Plant water uptake along a diversity gradient provides evidence for complementarity in hydrological niches

Biodiversity enhances a variety of ecosystem processes, and yet the underlying mechanisms through which these relationships occur remain a critical knowledge gap. Here, we used the natural abundance of stable isotopes to measure depth of water uptake in five common grassland species (Asclepias tuberosa, Lespedeza capitata, Liatris aspera, Schizachyrium scoparium and Sorghastrum nutans) growing across an experimental grassland diversity gradient. Using this approach, we addressed the following questions: 1) does the depth‐specific provenance of water uptake differ among species and/or do interspecific differences in water source manifest with increasing community diversity? 2) Does the isotopic niche space occupied by plants change with increasing diversity? 3) Is plasticity in water uptake depth across a diversity gradient associated with functional plant responses? We found that the depth of soil water used by plants was inherently different among species when grown in monocultures. All species used less shallow soil water and more intermediate‐depth soil water in mixed assemblages than in monocultures, resulting in similar interspecific differences in water source across the diversity gradient. However, plasticity in the locations of water used were positively associated with increases in plant growth in higher diversity treatments. These results indicate that plasticity in water‐use may contribute to positive biodiversity–productivity relationships commonly observed in temperate grasslands.     

Muggles,Wizards, and Witches Using Harry Potter Characters to Teach Human Pedigrees

These activities allow students to investigate behavioral responses of the large Milkweed bug, Oncopeltus fasciatus, and the mealworm, Tenebrio molitor or Tenebrio obscurus, to external stimuli of light, color, and temperature. During the activities, students formulate hypotheses to research questions presented. They also observe insects for a period of time, record observations, analyze the data, and draw conclusions. Important outcomes include experience with critical and analytical thinking and appreciation for the process of science as well as the biology of living things. The activities described herein are appropriate for upper elementary grades, middle school, and high school biology classes.     

Co‐occurring woody species have diverse hydraulic strategies and mortality rates during an extreme drought

From 2011 to 2013, Texas experienced its worst drought in recorded history. This event provided a unique natural experiment to assess species‐specific responses to extreme drought and mortality of four co‐occurring woody species: Quercus fusiformis, Diospyros texana, Prosopis glandulosa, and Juniperus ashei. We examined hypothesized mechanisms that could promote these species' diverse mortality patterns using postdrought measurements on surviving trees coupled to retrospective process modelling. The species exhibited a wide range of gas exchange responses, hydraulic strategies, and mortality rates. Multiple proposed indices of mortality mechanisms were inconsistent with the observed mortality patterns across species, including measures of the degree of iso/anisohydry, photosynthesis, carbohydrate depletion, and hydraulic safety margins. Large losses of spring and summer whole‐tree conductance (driven by belowground losses of conductance) and shallower rooting depths were associated with species that exhibited greater mortality. Based on this retrospective analysis, we suggest that species more vulnerable to drought were more likely to have succumbed to hydraulic failure belowground.     

The Moral Aesthetics of Simulated Suffering in Standardized Patient Performances

Standardized patient (SP) performances are staged clinical encounters between health-professional students and people who specialize in role-playing the part of patients. Such performances have in recent years become increasingly central to the teaching and assessment of clinical skills in U.S. medical schools. SP performances are valued for being both “real” (in that they involve interaction with a real person, unlike written examinations) and “not real” (in that the SP does not actually suffer from the condition portrayed, unlike an actual patient). This article considers how people involved in creating SP performances reconcile a moral commitment to avoid suffering (to keep it “not real”), with an aesthetic commitment to realistically portray it (to keep it “real”). The term “moral aesthetic” is proposed, to indicate a sensibility that combines ideas about what is morally right with ideas about what is aesthetically compelling. Drawing on ethnographic research among SPs and SP program staff and medical faculty who work closely with them, this article argues that their work of creating “realism” in simulated clinical encounters encompasses multiple different (and sometimes conflicting) understandings and practices of realism, informed by three different moral aesthetics: (1) a moral aesthetic of induction, in which an accurate portrayal with a well-documented provenance serves to introduce experientially distant forms of suffering; (2) a moral aesthetic of inoculation, in which the authenticity and emotional impact of a performance are meant to inoculate students against the impact of future encounters with suffering; (3) a moral aesthetic of presence, generating forms of voice and care that are born out of the embodied presence of suffering individuals in a clinical space. All are premised on the assumption that risk and suffering can be banished from SP performances. This article suggests, however, that SP performances necessarily raise the same difficult, important, fundamentally ethical questions that are always involved in learning from and on human beings who are capable of suffering, and who need and deserve recognition and respect as well as care.     

