Making choices between rules or between actions

A new study by Klaes et al. in this issue of Neuron shows that the brain can simultaneously apply two rules to the same sensory information in order to specify two parallel potential action goals, which then compete for execution in the sensorimotor system.     

Correlations between measures of thermal stress resistance within and between species

Resistance to an environmental stress such as elevated temperature can almost always be measured in several different ways. A number of recent studies in Drosophila show that lethal and non-lethal measures of resistance to heat stress are genetically independent. In contrast, data reported here suggest that there are interspecific correlations between measures of thermal stress resistance. Together, these results show that studies of intraspecific variation in stress resistance must demonstrate the ecological relevance of the measures of stress resistance chosen for study. In contrast, interspecific comparisons could be based on any of several measures of resistance. It would be interesting to determine if this pattern holds for resistance to other major environmental stresses.     

Correspondences between classifications and between classes of entities in molecular genetics

Certain correspondences appear between the classifications and between the classes of various entities at molecular genetic level: types of fundamental correspondences between classifications and between classes of normal entities, on the one hand, and of mutant entities on the other hand; ranks of correspondences between classifications and between classes of entities. The concept of universality of the genetic code was reformulated on the basis of the above correspondences.     

Tissue compatibility between colonies and between newly settled larvae of Pocillopora damicornis

Grafting experiments with newly settled larvae and with adult colonies of Pocillopora damicornis were performed. When pairs of newly settled larvae released from different colonies were kept in contact, they fused to form an aggregated colony. Even newly settled larvae derived from colonies belonging to different color morphs fused with each other and no sign of allogeneic rejection was observed. However, when branches of adult colonies belonging to different color morphs were kept in contact, they did not fuse. Fusion was observed only when branches derived from the same colony were paired. The present results suggest that juvenile corals lack the functional histocompatibility system as shown by adult colonies.     

Movement of viruses between biomes

Viruses are abundant in all known ecosystems. In the present study, we tested the possibility that viruses from one biome can successfully propagate in another. Viral concentrates were prepared from different near-shore marine sites, lake water, marine sediments, and soil. The concentrates were added to microcosms containing dissolved organic matter as a food source (after filtration to allow 100-kDa particles to pass through) and a 3% (vol/vol) microbial inoculum from a marine water sample (after filtration through a 0.45-microm-pore-size filter). Virus-like particle abundances were then monitored using direct counting. Viral populations from lake water, marine sediments, and soil were able to replicate when they were incubated with the marine microbes, showing that viruses can move between different ecosystems and propagate. These results imply that viruses can laterally transfer DNA between microbes in different biomes.     

水稻种子萌发过程中α—淀粉酶与萌发速率关系的分析

用丙烯酰胺凝胶电泳技术和3,5－二硝基水杨酸（DNS）测定还原糖法,对不同萌发时间农垦58F,农垦58S和农垦58种子胚中α－淀粉酶同工酶及其酶活性变化进行研究,0－36小时萌发过程中,农垦58F和农垦58Sα-淀粉酶活性高于农垦58。胚中检测出五条酶,A2,A4和A5为上述种子共有酶带,A3为农垦58F和农垦58S特异性酶带,A1为农垦58特异性酶带,据此认为α-淀粉酶对水稻种子萌发速度起重要调控作用,A1和A3可能是调控种子发芽快慢的重要酶分子。     

Lack of correlation between crossing-over and chromosome distance between inversions in Drosophila ananassae

Two linked inversions, AL and ZE, located in the opposite limbs of the second chromosome of Drosophila ananassae are separated from each other by nearly 32% of the total length of the second chromosome. Crossing-over between these inversions when heterozygous was studied in females and males by the salivary-gland smear technique using karyotypically homozygous stocks. The results of recombination experiments show that there is a strong suppression of recombination between inversions when heterozygous, in spite of a large euchromatic distance available for crossing-over between them. Thus there is no correlation between chromosome distance and crossing-over between heterozygous inversions in the second chromosome of D. ananassae when studied cytologically.     

Movement of Viruses between Biomes

Viruses are abundant in all known ecosystems. In the present study, we tested the possibility that viruses from one biome can successfully propagate in another. Viral concentrates were prepared from different near-shore marine sites, lake water, marine sediments, and soil. The concentrates were added to microcosms containing dissolved organic matter as a food source (after filtration to allow 100-kDa particles to pass through) and a 3% (vol/vol) microbial inoculum from a marine water sample (after filtration through a 0.45-μm-pore-size filter). Virus-like particle abundances were then monitored using direct counting. Viral populations from lake water, marine sediments, and soil were able to replicate when they were incubated with the marine microbes, showing that viruses can move between different ecosystems and propagate. These results imply that viruses can laterally transfer DNA between microbes in different biomes.     

Competition between phenotypes

Summary We present two models for phenotypic-dependent interspecific competition. In both cases the survivorship of individuals of one population depends on the entire phenotypic distribution of the other species. The first model considers a continuously varying metric trait, with assortative or random mating; the second model examines a character controlled by two alleles at a single locus. Pursuing the notion that each population maximizes its mean fitness we define a vector-optimum strategy using the concepts of cooperative and competitive optima. It is found that the dynamical constraints placed on the equations of motion by Mendelian genetics often prevent a population from evolving to a strategic optimum. However, for the single locus case with complete dominance, the competitive optimum always coincides with some dynamical equilibrium on the Hardy-Weinberg manifold.     

Games between relatives

The idea of an evolutionarily stable strategy, or ESS, is extended to games between related individuals. There are two possible approaches. The “personal fitness” approach, proposed by Grafen (1979), modifies the fitness of an individual by allowing for the fact that an individual is more likely than other members of the population to meet an opponent adopting the same strategy as himself. The “inclusive fitness” approach adds to the payoff of an individual r times the payoff to his opponent, where r is the coefficient of relationship between them. We regard the former method as correct, but show that if a strategy p meets the inclusive fitness criterion this is necessary but not sufficient to ensure that it meets the personal fitness criterion. If the vector p gives the probability distribution of policies in a mixed ESS, and $\text{p}{}^1$ the frequency distribution of pure strategists in a stable population playing the same game, p and $\text{p}{}^1$ are in general not the same if opponents are related, as they usually are if opponents are unrelated. ESS's are given for the Hawk-Dove game and the War of Attrition, which illustrate these points.     

基因间的同源关系

同源是指从共同祖先的特性遗传下来的通常带有分歧的两个特征之间的关系。同源概念组成了进化基因组学的基础并对功能基因组学有巨大作用,但基于对同源概念的不准确理解,当前对其有诸多模糊表述,因此了解其确切含义具有重要意义。本文就同源、直系同源和旁系同源的概念和性质进行综述。     

基因间的同源关系

同源是指从共同祖先的特性遗传下来的通常带有分歧的两个特征之间的关系。同源概念组成了进化基因组学的基础并对功能基因组学有巨大作用,但基于对同源概念的不准确理解,当前对其有诸多模糊表述,因此了解其确切含义具有重要意义。本文就同源、直系同源和旁系同源的概念和性质进行综述。     

Competition between kingdoms

Although studies of interspecific competition have traditionally been concerned with interactions between closely related species, ecological systems teem with examples of competition between representatives not only from different phyla, but even from different kingdoms. Indeed, inter-kingdom competition may be one of the commonest forms of interaction in nature; particularly prevalent are competitive interactions for shared hosts between insect parasitoids and pathogens from four other kingdoms. Ecologists have barely started to explore the ecological and evolutionary implications of interkingdom competition.