Speciation is the process by which one or more species arises from a common ancestor, and “macroevolution” refers to patterns and processes at and above the species level – or, transitions in higher taxa, such as new families, phyla or genera. “Macroevolution” is contrasted with “microevolution,” evolutionary change within populations, due to migration, assortative mating, selection, mutation and drift. In the evolutionary synthesis of the 1930’s and 40’s, Haldane , Dobzhansky , Mayr , and Simpson argued that the origin of (...) species and higher taxa were, given the right environmental conditions and sufficient time, the product of the same microevolutionary factors yielding change within populations. Dobzhansky reviewed the evidence from genetics, and argued, “nothing in the known macroevolutionary phenomena would require other than the known genetic principles for causal explanation” . In sum, genetic variation between species was not different in kind from the genetic variation within species. Dobzhansky concluded that one may “reluctantly put an equal sign” between micro- and macroevolution. In this chapter, I review arguments for and against this "neo-Darwinian" consensus on speciation, as well as debates concerning macroevolution and punctuated equilibrium. (shrink)

The neutral theory of biodiversity purports that patterns in the distribution and abundance of species do not depend on adaptive differences between species (i.e. niche differentiation) but solely on random fluctuations in population size (“ecological drift”), along with dispersal and speciation. In this framework, the ultimate driver of biodiversity is speciation. However, the original neutral theory made strongly simplifying assumptions about the mechanisms of speciation, which has led to some clearly unrealistic predictions. In response, several recent studies have combined neutral (...) community models with more elaborate speciation models. These efforts have alleviated some of the problems of the earlier approaches, while confirming the general ability of neutral theory to predict empirical patterns of biodiversity. However, the models also show that the mode of speciation can have a strong impact on relative species abundances. Future work should compare these results to diversity patterns arising from non‐neutral modes of speciation, such as adaptive radiations. (shrink)

Recent discussion of mechanism has suggested new approaches to several issues in the philosophy of science, including theory structure, causal explanation, and reductionism. Here, I apply what I take to be the fruits of the 'new mechanical philosophy' to an analysis of a contemporary debate in evolutionary biology about the role of natural selection in speciation. Traditional accounts of that debate focus on the geographic context of genetic divergence--namely, whether divergence in the absence of geographic isolation is possible (or significant). (...) Those accounts are at best incomplete, I argue, because they ignore the mechanisms producing divergence and miss what is at stake in the biological debate. I argue that the biological debate instead concerns the scope of particular speciation mechanisms which assign different roles to natural selection at various stages of divergence. The upshot is a new interpretation of the crux of that debate--namely, whether divergence with gene flow is possible (or significant) and whether the isolating mechanisms producing it are adaptive. (shrink)

Several features of the yeast mitochondrial genome, including high mutation rate, dynamic genomic structure, small effective population size, and dispensability for cellular viability, make it a promising candidate for generating hybrid incompatibility and driving speciation. Cytonuclear incompatibility, a specific type of Dobzhansky‐Muller genetic incompatibility caused by improper interactions between mitochondrial and nuclear genomes, has previously been observed in a variety of organisms, yet its role in speciation remains obscure. Recent studies in Saccharomyces yeast species provide a new insight, with experimental (...) evidence that cytonuclear incompatibility and DNA sequence divergence are both causes of the reproductive isolation of different yeast species. Interestingly, these two mechanisms seem to be perfectly complementary to each other in terms of their effects and evolutionary trajectories. Direct molecular analyses of the incompatible genes in yeasts have started to shed light on the evolutionary forces driving speciation. Editor's suggested further reading in BioEssaysThe cytoplasmic structure hypothesis for ribosome assembly, vertical inheritance, and phylogeny AbstractMitochondrial bioenergetics as a major motive force of speciation Abstract. (shrink)

