.H.,University of Edinburgh | Chew Y.H.,Synthetic and Systems Biology Center | Wilczek A.M.,Deep Springs College | Welch S.M.,Kansas State University | And 3 more authors.
New Phytologist | Year: 2012

In this study, we used a combination of theoretical (models) and experimental (field data) approaches to investigate the interaction between light and temperature signalling in the control of Arabidopsis flowering. We utilised our recently published phenology model that describes the flowering time of Arabidopsis grown under a range of field conditions. We first examined the ability of the model to predict the flowering time of field plantings at different sites and seasons in light of the specific meteorological conditions that pertained. Our analysis suggested that the synchrony of temperature and light cycles is important in promoting floral initiation. New features were incorporated into the model that improved its predictive accuracy across seasons. Using both laboratory and field data, our study has revealed an important seasonal effect of night temperatures on flowering time. Further model adjustments to describe phytochrome (phy) mutants supported our findings and implicated phyB in the temporal gating of temperature-induced flowering. Our study suggests that different molecular pathways interact and predominate in natural environments that change seasonally. Temperature effects are mediated largely during the photoperiod during spring/summer (long days) but, as days shorten in the autumn, night temperatures become increasingly important. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Banta J.A.,University of Texas at Tyler | Ehrenreich I.M.,University of Southern California | Gerard S.,Harvard University | Chou L.,Animal Medical Center | And 4 more authors.
Ecology Letters | Year: 2012

Species often harbour large amounts of phenotypic variation in ecologically important traits, and some of this variation is genetically based. Understanding how this genetic variation is spatially structured can help to understand species' ecological tolerances and range limits. We modelled the climate envelopes of Arabidopsis thaliana genotypes, ranging from early- to late-flowering, as a function of several climatic variables. We found that genotypes with contrasting alleles at individual flowering time loci differed significantly in potential range size and niche breadth. We also found that later flowering genotypes had more restricted range potentials and narrower niche breadths than earlier flowering genotypes, indicating that local selection on flowering can constrain or enhance the ability of populations to colonise other areas. Our study demonstrates how climate envelope models that incorporate ecologically important genetic variation can provide insights into the macroecology of a species, which is important to understand its responses to changing environments. © 2012 Blackwell Publishing Ltd/CNRS.

Groen S.C.,Harvard University | Groen S.C.,University of Cambridge | Whiteman N.K.,Harvard University | Whiteman N.K.,University of Arizona | And 19 more authors.
Plant Cell | Year: 2013

Multicellular eukaryotic organisms are attacked by numerous parasites from diverse phyla, often simultaneously or sequentially. An outstanding question in these interactions is how hosts integrate signals induced by the attack of different parasites.We used a model system comprised of the plant host Arabidopsis thaliana, the hemibiotrophic bacterial phytopathogen Pseudomonas syringae, and herbivorous larvae of the moth Trichoplusia ni (cabbage looper) to characterize mechanisms involved in systemicinduced susceptibility (SIS) to T. ni herbivory caused by prior infection by virulent P. syringae. We uncovered a complex multilayered induction mechanism for SIS to herbivory. In this mechanism, antiherbivore defenses that depend on signaling via (1) the jasmonic acid-isoleucine conjugate (JA-Ile) and (2) other octadecanoids are suppressed by microbe-associated molecular pattern-triggered salicylic acid (SA) signaling and infection-triggered ethylene signaling, respectively. SIS to herbivory is, in turn, counteracted by a combination of the bacterial JA-Ile mimic coronatine and type III virulence-associated effectors. Our results show that SIS to herbivory involves more than antagonistic signaling between SA and JA-Ile and provide insight into the unexpectedly complex mechanisms behind a seemingly simple trade-off in plant defense against multiple enemies. © 2013 American Society of Plant Biologists. All rights reserved.

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