基因及其顺式调控元件在动物表型进化中的作用

顺式调控假说是当前进化发育生物学中重要的理论之一, 该假说认为顺式调控元件的进化是调控外表性状进化的主要遗传机制。然而越来越多的实验结果表明, 仅靠顺式调控假说远不足以解释复杂的进化发育过程, 其他因素也会导致表型的进化, 如：与顺式调控元件相联基因的蛋白序列改变; 基因及染色体组复制; 蛋白结构域与顺式调控元件的灵活性等。文章回顾了近年来顺式调控元件以及与顺式调控元件相联基因的进化发育研究, 探讨了进化发育生物学研究的新方法与新思路。     

Morphology and behaviour: functional links in development and evolution

Development and evolution of animal behaviour and morphology are frequently addressed independently, as reflected in the dichotomy of disciplines dedicated to their study distinguishing object of study (morphology versus behaviour) and perspective (ultimate versus proximate). Although traits are known to develop and evolve semi-independently, they are matched together in development and evolution to produce a unique functional phenotype. Here I highlight similarities shared by both traits, such as the decisive role played by the environment for their ontogeny. Considering the widespread developmental and functional entanglement between both traits, many cases of adaptive evolution are better understood when proximate and ultimate explanations are integrated. A field integrating these perspectives is evolutionary developmental biology (evo-devo), which studies the developmental basis of phenotypic diversity. Ultimate aspects in evo-devo studies--which have mostly focused on morphological traits--could become more apparent when behaviour, 'the integrator of form and function', is integrated into the same framework of analysis. Integrating a trait such as behaviour at a different level in the biological hierarchy will help to better understand not only how behavioural diversity is produced, but also how levels are connected to produce functional phenotypes and how these evolve. A possible framework to accommodate and compare form and function at different levels of the biological hierarchy is outlined. At the end, some methodological issues are discussed.     

An exact form of the breeder's equation for the evolution of a quantitative trait under natural selection

Starting with the Price equation, I show that the total evolutionary change in mean phenotype that occurs in the presence of fitness variation can be partitioned exactly into five components representing logically distinct processes. One component is the linear response to selection, as represented by the breeder's equation of quantitative genetics, but with heritability defined as the linear regression coefficient of mean offspring phenotype on parent phenotype. The other components are identified as constitutive transmission bias, two types of induced transmission bias, and a spurious response to selection caused by a covariance between parental fitness and offspring phenotype that cannot be predicted from parental phenotypes. The partitioning can be accomplished in two ways, one with heritability measured before (in the absence of) selection, and the other with heritability measured after (in the presence of) selection. Measuring heritability after selection, though unconventional, yields a representation for the linear response to selection that is most consistent with Darwinian evolution by natural selection because the response to selection is determined by the reproductive features of the selected group, not of the parent population as a whole. The analysis of an explicitly Mendelian model shows that the relative contributions of the five terms to the total evolutionary change depends on the level of organization (gene, individual, or mated pair) at which the parent population is divided into phenotypes, with each frame of reference providing unique insight. It is shown that all five components of phenotypic evolution will generally have nonzero values as a result of various combinations of the normal features of Mendelian populations, including biparental sex, allelic dominance, inbreeding, epistasis, linkage disequilibrium, and environmental covariances between traits. Additive genetic variance can be a poor predictor of the adaptive response to selection in these models. The narrow-sense heritability sigma2A/sigma2P should be viewed as an approximation to the offspring-parent linear regression rather than the other way around.     

Neutrality and Robustness in Evo-Devo: Emergence of Lateral Inhibition

Embryonic development is defined by the hierarchical dynamical process that translates genetic information (genotype) into a spatial gene expression pattern (phenotype) providing the positional information for the correct unfolding of the organism. The nature and evolutionary implications of genotype–phenotype mapping still remain key topics in evolutionary developmental biology (evo-devo). We have explored here issues of neutrality, robustness, and diversity in evo-devo by means of a simple model of gene regulatory networks. The small size of the system allowed an exhaustive analysis of the entire fitness landscape and the extent of its neutrality. This analysis shows that evolution leads to a class of robust genetic networks with an expression pattern characteristic of lateral inhibition. This class is a repertoire of distinct implementations of this key developmental process, the diversity of which provides valuable clues about its underlying causal principles.     

How developmental is evolutionary developmental biology?

