共查询到20条相似文献,搜索用时 15 毫秒
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Meyer CG Amedofu GK Brandner JM Pohland D Timmann C Horstmann RD 《Nature medicine》2002,8(12):1332-1333
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Saito Y 《Experimental & applied acarology》2000,24(5-6):351-363
Between the two subsocial spider mites, Schizotetranychus longus Saito and S. miscanthi Saito, a big difference exists in male reproductive behavior. The males of the former species have an extraordinarily mild relationship with conspecific males, whereas those of the latter species show mortal aggression against conspecific males. Field and experimental observations on the structure of mating populations showed that S. longus is under inbreeding conditions because of a lack of males in early spring, whereas S. miscanthi is under outbreeding conditions. Therefore, I hypothesized that the difference in male antagonism between the two species may reflect the difference in relatedness of males, that is, it has evolved by kin selection. The recent discovery of two clinal trends in male–male aggression in S. miscanthi provided evidence in favour of this hypothesis. Furthermore, a correlation analyses between experimentally evaluated male aggression and distribution patterns of males in the field indicated that the variation in male antagonism is actually reflected in field populations. Based on these studies, I discuss the solidity of the kin-selection hypothesis. Lastly I address how spider mites are fruitful model animals for conducting behavioral, ecological and genetic studies to understand the evolution of haplo-diploidy. 相似文献
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In considerations of sexual floral size dimorphism, there is a conflict between sexual selection theory, which predicts that
larger floral displays attract more pollinators, and optimality theory—particularly the ideal free distribution—which predict
that pollinators' visits should match nutritional rewards. As an alternate explanation of this dimorphism, Müller reported
that pollinators tend to visit larger male flowers before visiting smaller female flowers, thereby promoting effective pollination.
To investigate optimality predictions, I offered pollinators a choice between smaller, less numerous, but more rewarding flowers;
and larger, more numerous, but less rewarding flowers. Foragers initially favored the larger and more numerous flowers, but
rapidly shifted preferences to conform with the predictions of the ideal free distribution. To test Müller's hypothesis, I
offered pollinators choices between larger and smaller corollas of equal caloric reward. Results showed that although pollinators
tended to visit larger corollas first, they did not visit them more often. These experiments highlight the need for further
investigation into the tradeoff between natural and sexual selection, and their respective influences in pollination ecology. 相似文献
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Shozo Yokoyama 《Genetics》1983,103(1):143-148
Extremely high incidences of single and double deletions of α-globin genes are known among Asian populations. To study possible mechanisms for the maintenance of such deletions, mathematical analyses have been conducted. It has been shown that a stable polymorphism can be achieved easily through heterozygote advantage using deterministic models. The results strongly suggest that high incidences of single and double deletion of α-globin genes among Asian populations are maintained by some type of heterozygote advantage. 相似文献
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《Journal of biological education》2012,46(3):221-235
Class Work with Fungi. H. A. DADE and JEAN GUNNELL. Pp. 64. London: Commonwealth Mycological Institute, Kew. 1969. 10s. Review by B. M. Jones The Insects: Structure and Function. R. F. CHAPMAN. Pp. xiii + 819 + 509 figs. London: The English Universities Press Ltd., 1969. £4.25. Review by T. G. Onions An Introduction to the Principles of Plant Physiology. WALTER STILES and E. C. COCKING. Pp. 633. London: Methuen &; Co., Ltd. Third edition, 1969. 168s. Review by B. M. Jones Background Notes to the Study of Human Biology for Nurses. T. ROBERTS. Pp. 80. London: Edward Arnold. Semistiff Back, 10s. (50p.). Review by J. H. Elliott 相似文献
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Four examples of Israeli communities or large families in which high consanguinity is common are presented, with two different lysosomal storage disorders within each community. In each of the four cases the stored substances share common chemical structure, despite the different lysosomal hydrolases involved in each disease. A similar phenomenon is known among the Ashkenazi Jews, in whom four of the most frequent hereditary disorders are lysosomal storage disorders, which are characterized by storage of sphingolipid derivatives. Similar findings are reported in the literature in other communities. We suggest that this phenomenon indicates a selection in favor of lysosomal storage disorders of similar nature in certain populations. The selection forces leading to this phenomenon have not been identified yet, and it has not yet been determined whether these forces are the same in the different communities presented here. 相似文献