Fighting for food: a dynamic version of the Hawk-Dove game

Summary The Hawk-Dove game (Maynard Smith, 1982) has been used to analyse conflicts over resources such as food. At the evolutionarily stable strategy (ESS), either a proportionp* of animals always play Hawk, or each animal has a probabilityp* of playing Hawk. We modify the standard Hawk-Dove game to include a state variable,x, that represents the animal's level of energy reserves. A strategy is now a rule for choosing an action as a function ofx and time of day. We consider a non-reproductive period and adopt the criterion of minimizing mortality over this period. We find the ESS, which has the form play Hawk if reserves are belowc* (t) at timet, otherwise play Dove. This ESS is very different from the ESS in the standard Hawk-Dove game. It is a pure ESS that depends on the animal's state and on time. Furthermore, it is characterized by the strong condition that any single mutant that does not adopt the ESS suffers a reduction in fitness. The standard Hawk-Dove game assumes pay-offs that are related to fitness; our approach starts from a definition of fitness and derives the pay-offs in the process of finding the ESS. When the environment becomes worse (e.g. food becomes less reliable or energy expenditure increases) the ESS changes in such a way as to increase the proportion of animals that will play Hawk.     

Diatom growth responses to photoperiod and light are predictable from diel reductant generation

Light drives phytoplankton productivity, so phytoplankton must exploit variable intensities and durations of light exposure, depending upon season, latitude, and depth. We analyzed the growth, photophysiology and composition of small, Thalassiosira pseudonana, and large, Thalassiosira punctigera, centric diatoms from temperate, coastal marine habitats, responding to a matrix of photoperiods and growth light intensities. T. pseudonana showed fastest growth rates under long photoperiods and low to moderate light intensities, while the larger T. punctigera showed fastest growth rates under short photoperiods and higher light intensities. Photosystem II function and content responded primarily to instantaneous growth light intensities during the photoperiod, while diel carbon fixation and RUBISCO content responded more to photoperiod duration than to instantaneous light intensity. Changing photoperiods caused species‐specific changes in the responses of photochemical yield (e^?/photon) to growth light intensity. These photophysiological variables showed complex responses to photoperiod and to growth light intensity. Growth rate also showed complex responses to photoperiod and growth light intensity. But these complex responses resolved into a close relation between growth rate and the cumulative daily generation of reductant, across the matrix of photoperiods and light intensities.     

Vertical Distribution, Size Structure, and Habitat Associations of Four Blenniidae Species on Gas Platforms in the Northcentral Gulf of Mexico

We counted individuals of the family Blenniidae and estimated their sizes on gas platforms southeast of Dauphin Island, Alabama. We observed species abundance decreasing as depth increased. Fish sizes also decreased with depth. The most abundant species was molly miller, Scartella cristata, followed by plumed blenny, Hypleurochilus multifilis, tessellated blenny, Hypsoblennius invemar, and seaweed blenny, Parablennius marmoreus. Total blenny abundance was positively related to the barnacle, Megabalanus antillensis, and dissolved oxygen concentrations, and inversely related to Anthozoa. Individually, S. cristata was correlated with M. antillensis, and inversely related to salinity, while the other blenny species showed more complex correlations to invertebrates. As a community, blennies showed a clear separation based on depth independent of offshore/inshore sites and sample date based on multidimensional scaling analyses. Our study suggests that attached invertebrates, particularly M. antillensis, provided a predation refuge, allowing these blenny species to exist in an otherwise unsuitable habitat, i.e. open shallow waters of the northern Gulf of Mexico.     

Use of Galvanic Skin Responses,Salivary Biomarkers,and Self-reports to Assess Undergraduate Student Performance During a Laboratory Exam Activity

Typically, self-reports are used in educational research to assess student response and performance to a classroom activity. Yet, addition of biological and physiological measures such as salivary biomarkers and galvanic skin responses are rarely included, limiting the wealth of information that can be obtained to better understand student performance. A laboratory protocol to study undergraduate students'' responses to classroom events (e.g., exams) is presented. Participants were asked to complete a representative exam for their degree. Before and after the laboratory exam session, students completed an academic achievement emotions self-report and an interview that paralleled these questions when participants wore a galvanic skin sensor and salivary biomarkers were collected. Data collected from the three methods resulted in greater depth of information about students'' performance when compared to the self-report. The work can expand educational research capabilities through more comprehensive methods for obtaining nearer to real-time student responses to an examination activity.     

Species‐specific differences in water uptake depth of mature temperate trees vary with water availability in the soil

• Temperate tree species differ in their physiological sensitivity to declining soil moisture and drought. Although species‐specific responses to drought have often been suggested to be the result of different water uptake depths, empirical evidence for such a mechanism is scarce.
• Here we test if differences in water uptake depths can explain previously observed species‐specific physiological responses of temperate trees to drought and if the water uptake depth of different species varies in response to declining soil moisture. For this purpose, we employed stable oxygen and hydrogen isotopes of soil and xylem water that we collected over the course of three growing seasons in a mature temperate forest in Switzerland.
• Our data show that all investigated species utilise water from shallow soil layers during times of sufficient soil water supply. However, Fraxinus excelsior, Fagus sylvatica and Acer pseudoplatanus were able to shift their water uptake to deeper soil layers when soil water availability decreased in the topsoil. In contrast, Picea abies, was not able to shift its water uptake to deeper soil layers.
• We conclude from our data that more drought‐resistant tree species are able to shift their water uptake to deeper soil layers when water availability in the topsoil is becoming scarce. In addition, we were able to show that water uptake depth of temperate tree species is a trait with high plasticity that needs to be characterised across a range of environmental conditions.

     

Neomycin: An Effective Inhibitor of Jasmonate-Induced Reactions in Plants

Jasmonates are important phytohormones involved in both plant developmental processes as well as defense reactions. Many JA-mediated plant defense responses have been studied in model plants using mutants of the jasmonate signaling pathway. However, in plant species where JA-signaling mutants are not accessible, the availability of a tool targeting JA signaling is crucial to investigate jasmonate-dependent processes. Neomycin is a poly-cationic aminoglycoside antibiotic that blocks the release of Ca²⁺ from internal stores. We examined the inhibitory activities of neomycin on different jasmonate-inducible responses in eight different plant species: Intracellular calcium measurements in Nicotiana tabacum cell culture, Sporamin gene induction in Ipomoea batatas, PDF2.2 gene expression in Triticum aestivum, Nepenthesin protease activity measurement in Nepenthes alata, extrafloral nectar production in Phaseolus lunatus, nectary formation in Populus trichocarpa, terpene accumulation in Picea abies, and secondary metabolite generation in Nicotiana attenuata. We are able to show that neomycin, an easily manageable and commercially available compound, inhibits JA-mediated responses across the plant kingdom.

     

Der problemlöser robbimat

We first show how to formalize environments in which situations can be changed only by action, and in which a situation should be brought about that is acceptable. This leads us to the concept of a problem constellation that consists of an action system, a reaction system, a judgement system, and an initial situation. We then present a cybernetical system which we call Robbimat. It is capable of testing problem constellations, of modifying them according to the results of the tests, and of judging the final constellation. We designed Robbimat in order to have favourable problem constellations automatically generated. As an example we discuss a simple game. It constitutes a win-loss-environment the structure of which can be deduced from the payoff function. We show how Robbimat analyses such an environment, and utilizing its structure classifies the initial situation.

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Wir danken Herrn Manfred Linder für seine Mitarbeit.     

Exploring the influence of plant and animal item contexts on student response patterns to natural selection multiple choice items

Background

Research has shown that students have a variety of ideas about natural selection that may be context dependent. Prior analyses of student responses to open-ended evolution items have demonstrated that students apply more core ideas about natural selection when asked about animals, but respond with the same number of naive ideas for plant and animal items. Other research has shown that changing an item to ask about trait loss or gain shifted the types of naive ideas applied by students in their responses. In this paper, we take up both of these findings to determine if differences exist in the types of ideas students apply to similar items with either a plant or an animal in the item stem.

Results

In order to understand if students applied different ideas to plants or animals in distractor-driven multiple-choice questions, we analyzed high school biology students’ responses to matched-item pairs. Dichotomous scoring revealed that students chose the correct response more often for the animal items as compared to the plant items. Chi squared analyses revealed significant differences in the distribution of student responses to matched items. For example, more students chose responses that defined animal fitness as related to their strength and plants’ fitness related to its longevity.

Conclusions

These results suggest that varied context of plants or animals in item stems on diagnostic assessments can provide teachers with a more complete picture of their students’ ideas about natural selection prior to instruction. This is particularly important in assessments used prior to instruction; as teachers will gain greater insight into the variety of ways students think about natural selection across different types of plants and animals.

     

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient‐poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient‐poor grassland species.     