A new set of models has resurrected a role for chromosomal inversions in the formation of new species.1-3 Traditional models, which are generally considered to be unlikely in most cases, had imagined that inversions might aid speciation by directly causing low hybrid fitness. In contrast, the newer models focus on the effect that inversions have on local recombination rates. A test of these models found a strikingly high rate of amino-acid substitution within regions where humans and chimpanzees differ by inversions, (...) suggesting perhaps that our ancestral species underwent a divergence process in which gene flow and inversions played a key role.4 However, it remains uncertain whether this interesting finding is actually consistent with the proposed model. BioEssays 25:825–828, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

This is the first volume to address directly the question of the speciation of modern Homo sapiens. The subject raises profound questions about the nature of the species, our defining characteristic (it is suggested it is language), and the brain changes and their genetic basis that make us distinct. The British Academy and the Academy of Medical Sciences have brought together experts from palaeontology, archaeology, linguistics, psychology, genetics and evolutionary theory to present evidence and theories at the cutting edge of (...) our understanding of these issues. Palaeontological and genetic work suggests that the transition from a precursor hominid species to modern man took place between 100,000 and 150,000 years ago. Some contributors discuss what is most characteristic of the species, focussing on language and its possible basis in brain lateralization. This work is placed in the context of speciation theory, which has remained a subject of considerable debate since the evolutionary synthesis of Mendelian genetics and Darwinian theory. The timing of specific transitions in hominid evolution is discussed, as also is the question of the neural basis of language. Other contributors address the possible genetic nature of the transition, with reference to changes on the X and Y chromosomes that may account for sex differences in lateralization and verbal ability. These differences are discussed in terms of the theory of sexual selection, and with reference to the mechanisms of speciation. These essays will be vital reading for anyone interested in the nature and origins of the species, and specifically human abilities. (shrink)

This is the first volume to address directly the question of the speciation of modern Homo sapiens. The subject raises profound questions about the nature of the species, our defining characteristic, and the brain changes and their genetic basis that make us distinct. The British Academy and the Academy of Medical Sciences have brought together experts from palaeontology, archaeology, linguistics, psychology, genetics and evolutionary theory to present evidence and theories at the cutting edge of our understanding of these issues.Palaeontological and (...) genetic work suggests that the transition from a precursor hominid species to modern man took place between 100,000 and 150,000 years ago. Some contributors discuss what is most characteristic of the species, focussing on language and its possible basis in brain lateralization. This work is placed in the context of speciation theory, which has remained a subject of considerable debate since the evolutionary synthesis of Mendelian genetics and Darwinian theory. The timing of specific transitions in hominid evolution is discussed, as also is the question of the neural basis of language. Other contributors address the possible genetic nature of the transition, with reference to changes on the X and Y chromosomes that may account for sex differences in lateralization and verbal ability. These differences are discussed in terms of the theory of sexual selection, and with reference to the mechanisms of speciation.These essays will be vital reading for anyone interested in the nature and origins of the species, and specifically human abilities. (shrink)

Speciation—the origin of new species—has been one of the most active areas of research in evolutionary biology, both during, and since the Modern Synthesis. While the Modern Synthesis certainly shaped research on speciation in significant ways, providing a core framework, and set of categories and methods to work with, the history of work on speciation since the mid-twentieth century is a history of divergence and diversification. This piece traces this divergence, through both theoretical advances, and empirical insights into how different (...) lineages, with different genetics and ecological conditions, are shaped by very different modes of diversification. (shrink)

A recent phylogenetic survey of the New World orioles (genus Icterus; Omland et al. 1999) suggested that the Baltimore Oriole (I. galbula) and the Black-backed Oriole (I. abeillei) are sister taxa. That survey examined mitochondrial DNA (mtDNA) from a single representative of each species in the genus. Here, we examine mtDNA sequences from 15 Blackbacked and 20 Baltimore Orioles. The two species appear to be very recently diverged, with average sequence divergences for both cytochrome b (cyt b) and the control (...) region indicating a probable late Pleistocene split. Despite this very recent divergence, there is one fixed base-pair difference between the species in cyt b and another in the control region, suggesting that one or both species have undergone a bottleneck during or since speciation. This molecular evidence of recent divergence suggests that male plumage differences between Black-backed and Baltimore Orioles evolved very rapidly. (shrink)

