论大白菜及其近缘芸薹属作物核不育材料的育性遗传兼基因互作的抑制效应

根据大白菜及其近缘芸薹属作物核不育材料育成的纯合两型系和杂合两型系可育株间互交F~1|可育株自交,其子代可能出现无育性分离情况或者产生13(可育株)∶3(不育株)两种表型的育性比资料,认为前者宜用复等位基因假说解释,而后者用抑制作用解释为妥。抑制作用的内涵有两种可能,一是由一对决定育性表现的育性基因与另一对不决定育性表现的抑制基因互作表现抑制作用,即抑制作用假说;二是由性质相同、作用相反且可育基因起上位作用的两对育性基因彼此互作产生抑制效应,权称之为上位抑制假说解释其育性遗传现象。 Abstract:The heading Chinese cabbage-pe-tsai and related crops genic male sterile materials can breed up homozygous two-type line and hyterozygous two-type line,intercrossing between fertile plants of this two lines,its F1 fertile plant selfed,generation show two possibles,one is being without fertility segregation,another is fertility segregation rate of 13 (fertile) ∶3(sterile).According literature above,its considerd that the former is proper to be interpreted by means of multiple alleles hypothesis,and the fertility heredity of the latter is appropriate to be interpreted using inhibition.The implecation of the inhibition has two possibilities,one is that a pair of fertility genes controlling fertility and another pair of inhibition genes not controlling fertility interact showing inhibition,i.e.,inhibiting effect hypothesis,and the other is that two pairs of fertility genes with identical property and contrary action and its fertile genes acting epistatically interact demonstrating inhibiting effect.It was temporarily here defined as epistatic inhibition hypothesis interpreting its fertility inheritance phenomenon.     

Song sparrows, top carnivores and nest predation: a test of the mesopredator release hypothesis

Ground-nesting North American landbirds have declined in the longterm, including species with a variety of migratory strategies. The mesopredator release hypothesis explains declines by suggesting that the virtual elimination of top carnivores (large-bodied canids and felids) from much of North America has “released” populations of nest-destroying mesopredators (i.e., medium-sized terrestrial omnivores such as the raccoon Procyon lotor). The hypothesis predicts (1) higher nest success in the presence than in the absence of top carnivores, and (2) a positive relationship between mesopredator abundance and nest predation. Results from a 4-year "natural experiment" in the agricultural landscape of southern Michigan tended to support prediction 1. When coyotes (Canis latrans) were absent in 1993 and present in 1994, 1995 and 1996, Mayfield nest survival in song sparrows (Melospiza melodia), a ground-nesting landbird, increased significantly during the same 4-year interval. Relative frequency of nest predation, the most common cause of nest failure, declined significantly over the four years. Coyotes may have decreased nest predation in 1994–1996 by reducing the abundance of raccoons, apparently the main nest predator in the study area. In an experiment testing prediction 2, mesopredator abundance and predation rate on artificial nests were positively related, as predicted by the hypothesis. Although the present study is not wholly conclusive by itself, we cautiously suggest it contributes to a growing body of evidence derived from a number of studies supporting the mesopredator release hypothesis. Received: 23 May 1997 / Accepted: 12 January 1998     

Plant–soil biota interactions and spatial distribution of black cherry in its native and invasive ranges

One explanation for the higher abundance of invasive species in their non‐native than native ranges is the escape from natural enemies. But there are few experimental studies comparing the parallel impact of enemies (or competitors and mutualists) on a plant species in its native and invaded ranges, and release from soil pathogens has been rarely investigated. Here we present evidence showing that the invasion of black cherry (Prunus serotina) into north‐western Europe is facilitated by the soil community. In the native range in the USA, the soil community that develops near black cherry inhibits the establishment of neighbouring conspecifics and reduces seedling performance in the greenhouse. In contrast, in the non‐native range, black cherry readily establishes in close proximity to conspecifics, and the soil community enhances the growth of its seedlings. Understanding the effects of soil organisms on plant abundance will improve our ability to predict and counteract plant invasions.     

