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41.
Escalation of a coevolutionary arms race through host rejection of brood parasitic young 总被引:6,自引:0,他引:6
Cuckoo nestlings that evict all other young from the nest soon after hatching impose a high reproductive cost on their hosts. In defence, hosts have coevolved strategies to prevent brood parasitism. Puzzlingly, they do not extend beyond the egg stage. Thus, hosts adept at recognizing foreign eggs remain vulnerable to exploitation by cuckoo nestlings. Here we show that the breach of host egg defences by cuckoos creates a new stage in the coevolutionary cycle. We found that defences used during the egg-laying period by host superb fairy-wrens (Malurus cyaneus) are easily evaded by the Horsfield's bronze-cuckoo (Chrysococcyx basalis), a specialist fairy-wren brood parasite. However, although hosts never deserted their own broods, they later abandoned 40% of nests containing a lone Horsfield's bronze-cuckoo nestling, and 100% of nests with a lone shining bronze-cuckoo nestling (Chrysococcyx lucidus), an occasional fairy-wren brood parasite. Our experiments demonstrate that host discrimination against evictor-cuckoo nestlings is possible, and suggest that it has selected for the evolution of nestling mimicry in bronze-cuckoos. 相似文献
42.
The Carnivora are one of only four orders of terrestrial mammals living in Madagascar today. All four (carnivorans, primates, rodents and lipotyphlan insectivores) are placental mammals with limited means for dispersal, yet they occur on a large island that has been surrounded by a formidable oceanic barrier for at least 88 million years, predating the age of origin for any of these groups. Even so, as many as four colonizations of Madagascar have been proposed for the Carnivora alone. The mystery of the island's mammalian origins is confounded by its poor Tertiary fossil record, which leaves us with no direct means for estimating dates of initial diversification. Here we use a multi-gene phylogenetic analysis to show that Malagasy carnivorans are monophyletic and thus the product of a single colonization of Madagascar by an African ancestor. Furthermore, a bayesian analysis of divergence ages for Malagasy carnivorans and lemuriforms indicates that their respective colonizations were temporally separated by tens of millions of years. We therefore conclude that a single event, such as vicariance or common dispersal, cannot explain the presence of both groups in Madagascar. 相似文献
43.
During the evolution of cooperation it may have become critical for individuals to compare their own efforts and pay-offs with those of others. Negative reactions may occur when expectations are violated. One theory proposes that aversion to inequity can explain human cooperation within the bounds of the rational choice model, and may in fact be more inclusive than previous explanations. Although there exists substantial cultural variation in its particulars, this 'sense of fairness' is probably a human universal that has been shown to prevail in a wide variety of circumstances. However, we are not the only cooperative animals, hence inequity aversion may not be uniquely human. Many highly cooperative nonhuman species seem guided by a set of expectations about the outcome of cooperation and the division of resources. Here we demonstrate that a nonhuman primate, the brown capuchin monkey (Cebus apella), responds negatively to unequal reward distribution in exchanges with a human experimenter. Monkeys refused to participate if they witnessed a conspecific obtain a more attractive reward for equal effort, an effect amplified if the partner received such a reward without any effort at all. These reactions support an early evolutionary origin of inequity aversion. 相似文献
44.
45.
The genome sequence of the filamentous fungus Neurospora crassa 总被引:1,自引:0,他引:1
Galagan JE Calvo SE Borkovich KA Selker EU Read ND Jaffe D FitzHugh W Ma LJ Smirnov S Purcell S Rehman B Elkins T Engels R Wang S Nielsen CB Butler J Endrizzi M Qui D Ianakiev P Bell-Pedersen D Nelson MA Werner-Washburne M Selitrennikoff CP Kinsey JA Braun EL Zelter A Schulte U Kothe GO Jedd G Mewes W Staben C Marcotte E Greenberg D Roy A Foley K Naylor J Stange-Thomann N Barrett R Gnerre S Kamal M Kamvysselis M Mauceli E Bielke C Rudd S Frishman D Krystofova S Rasmussen C Metzenberg RL 《Nature》2003,422(6934):859-868
Neurospora crassa is a central organism in the history of twentieth-century genetics, biochemistry and molecular biology. Here, we report a high-quality draft sequence of the N. crassa genome. The approximately 40-megabase genome encodes about 10,000 protein-coding genes--more than twice as many as in the fission yeast Schizosaccharomyces pombe and only about 25% fewer than in the fruitfly Drosophila melanogaster. Analysis of the gene set yields insights into unexpected aspects of Neurospora biology including the identification of genes potentially associated with red light photobiology, genes implicated in secondary metabolism, and important differences in Ca2+ signalling as compared with plants and animals. Neurospora possesses the widest array of genome defence mechanisms known for any eukaryotic organism, including a process unique to fungi called repeat-induced point mutation (RIP). Genome analysis suggests that RIP has had a profound impact on genome evolution, greatly slowing the creation of new genes through genomic duplication and resulting in a genome with an unusually low proportion of closely related genes. 相似文献
46.
