Environmental variation and the maintenance of polymorphism : the effect of ambient light spectrum on mating behaviour and sexual selection in guppies

The intensity of sexual selection is influenced by environmental conditions because these conditions influence signal propagation and the risks of the signal being exploited by predators and parasites. We explore the possibility that spatial or temporal heterogeneity in environmental signalling conditions (in this case light spectrum) may induce fluctuating sexual selection on male behaviour and ornamentation in guppies. We used shade cloth and filters to experimentally manipulate light spectrum, mimicking conditions found naturally: early morning/late afternoon light (SC treatment), midday forest shade (F89 filter treatment) and midday woodland shade (F55 filter treatment). Females were more responsive to male courtship and males were less likely to attempt sneak copulations under F55 light than the other two treatments. By contrast, male display rate was not influenced by treatment. Females tended to prefer the same males under SC and F55 light, but attractiveness in these treatments was unrelated to attractiveness under F89 light. There were similarities among treatments in the traits that females preferred: females preferred males with larger areas of orange in all three treatments. There were, however, also some differences, including preference for larger males under F89 light and for smaller males under the other treatments. Overall, the influence of ambient light spectrum on the relative importance of mate choice and male sneak copulation may have important implications for the mode and strength of sexual selection in different environments. The findings on attractiveness and preference functions, however, suggest that light spectrum only weakly affects the direction of sexual selection by female choice.

Changing preferences : conventional photography to digital imaging in communicating architecture

Architectural photography is merging into a new form of image capture and output which is a mix of conventional photography and digital imagery. As this transition takes place it is anticipated that the credibility of the image may also change. the aim of the project is to research the perception of the quality, content and authenticity of both conventional photography and digitally produced images used within the architectural profession.

Mating system variation in the hermaphroditic brooding coral, Seriatopora hystrix

Self-compatible, hermaphroditic marine invertebrates have the potential to self-fertilize in the absence of mates or under sperm-limited conditions, and outcross when sperm is available from a variety of males. Hence, many hermaphroditic marine invertebrates may have evolved mixed-mating systems that involve facultative self-fertilization. Such mixed-mating strategies are well documented for plants but have rarely been investigated in animals. Here, I use allozyme markers to make estimates of selfing from population surveys of reef slope and reef flat sites, and contrast this with direct estimates of selfing from progeny-array analysis, for the brooding coral Seriatopora hystrix. Consistent heterozygote deficits previously reported for S. hystrix suggests that inbreeding (including the extreme of selfing) may be common in this species. I detected significant levels of inbreeding within populations (FIS=0.48) and small but significant differentiation among all sites (FST=0.04). I detected no significant differentiation among habitats (FHT=0.009) though among site differentiation did occur within the reef slope habitat (FSH=0.06), but not within the reef flat habitat (FSH=0.015). My direct estimates of outcrossing for six colonies and their progeny from a single reef flat site revealed an intermediate value (tm (±s.d.)=0.53±0.20). Inbreeding coefficients calculated from progeny arrays (Fe=0.31) were similar to indirect estimates based on adult genotype frequencies for that site (FIS=0.38). This study confirms that the mating system of this brooding coral is potentially variable, with both outcrossing and selfing.

The kalai/smorodinsky solution with time preferences

Even under complete information, the Rubinstein scheme does not generate a unique (subgame) perfect equilibrium partition unless the players are risk neutral. In the standard cooperative bargaining literature, on the other hand, time preferences of players do not play any role. It is assumed that players negotiate as long as they want to without foregoing any portion of the pie. The discount factors are not used, even when they are available; this amounts to limiting the available information use in the bargaining problem. By characterizing a modified Kalai/Smorodinsky solution axiomatically the above problems have been tried to be solved.

Is extrapair mating random? On the probability distribution of extrapair young in avian broods

A dichotomy in female extrapair copulation (EPC) behavior, with some females seeking EPC and others not, is inferred if the observed distribution of extrapair young (EPY) over broods differs from a random process on the level of individual offspring (binomial, hypergeometrical, or Poisson). A review of the literature shows such null models are virtually always rejected, with often large effect sizes. We formulate an alternative null model, which assumes that 1) the number of EPC has a random (Poisson) distribution across females (broods) and that 2) the probability for an offspring to be of extrapair origin is zero without any EPC and increases with the number of EPC. Our brood-level model can accommodate the bimodality of both zero and medium rates of EPY typically found in empirical data, and fitting our model to EPY production of 7 passerine bird species shows evidence of a nonrandom distribution of EPY in only 2 species. We therefore argue that 1) dichotomy in extrapair mate choice cannot be inferred only from a significant deviation in the observed distribution of EPY from a random process on the level of offspring and that 2) additional empirical work on testing the contrasting critical predictions from the classic and our alternative null models is required.

Heightened sour preferences during childhood

Basic research has revealed that the chemical sensory world of children is different from that of adults, as evidenced by their heightened preferences for sweet and salty tastes. However, little is known about the ontogeny of sour taste preferences, despite the growing market of extreme sour candies. The present study investigated whether the level of sourness most preferred in a food matrix and the ability to discriminate differences in sour intensity differed between 5- to 9-year-old children and their mothers, by using a rank-by-elimination procedure embedded in the context of a game. Mothers also completed a variety of questionnaires and children were asked several questions to assess whether children's temperament and food preferences and habits related to sour preferences. The results indicated that, although every mother and all but two of the children (92%) were able to rank the gelatins from most to least sour, more than one-third (35%) of the children, but virtually none of the adults, preferred the high levels of sour taste (0.25 M citric acid) in gelatin. Those children who preferred the extreme sour tastes were significantly less food neophobic (P < 0.05) and tended to experience a greater variety of fruits when compared with the remaining children (P = 0.11). Moreover, the children's preference for sour tastes generalized to other foods, such as candies and lemons, as reported by both children and mothers. These findings are the first experimental evidence to demonstrate that sour taste preferences are heightened during childhood and that such preferences are related to children's food habits and preferences. Further research is needed to unfold the relationship between the level of sour taste preferred and the actual consumption of sour-tasting foods and flavors in children.

Sour taste preferences of children relates to preference for novel and intense stimuli

Previous research has suggested that some children have a preference for sour tastes. The origin of this preference remains unclear. We investigated whether preference for sour tastes is related to a difference in rated sour intensity due to physiological properties of saliva, or to an overall preference for intense and new stimuli. Eighty-nine children 7–12 years old carried out a rank-order procedure for preference and category scale for perceived intensity for four gelatins (i.e. 0.0 M, 0.02 M, 0.08 M, 0.25 M added citric acid) and four yellow cards that differed in brightness. In addition, we measured their willingness to try a novel candy and their flow and buffering capacity of their saliva. Fifty-eight percent of the children tested preferred one of the two most sour gelatins. These children had a higher preference for the brightest color (P < 0.05) and were more likely to try the candy with the unknown flavor (P < 0.001) than children who did not prefer the most sour gelatins. Preference for sour taste was not related with differences in rated sour intensity, however those who preferred sour taste had a higher salivary flow (P < 0.05). These findings show that a substantial proportion of young children have a preference for extreme sour taste. This appears to be related to the willingness to try unknown foods and preference for intense visual stimuli. Further research is needed to investigate how these findings can be implemented in the promotion of sour-tasting food such as fruit.

Sweet and sour preferences during childhood : role of early experiences

We investigated the effects of early experience on sweet and sour preferences in children. Eighty-three children were divided into four groups based on the type of formula fed during infancy and age. By using a forced-choice, sip-and-swallow procedure, we determined the level of sweetness and sourness preferred in juice. Children who were fed protein hydrolysate formulas, which have a distinctive sour and bitter taste and unpleasant odor, preferred higher levels of citric acid in juice when compared to older children who were fed similar formulas. No such difference was observed between the groups for sweet preference. However, the level of sweetness preferred in juice was related to the sugar content of the child's favorite cereal and whether the mother routinely added sugar to their foods. These data illustrate the wide variety of experiential factors that can influence flavor preferences during childhood.

Sweet preferences and sugar consumption of 4- and 5-year-old children : role of parents

We investigated the relationships in children between rules that restrict consumption of mono- and disaccharides (MDS), consumption of MDS and preferences for sucrose-containing orangeade. The background ideas of restriction rules we also investigated. To this end, 44 children (5.1 ^ 0.5 years) performed a rank-order and paired-comparison test of preference for five orangeades, which differed in sucrose concentration (0.14, 0.20, 0.29, 0.42, 0.61 M sucrose). Parents filled out a questionnaire concerning restriction rules and their children’s consumption of MDS-containing foods. Stronger restriction rules were related to a lower consumption of beverages that contained MDS and to a lower consumption of MDS-containing foods during breakfast and lunch. The most freedom to choose foods that contain MDS was given during the afternoon. Fifty-five percent of the children who were highly restricted showed a preference for the highest concentration of sucrose in orangeade. None of these children preferred the orangeade with the lowest concentration of sucrose. While 19% of the children who were little restricted preferred the beverage with the lowest concentration of sucrose, 33% preferred the beverage with the highest concentration. These parents generally believed that sugar has a bad effect on health and had similar background ideas concerning restriction
rules.

The career preferences of undergraduate nursing students

A quasi-experimental design was used to test the hypothesis "there is a positive relationship between theoretical and clinical exposure to psychiatric nursing and the desirability of psychiatric nursing as a career choice." Results found that overall psychiatric nursing initially emerged as being a relatively unpopular career option.