Genotypic characterization of Salmonella typhi by amplified fragment length polymorphism fingerprinting provides increased discrimination as compared to pulsed-field gel electrophoresis and ribotyping

Amplified fragment length polymorphism (AFLP) is a recently developed, PCR-based high resolution fingerprinting method that is able to generate complex banding patterns which can be used to delineate intraspecific genetic relationships among bacteria. In the present study, AFLP was evaluated for its usefulness in the molecular typing of Salmonella typhi in comparison to ribotyping and pulsed-field gel electrophoresis (PFGE). Six S. typhi isolates from diverse geographic areas (Malaysia, Indonesia, India, Chile, Papua New Guinea and Switzerland) gave unique, heterogeneous profiles when typed by AFLP, a result which was consistent with ribotyping and PFGE analysis. In a further study of selected S. typhi isolates from Papua New Guinea which caused fatal and non-fatal disease previously shown to be clonally related by PFGE, AFLP discriminated between these isolates but did not indicate a linkage between genotype with virulence. We conclude that AFLP (discriminatory index=0.88) has a higher discriminatory power for strain differentiation among S. typhi than ribotyping (DI=0.63) and PFGE (DI=0.74).     

Feel good,do good? Disentangling reciprocity from unconditional prosociality

Direct and generalised reciprocity can establish evolutionarily stable levels of cooperation among unrelated individuals, with animals reciprocating help based on whether they have been helped by a social partner before. It has been argued that the actual cooperative act by a social partner may be of minor importance for seemingly reciprocal cooperation and that a mere positive experience might suffice to enhance helpful behaviour towards a conspecific (‘feel good, do good’). However, this effect could easily be exploited by defectors free‐riding on an individual's enhanced propensity to cooperate after an unspecific positive experience, without investing in reciprocity themselves. Here, we use female Norway rats (Rattus norvegicus) to test if a positive experience that was not provided by a helping partner increases the propensity to subsequently help a social partner. We manipulated the experience of test subjects by providing them with treats, either in the presence or absence of a conspecific. Thereafter, we assessed whether they produce treats and if so, how many, for an unfamiliar social partner compared to a situation in which they had not received treats before. As the treats the test subject received had not been provided by a social partner even if the partner was present, we predicted that the rats should not be more cooperative after they had received treats than if they had not. Indeed, the helping behaviour of rats was apparently not influenced by prior experience made either in a social or non‐social context. Rats have been shown previously to perform both direct and generalised reciprocity in the same variant of the iterated prisoner's dilemma game. Our results suggest that this behaviour cannot be explained by an unspecific positive experience. The decision to help a social partner seems to be contingent on previously receiving help from a social partner (reciprocity), not on any positive experience (unconditional prosociality).     

Does seasonality drive spatial patterns in demography? Variation in survival in African reed warblers Acrocephalus baeticatus across southern Africa does not reflect global patterns

Among birds, northern temperate species generally have larger clutches, shorter development periods and lower adult survival than similarly‐sized southern and tropical species. Even though this global pattern is well accepted, the driving mechanism is still not fully understood. The main theories are founded on the differing environmental seasonality of these zones (higher seasonality in the North). These patterns arise in cross‐species comparisons, but we hypothesized that the same patterns should arise among populations within a species if different types of seasonality select for different life histories. Few studies have examined this. We estimated survival of an azonal habitat specialist, the African reed warbler, across the environmentally diverse African subcontinent, and related survival to latitude and to the seasonality of the different environments of their breeding habitats. Data (1998–2010) collected through a public ringing scheme were analyzed with hierarchical capture‐mark‐recapture models to determine resident adult survival and its spatial variance across sixteen vegetation units spread across four biomes. The models were defined as state‐space multi‐state models to account for transience and implemented in a Bayesian framework. We did not find a latitudinal trend in survival or a clear link between seasonality and survival. Spatial variation in survival was substantial across the sixteen sites (spatial standard deviation of the logit mean survival: 0.70, 95% credible interval (CRI): 0.33–1.27). Mean site survival ranged from 0.49 (95% CRI: 0.18–0.80) to 0.83 (95% CRI: 0.62–0.97) with an overall mean of 0.67 (95% CRI: 0.47–0.85). A hierarchical modeling approach enabled us to estimate spatial variation in survival of the African reed warbler across the African subcontinent from sparse data. Although we could not confirm the global pattern of higher survival in less seasonal environments, our findings from a poorly studied region contribute to the study of life‐history strategies.     

Zur mathematischen Behandlung der Stoffaufnahme lebender Protoplaste

Zusammenfassung Die vorliegende Arbeit bringt unter bestimmten Voraussetzungen Ableitungen einfacher Formeln zur Berechnung von Permeationskonstanten aus den an nackten (plasmolysierten) Protoplasten beobachteten Volumänderungen, die während der Endosmose oder der Exosmose des auf seine Permeationsstärke untersuchten Anelektrolyten verlaufen. Für die Aufstellung der Formeln wurde gefordert: höchstmögliche Exaktheit, allgemeine Anwendungsmöglichkeit und eine Definition der Konstanten in hergebrachter Weise. — Um die Wasserpermeation in eine mathematische Beziehung zur Anelektrolytpermeation zu bringen, wird sie auf der Grundlage der osmotischen Unterdrucktheorie dem Fickschen Diffusionsgesetz unterstellt; für 19,5° C ist P_wasser=8 · k (P unter anderem auf die Einheit der Konzentrationsdifferenz und k unter anderem auf die Einheit der osmotischen Druckdifferenz bezogen). — Der Begriff der Protoplasten-Permeabilität wird an dem Beispiel der Wasseraufnahme eingehender erläutert. Einige neue Beziehungen zwischen der Protoplasten-Permeabilität und der Zeit bei der Wasser- und Anelektrolytaufnahme und -abg abe werden abgeleitet; sie geben, bezogen auf natürliche Zustandsgrößen, die Möglichkeit zu einem allgemeinen Vergleich der Eigenschaften verschiedenartiger Protoplaste unter natürlichen Bedingungen. — Im letzten Abschnitt wird das Verhältnis der Zeitdauer der Anelektrolytaufnahme zu der Zeitdauer der Abgabe einer gleich großen Anelektrolytmenge in seiner Abhängigkeit von den Milieuverhältnissen formelmäßig dargestellt.     

Revisiting the Effect of Capture Heterogeneity on Survival Estimates in Capture-Mark-Recapture Studies: Does It Matter?

Recently developed capture-mark-recapture methods allow us to account for capture heterogeneity among individuals in the form of discrete mixtures and continuous individual random effects. In this article, we used simulations and two case studies to evaluate the effectiveness of continuously distributed individual random effects at removing potential bias due to capture heterogeneity, and to evaluate in what situation the added complexity of these models is justified. Simulations and case studies showed that ignoring individual capture heterogeneity generally led to a small negative bias in survival estimates and that individual random effects effectively removed this bias. As expected, accounting for capture heterogeneity also led to slightly less precise survival estimates. Our case studies also showed that accounting for capture heterogeneity increased in importance towards the end of study. Though ignoring capture heterogeneity led to a small bias in survival estimates, such bias may greatly impact management decisions. We advocate reducing potential heterogeneity at the sampling design stage. Where this is insufficient, we recommend modelling individual capture heterogeneity in situations such as when a large proportion of the individuals has a low detection probability (e.g. in the presence of floaters) and situations where the most recent survival estimates are of great interest (e.g. in applied conservation).     

Roles of Spatial Scale and Rarity on the Relationship between Butterfly Species Richness and Human Density in South Africa

Wildlife and humans tend to prefer the same productive environments, yet high human densities often lead to reduced biodiversity. Species richness is often positively correlated with human population density at broad scales, but this correlation could also be caused by unequal sampling effort leading to higher species tallies in areas of dense human activity. We examined the relationships between butterfly species richness and human population density at five spatial resolutions ranging from 2'' to 60'' across South Africa. We used atlas-type data and spatial interpolation techniques aimed at reducing the effect of unequal spatial sampling. Our results confirm the general positive correlation between total species richness and human population density. Contrary to our expectations, the strength of this positive correlation did not weaken at finer spatial resolutions. The patterns observed using total species richness were driven mostly by common species. The richness of threatened and restricted range species was not correlated to human population density. None of the correlations we examined were particularly strong, with much unexplained variance remaining, suggesting that the overlap between butterflies and humans is not strong compared to other factors not accounted for in our analyses. Special consideration needs to be made regarding conservation goals and variables used when investigating the overlap between species and humans for biodiversity conservation.     

An index to compare geographical distributions of species

We present an index for the dissimilarity/distance between geographical distributions based on reporting rates recorded on a regular lattice. Reporting rate data are common, for example, in bird atlas projects where observers fill in check lists of encountered species in a particular area. Our index is a variation of the Euclidean distance, with the contribution of each grid cell weighted by the number of checklists collected for the grid cell, and a scaling factor to ensure that the dissimilarity ranges between zero and one. Reporting rates were transformed to ordered percentile classes to make species with different mean reporting rates comparable. The index was developed for the comparison of distributions of The Atlas of Southern African Birds . We illustrate the dissimilarity index comparing distributions of whydahs and indigobirds (widowfinches), which are specialized brood parasites, to the distributions of their hosts: waxbills and other finches.     

Numerical classification and identification of Aeromonas genospecies

P. KÄMPFER AND M. ALTWEGG. 1992. A total of 176 Aeromonas strains representing all currently characterized genospecies were tested for 329 biochemical characters. Overall similarities of all strains were determined by numerical taxonomic techniques, the UPGMA algorithm and the S _SM and the S _J coefficients as measures of similarity. Sixteen clusters (two or more strains) and seven unclustered strains were recovered at the 93.5% similarity level ( S _SM). Genospecies 1, 4, 5, 6, 7, 9, 12 and 13 were largely represented by single phena, whereas strains of genospecies 2 and 3 were found in closely-related phena. Strains belonging to genospecies 8 formed two distinct biotypes. Strains belonging to genospecies 11 formed a subcluster within a cluster representing different genospecies. In general, similar groupings were obtained with the Jaccard coefficient at a similarity level of 80.0% ( S _J) with minor changes in the definition of clusters. The phenetic data showed good correlation with the taxa defined by DNA/DNA hybridization and those obtained by multilocus enzyme analysis. For all genospecies (independent from cluster assignment) 30 diagnostic characters were selected to construct a matrix for probabilistic identification. The correct identification rate of the matrix was 71.51% taking a Willcox probability < 0.99, and 83.7% taking a Willcox probability > 0.9 as identification threshold levels.