Why Do Unrelated Insertion Sequences Occur Together in the Genome of Escherichia Coli?

Natural isolates of Escherichia coli are polymorphic for the presence or absence of insertion sequences. Among the ECOR reference collection of 71 natural isolates studied for the number of copies of the insertion sequences IS1, IS2, IS3, IS4, IS5 and IS30, the number of strains containing no copies of the insertion sequences were 11, 28, 23, 43, 46 and 36, respectively. Significant correlations occur in the ECOR strains in the presence or absence of unrelated insertion sequences in the chromosome and plasmid complements. Strains containing any insertion sequence are more likely to contain additional, unrelated insertion sequences than would be expected by chance. We suggest that the positive correlations result from horizontal transfer mediated by plasmids. A branching-process model for the plasmid-mediated transmission of insertion sequences among hosts yields such a correlation, even in the absence of interactions affecting transposition or fitness. The predictions of the model are quantitatively in agreement with the observed correlations among insertion sequences.     

Who Learns More? Cultural Differences in Implicit Sequence Learning

Background

It is well documented that East Asians differ from Westerners in conscious perception and attention. However, few studies have explored cultural differences in unconscious processes such as implicit learning.

Methodology/Principal Findings

The global-local Navon letters were adopted in the serial reaction time (SRT) task, during which Chinese and British participants were instructed to respond to global or local letters, to investigate whether culture influences what people acquire in implicit sequence learning. Our results showed that from the beginning British expressed a greater local bias in perception than Chinese, confirming a cultural difference in perception. Further, over extended exposure, the Chinese learned the target regularity better than the British when the targets were global, indicating a global advantage for Chinese in implicit learning. Moreover, Chinese participants acquired greater unconscious knowledge of an irrelevant regularity than British participants, indicating that the Chinese were more sensitive to contextual regularities than the British.

Conclusions/Significance

The results suggest that cultural biases can profoundly influence both what people consciously perceive and unconsciously learn.     

Why Are Autism Spectrum Conditions More Prevalent in Males?

Autism Spectrum Conditions (ASC) are much more common in males, a bias that may offer clues to the etiology of this condition. Although the cause of this bias remains a mystery, we argue that it occurs because ASC is an extreme manifestation of the male brain. The extreme male brain (EMB) theory, first proposed in 1997, is an extension of the Empathizing-Systemizing (E-S) theory of typical sex differences that proposes that females on average have a stronger drive to empathize while males on average have a stronger drive to systemize. In this first major update since 2005, we describe some of the evidence relating to the EMB theory of ASC and consider how typical sex differences in brain structure may be relevant to ASC. One possible biological mechanism to account for the male bias is the effect of fetal testosterone (fT). We also consider alternative biological theories, the X and Y chromosome theories, and the reduced autosomal penetrance theory. None of these theories has yet been fully confirmed or refuted, though the weight of evidence in favor of the fT theory is growing from converging sources (longitudinal amniocentesis studies from pregnancy to age 10 years old, current hormone studies, and genetic association studies of SNPs in the sex steroid pathways). Ultimately, as these theories are not mutually exclusive and ASC is multi-factorial, they may help explain the male prevalence of ASC.     

Why Do Some People Do “More” to Mitigate Climate Change than Others? Exploring Heterogeneity in Psycho-Social Associations

The urgency of climate change mitigation calls for a profound shift in personal behavior. This paper investigates psycho-social correlates of extra mitigation behavior in response to climate change, while also testing for potential (unobserved) heterogeneity in European citizens'' decision-making. A person''s extra mitigation behavior in response to climate change is conceptualized—and differentiated from common mitigation behavior—as some people''s broader and greater levels of behavioral engagement (compared to others) across specific self-reported mitigation actions and behavioral domains. Regression analyses highlight the importance of environmental psychographics (i.e., attitudes, motivations, and knowledge about climate change) and socio-demographics (especially country-level variables) in understanding extra mitigation behavior. By looking at the data through the lens of segmentation, significant heterogeneity is uncovered in the associations of attitudes and knowledge about climate change—but not in motivational or socio-demographic links—with extra mitigation behavior in response to climate change, across two groups of environmentally active respondents. The study has implications for promoting more ambitious behavioral responses to climate change, both at the individual level and across countries.     

Do Pheromone Binding Proteins Converge in Amino Acid Sequence When Pheromones Converge?

Convergence in amino acid sequences between proteins can be strong evidence for selection. Here, I look for evidence of convergence in the amino acid sequences of pheromone binding protein (PBP) in response to convergence in pheromones. PBPs are involved in sex pheromone reception by the antennae of male moths. In this role PBPs may selectively bind pheromone components and experience convergent selection in response to convergence in pheromone components. However, examination of the PBPs of the taxa that have converged upon the use of (E)- or (Z)-11-tetradecenyl acetate as their major pheromone component reveals little evidence for convergence in the PBPs identified from these taxa. A few sites show a pattern consistent with convergence or parallelism; however, it cannot be ruled out that these sites share the ancestral state. Two of these sites fall within the proposed binding region of PBPs. These results suggest that PBPs either have not converged in sequence or have converged at very few sites in response to convergence on the same pheromone component. Received: 29 July 1999 / Accepted: 8 November 1999     

Why Do We Expect Carotenoids to be Antioxidants in vivo?

The antioxidant properties of β-carotene, in addition to its proposed immunomodulatory effects, have often been cited as the factors underlying its role in preventing disease initiation and propagation, yet the strongest evidence for diet and cancer prevention is based on fruit and vegetable intake and not β-carotene or other dietary carotenoids, per se. In the light of the outcome of the ATBC trial, the Physicians Health Study and the premature termination of the CARET study, this review addresses the issue of the antioxidant properties of the carotenoids and poses the questions: do dietary carotenes and xanthophylls have a clear role in disease prevention and are their antioxidant properties relevant to this role? What. do we know about their mechanisms of action in vitro as free radical scavengers?     

Do Bells Affect Behaviour and Heart Rate Variability in Grazing Dairy Cows?

In alpine regions cows are often equipped with bells. The present study investigated the impact of wearing a bell on behaviour and heart rate variability in dairy cows. Nineteen non-lactating Brown-Swiss cows with bell experience were assigned to three different treatments. For 3 days each, cows were equipped with no bell (control), with a bell with inactivated clapper (silent bell) or with a functional bell (functional bell). The bells weighed 5.5 kg and had frequencies between 532 Hz and 2.8 kHz and amplitudes between 90 and 113 dB at a distance of 20 cm. Data were collected on either the first and third or on all 3 days of each treatment. Whereas duration of rumination was reduced with a functional bell and a silent bell compared with no bell, feeding duration was reduced with a silent bell and was intermediate with a functional bell. Head movements were reduced when wearing a silent bell compared with no bell and tended to be reduced when wearing a functional compared to no bell. With a functional bell, lying duration was reduced by almost 4 hours on the third day of treatment compared with the first day with a functional bell and compared with no bell or a silent bell. All additional behavioural measures are consistent with the hypothesis of a restriction in the behaviour of the cows wearing bells, although this pattern did not reach significance. There was no treatment effect on heart rate variability, suggesting that the bells did not affect vago-sympathetic balance. An effect of experimental day was found for only 1 out of 10 behavioural parameters, as shown by a decrease in lying with a functional bell on day 3. The results indicate behavioural changes in the cows wearing a bell over 3 days, without indication of habituation to the bell. Altogether, the behavioural changes suggest that the behaviour of the cows was disturbed by wearing a bell. If long-lasting, these effects may have implications for animal welfare.     

Why Do Dolphins Form Mixed‐Species Associations in the Azores?

Mixed‐species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed‐species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed‐species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed‐species groups were compared with those of single‐species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed‐species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed‐species groups depends on several environmental factors, and therefore may constitute an adaptive response.     

Eye Tracking the Face in the Crowd Task: Why Are Angry Faces Found More Quickly?

Among a crowd of distractor faces, threatening or angry target faces are identified more quickly and accurately than are nonthreatening or happy target faces, a finding known as the “face in the crowd effect.” Two perceptual explanations of the effect have been proposed: (1) the “target orienting” hypothesis (i.e., threatening targets orient attention more quickly than do nonthreatening targets and (2) the “distractor processing” hypothesis (i.e., nonthreatening distractors paired with a threatening target are processed more efficiently than vice versa, leading to quicker detection of threatening targets). Using a task, with real faces and multiple identities, the current study replicated the face in the crowd effect and then, via eye tracking, found greater support for the target orienting hypothesis. Across both the classical search asymmetry paradigm (i.e., one happy target in a crowd of angry distractors vs. one angry target in a crowd of happy distractors) and the constant distractor paradigm (i.e., one happy target in a crowd of neutral distractors vs. one angry target in a crowd of neutral distractors), fewer distractors were fixated before first fixating angry targets relative to happy targets, with no difference in the processing efficiency of distractors. These results suggest that the face in the crowd effect on this task is supported to a greater degree by attentional patterns associated with properties of target rather those of the crowd.     

Why Do Floral Perfumes Become Different? Region-Specific Selection on Floral Scent in a Terrestrial Orchid

Geographically structured phenotypic selection can lead to adaptive divergence. However, in flowering plants, such divergent selection has rarely been shown, and selection on floral signals is generally little understood. In this study, we measured phenotypic selection on display size, floral color, and floral scent in four lowland and four mountain populations of the nectar-rewarding terrestrial orchid Gymnadenia odoratissima in two years. We also quantified population differences in these traits and pollinator community composition. Our results show positive selection on display size and positive, negative, or absence of selection on different scent compounds and floral color. Selection on the main scent compounds was consistently stronger in the lowlands than in the mountains, and lowland plants emitted higher amounts of most of these compounds. Pollinator community composition also differed between regions, suggesting different pollinators select for differences in floral volatiles. Overall, our study is the first to document consistent regional differences in selection on floral scent, suggesting this pattern of selection is one of the evolutionary forces contributing to regional divergence in floral chemical signaling.     

Zur Sauerstoffabh?ngigkeit der Rate strahleninduzierter Chromosomenaberrationen in Oozyten vonDrosophila melanogaster

Summary Abrahamson's (1959) results concerning the influence of oxygen on the frequency of X-ray induced structural changes (half-translocations) inDrosophila oocytes were generally reproduced, especially the demonstration of a reverse oxygen effect (under special experimental conditions protecting action of oxygen, sensitization by nitrogen). In the course of our investigations the following new findings were obtained: 1. The added aberration frequencies of the 3rd and 4th day after the various treatments generally tend to decrease as compared with those of the first two days (dependence on state of maturity of the treated oocytes). 2.Preirradiation treatment by nitrogen increases the aberration frequency significantly. Possible explanations of this effect are discussed.

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Why Do People Feed Free-roaming Cats? The Role of Anticipated Regret in an Extended Theory of Planned Behavior in Malaysia

Free-roaming cats are common in residential and public areas in Malaysia and approach people for food. However, the psychological determinants of public feeding are unknown. This study investigated public perceptions of feeding free-roaming cats, based on an extended theory of planned behavior (TPB). It consisted of qualitative belief-elicitation interviews with 25 participants, followed by a quantitative survey of 167 participants, representative of the country’s population. The majority (87.2%) of the sample had fed free-roaming cats. The mean intention score (4.88 out of 7) indicated the public was likely, and would make an effort, to feed free-roaming cats in the future. The public’s benevolence toward animals largely explained the findings, based on generally positive attitudes and perceptions of moderate social credence and capability and confidence, underpinned by affective and cognitive beliefs. An important finding was the role of anticipated regret in predicting and explaining intentions, which contributed variance over and above that explained by the TPB constructs. The extended framework is explained by the influence of anticipated regret on the perceived evaluation of potential TPB outcomes, which in turn leads to the behavior becoming less volitional. Therefore, future TPB studies of people’s interactions with animals, such as free-roaming cats, should take account of affective and emotional antecedents of behavior, such as anticipated regret, to improve explanatory power. The study also has implications for managing public feeding of free-roaming cats, such as drawing on and strengthening the Malaysian public’s positive attitudes and emotional concern to redirect current feeding practices toward more constructive animal welfare initiatives. Such humane approaches align with the public’s sensitivity toward animal welfare and the historical development of cat population control from lethal methods to humane non-lethal methods to ensure adequate care.     

Why Do You Believe in God? Relationships between Religious Belief,Analytic Thinking,Mentalizing and Moral Concern

Prior work has established that analytic thinking is associated with disbelief in God, whereas religious and spiritual beliefs have been positively linked to social and emotional cognition. However, social and emotional cognition can be subdivided into a number of distinct dimensions, and some work suggests that analytic thinking is in tension with some aspects of social-emotional cognition. This leaves open two questions. First, is belief linked to social and emotional cognition in general, or a specific dimension in particular? Second, does the negative relationship between belief and analytic thinking still hold after relationships with social and emotional cognition are taken into account? We report eight hypothesis-driven studies which examine these questions. These studies are guided by a theoretical model which focuses on the distinct social and emotional processing deficits associated with autism spectrum disorders (mentalizing) and psychopathy (moral concern). To our knowledge no other study has investigated both of these dimensions of social and emotion cognition alongside analytic thinking. We find that religious belief is robustly positively associated with moral concern (4 measures), and that at least part of the negative association between belief and analytic thinking (2 measures) can be explained by a negative correlation between moral concern and analytic thinking. Using nine different measures of mentalizing, we found no evidence of a relationship between mentalizing and religious or spiritual belief. These findings challenge the theoretical view that religious and spiritual beliefs are linked to the perception of agency, and suggest that gender differences in religious belief can be explained by differences in moral concern. These findings are consistent with the opposing domains hypothesis, according to which brain areas associated with moral concern and analytic thinking are in tension.     

Where,When and Why Do Tsetse Contact Humans? Answers from Studies in a National Park of Zimbabwe

Background

Sleeping sickness, also called human African trypanosomiasis, is transmitted by the tsetse, a blood-sucking fly confined to sub-Saharan Africa. The form of the disease in West and Central Africa is carried mainly by species of tsetse that inhabit riverine woodland and feed avidly on humans. In contrast, the vectors for the East and Southern African form of the disease are usually savannah species that feed mostly on wild and domestic animals and bite humans infrequently, mainly because the odours produced by humans can be repellent. Hence, it takes a long time to catch many savannah tsetse from people, which in turn means that studies of the nature of contact between savannah tsetse and humans, and the ways of minimizing it, have been largely neglected.

Methodology/Principal Findings

The savannah tsetse, Glossina morsitans morsitans and G. pallidipes, were caught from men in the Mana Pools National park of Zimbabwe. Mostly the catch consisted of young G. m. morsitans, with little food reserve. Catches were increased by 4–8 times if the men were walking, not stationary, and increased about ten times more if they rode on a truck at 10 km/h. Catches were unaffected if the men used deodorant or were baited with artificial ox odour, but declined by about 95% if the men were with an ox. Surprisingly, men pursuing their normal daily activities were bitten about as much when in or near buildings as when in woodland. Catches from oxen and a standard ox-like trap were poor indices of the number and physiological state of tsetse attacking men.

Conclusion/Significance

The search for new strategies to minimize the contact between humans and savannah tsetse should focus on that occurring in buildings and vehicles. There is a need to design a man-like trap to help to provide an index of sleeping sickness risk.     

Why hide? Concealed sex in dominant Arabian babblers (Turdoides squamiceps) in the wild

Striking uniformity exists in humans' preference to conceal sexual activity from conspecifics' view. Yet, little is known about the selective pressures acting upon its evolution. To investigate this question, we studied the cooperatively breeding Arabian babbler (Turdoides squamiceps), which has been suggested being the only other species where dominant individuals conceal sex regularly. We examined whether birds indeed conceal sex and tested different hypotheses postulating that sex concealment functions to avoid predators, signal dominance status, or to avoid social interference. The results showed that the birds concealed sex in all observed cases of copulation, did not prefer to copulate under shelters and concealed mating solicitations from adult conspecifics. In addition, subordinates did not attack dominants who courted the respective female. Hence, none of the tested hypotheses explains these results satisfactorily. We postulate that dominant Arabian babblers conceal sex to maintain cooperation with those helpers they prevent from mating. Empirical desiderata for testing this ‘Cooperation-Maintenance’ hypothesis are discussed.     

Why Do Species Co-Occur? A Test of Alternative Hypotheses Describing Abiotic Differences in Sympatry versus Allopatry Using Spadefoot Toads

Areas of co-occurrence between two species (sympatry) are often thought to arise in regions where abiotic conditions are conducive to both species and are therefore intermediate between regions where either species occurs alone (allopatry). Depending on historical factors or interactions between species, however, sympatry might not differ from allopatry, or, alternatively, sympatry might actually be more extreme in abiotic conditions relative to allopatry. Here, we evaluate these three hypothesized patterns for how sympatry compares to allopatry in abiotic conditions. We use two species of congeneric spadefoot toads, Spea multiplicata and S. bombifrons, as our study system. To test these hypotheses, we created ecological niche models (specifically using Maxent) for both species to create a map of the joint probability of occurrence of both species. Using the results of these models, we identified three types of locations: two where either species was predicted to occur alone (i.e., allopatry for S. multiplicata and allopatry for S. bombifrons) and one where both species were predicted to co-occur (i.e., sympatry). We then compared the abiotic environment between these three location types and found that sympatry was significantly hotter and drier than the allopatric regions. Thus, sympatry was not intermediate between the alternative allopatric sites. Instead, sympatry occurred at one extreme of the conditions occupied by both species. We hypothesize that biotic interactions in these extreme environments facilitate co-occurrence. Specifically, hybridization between S. bombifrons females and S. multiplicata males may facilitate co-occurrence by decreasing development time of tadpoles. Additionally, the presence of alternative food resources in more extreme conditions may preclude competitive exclusion of one species by the other. This work has implications for predicting how interacting species will respond to climate change, because species interactions may facilitate survival in extreme habitats.     

Why do sex ratio dimorphisms exist in Quercus masting? Evolution of imperfect synchronous reproduction in Monoecious trees

Masting is synchronous intermittent production of seeds in perennial plant populations. Some self-compatible monoecious Quercus species, such as oaks, exhibit sex ratio dimorphism and produce a certain proportion of male flowers, even in a year when no seed set occurs. To investigate sex ratio dimorphism in masting trees, we introduced sexual allocation as an evolutionary trait into the Resource Budget Model and examined the evolution of the sex ratio. Analytical and numerical findings show that (1) perfectly synchronous intermittent reproduction does not evolve; (2) if the fruiting cost of female flowers R_c is sufficiently large and the pollen limitation β is intermediate, annual reproduction does not evolve; (3) under conditions (2), sex ratio dimorphism can evolve across a wide region of parameter space; (4) after dimorphism is established, individuals with a female-biased sex ratio receive much more pollen supply from male-biased individuals and tend to show intermittent reproduction with or without synchrony; and (5) dimorphism is maintained with irregular and nearly discontinuous changes of sex ratio. These results suggest that sex ratio dimorphism contributes to improving pollen availability and causes resource depletion and the occurrence of intermittent reproduction in female-biased individuals.