Sympatric speciation illustrates how natural and sexual selection may create new species in isolation without geographic barriers. However, recent genomic reanalyses of classic examples of sympatric speciation reveal complex histories of secondary gene flow from outgroups into the radiation. In contrast, the rich theoretical literature on this process distinguishes among a diverse range of models based on simple genetic histories and different types of reproductive isolating barriers. Thus, there is a need to revisit how to connect theoretical models of sympatric (...) speciation and their predictions to empirical case studies in the face of widespread gene flow. Here, theoretical differences among different types of sympatric speciation and speciation‐with‐gene‐flow models are reviewed and summarized, and genomic analyses are proposed for distinguishing which models apply to case studies based on the timing and function of adaptive introgression. Investigating whether secondary gene flow contributed to reproductive isolation is necessary to test whether predictions of theory are ultimately borne out in nature. (shrink)

This paper, like many before it, aims to solve the “species problem” by declaring it a non-problem. It borrows its title from an earlier article by Jeff Lawrence and its philosophical concepts from Marc Ereshefsky, John Dupré, Peter Godfrey-Smith, Ken Waters, and Jody Hey. The emphasis is on bacteria, but my pragmatic species anti-realist conclusion may be a general one.

Standard biological and philosophical treatments assume that dramatic genotypic or phenotypic change constitutes instantaneous speciation, and that barring such saltation, speciation is gradual evolutionary change in individual properties. Both propositions appear to be incongruent with standard theoretical perspectives on species themselves, since these perspectives are (a) non-pheneticist, and (b) tend to disregard intermediate cases. After reviewing certain key elements of such perspectives, it is proposed that species-membership is mediated by membership in a population. Species-membership depends, therefore, not on intrinsic characteristics (...) of an organism, but on relationship of an organism to others. A new definition of speciation is proposed in the spirit of this proposal. This definition implies that dramatic change is neither necessary nor sufficient for speciation. It also implies, surprisingly, that an organism can change species during its lifetime. (shrink)

Graphical AbstractSquamates may be an attractive group in which to study the influence of sex chromosomes on speciation rates because of the repeated evolution of heterogamety (both XY and ZW), as well as an apparently large number of taxa with environmental sex-determination.

Darwin's “mystery of mysteries,” the origin of species, is caused by the evolution of speciation phenotypes, i.e. phenotypic differences that depress gene flow between daughter species during speciation. Postmating, prezygotic (PMPZ) differentiation characterizes many closely related species causing conspecific sperm precedence (CSP), wherein a female preferentially utilizes conspecific over heterospecific sperm in fertilization. Until recently, the components of CSP have been difficult to observe and study in internally fertilizing organisms. Research into the mechanisms of CSP is now progressing rapidly with (...) the help of new innovative research tools. With the recent development of a sperm labeling system enabling distinct labels for different males, direct observations of competing male sperm within the female reproductive tract are possible, revealing multiple PMPZ phenotypes that combine to cause CSP. The discovery of mechanisms underlying CSP predicts an exciting future for studies of PMPZ speciation phenotypes and possible general principles underlying the origin of species. (shrink)