Evolutionary developmental biology (evo-devo) offers both an account of developmental processes and also new integrative frameworks for analyzing interactions between development and evolution. Biologists and philosophers are keen on evo-devo in part because it appears to offer a comfort zone between, on the one hand, what some take to be the relative inability of mainstream evolutionary biology to integrate a developmental perspective; and, on the other hand, what some take to be more intractable syntheses of development and evolution. In this article, I outline core concerns of evo-devo, distinguish theoretical and practical variants, and counter Sterelny's recent argument that evo-devo's attention to development, while important, offers no significant challenge to evolutionary theory as we know it. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evolutionary quantitative genetics of nonlinear developmental systems

In quantitative genetics, the effects of developmental relationships among traits on microevolution are generally represented by the contribution of pleiotropy to additive genetic covariances. Pleiotropic additive genetic covariances arise only from the average effects of alleles on multiple traits, and therefore the evolutionary importance of nonlinearities in development is generally neglected in quantitative genetic views on evolution. However, nonlinearities in relationships among traits at the level of whole organisms are undeniably important to biology in general, and therefore critical to understanding evolution. I outline a system for characterizing key quantitative parameters in nonlinear developmental systems, which yields expressions for quantities such as trait means and phenotypic and genetic covariance matrices. I then develop a system for quantitative prediction of evolution in nonlinear developmental systems. I apply the system to generating a new hypothesis for why direct stabilizing selection is rarely observed. Other uses will include separation of purely correlative from direct and indirect causal effects in studying mechanisms of selection, generation of predictions of medium‐term evolutionary trajectories rather than immediate predictions of evolutionary change over single generation time‐steps, and the development of efficient and biologically motivated models for separating additive from epistatic genetic variances and covariances.     

植物进化发育生物学的形成与研究进展

植物进化发育生物学是最近十几年来才兴起的一门学科, 它是进化发育生物学的主要分支之一。进化发育生物学的产生经历了进化生物学与胚胎学、遗传学和发育生物学的三次大的综合, 其历史可追溯到19世纪初冯.贝尔所创立的比较胚胎学。相关研究曾沉寂了近一个世纪, 直到20世纪80年代早期, 动物中homeobox基因被发现, 90年代初花发育的 ABC模型被提出, 加之对发育相关基因研究的不断深入, 才使基因型与表型联系了起来, 进而促进了进化发育生物学的飞速发展。目前进化发育生物学已成为21世纪生命科学领域的研究热点之一。本文详细阐述了进化发育生物学产生和发展的历程, 综述了最近十几年来植物进化发育生物学的主要研究进展。文中重点介绍了与植物发育密切相关的MADS-box基因在植物各大类群中的研究现状, 讨论了植物进化发育生物学领域的研究成果对花被演化、花对称性以及叶的进化等重要问题的启示。     

植物进化发育生物学的形成与研究进展

植物进化发育生物学是最近十几年来才兴起的一门学科,它是进化发育生物学的主要分支之一。进化发育生物学的产生经历了进化生物学与胚胎学、遗传学和发育生物学的三次大的综合,其历史可追溯到19世纪初冯.贝尔所创立的比较胚胎学。相关研究曾沉寂了近一个世纪,直到20世纪80年代早期,动物中homeobox基因被发现,90年代初花发育的ABC模型被提出,加之对发育相关基因研究的不断深入,才使基因型与表型联系了起来,进而促进了进化发育生物学的飞速发展。目前进化发育生物学已成为21世纪生命科学领域的研究热点之一。本文详细阐述了进化发育生物学产生和发展的历程,综述了最近十几年来植物进化发育生物学的主要研究进展。文中重点介绍了与植物发育密切相关的MADS-box基因在植物各大类群中的研究现状,讨论了植物进化发育生物学领域的研究成果对花被演化、花对称性以及叶的进化等重要问题的启示。     

Beyond Arabidopsis. Translational biology meets evolutionary developmental biology

Developmental processes shape plant morphologies, which constitute important adaptive traits selected for during evolution. Identifying the genes that act in developmental pathways and determining how they are modified during evolution is the focus of the field of evolutionary developmental biology, or evo-devo. Knowledge of genetic pathways in the plant model Arabidopsis serves as the starting point for investigating how the toolkit of developmental pathways has been used and reused to form different plant body plans. One productive approach is to identify genes in other species that are orthologous to genes known to control developmental pathways in Arabidopsis and then determine what changes have occurred in the protein coding sequence or in the gene's expression to produce an altered morphology. A second approach relies on natural variation among wild populations or crop plants. Natural variation can be exploited to identify quantitative trait loci that underlie important developmental traits and, thus, define those genes that are responsible for adaptive changes. The possibility of applying comparative genomics approaches to Arabidopsis and related species promises profound new insights into the interplay of evolution and development.     

