Hybrid swarms: catalysts for multiple evolutionary events in Senecio in the British Isles

Background: Introgressive hybridisation is an evolutionary catalyst producing novel variants able to explore new ecological niches and evolve as new hybrid taxa. However, the role of ‘hybrid swarms’ – highly variable populations produced following interspecific hybridisation – in generating this evolutionary novelty has been poorly studied.

Aims: We examine the alternative origins of tetraploid hybrid derivatives of Senecio vulgaris and S. squalidus, via local polytopic formation or long-distance dispersal from a single perennial hybrid swarm around Cork, Ireland.

Methods: Morphometric, isozyme and chloroplast DNA analysis.

Results: The Cork hybrid swarm and UK hybrid swarms exhibited a broad range of morphological variation and contained individuals similar to the stable tetraploid hybrid derivatives; S. eboracensis and S. vulgaris var. hibernicus. Chloroplast DNA analysis shows that S. eboracensis did not evolve from the Cork hybrid swarm. However, UK S. vulgaris var. hibernicus populations exhibit a broad range of variation for both chloroplast and isozyme markers, but were not distinguishable from Cork material.

Conclusions: Our study confirms that S. eboracensis did not evolve from the Cork hybrid swarm, and while our analyses could not demonstrate this conclusively for S. vulgaris var. hibernicus the ease with which hybrid swarms have been generated in the past makes a polytopic origin for S. vulgaris var. hibernicus the most likely scenario.     

果实生态学的概念、研究现状及研究方向

总结了果实生态学的概念及主要研究内容,对国内外的果实生态学研究领域的进展进行了综述,分析了这些研究尚存在的不足之处,并指出了未来研究的科学问题.迄今为止,果实生态学在果实与种子的关系、果实颜色与环境、果实化学成分与环境、群落果实构成式样的地理分布特征、果实及食果动物的协同进化等方面已经取得了若干进展.果实重量谱等物理性状的空间分异格局及机理、果实化学成分的时空变异格局、果实类型的组成式样及大尺度地理分布格局及其机制的探讨、果实传播与食果动物的协同进化等是未来亟待开展的工作.     

Ultrastructures and evolutionary modalities of flagellar and ciliary systems in protists

Summary— As both the ultrastructure and function of flagella and cilia have been for the main part remarkably conserved during Eukaryote, evolution, the question arises as to whether the variations observed at the organite ultrastural level, or at the level of the development of a flagellar or ciliary cellular system could be considered as systematic or phylogenetic criteria. With regard to the fundamental structure, the known variations concern: 1) the kinetosome (length, position and number of cartwheels, number of triplets, and respective lengths of the microtubules); 2) the transition zone (various structural types); 3) the axoneme (number of doublets, central tubules, arms); 4) the paraxonemal formations (presence, position, structure); 5) the membrane (intramembranous particles; intramembranous particles; addition of components, mastigonemes, scales); 6) the fibres associated with the kinetosomes. Some of these variations are characteristic of taxa, and are considered as phylogenetic markers. Regarding the variations in the number of ciliary or flagellar units per cell, the following can be distinguished: cells with only one kinetosome (Ks), carrying one flagellum; cells with 2 neighbouring Ks (primary Ks = 2A), only one Ks, or the 2 Ks, bearing a flagellum; cells with numerous flagella or cilia. We consider that this configuration can result from: a) addition of new Ks around the primary Ks, forming a primary group (PG): either by replication of the primary couple (2 × 2A in Karotomorpha; 2 × 2A in Phaeopolykrikos; 4(2 × 2A) in Polkrikos), or by addition of new Ks (N) without copy or replication of the primary Ks (2A + 2N in Polytomella; 2A +3N in Tetratrichomonas; 2A + 3N in Tetratrichomonas; 2A + 4N in Hexamastix; 2A + 6N in Pyramimonas octopus). b) amplification of each constituent of the primordial couple in opalinids. c) amplification of the primary group [yx(AA + 2N) with y = 2 in diplomonadida and y > 2 in calonymphidae. d) appearance in morphogenetic fields situated outside the primary group (but possibly related to it) of new Ks which then form secondary groups (SG) where they are arranged in polarized rows composed of juxtaposed cortical units (monokinetids). In this case, PG can be of type 2A+2N (1PG+1SG in lophomonadida; 1PG+2SG in some trichonymphina), or can lose some Ks, resulting in reduced PG (4 reduced PG+4GS in Staurojoenina, n reduced PG + nGS in spirotrichonymphina). The PG may even disappear; either partially leaving remnants in the form of MTOCs in Stephanopogon, or completely, as in cilliates where the general ciliature would represent on the SG. From the above, it is seen that: a) the pluriflagellar state in protists depends on only a small number of factors; b) the same factors are used in different groups; c) different states have been obtained within different groups. An analysis of the respective evolution of kinetosomes and centrioles is proposed.     

