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71.
When populations are separated for long periods and then brought into contact for a brief episode in part of their range, this can result in genetic admixture. To analyze this type of event we considered a simple model under which two parental populations (P1 and P2) mix and create a hybrid population (H). After that event, the three populations evolve under pure drift without exchange during T generations. We developed a new method, which allows the simultaneous estimation of the time since the admixture event (scaled by the population size t(i) = T/N(i), where N(i) is the effective population size of population i) and the contribution of one of two parental populations (which we call p1). This method takes into account drift since the admixture event, variation caused by sampling, and uncertainty in the estimation of the ancestral allele frequencies. The method is tested on simulated data sets and then applied to a human data set. We find that (i) for single-locus data, point estimates are poor indicators of the real admixture proportions even when there are many alleles; (ii) biallelic loci provide little information about the admixture proportion and the time since admixture, even for very small amounts of drift, but can be powerful when many loci are used; (iii) the precision of the parameters' estimates increases with sample size n = 50 vs. n = 200 but this effect is larger for the t(i)'s than for p1; and (iv) the increase in precision provided by multiple loci is quite large, even when there is substantial drift (we found, for instance, that it is preferable to use five loci than one locus, even when drift is 100 times larger for the five loci). Our analysis of a previously studied human data set illustrates that the joint estimation of drift and p1 can provide additional insights into the data. 相似文献
72.
Improved nitrogen removal by application of new nitrogen-cycle bacteria 总被引:14,自引:0,他引:14
Jetten Mike S.M. Schmid Markus Schmidt Ingo Wubben Mariska van Dongen Udo Abma Wiebe Sliekers Olav Revsbech Niels Peter Beaumont Hubertus J.E. Ottosen Lars Volcke Eveline Laanbroek H.J. Campos-Gomez Jose Luis Cole Jeff van Loosdrecht Mark Mulder Jan Willem Fuerst John Richardson David van de Pas Katinka Mendez-Pampin Ramon Third Katie Cirpus Irina van Spanning Rob Bollmann Annette Nielsen Lars Peter den Camp Huub Op Schultz Carl Gundersen Jens Vanrolleghem Peter Strous Marc Wagner Michael Kuenen J. Gijs 《Reviews in Environmental Science and Biotechnology》2002,1(1):51-63
In order to meet increasingly stringentEuropean discharge standards, new applicationsand control strategies for the sustainableremoval of ammonia from wastewater have to beimplemented. In this paper we discuss anitrogen removal system based on the processesof partial nitrification and anoxic ammoniaoxidation (anammox). The anammox process offersgreat opportunities to remove ammonia in fullyautotrophic systems with biomass retention. Noorganic carbon is needed in such nitrogenremoval system, since ammonia is used aselectron donor for nitrite reduction. Thenitrite can be produced from ammonia inoxygen-limited biofilm systems or in continuousprocesses without biomass retention. Forsuccessful implementation of the combinedprocesses, accurate biosensors for measuringammonia and nitrite concentrations, insight inthe complex microbial communities involved, andnew control strategies have to be developed andevaluated. 相似文献
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Joseph Diaz Remy Guegan Michel Beaumont Jean Benoit Jacques Clement Christian Fauchard Daniel Galtier Joseph Millan Claude Muneaux Yvette Muneaux Michel Vedel Robert Schwyzer 《Bioorganic chemistry》1979,8(4):429-442
A large-scale synthesis of somatostatin was developed. A stepwise C→N approach in solution was used, employing N(α)-t-butoxycarbonyl amino acid active esters. The scheme of semipermanent protection utilized 2-(methylsulfonyl)-ethoxycarbonyl for the -amino group of lysine; acetamidomethyl for the β-thiol groups of cysteine; the orange-colored 2-[4-(phenylazo)-phenylsulfonyl]-ethoxy group for the C-terminal carboxy group of cysteine. All condensations and N(α)-deprotections were carried out in homogeneous solution, while isolation and purification of peptides carrying the colored group was achieved by precipitation and washing of the solid products. Thus, the “alternating solution/solid-phase peptide synthesis” combines advantages of both the classical solution synthesis and the Merrifield solid-phase technique. The overall yield was 5%, or 16 g of somatostatin from 100 g of the novel amino acid derivative, N(α)-t-butoxycarbonyl-S-acetamidomethyl-
-cysteine 2-[4-(phenylazo)-phenylsulfonyl]-ethyl ester. An improved method for the preparation of S-acetamidomethyl-
-cysteine, free of thiazolidine carboxylic acid, is described. 相似文献
77.
T. M. Burland E. M. Barratt M. A. Beaumont P. A. Racey 《Proceedings. Biological sciences / The Royal Society》1999,266(1422):975
During summer the brown long-eared bat Plecotus auritus (Vespertilionidae) forms stable colonies, comprised of both adult females and males and young of the year. A long-term ringing study conducted in north-east Scotland has established that little movement occurs among colonies and that both sexes are recruited into their natal colony. The aim of the present study was to investigate, using microsatellite DNA markers, if genetic structure within the population reflects the spatial structure indicated by ringing. Inter-colony FST estimates obtained for all colony members, and for females and males separately, were low (0.019, 0.026 and 0.011, respectively), but all values differed significantly from zero. These data indicate high gene flow between colonies, although some coancestry among colony members is evident in both sexes. On combining the ringing and genetic data, it is concluded that gene flow occurs via extra-colony copulation, rather than natal dispersal, and that each colony behaves as a distinct subpopulation. Microgeographical genetic isolation by distance was demonstrated for, to our knowledge, the first time in a bat species, and found to be apparent both across the entire study area and along one river valley. The results suggest that extensive macrogeographical population genetic structure may be evident across the species'' range. 相似文献
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A journey through time: exploring temporal patterns amongst digitized plant specimens from Australia
MD. Mohasinul Haque David A. Nipperess John B. Baumgartner Linda J. Beaumont 《分类学与生物多样性》2018,16(6):604-613
Online access to species occurrence records has opened new windows into investigating biodiversity patterns across multiple scales. The value of these records for research depends on their spatial, temporal, and taxonomic quality. We assessed temporal patterns in records from the Australasian Virtual Herbarium, asking: (1) How temporally consistent has collecting been across Australia? (2) Which areas of Australia have the most reliable records, in terms of temporal consistency and inventory completeness? (3) Are there temporal trends in the completeness of attribute information associated with records? We undertook a multi-step filtering procedure, then estimated temporal consistency and inventory completeness for sampling units (SUs) of 50?km ×?50?km. We found temporal bias in collecting, with 80% of records collected over the period 1970–1999. South-eastern Australia, the Wet Tropics in north-east Queensland, and parts of Western Australia have received the most consistent sampling effort over time, whereas much of central Australia has had low temporal consistency. Of the SUs, 18% have relatively complete inventories with high temporal consistency in sampling. We also determined that 25% of digitized records had missing attribute information. By identifying areas with low reliability, we can limit erroneous inferences about distribution patterns and identify priority areas for future sampling. 相似文献
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