Genetics of adaptation: Experimental test of a biotic mechanism driving divergence in traits and genes.

The genes underlying adaptations are becoming known, yet the causes of selection on genes-a key step in the study of the genetics of adaptation-remains uncertain. We address this issue experimentally in a threespine stickleback species pair showing exaggerated divergence in bony defensive armor in association with competition-driven character displacement. We used semi-natural ponds to test the role of a native predator in causing divergent evolution of armor and two known underlying genes. Predator presence/absence altered selection on dorsal spines and allele frequencies at the Msx2a gene across a generation. Evolutionary trajectories of alleles at a second gene, Pitx1, and the pelvic spine trait it controls, were more variable. Our experiment demonstrates how manipulation of putative selective agents helps to identify causes of evolutionary divergence at key genes, rule out phenotypic plasticity as a sole determinant of phenotypic differences, and eliminate reliance on fitness surrogates. Divergence of predation regimes in sympatric stickleback is associated with coevolution in response to resource competition, implying a cascade of biotic interactions driving species divergence. We suggest that as divergence proceeds, an increasing number of biotic interactions generate divergent selection, causing more evolution in turn. In this way, biotic adaptation perpetuates species divergence through time during adaptive radiation in an expanding number of traits and genes

Rapid adaptive evolution of colour vision in the threespine stickleback radiation.

Vision is a sensory modality of fundamental importance for many animals, aiding in foraging, detection of predators and mate choice. Adaptation to local ambient light conditions is thought to be commonplace, and a match between spectral sensitivity and light spectrum is predicted. We use opsin gene expression to test for local adaptation and matching of spectral sensitivity in multiple independent lake populations of threespine stickleback populations derived since the last ice age from an ancestral marine form. We show that sensitivity across the visual spectrum is shifted repeatedly towards longer wavelengths in freshwater compared with the ancestral marine form. Laboratory rearing suggests that this shift is largely genetically based. Using a new metric, we found that the magnitude of shift in spectral sensitivity in each population corresponds strongly to the transition in the availability of different wavelengths of light between the marine and lake environments. We also found evidence of local adaptation by sympatric benthic and limnetic ecotypes to different light environments within lakes. Our findings indicate rapid parallel evolution of the visual system to altered light conditions. The changes have not, however, yielded a close matching of spectrum-wide sensitivity to wavelength availability, for reasons we discuss

Correlation Between the Microstructure and Mechanical Properties of Irradiated Fe-9Cr ODS

The growing global demand for energy will increasingly call upon fusion reactors and Generation IV nuclear fission reactors to supply safe and reliable energy worldwide. Ferritic/martensitic (F/M) alloys are leading candidates for structural components in these reactors because of their high strength, dimensional stability, and low activation. In novel reactor concepts, these materials will be subject to extreme operating conditions, accumulating doses of irradiation up to a few hundred displacements per atom (dpa) at temperatures as high as 600°C. Oxide dispersion strengthened (ODS) F/M alloys containing a dispersion of Y-Ti-0 nanoclusters have been developed to operate at even higher temperatures

Restoration vs. New Construction: How to Make the Right Decision

Restoration or new construction? That is a dilemma that educational leaders, particularly superintendents and school business officials, have had to wrestle with for years. In the past, state regulations often dictated whether school buildings should be renovated or torn down to make way for new construction. State reimbursement guidelines favored new construction over restoration for public school development by either withholding funds or denying the full state support for restoration projects. In fact, some states established complex formulas that mandated new construction if the cost of restoration exceeded approximately two-thirds of the new construction costs. Reversing the mindset among many educators and legislators that new construction is always the best option for districts has not been an easy sell for designers, preservationists, and school architects. However, restoration of school properties has been on the rise in recent years, fueled by citizens’ interest in maintaining community landmarks, by districts’ recognition of the importance of preserving existing schools as important community institutions, and by demonstrating that the restoration of aging buildings can be a cost-effective way to preserve history and create safe and exciting educational facilities

Principal Dispositions Regarding the Ohio Teacher Evaluation System

The Ohio Teacher Evaluation System (OTES) was first implemented during the 2013-14 school term. This study examined principals’ dispositions at the end of this school term. Findings revealed several major concerns. The most prominent were (a) not having sufficient time to implement the program properly, (b) basing a teacher’s performance heavily on student value-added data, and (c) being required to assist teachers in developing their annual improvement plans. Three independent variables, teaching experience, administrative experience, and level of school assignment, were found to have only a low level of association with principal dispositions. With respect to teacher evaluation generally, findings here were consistent with earlier studies reporting mixed principal dispositions; with respect to OTES specifically, findings here were consistent with studies in other states reporting that principal dispositions were more negative than positive

An Essential Role for Endocytosis of Rhodopsin through Interaction of Visual Arrestin with the AP-2 Adaptor

Previously, we have identified a class of retinal degeneration mutants in Drosophila in which the normally transient interaction between arrestin2 (Arr2) and rhodopsin is stabilized and the complexes are rapidly internalized into the cell body by receptor-mediated endocytosis. The accumulation of protein complexes in the cytoplasm eventually results in photoreceptor cell death. We now show that the endocytic adapter protein AP-2 is essential for rhodopsin endocytosis through an Arr2-AP-2beta interaction, and mutations in Arr2 that disrupt its interaction with the beta subunit of AP-2 prevent endocytosis-induced retinal degeneration. We further demonstrate that if the interaction between Arr2 and AP-2 is blocked, this also results in retinal degeneration in an otherwise wild-type background. This indicates that the Arr2-AP-2 interaction is necessary for the pathology observed in a number of Drosophila visual system mutants, and suggests that regular rhodopsin turnover in wild-type photoreceptor cells by Arr2-mediated endocytosis is essential for photoreceptor cell maintenance