Multistability in perception: binding sensory modalities, an overview

This special issue presents research concerning multistable perception in different sensory modalities. Multistability occurs when a single physical stimulus produces alternations between different subjective percepts. Multistability was first described for vision, where it occurs, for example, when different stimuli are presented to the two eyes or for certain ambiguous figures. It has since been described for other sensory modalities, including audition, touch and olfaction. The key features of multistability are: (i) stimuli have more than one plausible perceptual organization; (ii) these organizations are not compatible with each other. We argue here that most if not all cases of multistability are based on competition in selecting and binding stimulus information. Binding refers to the process whereby the different attributes of objects in the environment, as represented in the sensory array, are bound together within our perceptual systems, to provide a coherent interpretation of the world around us. We argue that multistability can be used as a method for studying binding processes within and across sensory modalities. We emphasize this theme while presenting an outline of the papers in this issue. We end with some thoughts about open directions and avenues for further research.     

Genes,germs, and schizophrenia: an evolutionary perspective

Literature on schizophrenia and other mental illnesses has emphasized the compatibility of evidence with genetic causation without adequately considering alternative hypotheses of disease causation. Although some studies from the mid-20th century reported associations between certain pathogens and schizophrenia, only recently has the possibility of infectious causation of schizophrenia again become an active focus of research. Infectious causation of schizophrenia is still, however, generally regarded as less well demonstrated than genetic causation. This article evaluates the evidence that has been used to support genetic and infectious causation. Our consideration of infectious causation focuses on the protozoan Toxoplasma gondii but also assesses other pathogens that may contribute to the development of some of the illnesses currently categorized as schizophrenia. Although evidence generally accepted as demonstrating genetic causation can be readily explained by hypotheses of infectious causation, some of the evidence implicating infectious causation cannot be similarly explained by genetic causation. This asymmetry indicates that a scientific approach to the causation of schizophrenia needs to put a greater emphasis on tests that distinguish hypotheses of genetic causation from those of infectious causation.     

Basic statistics and variational concepts behind the reverse Monte Carlo technique

We revise the statistical foundations of the reverse Monte Carlo (RMC) technique by constructing the associated functional of a variational principle which incorporates, without any ad hoc assumptions, the inherent errors accompanying the simulation and the experimental data. We propose a Bayesian criteria for acceptance/rejection of configurations, in terms of the variations of the functional. The loss function and variational functional minimization approaches are compared.     

EvoluZion: a computer simulator for teaching genetic and evolutionary concepts

EvoluZion is a forward-in-time genetic simulator developed in Java and designed to perform real time simulations on the evolutionary history of virtual organisms. These model organisms harbour a set of 13 genes that codify an equal number of phenotypic features. These genes change randomly during replication, and mutant genes can have null, positive or negative effects on the organisms’ fitness, allowing to model effects of both selection pressures and drift on gene evolution. There are two versions of this program: version 1.6.x_haploid; focused on macroevolutionary events and depicting prokaryote-like organisms, and version 2.3.x_diploid that simulate diploid, sexually reproducing organisms, and it is more adequate to teach micro-evolution as well as key genetic concepts such as Mendel’s laws, epistasis, genetic linkage, genetic mapping among others. Different data sets can be collected periodically during running in order to perform further analyses. In addition, the complete genealogy of extant as well as extinct organisms can be recorded. EvoluZion is well suited for teaching evolutionary biology concepts to students of all levels in a pedagogic way. This is mainly due to three main program features: (i) its intuitive and simple graphical interface (ii) a visualisation similar to videogames (iii) flexible integration of a wide range of biological phenomena into a single simulation.     

