Lytic to temperate switching of viral communities

Microbial viruses can control host abundances via density-dependent lytic predator–prey dynamics. Less clear is how temperate viruses, which coexist and replicate with their host, influence microbial communities. Here we show that virus-like particles are relatively less abundant at high host densities. This suggests suppressed lysis where established models predict lytic dynamics are favoured. Meta-analysis of published viral and microbial densities showed that this trend was widespread in diverse ecosystems ranging from soil to freshwater to human lungs. Experimental manipulations showed viral densities more consistent with temperate than lytic life cycles at increasing microbial abundance. An analysis of 24 coral reef viromes showed a relative increase in the abundance of hallmark genes encoded by temperate viruses with increased microbial abundance. Based on these four lines of evidence, we propose the Piggyback-the-Winner model wherein temperate dynamics become increasingly important in ecosystems with high microbial densities; thus ‘more microbes, fewer viruses’

Collusion, Collective Action and Protection: Theory and Evidence

This paper provides a novel explanation forthe formation of protectionist lobby groupsin imperfectly competitive sectors. Thelevel of collusion is shown to be a crucialdeterminant of the ability of firms tosustain lobbying. We show that greatercollusion reduces firm contributionsto tariff lobbying, when the governmentvalues welfare sufficiently and thecross-price elasticity between the domesticand foreign goods is sufficiently high. The empirical evidence from the U.S.supports the theory. Greater collusionreduces the level of PAC contributions. Copyright Kluwer Academic Publishers 2004

Assessing Inquiry in Physical Geology Laboratory Manuals

Many agencies, organizations, and researchers have called for the incorporation of inquiry-based learning in college classrooms. Providing inquiry-based activities in laboratory courses is one way to promote reformed, student-centered teaching in introductory geoscience courses. However, the literature on inquiry has relatively few geoscience examples and features an array of modifiers that complicate instructor efforts to identify or adapt inquiry-based activities for their courses. We review several measurement protocols developed to assess inquiry in laboratory activities. We apply one of these to assess the level of inquiry present in four published physical geology laboratory manuals. While the majority of activities used in the published manuals were classified at low levels of inquiry, these manuals also contained examples of higher-level activities that were not identified in previous analyses. We describe the development of inquiry-based lessons for inclusion in a freshman-level physical geology laboratory course at a large public research university in the southeast U.S. and apply the same protocol to assess the laboratory course activities and discuss how some activities were adapted to increase inquiry levels. We discuss how other instructors or laboratory course developers can adapt existing activities to incorporate higher levels of inquiry in their laboratory courses, matching them with the type of information or skill they want students to learn