Immigration history and gene dispersal: allozyme variation in Nordic populations of the red campion, Silene dioica (Caryophyllaceae)

Most of the Nordic region was ice-covered during the last (Weichselian) glaciation. During the postglacial period, plant and animal species recolonized the region from several directions and the geographic structuring of genetic variation within Nordic species may still contain a historic component that reflects patterns of postglacial immigration. The present investigation of 69 populations of Silene dioica represents the first large-scale allozyme study of a widespread herbaceous plant in the Nordic region. Although the frequencies of individual alleles showed a range of different geographic patterns, mapping of the axis scores from an ordination of variation at eight polymorphic loci revealed a division into two main geographic groups of populations. The broadly south-western and north-eastern distributions of these two groups of populations suggest that immigration into the region may have involved both eastern and southern geographic sources. However, the geographic boundaries between the two groups of populations are diffuse, and the relatively low between-population component of genetic diversity (G_ST = 16.4%) suggests a history of extensive gene dispersal by pollen.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 23–34.     

Mitochondrial DNA variability in viviparous and ovoviviparous populations of the urodele Salamandra salamandra

Mitochondrial DNA analysis of 13 populations of S. salamandra along a transect across the North of the Iberian Peninsula showed values of divergence between haplotypes ranging from d = 0.41% to 5.91%. Phenetic and cladistic analysis grouped the isofemale lineages into two main clusters with contrasting phylogeographic patterns. The first group encompasses populations located at each extreme of the Iberian Peninsula. Despite the large geographic distance separating these populations, they exhibit only a minor degree of divergence among haplotypes. In contrast, much higher diversification, in both number of distinct haplotypes, and overall genetic divergence, was observed in the second group of phylogenetically related populations. Surprisingly, this process of radiation and divergence in mtDNA haplotypes occurred in populations in close geographic proximity. All populations sampled in this group are located within a 300 km range, in the central part of our transect across the Northern edge of the Peninsula. Most populations in the central range of our transect exhibit viviparous reproduction — which is derived and highly unusual among urodeles. The genetic distances measured among Asturian (central portion of our transect), viviparous populations are higher than the distances measured between the two main taxonomic clusters. A viviparous population showing an unusual level of mtDNA heterogenetiy is reported and the potential implications of this focus of localized variability are discussed. The dynamics of isofemale lineages among the two reproductive modes was further explored in combination with the previous allozyme data. Several nuclear markers suggest that major mtDNA divergences could be explained by long-term extrinsic barriers to gene flow. Isofemale lineages indicate a narrow secondary contact zone among populations with different reproductive patterns. The existence of viviparous and ovovivparous populations sharing a common haplotype suggests that reproductive transition in S. salamandra could have arisen in absence of genetic mtDNA differentiation. We finally outline a genetic model system where the acquisition of water independence from a primitively aquatic dependent amphibian life cycle can be analyzed from a microevolutionary perspective.     

Treponematosis in regional and chronological perspective from central Gulf Coast Florida

Examination of five central Gulf Coast Florida archaeological skeletal series (n = 547) from the late prehistoric and early historic periods reveals the presence of pathological lesions characteristic of treponemal infection. These skeletal remains of native American populations represent a crucial time regarding hypotheses about the exchange of syphilis between the Old and New World or the mutation of one treponemal infection into another. Comparison of the lesions with those observed in modern studies of treponemal infection does not support an interpretation of veneral syphilis. The data from this study and from other archaeological skeletal series indicate the presence of a treponemal disease prior to European contact. The skeletal elements from Florida do not suggest that the disease changed dramatically following contact with Europeans. It is possible that cases of nonspecific postcranial pathology can be explained by the presence of this disease in the Florida populations. This study indicates that a treponemal disease was endemic throughout the region by at least A. D. 1000. © 1993 Wiley-Liss, Inc.     

