fastruct: model‐based clustering made faster

Bayesian model‐based clustering programs have gained increased popularity in studies of population structure since the publication of the software structure . These programs are generally acknowledged as performing well, but their running‐time may be prohibitive. fastruct is a non‐Bayesian implementation of the classical model with no‐admixture uncorrelated allele frequencies. This new program relies on the expectation–maximization principle, and produces assignment rivalling other model‐based clustering programs. In addition, it can be manyfold faster than Bayesian implementations. The software consists of a command‐line engine, which is suitable for batch analysis of data, and a graphical interface, which is convenient for exploring data.     

Trophic level modulates carabid beetle responses to habitat and landscape structure: a pan‐European study

1. Anthropogenic pressures have produced heterogeneous landscapes expected to influence diversity differently across trophic levels and spatial scales. 2. We tested how activity density and species richness of carabid trophic groups responded to local habitat and landscape structure (forest percentage cover and habitat richness) in 48 landscape parcels (1 km²) across eight European countries. 3. Local habitat affected activity density, but not species richness, of both trophic groups. Activity densities were greater in rotational cropping compared with other habitats; phytophage densities were also greater in grassland than forest habitats. 4. Controlling for country and habitat effects, we found general trophic group responses to landscape structure. Activity densities of phytophages were positively correlated, and zoophages uncorrelated, with increasing habitat richness. This differential functional group response to landscape structure was consistent across Europe, indicated by a lack of a country × habitat richness interaction. Species richness was unaffected by landscape structure. 5. Phytophage sensitivity to landscape structure may arise from relative dependency on seed from ruderal plants. This trophic adaptation, rare in Carabidae, leads to lower phytophage numbers, increasing vulnerability to demographic and stochastic processes that the greater abundance, species richness, and broader diet of the zoophage group may insure against.     

Short‐term effects of CO2 and O2 on citrate metabolism in illuminated leaves

Although there is now a considerable literature on the inhibition of leaf respiration (CO₂ evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO₂ and O₂ mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.) under different CO₂/O₂ conditions. Gas exchange coupled to online isotopic analysis showed that CO₂ evolved by leaves in the light came from ‘old’ carbon skeletons and there was a slight decrease in ¹³C natural abundance when [CO₂] increased. This suggested the involvement of enzymatic steps fractionating more strongly against ¹³C and thus increasingly limiting for the metabolic respiratory flux as [CO₂] increased. Isotopic labelling with ¹³C₂‐2,4‐citrate lead to ¹³C‐enriched Glu and 2‐oxoglutarate (2OG), clearly demonstrating poor metabolism of citrate by the TCAP. There was a clear relationship between the ribulose‐1,5‐bisphosphate oxygenation‐to‐carboxylation ratio (v_o/v_c) and the ¹³C commitment to 2OG, demonstrating that 2OG and Glu synthesis via the TCAP is positively influenced by photorespiration.     

Characterization of seven polymorphic microsatellites for the study of two Ranunculaceae: Ranunculus nodiflorus L., a rare endangered species and Ranunculus flammula L., a common closely related species

Ranunculus nodiflorus and Ranunculus flammula are two closely related Ranunculaceae. In France, the first one is rare and endangered, whereas the second is common. To compare their population genetic structure, seven polymorphic microsatellite markers were characterized. We found no polymorphism in R. nodiflorus, whereas R. flammula was polymorphic at each locus. The total number of alleles per locus varied from three to eight. Observed heterozygosities ranged from 0 to 0.261. This set of microsatellites offers an efficient tool to study population genetic structure and to compare the results between closely related endangered and common species.     

In vivo activity of nifurzide and nifuroxazide in intestinal bacteria in man and gnotobiotic mice

Although Gram-negative enteropathogenic bacteria are the target strains of nifurzide and nifuroxazide treatments, neither drug affected faecal counts of in vitro -susceptible Enterobacteriaceae in healthy volunteers. This absence of activity was shown to be due to the poor solubility of the drugs tested. Therefore, effect of high doses of nifurzide was investigated in gnotobiotic mice. Activity against in vitro susceptible enteropathogens was then observed. Normal bacterial cells were replaced in the faeces by elongated, nonseptate and unflagellated mutants. Moreover, the resistance to colonization by enterotoxigenic Escherichia coli and Shigella flexeri of an anaerobic flora of human origin was sharply decreased.