Reduce, reuse, and recycle: developmental evolution of trait diversification

A major focus of evolutionary developmental (evo-devo) studies is to determine the genetic basis of variation in organismal form and function, both of which are fundamental to biological diversification. Pioneering work on metazoan and flowering plant systems has revealed conserved sets of genes that underlie the bauplan of organisms derived from a common ancestor. However, the extent to which variation in the developmental genetic toolkit mirrors variation at the phenotypic level is an active area of research. Here we explore evidence from the angiosperm evo-devo literature supporting the frugal use of genes and genetic pathways in the evolution of developmental patterning. In particular, these examples highlight the importance of genetic pleiotropy in different developmental modules, thus reducing the number of genes required in growth and development, and the reuse of particular genes in the parallel evolution of ecologically important traits.     

r- and K-tactics in the evolution of protist developmental systems: cell and genome size, phenotype diversifying selection, and cell cycle patterns

I outline the significance for protist evolution of the r-, K-selection spectrum,, and of my earlier theory that the most fundamental way organisms adapt to this spectrum is by evolutionary variations in their cell volumes, cell growth rates and genome sizes. Then I introduce the concept of phenotype diversifying selection; this refers to those selective forces which favour an increase in the number of phenotypes produced during a single life cycle by an organism's genotype and epigenetic system. These ideas are then used to discuss the evolution of protist development, with special reference to modifications of the cell cycle whose evolutionary causes and consequences can be related to K-selection for large size and r-selection for rapid reproduction. The significance of multiple fission, syncytia, multicellularity, nuclear dimorphism plus polyploidy, and reversible polyploidy, is treated in detail. Predictions are made of the effects of these different developmental patterns on genome size and the distribution and amounts of nucleoskeletal RNA and heterochromatin. I suggest that heterochromatin exists primarily because of phenotype diversifying selection for differing nuclear volumes. The possibility of applying these ideas to other cell properties like mitotic or cytokinetic mechanisms is also briefly discussed.     

Genetics, development and evolution of adaptive pigmentation in vertebrates

The study of pigmentation has played an important role in the intersection of evolution, genetics, and developmental biology. Pigmentation's utility as a visible phenotypic marker has resulted in over 100 years of intense study of coat color mutations in laboratory mice, thereby creating an impressive list of candidate genes and an understanding of the developmental mechanisms responsible for the phenotypic effects. Variation in color and pigment patterning has also served as the focus of many classic studies of naturally occurring phenotypic variation in a wide variety of vertebrates, providing some of the most compelling cases for parallel and convergent evolution. Thus, the pigmentation model system holds much promise for understanding the nature of adaptation by linking genetic changes to variation in fitness-related traits. Here, I first discuss the historical role of pigmentation in genetics, development and evolutionary biology. I then discuss recent empirically based studies in vertebrates, which rely on these historical foundations to make connections between genotype and phenotype for ecologically important pigmentation traits. These studies provide insight into the evolutionary process by uncovering the genetic basis of adaptive traits and addressing such long-standing questions in evolutionary biology as (1) are adaptive changes predominantly caused by mutations in regulatory regions or coding regions? (2) is adaptation driven by the fixation of dominant mutations? and (3) to what extent are parallel phenotypic changes caused by similar genetic changes? It is clear that coloration has much to teach us about the molecular basis of organismal diversity, adaptation and the evolutionary process.     

Evo-devo of non-bilaterian animals

The non-bilaterian animals comprise organisms in the phyla Porifera, Cnidaria, Ctenophora and Placozoa. These early-diverging phyla are pivotal to understanding the evolution of bilaterian animals. After the exponential increase in research in evolutionary development (evo-devo) in the last two decades, these organisms are again in the spotlight of evolutionary biology. In this work, I briefly review some aspects of the developmental biology of nonbilaterians that contribute to understanding the evolution of development and of the metazoans. The evolution of the developmental genetic toolkit, embryonic polarization, the origin of gastrulation and mesodermal cells, and the origin of neural cells are discussed. The possibility that germline and stem cell lineages have the same origin is also examined. Although a considerable number of non-bilaterian species are already being investigated, the use of species belonging to different branches of non-bilaterian lineages and functional experimentation with gene manipulation in the majority of the non-bilaterian lineages will be necessary for further progress in this field.     