Peer instruction enhanced student performance on qualitative problem-solving questions

We tested the hypothesis that peer instruction enhances student performance on qualitative problem-solving questions. To test this hypothesis, qualitative problems were included in a peer instruction format during our Physiology course. Each class of 90 min was divided into four to six short segments of 15 to 20 min each. Each short segment was followed by a qualitative problem-solving scenario that could be answered with a multiple-choice quiz. All students were allowed 1 min to think and to record their answers. Subsequently, students were allowed 1 min to discuss their answers with classmates. Students were then allowed to change their first answer if desired, and both answers were recorded. Finally, the instructor and students discussed the answer. Peer instruction significantly improved student performance on qualitative problem-solving questions (59.3 +/- 0.5% vs. 80.3 +/- 0.4%). Furthermore, after peer instruction, only 6.5% of the students changed their correct response to an incorrect response; however, 56.8% of students changed their incorrect response to a correct response. Therefore, students with incorrect responses changed their answers more often than students with correct responses. In conclusion, pausing four to six times during a 90-min class to allow peer instruction enhanced student performance on qualitative problem-solving questions.     

Long‐term influence of sod cutting depth on the restoration of degraded wet heaths

Temperate heaths have an unfavorable conservation status in most European biogeographical regions. Increasing nitrogen levels promote competitive grass species such as Molinia caerulea, which is a main threat to heathland conservation in Europe. This article investigates the long‐term influence of sod cutting and the resulting changes in soil properties on the heath composition, integrity, and structure. In 15 nature reserves across the northern half of Belgium, we used (1) a large number of plots (203); (2) a broad range of sod cut depths (2–40 cm), and (3) a temporal dimension that describes how long the effects of sod cutting persist (census up to 19 years after sod cutting). Multivariate analyses were used in order to explore the influence of sod cut depth and time after sod cutting on the soil and vegetation properties. There was a positive relationship between sod cut depth and soil pH and water level, and a negative relationship with Al³⁺, NH₄⁺, and total organic matter (TOM). However, only a limited number of typical (target) species appeared after sod cutting, and then only weakly. Most of the time they remained a minor component of the restored vegetation. Moreover, M. caerulea reappeared and its cover significantly increased during the years following sod cutting. Although we were able to show that sod cut depth has a differential effect on soil properties and vegetation recovery, it also appeared that sod cutting does not restore wet heaths in the long term when applied in regions with high nitrogen deposition.     

Response of wetland plant species to hydrologic conditions

Understanding hydrologic requirements of native and introduced species is critical to sustaining native plant communities in wetlands of disturbed landscapes. We examined plant assemblages, and 31 of the most common species comprising them, from emergent wetlands in an urbanizing area of the Pacific Northwest, USA, in relation to in situ, fine-scale hydrology. Percent cover by plant species was estimated in 2208 1-m² plots across 43 sites, with water depth at time of vegetation sampling measured in 432 plots. Three years of bi-weekly hydrologic data from each of the 43 sites were used to estimate mean surface water level and mean absolute difference (MAD) in surface water level for every plot. Nine assemblages of plant species that co-occur in the field were identified using TWINSPAN. The assemblage richest in native species occurred under intermediate hydrologic conditions and was bracketed by pasture grass dominated assemblages at drier conditions with low water level variability, and Phalaris arundinacea L. assemblages with higher mean water levels and variability. Results suggest minor changes in average water levels (10 cm) or in variability (±2 cm in MAD) could promote a shift from assemblages dominated by natives to those dominated by invasive or alien taxa. Canonical correspondence analysis segregated the species into four groups related to hydrologic gradients. Each species response group was typified by taxa with similar optima for a given environmental variable, with each group related to a characteristic suite of hydrologic conditions. The most common species (P. arundinacea, Juncus effusus L., and Typha latifolia L.), each representing a different response group, exhibited unique responses in occurrence/abundance in relation to water level variability, but were abundant over a wide range of water depth. The realized niches of other species in each response group were more restricted, with peaks in cover confined to narrower ranges of water depth and variability.     