Factors influencing the acaricidal activity of flucycloxuron

Contact activities of flucycloxuron on immature stages of the two-spotted spider mite (Tetranychus urticae (Koch)) and the European red mite (Panonychus ulmi (Koch)) gradually decrease in the successive developmental stages. The levels of contact activity of flucycloxuron on larvae and protonymphs ofT. urticae andP. ulmi are of the same order. Deutonymphs ofT. urticae are less susceptible to contact activity than the similar stage ofP. ulmi. In adultT. urticae, the transovarial ovicidal activity was used as an indicator for cuticular penetration. More than 90% of the maximal penetration into adult mites occurs within 8 h. Reversibility of the transovarial activity was not observed after 24 h, but did occur after a subsequent 48 h stay on untreated leaves. The ovo-larvicidal activity of flucycloxuron onP. ulmi after treatment of apple leaves is strongly negatively influenced by leaf age, partly by lower retention of the spray liquid on the leaves. Leaf penetration was measured by application of flucycloxuron on leaf uppersides and assessment of the transovarial activity in mites (P. ulmi orT. urticae) infested on the undersides, one day after treatment. In this test system, leaf penetration was found to be strongly species dependent. Penetration was high in cucumber, moderate in French beans, cotton, roses and strawberry, but low in apple and pepper. Leaf penetration in French bean plants is drastically reduced at increasing leaf age. The overall positive effect of increase in relative air humidity on leaf penetration, is statistically highly significant (P=0.001) for French beans and almost significant (P=0.08) for cucumbers. WithT. urticae on French bean it was found that in this test flucycloxuron needs more than one day for maximal leaf penetration. Although in apple leaves penetration from uppersides was low, penetration from undersides was much higher. The surfactants Arkopal N 130, Silwet L-77 and X2-5309 enhance penetration from leaf under-sides.     

Widespread latitudinal asymmetry in the performance of marginal populations: A meta-analysis

Aim

Range shifts are expected to occur when populations at one range margin perform better than those at the other margin, yet no global trend in population performances at range margins has been demonstrated empirically across a wide range of taxa and biomes. Here we test the prediction that, if impacts of ongoing climate change on performance in marginal populations are widespread, then populations from the high-latitude margin (HLM) should perform as well as or better than central populations, whereas low-latitude margin (LLM) populations should perform worse.

Location

Global.

Time period

1995–2019.

Major taxa studied

Plants and animals.

Methods

To test our prediction, we used a meta-analysis to quantify empirical support for asymmetry in the performance of high- and low-latitude margin populations compared to central populations. Performance estimates (survival, reproduction, or lifetime fitness) for populations occurring in their natural environment were derived from 51 papers involving 113 margin-centre comparisons from 54 species and 705 populations from the Americas, Europe, Africa and Australia. We then related these performance differences to climatic differences among populations. We also tested whether patterns are consistent across taxonomic kingdoms (plants vs animals) and across realms (marine vs terrestrial).

Results

Populations at margins performed significantly worse than central populations, and this trend was primarily driven by the low-latitude margin. Although the difference was of small magnitude, it was largely consistent across biological kingdoms and realms. Differences in performance were weakly (p = .08) related to the difference in average temperatures between central and marginal populations.

Main conclusions

The observed asymmetry in performance in marginal populations is consistent with predictions about the effects of global climate change, though further research is needed to confirm the effect of climate. It indicates that changes in demographic rates in marginal populations can serve as early-warning signals of impending range shifts.     

Phylogenetic frameworks: towards a firmer foundation for the comparative approach

The growing interest in using phylogenies to test evolutionary hypotheses has focused attention on the need for robust estimates of phylogenetic history. Whether specific branching structures are correct summaries of evolutionary history can be estimated only through the examination of congruence of many sets of characters. After consideration of practical and philosophical aspects of congruence, I conclude that taxonomic congruence (analysis of congruence of topologies produced from independent datasets) is preferable to character congruence (analysis of congruence between individual characters) for estimating accuracy of phylogenetic hypotheses. Existing methods for examining taxonomic congruence are discussed and the combinable components approach, when preceded by application of rigorous statistical manipulations (e.g. jackknifing or bootstrapping), found most appropriate. Implementation of the method of combinable components is described, and is demonstrated using published data for Menidia and Rana. The robust branching structure resulting from this analysis (a phylogenetic framework) contains those nodes (phylogenetic hypotheses) that are strongly supported by at least one dataset and are consistent with all others. This approach is the most appropriate/conservative for testing hypotheses about evolutionary history.