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Over the past four decades, the predominant view of molecular evolution saw little connection between natural selection and genome evolution, assuming that the functionally constrained fraction of the genome is relatively small and that adaptation is sufficiently infrequent to play little role in shaping patterns of variation within and even between species. Recent evidence from Drosophila, reviewed here, suggests that this view may be invalid. Analyses of genetic variation within and between species reveal that much of the Drosophila genome is under purifying selection, and thus of functional importance, and that a large fraction of coding and noncoding differences between species are adaptive. The findings further indicate that, in Drosophila, adaptations may be both common and strong enough that the fate of neutral mutations depends on their chance linkage to adaptive mutations as much as on the vagaries of genetic drift. The emerging evidence has implications for a wide variety of fields, from conservation genetics to bioinformatics, and presents challenges to modelers and experimentalists alike. 相似文献
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Habitat selection is an important behavioural process widely studied for its population-level effects. Models of habitat selection are, however, often fit without a mechanistic consideration. Here, we investigated whether patterns in habitat selection result from instinct or learning for a population of grizzly bears (Ursus arctos) in Alberta, Canada. We found that habitat selection and relatedness were positively correlated in female bears during the fall season, with a trend in the spring, but not during any season for males. This suggests that habitat selection is a learned behaviour because males do not participate in parental care: a genetically predetermined behaviour (instinct) would have resulted in habitat selection and relatedness correlations for both sexes. Geographic distance and home range overlap among animals did not alter correlations indicating that dispersal and spatial autocorrelation had little effect on the observed trends. These results suggest that habitat selection in grizzly bears are partly learned from their mothers, which could have implications for the translocation of wildlife to novel environments. 相似文献
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Are Random Drift and Natural Selection Conceptually Distinct? 总被引:3,自引:0,他引:3
Roberta L. Millstein 《Biology & philosophy》2002,17(1):33-53
The latter half of thetwentieth century has been marked by debates inevolutionary biology over the relativesignificance of natural selection and randomdrift: the so-called ``neutralist/selectionist'debates. Yet John Beatty has argued that it isdifficult, if not impossible, to distinguishthe concept of random drift from the concept ofnatural selection, a claim that has beenaccepted by many philosophers of biology. Ifthis claim is correct, then theneutralist/selectionist debates seem at bestfutile, and at worst, meaningless. I reexaminethe issues that Beatty raises, and argue thatrandom drift and natural selection, conceivedas processes, can be distinguished from one another. 相似文献
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Alter SG 《Journal of the history of biology》2007,40(2):231-258
This essay traces the interlinked origins of two concepts found in Charles Darwin’s writings: “unconscious selection,” and
sexual selection as applied to humanity’s anatomical race distinctions. Unconscious selection constituted a significant elaboration
of Darwin’s artificial selection analogy. As originally conceived in his theoretical notebooks, that analogy had focused exclusively
on what Darwin later would call “methodical selection,” the calculated production of desired changes in domestic breeds. By
contrast, unconscious selection produced its results unintentionally and at a much slower pace. Inspiration for this concept
likely came from Darwin’s early reading of works on both animal breeding and physical ethnology. Texts in these fields described
the slow and unplanned divergence of anatomical types, whether animal or human, under the guidance of contrasting ideals of
physical perfection. These readings, it is argued, also led Darwin to his theory of sexual selection as applied to race, a
theme he discussed mainly in his book The Descent of Man (1871). There Darwin described how the racial version of sexual selection operated on the same principle as unconscious selection.