Diameter Growth of Juvenile Trees after Gap Formation in a Bolivian Rain Forest: Responses are Strongly Species‐specific and Size‐dependent

We evaluated growth responses to gap formation for juvenile individuals of three canopy rain forest species: Peltogyne cf. heterophylla, Clarisia racemosa and Cedrelinga catenaeformis. Gaps were formed during selective logging operations 7 yr before sampling in a Bolivian rain forest. We collected wood samples for tree‐ring analyses at different distances to the stump (<10, 10–40 and >40 m) and from trees with different diameters (5–30 cm diameter at breast height [dbh]). Tree‐rings width was measured in at least two radii and converted to average diameter growth. Changes in 7‐yr median diameter growth before and after selective logging were analyzed. Diameter growth rates significantly increased by 0.7–0.8 mm/yr after gap formation for P. heterophylla and C. catenaeformis, but not for C. racemosa. We applied a multiple regression analysis to explain variation in growth responses of P. heterophylla and C. catenaeformis by distance to logging gap and tree size. For P. heterophylla we found that growth increase occurring close to logging gaps was strongest for large juvenile trees (20–25 cm dbh) and almost absent in small juveniles. For C. catenaeformis, variation in growth responses was not related to tree size or distance to gaps. Our results show that growth responses to gap formation strongly differ across species and tree sizes. This finding calls for caution in the interpretation of growth releases in tree‐ring series, as gap formation does not necessarily invoke growth responses and if such growth responses occur, their strength is species‐ and size specific.     

Plasticity of the mate choice mind: courtship evokes choice‐like brain responses in females from a coercive mating system

Female mate choice is fundamental to sexual selection, and determining molecular underpinnings of female preference variation is important for understanding mating character evolution. Previously it was shown that whole‐brain expression of a synaptic plasticity marker, neuroserpin, positively correlates with mating bias in the female choice poeciliid, Xiphophorus nigrensis, when exposed to conspecific courting males, whereas this relationship is reversed in Gambusia affinis, a mate coercive poeciliid with no courting males. Here we explore whether species‐level differences in female behavioral and brain molecular responses represent ‘canalized’ or ‘plastic’ traits. We expose female G. affinis to conspecific males and females, as well as coercive and courting male Poecilia latipinna, for preference assays followed by whole‐brain gene expression analyses of neuroserpin, egr‐1 and early B. We find positive correlations between gene expression and female preference strength during exposure to courting heterospecific males, but a reversed pattern following exposure to coercive heterospecific males. This suggests that the neuromolecular processes associated with female preference behavior are plastic and responsive to different male phenotypes (courting or coercive) rather than a canalized response linked to mating system. Further, we propose that female behavioral plasticity may involve learning because female association patterns shifted with experience. Compared to younger females, we found larger, more experienced females spend less time near coercive males but associate more with males in the presence of courters. We thus suggest a conserved learning‐based neuromolecular process underlying the diversity of female mate preference across the mate choice and coercion‐driven mating systems.     

Using Role Play to Debate Animal Testing

The use of animals in biomedical research is a socio-scientific issue in which decision-making is complicated. In this article, we describe an experience involving a role play activity performed during school visits to the Barcelona Biomedical Research Park (PRBB) to debate animal testing. Role playing games require students to defend different positions and permit participants to debate and reflect on their personal opinions. A total of 262 students from 15- to 30-years-old participated in the activity. The article presents an analysis of the students’ opinions on this topic before and after performing the activity. Our results show that students actively took part in debate and made use of the new information provided by the game, especially the legal aspects. In conclusion, the role play activity helped participants to create a more informed opinion, stimulated critical thinking and argumentation skills. We encourage science teachers to use role playing games to discuss socio-scientific issues.     

Graduate entry medicine: selection criteria and student performance

Background

Graduate entry medicine raises new questions about the suitability of students with different backgrounds. We examine this, and the broader issue of effectiveness of selection and assessment procedures.

Methods

The data included background characteristics, academic record, interview score and performance in pre-clinical modular assessment for two years intake of graduate entry medical students. Exploratory factor analysis is a powerful method for reducing a large number of measures to a smaller group of underlying factors. It was used here to identify patterns within and between the selection and performance data.

Principal Findings

Basic background characteristics were of little importance in predicting exam success. However, easily interpreted components were detected within variables comprising the ‘selection’ and ‘assessment’ criteria. Three selection components were identified (‘Academic’, ‘GAMSAT’, ‘Interview’) and four assessment components (‘General Exam’, ‘Oncology’, ‘OSCE’, ‘Family Case Study’). There was a striking lack of relationships between most selection and performance factors. Only ‘General Exam’ and ‘Academic’ showed a correlation (Pearson''s r = 0.55, p<0.001).

Conclusions

This study raises questions about methods of student selection and their effectiveness in predicting performance and assessing suitability for a medical career. Admissions tests and most exams only confirmed previous academic achievement, while interview scores were not correlated with any consequent assessment.