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Background: Tree thinking refers to an approach to evolution education that emphasizes reading and interpreting phylogenetic trees. We studied the relationship between introductory biology students' tree-thinking ability and their acceptance of evolutionary theory. Results:Comparisons between a semester in which interpretation of phylogenetic trees and related concepts were taught as stand-alone topics versus one in which tree thinking was used as an organizing framework for the course curriculum found significant increases in students' ability to read and interpret trees in both semesters, but only in the tree thinking semester was there a significant increase in students' scores on the Measure of the Acceptance of the Theory of Evolution (MATE) instrument. Over four additional semesters, the Tree Thinking Concept Inventory (TTCI) was used to assess students' tree-thinking abilities before and after the course. We found that MATE posttest scores correlated with gains in tree-thinking ability. These increases in MATE posttest scores were predominantly due to students' reporting greater acceptance of the scientific evidence supporting evolutionary theory. Conclusions:Increased acceptance of evolution in a tree-thinking versus non-tree-thinking semester and significant positive correlations between TTCI and MATE scores indicate there is a relationship between tree-thinking ability and acceptance of evolution. This result suggests that, as a framework to connect different forms of data and investigate a variety of biological phenomena, tree thinking can promote greater acceptance of the evidence and scientific validity of evolutionary theory in introductory biology students.

The Navigation by Chemotextural Familiarity Hypothesis (NCFH) suggests that scorpions use their midventral pectines to gather chemical and textural information near their burrows and use this information as they subsequently return home. For NCFH to be viable, animals must somehow acquire home-directed “tastes” of the substrate, such as through path integration (PI) and/or learning walks. We conducted laboratory behavioral trials using desert grassland scorpions (Paruroctonus utahensis). Animals reliably formed burrows in small mounds of sand we provided in the middle of circular, sand-lined behavioral arenas. We processed overnight infrared video recordings with a MATLAB script that tracked animal movements at 1-2 s intervals. In all, we analyzed the movements of 23 animals, representing nearly 1500 hours of video recording. We found that once animals established their home burrows, they immediately made one to several short, looping excursions away from and back to their burrows before walking greater distances. We also observed similar excursions when animals made burrows in level sand in the middle of the arena (i.e., no mound provided). These putative learning walks, together with recently reported PI in scorpions, may provide the crucial home-directed information requisite for NCFH.

Fusarium spp. are important soil- and seedborne pathogens of Douglas fir (Pseudotsuga menziesii) in conifer seedling nurseries. We investigated the effects of culture media and cold stratification on isolation of Fusarium spp. from three Douglas fir seedlots and tested whether the numbers and species mixtures found on stratified seeds could cause disease. Nearly all cold-stratified seeds plated on three semiselective culture media yielded Fusarium spp., including F. avenaceum, F. culmorum, F. lateritium, F. moniliforme, F. poae, F. proliferatum, F. sambucinum, F. solani, and F. tricinctum. Species composition did not differ significantly among the media. Isolation of Fusarium spp. from seeds plated on Komada's medium (pH 6.8) at various stages of imbibition and cold stratification progressively increased from 10 to 22% to 65 to 100%. When stratified seeds were planted in conditions conducive to disease development, however, little disease attributable to Fusarium spp. resulted. A subsequent study was conducted to determine whether a biological control agent applied during imbibition could reduce the proliferation of Fusarium spp. during stratification. Unstratified Douglas fir seeds were imbibed for 24 h in a suspension of Pseudomonas chlororaphis isolate RD31-3A, a rifampicin-resistant fluorescent pseudomonad with previously demonstrated biocontrol activity against F. oxysporum. This treatment reduced the proliferation of Fusarium spp. during cold stratification without significantly affecting subsequent seed germination. The greatest reduction in poststratification populations of seedborne Fusarium spp. was achieved when preimbibition treatment with hydrogen peroxide was followed by seed imbibition in live bacteria. Seed imbibition in bacterial suspensions may be an effective means to deliver biological control agents to Douglas fir seeds.

Students often enter introductory biology courses with misconceptions about evolution. For example, many students believe that traits arise when a species needs them or that evolutionary processes are goal-oriented. To address these and other misconceptions, we have developed an activity called "Boost Your Evolution IQ." Student groups compete against one another in a fast-paced, challenging quiz that is presented using PowerPoint. Questions get harder from beginning to end, and the stakes get higher: Each correct answer earns double points in round 2 and then triple points in round 3. Student collaboration throughout the activity helps reinforce the concepts in advanced students and allows struggling students to hear evolution explained in various ways. Further, the same misconception is often tested multiple times, allowing students to learn from their mistakes. This activity is useful as a review before an evolution exam or as a preand post-test. It may also be adapted for large classes using clicker technology. We provide a detailed explanation of the approach in the attached video (Supporting File S1).