Offshore port service concepts: classification and economic feasibility

Most prevalent among the approaches to address the ever increasing demands for port capacity are the construction of new berths, installation of faster cranes and optimization of existing resources. A less common approach is to employ offshore port service concepts. Here, we endeavor to provide a complete survey of such nontraditional offshore service concepts and demonstrate that all, except a few very unusual concepts, can be well classified into one of thirty two structures or their combinations. Advantages, disadvantages and the container handling chain are discussed. We identify which of these structures can provide any of six possible operational modes. We next focus on a subset of the thirty two structures called the mobile harbor. This concept has recently been proposed and shares some similarities with midstream operation in Hong Kong. We endeavor to address the fundamental question: “Should such a concept be implemented?” We develop an estimate of the cost per unit threshold below which this concept will be viable. The per unit cost estimate of current MH designs is within about 6% of the economic viability threshold for traditional operation in Hong Kong. Other operational modes are not as favorable. As our focus is on the feasibility of the operational paradigm, we do not here address technology issues except to note ongoing efforts to resolve technology hurdles.     

生态交错带及其研究进展

生态交错带研究对探索自然生态规律和保护环境有重要意义。近30a来,有关生态交错带的论文数平均年增57%,显示其得到了愈来愈广泛的关注。回顾了生态交错带概念的产生与发展,区分了它与边缘、生态边界层与生态过渡带等概念的异同;简述了其7个基本属性,即高生物多样性、丰富的特有种、大量外来种、频繁的物质流动、敏感的时空动态性、结构的异质性和脆弱性;总结提炼了生态交错带的基本原理和假说;综述了生态交错带的生物多样性产生机制、对全球变化的响应与反馈、生态设计与管理以及生态交错带模型发展和整合的研究进展。提出今后需要大力发展理论研究、多尺度模型转化和多因子综合分析,以完善生态交错带理论并支持生态学机理的探索。     

Nutritional psychiatry research: an emerging discipline and its intersection with global urbanization,environmental challenges and the evolutionary mismatch

In 21st-century public health, rapid urbanization and mental health disorders are a growing global concern. The relationship between diet, brain function and the risk of mental disorders has been the subject of intense research in recent years. In this review, we examine some of the potential socioeconomic and environmental challenges detracting from the traditional dietary patterns that might otherwise support positive mental health. In the context of urban expansion, climate change, cultural and technological changes and the global industrialization and ultraprocessing of food, findings related to nutrition and mental health are connected to some of the most pressing issues of our time. The research is also of relevance to matters of biophysiological anthropology. We explore some aspects of a potential evolutionary mismatch between our ancestral past (Paleolithic, Neolithic) and the contemporary nutritional environment. Changes related to dietary acid load, advanced glycation end products and microbiota (via dietary choices and cooking practices) may be of relevance to depression, anxiety and other mental disorders. In particular, the results of emerging studies demonstrate the importance of prenatal and early childhood dietary practices within the developmental origins of health and disease concept. There is still much work to be done before these population studies and their mirrored advances in bench research can provide translation to clinical medicine and public health policy. However, the clear message is that in the midst of a looming global epidemic, we ignore nutrition at our peril.     

Current concepts in apoptosis: The physiological suicide program revisited

Apoptosis, or programmed cell death (PCD), involves a complex network of biochemical pathways that normally ensure a homeostatic balance between cellular proliferation and turnover in nearly all tissues. Apoptosis is essential for the body, as its deregulation can lead to several diseases. It plays a major role in a variety of physiological events, including embryonic development, tissue renewal, hormone-induced tissue atrophy, removal of inflammatory cells, and the evolution of granulation tissue into scar tissue. It also has an essential role in wound repair. The various cellular and biochemical mechanisms involved in apoptosis are not fully understood. However, there are two major pathways, the extrinsic pathway (receptor-mediated apoptotic pathway) and the intrinsic pathway (mitochondria-mediated apoptotic pathway), which are both well established. The key component in both is the activation of the caspase cascade. Caspases belong to the family of proteases that ultimately, by cleaving a set of proteins, cause disassembly of the cell. Although the caspase-mediated proteolytic cascade represents a central point in the apoptotic response, its initiation is tightly regulated by a variety of other factors. Among them, Bcl-2 family proteins, TNF and p53 play pivotal roles in the regulation of caspase activation and in the regulation of apoptosis. This review summarizes the established concepts in apoptosis as a physiological cell suicide program, highlighting the recent and significant advances in its study.