Experimental evolution of adaptive divergence under varying degrees of gene flow

Adaptive divergence is the key evolutionary process generating biodiversity by means of natural selection. Yet, the conditions under which it can arise in the presence of gene flow remain contentious. To address this question, we subjected 132 sexually reproducing fission yeast populations, sourced from two independent genetic backgrounds, to disruptive ecological selection and manipulated the level of migration between environments. Contrary to theoretical expectations, adaptive divergence was most pronounced when migration was either absent (allopatry) or maximal (sympatry), but was much reduced at intermediate rates (parapatry and local mating). This effect was apparent across central life-history components (survival, asexual growth and mating) but differed in magnitude between ancestral genetic backgrounds. The evolution of some fitness components was constrained by pervasive negative correlations (trade-off between asexual growth and mating), while others changed direction under the influence of migration (for example, survival and mating). In allopatry, adaptive divergence was mainly conferred by standing genetic variation and resulted in ecological specialization. In sympatry, divergence was mainly mediated by novel mutations enriched in a subset of genes and was characterized by the repeated emergence of two strategies: an ecological generalist and an asexual growth specialist. Multiple loci showed consistent evidence for antagonistic pleiotropy across migration treatments providing a conceptual link between adaptation and divergence. This evolve-and-resequence experiment shows that rapid ecological differentiation can arise even under high rates of gene flow. It further highlights that adaptive trajectories are governed by complex interactions of gene flow, ancestral variation and genetic correlations

Exploring a guided, silent reading intervention: Effects on struggling third-grade readers’ achievement

The authors’ purpose was to explore the effects of a supplementary, guided, silent reading intervention with 80 struggling third-grade readers who were retained at grade level as a result of poor performance on the reading portion of a criterion referenced state assessment. The students were distributed in 11 elementary schools in a large, urban school district in the state of Florida. A matched, quasi-experimental design was constructed using propensity scores for this study. Students in the guided, silent reading intervention, Reading Plus, evidenced higher, statistically significant mean scores on the Florida Comprehensive Assessment Test criterion assessment measure of reading at posttest. The effect size, favoring the guided, silent reading intervention group was large, 1 full standard deviation, when comparing the 2 comparison groups’ mean posttest scores. As such, the results indicate a large advantage for providing struggling third-grade readers guided silent reading fluency practice in a computer-based practice environment. No significant difference was found between the treatment and control group on the Stanford Achievement Test–10 (SAT-10) posttest scores, although posttest scores for the treatment group trended higher than the control. After conducting a power analysis, it was determined that the sample size (n = 80) was too small to provide sufficient statistical power to detect a difference in third-grade students’ SAT-10 scores

Regio Basiliensis im Vergleich

Wandel der Siedlungsstrukturen am Übergang von der Spätlatènezeit zur frühen Kaiserzeit, dargestellt an den Beispielen Basel Gasfabrik, Basel Münsterhügel und Augusta Rauric