1,721,039 research outputs found
Foraging on individual leaves by an intracellular feeding insect is not associated with leaf biomechanical properties or leaf orientation.
Full text linkNearly all herbivorous arthropods make foraging-decisions on individual leaves, yet systematic investigations of the adaptive significance and ecological factors structuring these decisions are rare with most attention given to chewing herbivores. This study investigated why an intracellular feeding herbivore, Western flower thrips (WFT) Frankliniella occidentalis Pergande, generally avoids feeding on the adaxial leaf surface of cotton cotyledons. WFT showed a significant aversion to adaxial-feeding even when excised-cotyledons were turned up-side (abaxial-side 'up'), suggesting that negative-phototaxis was not a primary cause of thrips foraging patterns. No-choice bioassays in which individual WFT females were confined to either the abaxial or adaxial leaf surface showed that 35% fewer offspring were produced when only adaxial feeding was allowed, which coincided with 32% less plant feeding on that surface. To test the hypothesis that leaf biomechanical properties inhibited thrips feeding on the adaxial surface, we used a penetrometer to measure two variables related to the 'toughness' of each leaf surface. Neither variable negatively co-varied with feeding. Thus, while avoiding the upper leaf surface was an adaptive foraging strategy, the proximate cause remains to be elucidated, but is likely due, in part, to certain leaf properties that inhibit feeding
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Smaller Bumble Bee Workers are Safeguards Against Poor Resource Environments
No full textBumble bees workers (Bombus sp.) exhibit a large variation in worker body size, with up to a ten fold weight difference between full genetic sisters. Stranger still is that there appears to be little adaptive benefit for producing them as smaller workers are worse at performing colony tasks. However smaller workers can survive starvation for longer than their larger sisters. We test the hypothesis that smaller workers are either adaptations to poor resource environments or highly variable resource environments. By raising colonies in the lab of different resource regimes we find that colonies in poor resource treatments show decreased average body size, but there appears to be no tradeoff in producing either larger or more workers
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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BUMBLE BEES SHOW NO PREFERENCE OR INCREASED LANDING SUCCESS ON FLOWERS WITH A LABELLUM VERSUS WITHOUT
No full textFlower morphology and insect pollinator interaction are closely interrelated, and the study of bees specifically is particularly prominent in the investigation of foraging behavior in scientific literature (Harder 1985, Lamb & Wells 1995). In this study, we examined the behavior of the common eastern bumble bee (Bombus impatiens) in foraging on flowers with and without a labellum to test whether bees prefer flowers with labellums, or if the presence of a labellum influences bees’ success in landing on flowers. The purpose of this study was to further explore the relationship between the environment provided by the structure of a flower and bees’ behavior and learning, and perhaps more broadly the evolutionary rationale behind flower and pollinator interaction. Using data from 58 bees, each having participated in foraging trials including flowers with and without a labellum, we found that bumble bees show no preference for flowers with a labellum, nor do they demonstrate greater success landing on flowers with a labellum. These findings somewhat contradict much previous research that propose that flowers’ bright colors, patterns, and structural modifications help attract and engage pollinators and facilitate foraging (Dafni & Giurfa 1999, Leonard & Papaj 2011, Whitney et al. 2009). This could indicate that labellums may not have evolved for the purpose of facilitating greater landing ease for bees, and that factors other than providing a platform for landing may be responsible for attracting them and guiding them to nectar
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INCREASED DOPAMINE LEVELS DO NOT INFLUENCE AGGRESSIVE BEHAVIOR IN BLACK WIDOW SPIDERS (LATRODECTUS HESPERUS)
No full textDiscovering the driving forces of individual personality differences in animals is an emerging goal of animal behavior research. Biogenic amines have been known to mediate various aspects of behavior, including aggression, which is one of the most commonly varying individual personality differences among animals. In addition to aggression, a large number of other behaviors across a wide variety of species are influenced by biogenic amines. Arthropods specifically provide an ideal system to manipulate biogenic amines and observe behavioral changes. In this study, we used Latrodectus hesperus, the western black widow spider, as our model organism because of their consistent individual behavioral differences, which appear to relate to differing individual life history strategies. For example, higher aggression, as measured by attacks on simulated prey items, relates to higher rates of egg laying in “fast life history strategy” individuals. Here, Iinvestigated the role that dopamine (DA) has on the individual’s aggressive behavior, measured by the number of times they attack a potential prey in their web. I injected spiders with the neurotransmitter, which is a precise way to manipulate the biogenic amine concentration and observed the changes in behavior that may follow. I looked for whether there was a significant difference between aggressiveness of biogenic amine-injected individuals, individuals injected with a saline solution, and non-injected individuals. We discovered that the injection of dopamine had no effect on black widow aggression. These results indicate that biogenic amines may not play as big a role in individual personality differences as previously thought, and that aggressive behavior is influenced by other factors, such as genetics, metabolic rates, environment, or some other traits
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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DISTURBANCE ASSOCIATED TRAIL ABANDONMENT IN SOUTHERN FIRE ANTS
No full textAnts are known to use highly sophisticated techniques during foraging in order to optimize efficiency and reduce energy expenditure. This study investigated how Solenopsis xyloni (southern fire ant) workers responded to a gap in an established pheromone trail. Specifically, it determined whether individual foragers abandoned the trail after encountering a gap, and whether they successfully located a feeder if they did not abandon. Previous studies have investigated the navigational capabilities and trail laying strategies of ants. This research added context to those studies by examining the individual behavior of ants when excluded from the social memory. The setup for this experiment consisted of a T-shaped maze with a paper coating that could be replaced to make an artificial gap in a pheromone trail. Experimental trials were compared with control trials, where the pheromone trail remained intact. Three hypotheses were posited regarding the potential behavior of the ants. The data collected supported the first hypothesis, which predicted ants would generally abandon the pheromone trail upon encountering a perturbation. Some ants continued to search the setup when confronted with the gap, but showed less than a 50% success rate in locating the feeder, indicating that Solenopsis workers are not adept at individual foraging. Differences in forager behavior regarding abandonment may provide evidence of ant "personalities types" which can promote group success. Understanding how such systems operate is an important step for human applications in fields such as technology and engineering. The implications of this study can be used for developing more advanced swarm robots and more sophisticated antivirus programs
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VARIATION IN PERCEPTION OF TASK INITIATION AND COMPLETION BETWEEN TEMNOTHORAX RUGATUL8US NESTMATES DRIVES DIVISION OF LABOR
No full textDivision of labor is one of the defining characteristics of social insect societies. It is thought that
division of labor arises through simple logical rules and requires only that workers respond to
environmental stimuli they encounter. It has been proposed that the response threshold is one of
the primary rules that drives division of labor. We test this hypothesis by measuring response
thresholds in the ant species Temnothorax rugatulus to different task-associated stimuli and see
whether or not they can predict which tasks the ant takes on in the colony. We found that the
response threshold hypothesis successfully predicts the relationship between the sensitivity to
task-associated stimuli and performance of the task itself for one task, but it fails at predicting
the relationship of the other task. In fact, the results were the opposite of what the response
threshold predicted, suggesting that there may exist an alternative rule that functions in the
opposite direction of the response threshold and yet may also be capable of allocating tasks. Here
we coin the term ‘satisfaction threshold’ as a name for this alternative mechanism
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