Functional evolutionary developmental biology (evo-devo) of morphological novelties in plants

The origin of morphological and ecological novelties is a long-standing problem in evolutionary biology.Understanding these processes requires investigation from both the development and evolution standpoints,which promotes a new research field called evolutionary developmental biology (evo-devo).The fundamental mechanism for the origin of a novel structure may involve heterotopy,heterochrony,ectopic expression,or loss of an existing regulatory factor.Accordingly,the morphological and ecological traits cont...     

Phylogeny,fossils, and model systems in the study of evolutionary developmental biology

The emerging field of evolutionary developmental biology (evo-devo) continues to operate largely under a single paradigm. In this paradigm developmental regulatory genes and processes are compared among a collection of "model organisms" selected primarily on the basis of their historical utility in the study of development. This approach has proven to be extremely informative, revealing an unexpected deep evolutionary conservation among developmental genes and genetic systems. Despite its success, concern has been expressed regarding its limitations. We discuss the "model organism" paradigm in evo-devo research. Based on our interpretation of its limitations, we propose a separate but complementary approach that is centered on "model groups." These groups are selected on the basis of their taxonomic affinity and their relevance to questions of interest to evo-devo biologists. We further discuss the Tetraodontiformes (Teleostei, Pisces) as an example of a "model group" for the evo-devo study of vertebrate skeletal elements.     

Evo-devo and the evolution of social behavior

The integration of evolutionary biology with developmental genetics into the hybrid field of 'evo-devo' resulted in major advances in understanding multicellular development and morphological evolution. Here we show how insights from evo-devo can be applied to study the evolution of social behavior. We develop this idea by reviewing studies that suggest that molecular pathways controlling feeding behavior and reproduction in solitary insects are part of a 'genetic toolkit' underlying the evolution of a particularly complex form of social behavior, division of labor among workers in honeybee colonies. The evo-devo approach, coupled with advances in genomics for non-model genetic organisms, including the recent sequencing of the honeybee genome, promises to advance our understanding of the evolution of social behavior.     

Evo-devo and the I.I. Schmalhausen concept of the evolution of ontogeny

Evo-devo is considered a special field of knowledge emphasizing the role of developmental processes and mechanisms in evolution and integrating the data of many disciplines studying various structural levels of biosphere organization. A mechanical approach to estimation of events is regarded as a specific feature of the evo-devo concept. In our opinion, the I.I. Schmalhausen concept of the evolution of ontogeny, opposing the reductionist approach of many contemporary evo-devo adherents, can be regarded as the fundamental basis of evo-devo.     

History, chance and adaptation during biological invasion: separating stochastic phenotypic evolution from response to selection

Introduced species often exhibit changes in genetic variation, population structure, selection regime and phenotypic traits as they colonize and expand into new ranges. For these reasons, species invasions are increasingly recognized as promising systems for studying adaptive evolution over contemporary time scales. However, changes in phenotypic traits during invasion occur under non-equilibrium demographic conditions and may reflect the influences of prior evolutionary history and chance events, as well as selection. We briefly review the evidence for phenotypic evolution and the role of selection during invasion. While there is ample evidence for evolutionary change, it is less clear if selection is the primary mechanism. We then discuss the likelihood that stochastic events shift phenotypic distributions during invasion, and argue that hypotheses of adaptation should be tested against appropriate null models. We suggest two experimental frameworks for separating stochastic evolution from adaptation: statistically accounting for phenotypic variation among putative invasion sources identified by using phylogenetic or assignment methods and by comparing estimates of differentiation within and among ranges for both traits and neutral markers ( Q _ST vs. F _ST). Designs that incorporate a null expectation can reveal the role of history and chance in the evolutionary process, and provide greater insights into evolution during species invasions.     

Evolutionary Connectionism: Algorithmic Principles Underlying the Evolution of Biological Organisation in Evo-Devo,Evo-Eco and Evolutionary Transitions

The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term “evolutionary connectionism” to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions.