When less means more: evolutionary and developmental hypotheses in rodent molars

Tooth number in rodents is an example of reduction in evolution. All rodents have a toothless diastema lacking canine and most premolars present in most other mammals. Whereas some rodent lineages retained one premolar (p4), many others lost it during evolution. Recently, an 'inhibitory cascade' developmental model (IC) has been used to predict how the first molar (m1) influences the number and relative sizes of the following distal molars (m2 and m3). The model does not, however, consider the presence of premolars, and here we examine whether the premolar could influence and constrain molar proportions during development and evolution. By investigating a large data set of both extinct and extant rodent families over more than 40 million years, we show that the basal phenotype is characterized by the presence of premolars together with equally sized molars. More recent rodent families, with and without premolar, show more unequal molar sizes. Analysing molar areas, we demonstrated that (i) rodents harbour almost all the molar proportions known in mammals, and the IC model can explain about 80% of taxa in our data set; (ii) proportions of molars are influenced by the presence or absence of p4; and (iii) the most variable teeth in the dental row are m1 and m3, whether p4 is present or not. Moreover, m1 can represent up to half of the total molar area when p4 is absent. We hypothesize that p4 loss during evolution released the constraint on m1 development, resulting in a more variable size of m1 and thereby having an indirect effect on the evolution of the whole molar row.     

When more equals less: overtraining inhibits perceptual learning owing to lack of wakeful consolidation

Performance on perceptual tasks usually improves with training. However, too much consecutive training can be detrimental. Repeated within-day testing or overtraining demonstrates the detrimental effects this has on perceptual learning. Consolidation of learnt information during sleep has the power to prevent such deficits in learning. However, little is known regarding the role of wakeful consolidation in preventing the effects of overtraining. Here, we report that perceptual deterioration may result from the disruption of early wakeful consolidation processes. Three groups were tested on day 1 and again 24 h later, on a motion discrimination task. Participants who had a 1 h break between the two training sessions on the first day displayed improved accuracy on the second day (i.e. learning). Subjects who only completed the first training session on day 1 also exhibited learning. However, individuals who completed two blocks without a break ('overtraining') showed no improvement in accuracy on day 2. Interestingly, changes in reaction times were not susceptible to the effects of overtraining, but instead speeded up as a function of total performed trials. These data suggest that effects of overtraining might be due to disruption of wakeful consolidation processes.     

When less is more: accounting for overcompensation in mosquito SIT projects

Compensation and overcompensation under field conditions are confirmed in Aedes mosquitoes recently by Evans et al.: equal or increased densities of emerging adults may thus result from reduced larval densities. Here the consequences when applying the sterile insect technique and provide recommendations to avoid counterproductive effects are discussed.     

When more is less: the fitness consequences of predators attacking more unpalatable prey when more are presented

In 1879, Fritz Müller hypothesized that mimetic resemblance in which defended prey display the same warning signal would share the costs of predator education. Although Müller argued that predators would need to ingest a fixed number of prey with a given visual signal when learning to avoid unpalatable prey, this assumption lacks empirical support. We report an experiment which shows that, as the number of unpalatable prey presented to them increased, avian predators attacked higher numbers of those prey. We calculated that, when predators increase attacks, the fitness costs incurred by unpalatable prey can be substantial. This suggests that the survival benefits of mimicry could be lower than Müller proposed. An important finding is, however, that these costs decline in importance as the total number of available prey increases.     

When less means more: Reduction of both effort and survey methods boosts efficiency and diversity of harvestmen in a tropical forest

Several ecological studies and monitoring programs of biodiversity have shown that using fewer collecting methods in biological surveys is more efficient than several redundant ones. However, in an attempt to increase species detection, researchers are still using as many field methods as possible in the surveys of arthropods and other megadiverse groups of invertebrates. The challenge is to reduce the overall time and effort for surveys while still retaining as much information about species richness and assemblage composition as possible. Researchers usually face a trade-off of loosing some information in order to have more efficient surveys. Here we show that more species were obtained in harvestmen surveys using a reduced version of the traditional method of active nocturnal search. We evaluated both the congruence and efficiency of the beating tray, and three versions of active nocturnal search across a tropical forest area in the Amazon basin. As nocturnal search has long been proved to be the most efficient method to capture arachnids, we tested three variations of this method in an attempt to improve harvestmen survey. A total of 2338 individuals of 23 species, in 20 genera and 10 families, were recorded using all methods together. Just one method, the active cryptic nocturnal search, encountered all taxa sampled with the maximum effort (sum of all methods) and data from this method recovered the ecological patterns found by the more intensive methods. Financial costs and time spent sampling and identifying specimens were reduced by 87% when compared to the maximum effort. We suggest that only one method, active cryptic nocturnal search, is the most efficient method to both sample and monitor harvestmen in Amazon tropical forests.     

When less is more: A simple predictive model for repeated prostate biopsy outcomes

ObjectivesTo present a new predictive model for repeated prostate biopsy outcomes. Several practical problems are described that arise when searching for a proper model among those that already exist. A new model is developed with only two explanatory variables and a simple graphical output.MethodsThis is a retrospective cohort study based on data collected from December 2006 to June 2011 at the Clinic of Urology of the University Hospital in Olomouc, Czech Republic. The cohort consists of 221 patients who underwent the first repeated biopsy after an initial biopsy with a negative outcome. All patients had prostate-specific antigen (PSA) levels between 1.5 and 16.5 ng/mL and a prostate volume not greater than 100 mL. A logistic regression model was fitted.ResultsOf the 221 patients, 29 (13%) were diagnosed with prostate cancer on the repeated biopsy. The final model includes the PSA level and the transitory zone volume as predictors. Its accuracy is 76.4%. The cut-off point of 0.0687 in the predicted positive repeated biopsy outcome assures 95% sensitivity and prevents 42% of unnecessary biopsies.ConclusionsThe accuracy of the model is comparable to that of more complex models (with more than two predictors) published in the literature. The model includes only two routinely measured variables, and hence it is accessible for a wide range of practitioners. The simple graphical outcome makes the model even more attractive.     

Organelle proteomics: looking at less to see more

The recent finding that the human genome comprises between 21 000 and 39 000 genes, a number much lower than expected, has in no way simplified the complexity associated with the understanding of how cells perform their functions. Elucidation of the molecular mechanisms underlying cell functions will require a global knowledge of the expressed proteins, including splice variant products, their post-translational modifications, their subcellular localizations and their assembly into molecular machines as deduced from protein–protein interactions, at any given time during the life of the cell or under any cellular conditions. Current and expected advances in mass spectrometry and bioinformatics might help the realization of these goals in a shorter time than is currently predicted.     

When more is less: the negative effect of European rabbit release upon local warren occupancy

European rabbit translocation is an extended practice in Spain, France, and Portugal, for both conservation and hunting purposes. Some of these translocations are carried out with the aim of reinforcing existing rabbit populations. In these cases, some of the new rabbits are released into warrens already occupied by resident conspecifics. This could have a negative impact upon both the released and the resident individuals owing to the “dear enemy” effect and the territoriality of the resident rabbits. In this study, we evaluated the effect of rabbit release into occupied warrens, in small areas populated by low-density resident rabbit populations. We observed negative effects at two different levels: the number of active entrances per recipient warren and the number of active warrens per reinforced plot, in addition to a general lack of increase in rabbit abundance in the area and, therefore, the failure of the reinforcement actions. Our results strongly suggest that the release of European rabbits into warrens occupied by resident rabbits is contraindicated if the objective is to recover rabbit populations in the area.     

TOR and aging: less is more

Metabolism and mitochondrial activity are thought to be important determinants of life span. A new study in this issue of Cell Metabolism (Bonawitz et al., 2007) suggests that the TOR pathway controls mitochondrial respiration in yeast and that the harder mitochondria work, the longer yeast live.     

Speckle microscopy: when less is more

Fluorescent speckle microscopy is a new and simplified method for generating fiduciary marks on cellular structures. It promises to become the method of choice for studying polymer movement and dynamics in vivo.