Mitochondrial phylogeography and population history of pine martens Martes martes compared with polecats Mustela putorius

The flora and fauna of Europe are linked by a common biogeographic history, most recently the Pleistocene glaciations that restricted the range of most species to southern refugial populations. Changes in population size and migration, as well as selection, have all left a signature on the genetic differentiation. Thus, three paradigms of postglacial recolonization have been described, inferred from the patterns of DNA differentiation. Yet some species, especially wide-ranging carnivores, exhibit little population structuring between the proposed refugia, although relatively few have been studied due to the difficulty of obtaining samples. Therefore, we investigated mitochondrial variation in pine martens, Martes martes, in order to understand the extent to which they were affected by glacial cycles, and compared the results with an analysis of sequences from polecats, Mustela putorius. A general lack of ancient lineages, and a mismatch distribution that is consistent with an expanding population, is evidence that the present-day M. martes and Mu. putorius in central and northern Europe colonized from a single European refugium following a recent glaciation. There has also been interspecific mitochondrial introgression between M. martes and the sable M. zibellina in Fennoscandia.     

Morphologically cryptic biological species within the liverwort Frullania asagrayana

? Premise of the study: The Frullania tamarisci complex includes eight Holarctic liverwort species. One of these, F. asagrayana, is distributed broadly throughout eastern North America from Canada to the Gulf Coast. Preliminary genetic data suggested that the species includes two groups of populations. This study was designed to test whether the two groups are reproductively isolated biological species. ? Methods: Eighty-eight samples from across the range of F. asagrayana, plus 73 samples from one population, were genotyped for 13 microsatellite loci. Sequences for two plastid loci and nrITS were obtained from 13 accessions. Genetic data were analyzed using coalescent models and Bayesian inference. ? Key results: Frullania asagrayana is sequence-invariant at the two plastid loci and ITS2, but two clear groups were resolved by microsatellites. The two groups are largely reproductively isolated, but there is a low level of gene flow from the southern to the northern group. No gene flow was detected in the other direction. A local population was heterogeneous but displayed strong genetic structure. ? Conclusions: The genetic structure of F. asagrayana in eastern North America reflects morphologically cryptic differentiation between reproductively isolated groups of populations, near-panmixis within groups, and clonal propagation at local scales. Reproductive isolation between groups that are invariant at the level of nucleotide sequences shows that caution must be exercised in making taxonomic and evolutionary inferences from reciprocal monophyly (or lack thereof) between putative species.     

Properties of cyclic nucleotide phosphodiesterase in the central nervous system of Manduca sexta.

The properties of cyclic nucleotide phosphodiesterase were studied in soluble and particulate fractions from the central nervous system of Manduca sexta (Lepidoptera: Sphingidae). It was determined that: (1) The highest levels of phosphodiesterase occur in nervous tissue. (2) The total and specific enzyme activities of larval and adult brains are greater than those of the remaining ganglia. (3) Specific central nervous sy stem phosphodiesterase activities of the adult are lower than those of the larva, but both protein and total phosphodiesterase contents are considerably greater in the adult central nervous system. (4) Mg2+ is not absolutely required for either cyclic AMP-phosphodiesterase or cyclic GMP-phosphodiesterase activity. (5) Phosphodiesterase is inhibited by a variety of physiological and non-physiological compounds, nucleoside triphosphates being particularly effective; Some potent inhibitors of mammalian phosphodiesterase are comparatively ineffective toward Manduca sexta phosphodiesterase. (6) Kinetic analyses of soluble and particulate phosphodiesterase revealed non-linear double-reciprocal plots for the hydrolysis of both cyclic AMP and cyclic GMP, with Michaelis constants of approximately 10 mu M and 20 mu M; (7) The hydrolysis of both cyclic nucleotides appears in part to be the function of a single enzyme or related enzymes in the insect central nervous system. It follows that the intracellular level of one cyclic nucleotide may influence the concentration of the other by inhibiting its DEGRADATION.     

Parameter estimation for discretely observed linear birth‐and‐death processes

Birth‐and‐death processes are widely used to model the development of biological populations. Although they are relatively simple models, their parameters can be challenging to estimate, as the likelihood can become numerically unstable when data arise from the most common sampling schemes, such as annual population censuses. A further difficulty arises when the discrete observations are not equi‐spaced, for example, when census data are unavailable for some years. We present two approaches to estimating the birth, death, and growth rates of a discretely observed linear birth‐and‐death process: via an embedded Galton‐Watson process and by maximizing a saddlepoint approximation to the likelihood. We study asymptotic properties of the estimators, compare them on numerical examples, and apply the methodology to data on monitored populations.     

Self-monitoring of blood glucose in diabetic pregnancy.

Admission to hospital is usually recommended to achieve the best possible diabetic control during pregnancy. We have used blood glucose monitoring at home to find out if patients can achieve equally good control outside hospital. Twenty-five consecutive diabetic patients were studied, of whom 20 had taken insulin before pregnancy. Six of their 14 previous pregnancies had ended in perinatal death. The 25 women performed 4247 blood glucose measurements during their pregnancies. Overall the mean blood glucose concentration was 7.1 mmol/l (128 mg/100 ml); before meals the mean was 6.5 mmol/l (117 mg/100 ml). Mean concentrations were lower in the third trimester, but at no stage was control in hospital significantly better than at home. The mean hospital stay before delivery was 22 days, and all patients had live babies. Monitoring blood glucose concentrations at home produces greater understanding and motivation among patients, improves control early in pregnancy, and shortens time spent in hospital.     

DNA barcoding of stylommatophoran land snails: a test of existing sequences

DNA barcoding has attracted attention because it is a potentially simple and universal method for taxonomic assignment. One anticipated problem in applying the method to stylommatophoran land snails is that they frequently exhibit extreme divergence of mitochondrial DNA sequences, sometimes reaching 30% within species. We therefore trialled the utility of barcodes in identifying land snails, by analysing the stylommatophoran cytochrome oxidase subunit I sequences from GenBank. Two alignments of 381 and 228 base pairs were used to determine potential error rates among a test data set of 97 or 127 species, respectively. Identification success rates using neighbour‐joining phylogenies were 92% for the longer sequence and 82% for the shorter sequence, indicating that a high degree of mitochondrial variation may actually be an advantage when using phylogeny‐based methods for barcoding. There was, however, a large overlap between intra‐ and interspecific variation, with assignment failure (per cent of samples not placed with correct species) particularly associated with a low degree of mitochondrial variation (Kimura 2‐parameter distance < 0.05) and a small GenBank sample size (< 25 per species). Thus, while the optimum intra/interspecific threshold value was 4%, this was associated with an overall error of 32% for the longer sequences and 44% for the shorter sequences. The high error rate necessitates that barcoding of land snails is a potentially useful method to discriminate species of land snail, but only when a baseline has first been established using conventional taxonomy and sample DNA sequences. There is no evidence for a barcoding gap, ruling out species discovery based on a threshold value alone.     

Multiple actions of superoxide dismutase: why can it both inhibit and stimulate reduction of oxygen by hydroquinones?

Superoxide dismutase can either inhibit or stimulate autoxidation of different hydroquinones, suggesting multiple roles for O2.-. Inhibitory actions of superoxide dismutase include termination of O2.(-)-propagated reaction chains and metal chelation by the apoprotein. Together, chelation of metals and termination of O2.(-)-propagated chains can effectively prevent reduction of oxygen. Chain termination by superoxide dismutase can thus account for negligible accumulation of H2O2 without invoking a superoxide:semiquinone oxidoreductase activity for this enzyme. One stimulatory action of superoxide dismutase is to decrease thermodynamic limitations to reduction of oxygen. Whether superoxide dismutase inhibits or accelerates an autoxidation depends on the reduction potentials of the quinone and the availability of metal coordination for inner sphere electron transfers.     

Plasmodium yoelii: Adverse outcome of non-lethal P. yoelii malaria during co-infection with Schistosoma mansoni in BALB/c mouse model

Plasmodium yoelii and Schistosoma mansoni co-infections were studied in female BALB/c mice aged 4-6 weeks to determine the effect of time and stage of concomitant infections on malaria disease outcome. Patent S. mansoni infection in BALB/c mice increased malaria peak parasitemia and caused death from an otherwise non-lethal, self-resolving P. yoelii malaria infection. Exacerbation of malaria parasitemia occurred during both pre-patent and patent S. mansoni infection resulting in a delay of 4-8 days in malaria parasite resolution in co-infected mice. Praziquantel administered to mice with patent schistosome infection protected from fatal outcome during co-infection. However, this treatment did not completely clear the worm infestation, nor did it reduce the peak malaria parasitemia reached, which was nonetheless resolved completely. Hepatosplenomegaly was more marked in schistosome and malaria co-infected mice compared to either infection separately. The results suggest a complex relationship between schistosome co-infection and malaria disease outcome in which the timing of malaria infection in relation to schistosome acquisition is critical to disease outcome and pathology.     

Single‐cell genomics based on Raman sorting reveals novel carotenoid‐containing bacteria in the Red Sea

Cell sorting coupled with single‐cell genomics is a powerful tool to circumvent cultivation of microorganisms and reveal microbial ‘dark matter’. Single‐cell Raman spectra (SCRSs) are label‐free biochemical ‘fingerprints’ of individual cells, which can link the sorted cells to their phenotypic information and ecological functions. We employed a novel Raman‐activated cell ejection (RACE) approach to sort single bacterial cells from a water sample in the Red Sea based on SCRS. Carotenoids are highly diverse pigments and play an important role in phototrophic bacteria, giving strong and distinctive Raman spectra. Here, we showed that individual carotenoid‐containing cells from a Red Sea sample were isolated based on the characteristic SCRS. RACE‐based single‐cell genomics revealed putative novel functional genes related to carotenoid and isoprenoid biosynthesis, as well as previously unknown phototrophic microorganisms including an unculturable Cyanobacteria spp. The potential of Raman sorting coupled to single‐cell genomics has been demonstrated.     

Widely distributed native and alien plant species differ in arbuscular mycorrhizal associations and related functional trait interactions

It is debated whether alien plants in new environments benefit from being mycorrhizal and whether widely distributed natives and aliens differ in their associations with mycorrhizal fungi. Here, we compared whether species differing in their origin status, i.e. natives, archaeophytes (alien species introduced before the year 1500) and neophytes (introduced after the year 1500), and arbuscular mycorrhizal (AM) status (obligate, facultative, non‐mycorrhizal) differ in their area of occupancy in Germany (i.e. number of occupied grid cells, each ~130 km²). We used generalized linear models, incorporating main effects and up to three‐way interactions combining AM status, origin status and plant functional traits. The latter were chosen to describe the possible trade‐off in carbon allocation either towards the symbiosis or to other plant structures, such as storage organs (significant interactions involving traits were assumed to indicate the existence of such trade‐offs). AM status significantly explained the area of occupancy of natives and neophytes – with facultative mycorrhizal species occupying the largest area in both groups – but was less pronounced among archaeophytes. Archaeophytes may have reduced dependency on AM fungi, as they are generally agricultural weeds and the symbiosis potentially becomes obsolete for plants growing in habitats providing a steady provision of nutrients. Trait interactions between AM status and other functional traits were almost exclusively detected for neophytes. While facultative mycorrhizal neophytes benefit from trade‐offs with other traits related to high C cost in terms of area of occupancy, such trade‐offs were almost absent among natives. This indicates that natives and neophytes benefit differently from the symbiosis and suggests that native AM fungal partners might be less important for neophytic than for native plant species or that more time is required to establish similar relationships between neophytes and native fungal symbionts.