Kalscheuer VM Freude K Musante L Jensen LR Yntema HG Gécz J Sefiani A Hoffmann K Moser B Haas S Gurok U Haesler S Aranda B Nshedjan A Tzschach A Hartmann N Roloff TC Shoichet S Hagens O Tao J Van Bokhoven H Turner G Chelly J Moraine C Fryns JP Nuber U Hoeltzenbein M Scharff C Scherthan H Lenzner S Hamel BC Schweiger S Ropers HH 《Nature genetics》2003,35(4):313-315
We found mutations in the gene PQBP1 in 5 of 29 families with nonsyndromic (MRX) and syndromic (MRXS) forms of X-linked mental retardation (XLMR). Clinical features in affected males include mental retardation, microcephaly, short stature, spastic paraplegia and midline defects. PQBP1 has previously been implicated in the pathogenesis of polyglutamine expansion diseases. Our findings link this gene to XLMR and shed more light on the pathogenesis of this common disorder. 相似文献
47.
Haslett Tim Molineux John Olsen Jane Sarah Rod Stephens John Tepe Susanne Walker Beverly 《Systemic Practice and Action Research》2002,15(6):437-448
The Action Research (AR) PhD program at Monash University had its genesis in Systems Thinking and Organizational Learning. This paper discusses the role of the university in AR projects in business and the central role that AR projects can have in a Faculty's strategic positioning. The issues that have emerged in the project to date are discussed. 相似文献
48.
Sarah Deutsch 《Cellular and molecular life sciences : CMLS》1957,13(8):309-311
Summary By a quantitative study of pleochroic haloes in biotite, the haloe age of the Lausitz granodiorite, in comparison with the
granite age of the Elba Isle, was estimated to 280±150 M.Y. The granodiorite is either caledonian or hercynian.
Attachée à l'Institut Interuniversitaire des Sciences Nucléaires. 相似文献
Attachée à l'Institut Interuniversitaire des Sciences Nucléaires. 相似文献
49.
Clayton DG Walker NM Smyth DJ Pask R Cooper JD Maier LM Smink LJ Lam AC Ovington NR Stevens HE Nutland S Howson JM Faham M Moorhead M Jones HB Falkowski M Hardenbol P Willis TD Todd JA 《Nature genetics》2005,37(11):1243-1246
The main problems in drawing causal inferences from epidemiological case-control studies are confounding by unmeasured extraneous factors, selection bias and differential misclassification of exposure. In genetics the first of these, in the form of population structure, has dominated recent debate. Population structure explained part of the significant +11.2% inflation of test statistics we observed in an analysis of 6,322 nonsynonymous SNPs in 816 cases of type 1 diabetes and 877 population-based controls from Great Britain. The remainder of the inflation resulted from differential bias in genotype scoring between case and control DNA samples, which originated from two laboratories, causing false-positive associations. To avoid excluding SNPs and losing valuable information, we extended the genomic control method by applying a variable downweighting to each SNP. 相似文献
50.
Batourina E Tsai S Lambert S Sprenkle P Viana R Dutta S Hensle T Wang F Niederreither K McMahon AP Carroll TJ Mendelsohn CL 《Nature genetics》2005,37(10):1082-1089
Removal of toxic substances from the blood depends on patent connections between the kidney, ureters and bladder that are established when the ureter is transposed from its original insertion site in the male genital tract to the bladder. This transposition is thought to occur as the trigone forms from the common nephric duct and incorporates into the bladder. Here we re-examine this model in the context of normal and abnormal development. We show that the common nephric duct does not differentiate into the trigone but instead undergoes apoptosis, a crucial step for ureter transposition controlled by vitamin A-induced signals from the primitive bladder. Ureter abnormalities occur in 1-2% of the human population and can cause obstruction and end-stage renal disease. These studies provide an explanation for ureter defects underlying some forms of obstruction in humans and redefine the current model of ureter maturation. 相似文献