He thereby effectively reunited these kindred concepts. 相似文献
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Experimental populations of Drosophila simulans were established for the purpose of detecting the presence or absence of selection on a restriction fragment length polymorphism in mitochondrial DNA (mtDNA). It was then discovered that the founding strains differed with respect to the Rickettsia-mediated incompatibility system in this species, which is maternally transmitted together with the mtDNA differences. A population model was constructed using the known fitness effects of the incompatibility system, with the result that the population trajectories can be completely explained by the effects of the microorganism with no need to invoke selection on mtDNA. The strong conclusion is that in this case we can rule out the strong selection proposed by MacRae and Anderson to explain the "dramatic mtDNA changes" in their Drosophila pseudoobscura populations. The population theory used for the experiments is discussed in the context of natural populations. Estimated parameters include the possibility that with two populations, one with the organism and one without it, there may be no bias as to which will invade the other, which in turn suggests no global tendency for the infection to spread or decline. 相似文献
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Richard S. Cosby 《The Western journal of medicine》1957,87(1):24-28
In the selection of patients for mitral commissurotomy, five separate categories are to be considered: (1) true mitral block with small heart and high pulmonary artery pressure, (2) mitral stenosis without mitral block, (3) mitral stenosis with subacute carditis, (4) mitral stenosis with marked cardiac hypertrophy, and (5) mitral stenosis with embolism.Surgical results are good to excellent provided adequate preoperative evaluation has eliminated the groups with subacute carditis, and those without mitral block. Cardiac catheterization is a valuable adjunct in difficult problems. 相似文献
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Since hub nodes have been found to play important roles in many networks, highly connected hub genes are expected to play an important role in biology as well. However, the empirical evidence remains ambiguous. An open question is whether (or when) hub gene selection leads to more meaningful gene lists than a standard statistical analysis based on significance testing when analyzing genomic data sets (e.g., gene expression or DNA methylation data). Here we address this question for the special case when multiple genomic data sets are available. This is of great practical importance since for many research questions multiple data sets are publicly available. In this case, the data analyst can decide between a standard statistical approach (e.g., based on meta-analysis) and a co-expression network analysis approach that selects intramodular hubs in consensus modules. We assess the performance of these two types of approaches according to two criteria. The first criterion evaluates the biological insights gained and is relevant in basic research. The second criterion evaluates the validation success (reproducibility) in independent data sets and often applies in clinical diagnostic or prognostic applications. We compare meta-analysis with consensus network analysis based on weighted correlation network analysis (WGCNA) in three comprehensive and unbiased empirical studies: (1) Finding genes predictive of lung cancer survival, (2) finding methylation markers related to age, and (3) finding mouse genes related to total cholesterol. The results demonstrate that intramodular hub gene status with respect to consensus modules is more useful than a meta-analysis p-value when identifying biologically meaningful gene lists (reflecting criterion 1). However, standard meta-analysis methods perform as good as (if not better than) a consensus network approach in terms of validation success (criterion 2). The article also reports a comparison of meta-analysis techniques applied to gene expression data and presents novel R functions for carrying out consensus network analysis, network based screening, and meta analysis. 相似文献
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Coral reef ecosystems are based on coral–zooxanthellae symbiosis. During the initiation of symbiosis, majority of corals acquire their own zooxanthellae (specifically from the dinoflagellate genus Symbiodinium) from surrounding environments. The mechanisms underlying the initial establishment of symbiosis have attracted much interest, and numerous field and laboratory experiments have been conducted to elucidate this establishment. However, it is still unclear whether the host corals selectively or randomly acquire their symbionts from surrounding environments. To address this issue, we initially compared genetic compositions of Symbiodinium within naturally settled about 2-week-old Acropora coral juveniles (recruits) and those in the adjacent seawater as the potential symbiont source. We then performed infection tests using several types of Symbiodinium culture strains and apo-symbiotic (does not have Symbiodinium cells yet) Acropora coral larvae. Our field observations indicated apparent preference toward specific Symbiodinium genotypes (A1 and D1-4) within the recruits, despite a rich abundance of other Symbiodinium in the environmental population pool. Laboratory experiments were in accordance with this field observation: Symbiodinium strains of type A1 and D1-4 showed higher infection rates for Acropora larvae than other genotype strains, even when supplied at lower cell densities. Subsequent attraction tests revealed that three Symbiodinium strains were attracted toward Acropora larvae, and within them, only A1 and D1-4 strains were acquired by the larvae. Another three strains did not intrinsically approach to the larvae. These findings suggest the initial establishment of corals–Symbiodinium symbiosis is not random, and the infection mechanism appeared to comprise two steps: initial attraction step and subsequent selective uptake by the coral. 相似文献
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《Development genes and evolution》1910,29(2):383-383