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排序方式: 共有91条查询结果,搜索用时 15 毫秒
31.
Nkabeng T. Maruping‐Mzileni Sam Ferreira Kim Young Paul J. Funston 《Ecology and evolution》2020,10(15):7995-8006
The role of social cues in the reproduction of social mammals, particularly carnivores, has been thoroughly studied and documented in literature. However, environmental cues such as resources of water, food, and shelter have been identified to a lesser extent. Pregnant lions (Panthera leo) are notoriously secretive during the final stages of pregnancy and postpartum. Behavioral indicators depicted by movement patterns obtained by remote detection of collared female lions in the Kruger National Park were necessary for the monitoring of birth timing. Over the study period, eight plus a potential three parturition incidences of collared females were recorded. Of the variables measured (step length, range size, duration, prey biomass, and rainfall), range size during the month of parturition was the most indicative movement pattern of a successful birth. By backdating the potential birth month of the litters, date of conception was calculated and our results revealed a correlation between the birthing peaks of preferred prey during the month of conception. Birth timing in conjunction with remote sensing and ecological factors were thus identified behaviors associated with denning. 相似文献
32.
PJ Waller B-L Ljungström O Schwan L Rudby Martin DA Morrison A Rydzik 《Acta veterinaria Scandinavica》2006,47(1):23-10
Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned. 相似文献
33.
Background
Amino acid repeat-containing proteins have a broad range of functions and their identification is of relevance to many experimental biologists. In human-infective protozoan parasites (such as the Kinetoplastid and Plasmodium species), they are implicated in immune evasion and have been shown to influence virulence and pathogenicity. RepSeq is a new database of amino acid repeat-containing proteins found in lower eukaryotic pathogens. The RepSeq database is accessed via a web-based application which also provides links to related online tools and databases for further analyses. 相似文献34.
Cecilia Wieder Clment Frainay Nathalie Poupin Pablo Rodríguez-Mier Florence Vinson Juliette Cooke Rachel PJ Lai Jacob G. Bundy Fabien Jourdan Timothy Ebbels 《PLoS computational biology》2021,17(9)
Over-representation analysis (ORA) is one of the commonest pathway analysis approaches used for the functional interpretation of metabolomics datasets. Despite the widespread use of ORA in metabolomics, the community lacks guidelines detailing its best-practice use. Many factors have a pronounced impact on the results, but to date their effects have received little systematic attention. Using five publicly available datasets, we demonstrated that changes in parameters such as the background set, differential metabolite selection methods, and pathway database used can result in profoundly different ORA results. The use of a non-assay-specific background set, for example, resulted in large numbers of false-positive pathways. Pathway database choice, evaluated using three of the most popular metabolic pathway databases (KEGG, Reactome, and BioCyc), led to vastly different results in both the number and function of significantly enriched pathways. Factors that are specific to metabolomics data, such as the reliability of compound identification and the chemical bias of different analytical platforms also impacted ORA results. Simulated metabolite misidentification rates as low as 4% resulted in both gain of false-positive pathways and loss of truly significant pathways across all datasets. Our results have several practical implications for ORA users, as well as those using alternative pathway analysis methods. We offer a set of recommendations for the use of ORA in metabolomics, alongside a set of minimal reporting guidelines, as a first step towards the standardisation of pathway analysis in metabolomics. 相似文献
35.
Susan M. Miller Cindy K. Harper Paulette Bloomer Jennifer Hofmeyr Paul J. Funston 《PloS one》2015,10(12)
Population fragmentation is threatening biodiversity worldwide. Species that once roamed vast areas are increasingly being conserved in small, isolated areas. Modern management approaches must adapt to ensure the continued survival and conservation value of these populations. In South Africa, a managed metapopulation approach has been adopted for several large carnivore species, all protected in isolated, relatively small, reserves that are fenced. As far as possible these approaches are based on natural metapopulation structures. In this network, over the past 25 years, African lions (Panthera leo) were reintroduced into 44 fenced reserves with little attention given to maintaining genetic diversity. To examine the situation, we investigated the current genetic provenance and diversity of these lions. We found that overall genetic diversity was similar to that in a large national park, and included a mixture of four different southern African evolutionarily significant units (ESUs). This mixing of ESUs, while not ideal, provides a unique opportunity to study the impact of mixing ESUs over the long term. We propose a strategic managed metapopulation plan to ensure the maintenance of genetic diversity and improve the long-term conservation value of these lions. This managed metapopulation approach could be applied to other species under similar ecological constraints around the globe. 相似文献
36.
