The Andean farmer conserves and maintains the existing genetic diversity of potato cultivars by means of clonal propagation of tubers . However, surveys of traditional farms showed that botanical seed propagation was used for disease elimination, stock rejuvenation and the creation of new cultivars . Electrophoretic surveys based on 542 tubers collected from 18 markets sampled in the Cusco area disclosed a total of 229 different cultivars from diploid, triploid and tetraploid forms of Solanum tuberosum L . These could be classified by isozyme cluster analysis into four major groups and six minor groups . However, they did not agree with groups based on flesh or skin color . It is therefore concluded that all genotypes belong to a single, large gene pool with considerable gene flow between cultivars of different groups . When the samples were grouped by the three most common tuber skin colors, namely red/pink ('Q'ompis type'), purple ('Yana Imilla' type), and yellowish/brown ('Yuraq Kusi' type), similar allozymes were observed in all three classes . The structure of the isozymic phenotypes within each group indicate that they may have been derived as segregants after outcrossing of diverse parental types . In order to provide further evidence for the origin of new types by hybridization, two segregating diploid progenies were generated by crossing purple by yellow skin types . In the resulting F1, most of the tuber phenotypes observed in the Andean varieties were reproduced in these crosses . It can be concluded that the Andean potatoes form a large and plastic gene pool amplified and renovated by outcrossing followed in some cases by human selection of desirable phenotypes .

Classical ecology provides principles for construction and function of biological communities, but to what extent these apply to the animal-associated microbiota is just beginning to be assessed. Here, we investigated the influence of several well-known ecological principles on animal-associated microbiota by characterizing gut microbial specimens from bilaterally symmetrical animals (Bilateria) ranging from flies to whales. A rigorously vetted sample set containing 265 specimens from 64 species was assembled. Bacterial lineages were characterized by 16S rRNA gene sequencing. Previously published samples were also compared, allowing analysis of over 1,098 samples in total. A restricted number of bacterial phyla was found to account for the great majority of gut colonists. Gut microbial composition was associated with host phylogeny and diet. We identified numerous gut bacterial 16S rRNA gene sequences that diverged deeply from previously studied taxa, identifying opportunities to discover new bacterial types. The number of bacterial lineages per gut sample was positively associated with animal mass, paralleling known species-area relationships from island biogeography and implicating body size as a determinant of community stability and niche complexity. Samples from larger animals harbored greater numbers of anaerobic communities, specifying a mechanism for generating more-complex microbial environments. Predictions for species/abundance relationships from models of neutral colonization did not match the data set, pointing to alternative mechanisms such as selection of specific colonists by environmental niche. Taken together, the data suggest that niche complexity increases with gut size and that niche selection forces dominate gut community construction.

Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles—thus the reversible capacity—remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.

Real-world networks, e.g., the social relations or world-wide-web graphs, exhibit both small-world and scale-free behaviour. We interpret lattice triangulations as planar graphs by identifying triangulation vertices with graph nodes and one-dimensional simplices with edges. Since these triangulations are ergodic with respect to a certain Pachner flip, applying different Monte Carlo simulations enables us to calculate average properties of random triangulations, as well as canonical ensemble averages, using an energy functional that is approximately the variance of the degree distribution. All considered triangulations have clustering coefficients comparable with real-world graphs; for the canonical ensemble there are inverse temperatures with small shortest path length independent of system size. Tuning the inverse temperature to a quasi-critical value leads to an indication of scale-free behaviour for degrees ⩾ k 5. Using triangulations as a random graph model can improve the understanding of real-world networks, especially if the actual distance of the embedded nodes becomes important.

Three-dimensional difference pair distribution functions (3D-ΔPDFs) from X-ray and neutron diffraction experiments are reported for yttria-stabilized zirconia (Zr0.82Y0.18O1.91). A quantitative analysis of the signatures in the three-dimensional difference pair distribution functions is used to establish that oxygen ions neighbouring a vacancy shift by 0.525 (5) Å along 〈1, 0, 0〉 towards the vacancy while metal ions neighbouring a vacancy shift by 0.465 (2) Å along 〈1, 1, 1〉 away from the vacancy. The neutron 3D-ΔPDF shows a tendency for vacancies to cluster along 〈½, ½, ½〉, which results in sixfold coordinated metal ions.