Differential Effects of Early- and Late-Life Access to Carotenoids on Adult Immune Function and Ornamentation in Mallard Ducks (Anas platyrhynchos)

Environmental conditions early in life can affect an organism’s phenotype at adulthood, which may be tuned to perform optimally in conditions that mimic those experienced during development (Environmental Matching hypothesis), or may be generally superior when conditions during development were of higher quality (Silver Spoon hypothesis). Here, we tested these hypotheses by examining how diet during development interacted with diet during adulthood to affect adult sexually selected ornamentation and immune function in male mallard ducks (Anas platyrhynchos). Mallards have yellow, carotenoid-pigmented beaks that are used in mate choice, and the degree of beak coloration has been linked to adult immune function. Using a 2×2 factorial experimental design, we reared mallards on diets containing either low or high levels of carotenoids (nutrients that cannot be synthesized de novo) throughout the period of growth, and then provided adults with one of these two diets while simultaneously quantifying beak coloration and response to a variety of immune challenges. We found that both developmental and adult carotenoid supplementation increased circulating carotenoid levels during dietary treatment, but that birds that received low-carotenoid diets during development maintained relatively higher circulating carotenoid levels during an adult immune challenge. Individuals that received low levels of carotenoids during development had larger phytohemagglutinin (PHA)-induced cutaneous immune responses at adulthood; however, dietary treatment during development and adulthood did not affect antibody response to a novel antigen, nitric oxide production, natural antibody levels, hemolytic capacity of the plasma, or beak coloration. However, beak coloration prior to immune challenges positively predicted PHA response, and strong PHA responses were correlated with losses in carotenoid-pigmented coloration. In sum, we did not find consistent support for either the Environmental Matching or Silver Spoon hypotheses. We then describe a new hypothesis that should be tested in future studies examining developmental plasticity

Evolution of sex-specific pace-of-life syndromes: genetic architecture and physiological mechanisms

Sex differences in life history, physiology, and behavior are nearly ubiquitous across taxa, owing to sex-specific selection that arises from different reproductive strategies of the sexes. The pace-of-life syndrome (POLS) hypothesis predicts that most variation in such traits among individuals, populations, and species falls along a slow-fast pace-of-life continuum. As a result of their different reproductive roles and environment, the sexes also commonly differ in pace-of-life, with important consequences for the evolution of POLS. Here, we outline mechanisms for how males and females can evolve differences in POLS traits and in how such traits can covary differently despite constraints resulting from a shared genome. We review the current knowledge of the genetic basis of POLS traits and suggest candidate genes and pathways for future studies. Pleiotropic effects may govern many of the genetic correlations, but little is still known about the mechanisms involved in trade-offs between current and future reproduction and their integration with behavioral variation. We highlight the importance of metabolic and hormonal pathways in mediating sex differences in POLS traits; however, there is still a shortage of studies that test for sex specificity in molecular effects and their evolutionary causes. Considering whether and how sexual dimorphism evolves in POLS traits provides a more holistic framework to understand how behavioral variation is integrated with life histories and physiology, and we call for studies that focus on examining the sex-specific genetic architecture of this integration

Ab Initio Study of Proton Transfers Including Effects of Electron Correlation

Proton transfers in a number of systems are investigated using ab initio molecular orbital methods. Calculations are carried out with several different basis sets ranging in size from 4–31G to 6–311G**. Electron correlation is included using Møller–Plesset (MP) perturbation theory to second and third orders. Enlargements of the basis set invariably lead to higher energy barriers to proton transfer, while substantial reductions result from inclusion of correlation effects. Application to (HOHOH)− of third-order MP theory with a triple-valence basis set augmented by polarization functions on oxygens and the central proton, denoted MP3/6–311G*(*), leads to excellent agreement with the results of Roos et al. whose calculations involved an extensive CI treatment with a large basis set. For equivalent hydrogen bond lengths, the transfer barrier in the cation (H2OHOH2)+ is nearly identical to that for the (HOHOH)− anion while the barrier in (H3NHNH3)+ is somewhat smaller. The reduction of the SCF barrier height resulting from inclusion of correlation is greater for (O2H3)− than for the above cations. The lowest energy structure of (O2H5)+ contains a symmetric hydrogen bond in which the proton is located midway between the two oxygens whereas asymmetric H bonds are found in the equilibrium geometries of (N2H7)+ and (S2H5)+. The difference in energy between the symmetric and asymmetric configurations of (O2H3)− is extremely small

Energetics and Electronic Rearrangements of Proton Transfer in (H3NHOH2)+

Proton transfer between N and O in the hydrogen-bonded system (H3NHOH2)+ is studied by ab initio molecular orbital methods. Potential energy curves are calculated at the hartree–Fock level using the 4–31G basis set for hydrogen bond lengths R(NO) varying from the equilibrium value of 2.664 to 3.10 Å. Short hydrogen bonds are associated with asymmetric single-well potentials in which the minimum corresponds to the NHO configuration. For longer R(NO) separations, the potential is of double-well form, including both NHO and NHO as minima. It is found that the height of the energy barrier to proton transfer is sensitive to both stretches and bends of the hydrogen bond. Continuous changes in the electron density are monitored at various stages of proton transfer via density difference maps and Mulliken population analyses. The initial loss of density from the proton-accepting molecule during the first half of the transfer is accelerated during the second half. A correlation is drawn between the energetics of transfer in a number of systems and the net charge lost by the proton-acceptor group

Genecology of Thurber’s Needlegrass ( Achnatherum thurberianum [Piper] Barkworth) in the Western United States

Thurber's needlegrass (Achnatherum thurberianum [Piper] Barkworth) is a key restoration species in the Great Basin and surrounding areas, yet comprehensive studies of how climate relates to genetic variation and seed zones for restoration projects are lacking. Potentially adaptive phenotypic traits of 66 diverse populations of Thurber's needlegrass were measured in common gardens at Central Ferry, Washington and Reno, Nevada in 2012 and 2013. Extensive genetic variation was observed among phenology, morphology, and production traits (P < 0.01), and canonical correlation was used to relate traits to source climate variables. Only with the first two canonical variates were F values significant (P < 0.05), explaining 42% and 18% of the variation, respectively. For variates 1 and 2, strong canonical correlations of 0.97 and 0.94 linked genetic variationwith source climates, providing evidence for climate-driven evolution. Pearson linear correlations indicated that populations from warmer, drier locations generally had earlier blooming and longer awns than those from cooler, wetter locations. Plants from warmer, drier locations also had higher survival at Central Ferry and higher leaf length to width (narrower leaves) at Reno in 2012. Regression of the canonical variates 1 and 2 for traits with source climate variables produced very strongmodels, explaining 94% and 87% of the variation in plant traits. Thesemodelswere used to map 12 seed zones encompassing 465 079 km2 in the Great Basin and surrounding areas with six seed zones representing 90% of the mapped area. We recommend using these seed zones to guide restoration of Thurber's needlegrass. © Published by Elsevier Inc. on behalf of The Society for Range Management.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information