Barbora de Courten Michaela Jakubova Maximilian PJ de Courten Ivica Just Kukurova Silvia Vallova Patrik Krumpolec Ladislav Valkovic Timea Kurdiova Davide Garzon Silvia Barbaresi Helena J. Teede Wim Derave Martin Krssak Giancarlo Aldini Jozef Ukropec Barbara Ukropcova 《Obesity (Silver Spring, Md.)》2016,24(5):1027-1034
37.
C. Packer A. Loveridge S. Canney T. Caro S.T. Garnett M. Pfeifer K.K. Zander A. Swanson D. MacNulty G. Balme H. Bauer C.M. Begg K.S. Begg S. Bhalla C. Bissett T. Bodasing H. Brink A. Burger A.C. Burton B. Clegg S. Dell A. Delsink T. Dickerson S.M. Dloniak D. Druce L. Frank P. Funston N. Gichohi R. Groom C. Hanekom B. Heath L. Hunter H.H. DeIongh C.J. Joubert S.M. Kasiki B. Kissui W. Knocker B. Leathem P.A. Lindsey S.D. Maclennan J.W. McNutt S.M. Miller S. Naylor P. Nel C. Ng'weno K. Nicholls J.O. Ogutu E. Okot‐Omoya B.D. Patterson A. Plumptre J. Salerno K. Skinner R. Slotow E.A. Sogbohossou K.J. Stratford C. Winterbach H. Winterbach S. Polasky 《Ecology letters》2013,16(5):635-641
Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km−2, unfenced populations require budgets in excess of $2000 km−2 to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density‐independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years. 相似文献
38.
Improved analyses of human mtDNA sequences support a recent African origin for Homo sapiens 总被引:3,自引:1,他引:2
New quantitative methods are applied to the 135 human mitochondrial
sequences from the Vigilant et al. data set. General problems in analyzing
large numbers of short sequences are discussed, and an improved strategy is
suggested. A key feature is to focus not on individual trees but on the
general "landscape" of trees. Over 1,000 searches were made from random
starting trees with only one tree (a local optimum) being retained each
time, thereby ensuring optima were found independently. A new tree
comparison metric was developed that is unaffected by rearrangements of
trees around many very short internal edges. Use of this metric showed that
downweighting hypervariable sites revealed more evolutionary structure than
studies that weighted all sites equally. Our results are consistent with
convergence toward a global optimum. Crucial features are that the best
optima show very strong regional differentiation, a common group of 49
African sequences is found in all the best optima, and the best optima
contain the 16 !Kung sequences in a separate group of San people. The other
86 sequences form a heterogeneous mixture of Africans, Europeans,
Australopapuans, and Asians. Thus all major human lineages occur in Africa,
but only a subset occurs in the rest of the world. The existence of these
African-only groups strongly contradicts multiregional theories for the
origin of Homo sapiens that require widespread migration and interbreeding
over the entire range of H. erectus. Only when the multiregional model is
rejected is it appropriate to consider the root, based on a single locus,
to be the center of origin of a population (otherwise different loci could
give alternative geographic positions for the root). For this data, several
methods locate the root within the group of 49 African sequences and are
thus consistent with the recent African origin of H. sapiens. We
demonstrate that the time of the last common ancestor cannot be the time of
major expansion in human numbers, and our results are thus also consistent
with recent models that differentiate between the last common ancestor,
expansion out of Africa, and the major expansion in human populations. Such
a two-phase model is consistent with a wide range of molecular and
archeological evidence.
相似文献
39.
A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages 总被引:17,自引:13,他引:4
Lockhart PJ; Steel MA; Barbrook AC; Huson DH; Charleston MA; Howe CJ 《Molecular biology and evolution》1998,15(9):1183-1188
The aims of the work were (1) to develop statistical tests to identify
whether substitution takes place under a covariotide model in sequences
used for phylogenetic inference and (2) to determine the influence of
covariotide substitution on phylogenetic trees inferred for photosynthetic
and other organisms. (Covariotide and covarion models are ones in which
sites that are variable in some parts of the underlying tree are invariable
in others and vice versa.) Two tests were developed. The first was a
contingency test, and the second was an inequality test comparing the
expected number of variable sites in two groups with the observed number.
Application of these tests to 16S rDNA and tufA sequences from a range of
nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and
eukaryotes suggests the occurrence of a covariotide mechanism. The degree
of support for partitioning of taxa in reconstructed trees involving these
organisms was determined in the presence or absence of sites showing
particular substitution patterns. This analysis showed that the support for
splits between (1) photosynthetic eukaryotes and prokaryotes and (2)
photosynthetic and nonphotosynthetic organisms could be accounted for by
patterns arising from covariotide substitution. We show that the additional
problem of compositional bias in sequence data needs to be considered in
the context of patterns of covariotide/covarion substitution. We argue that
while covariotide or covarion substitution may give rise to
phylogenetically informative patterns in sequence data, this may not always
be so.
相似文献
40.