In birds and frogs, species pairs retain the capacity to produce viable hybrids for tens of millions of years, an order of magnitude longer than mammals. What accounts for these differences in relative rates of pre- and postzygotic isolation? We propose that reproductive mode is a critically important but previously overlooked factor in the speciation process. Viviparity creates a post-fertilization arena for genomic conflicts absent in egg-laying species. With viviparity, conflict can arise between: mothers and embryos; sibling embryos in the (...) womb, and maternal and paternal genomes within individual embryos. Such intra- and intergenomic conflicts result in perpetual antagonistic coevolution, thereby accelerating interpopulation postzygotic isolation. In addition, by generating intrapopulation genetic incompatibility, viviparity-driven conflict favors polyandry and limits the potential for precopulatory divergence. Mammalian diversification is characterized by rapid evolution of incompatible feto-maternal interactions, asymmetrical postzygotic isolation, disproportionate effects of genomically-imprinted genes, and “F2 hybrid enhancement.” The viviparity-driven conflict hypothesis provides a parsimonious explanation for these patterns in mammalian evolution. BioEssays 22:938–946, 2000. © 2000 John Wiley & Sons, Inc. (shrink)

(2008). Genetic Engineering and the Speciation of Superions from Humans. World Futures: Vol. 64, Postformal Thought and Hierarchical Complexity, pp. 436-443.

Speciation is an aspect of evolutionary biology that has received little philosophical attention apart from articles mainly by biologists such as Mayr (1988). The role of speciation as a terminus a quo for the individuality of species or in the context of punctuated equilibrium theory has been discussed, but not the nature of speciation events themselves. It is the task of this paper to attempt to bring speciation events into some kind of general scheme, based primarily upon the work of (...) Sergey Gavrilets on adaptive landscapes, using migration rate, or gene flow, as the primary scale, and concluding that adaptive and drift explanations are complementary rather than competing. I propose a distinction between intrinsic and extrinsic selection, and the notion of reproductive reach and argue that speciation modes should be discriminated in terms of gene flow, the nature of selection maintaining reproductive reach, and whether the predominant cause is selective or stochastic. I also suggest that the notion of an adaptive “quasispecies” for asexual species is the primitive notion of species, and that members of reproductively coherent sexual species are additionally coadapted to their mating partners. (shrink)

While its mechanism and biological significance are unknown, the utility of a short mitochondrial DNA sequence as a “barcode” providing accurate species identification has revolutionized the classification of organisms. Since highest accuracy was achieved with recently diverged species, hopes were raised that barcodes would throw light on the speciation process. Indeed, a failure of a maternally donated, rapidly mutating, mitochondrial genome to coadapt its gene products with those of a paternally donated nuclear genome could result in developmental failure, thus creating (...) a post-zygotic barrier leading to reproductive isolation and sympatric branching into independent species. However, the barcode itself encodes a highly conserved, species-invariant, protein, and the discriminatory power resides in the non-amino acid specific bases of synonymous codons. It is here shown how the latter could register changes in the oligonucleotide frequencies of nuclear DNA that, when they fail to match in pairing meiotic chromosomes, could reproductively isolate the parents so launching a primary divergence into two species. It is proposed that, while not itself contributing to speciation, the barcode sequence provides an index of the nuclear DNA oligonucleotide frequencies that drive speciation. (shrink)

Mitochondrial bioenergetics plays a key role in multiple basic cellular processes, such as energy production, nucleotide biosynthesis, and iron metabolism. It is an essential system for animals' life and death (apoptosis) and it is required for embryo development. This, in conjunction with its being subjected to adaptive processes in multiple species and its gene products being involved in the formation of reproductive barriers in animals, raises the possibility that mitochondrial bioenergetics could be a candidate genetic mechanism of speciation. Here, we (...) discuss genetic and biochemical evidence for the possible involvement of this unique system, encoded by two genomes (the mitochondrial and nuclear genomes), that differ by an order of magnitude in their mutation rates in processes leading to speciation events. (shrink)

The Tree of Life hypothesis frames the evolutionary process as a series of events whereby lineages diverge from one another, thus creating the diversity of life as descendent lineages modify properties from their ancestors. This hypothesis is under scrutiny due to the strong evidence for lateral gene transfer between distantly related bacterial taxa, thereby providing extant taxa with more than one parent. As a result, one argues, the Tree of Life becomes confounded as the original branching structure is gradually superseded (...) by reticulation, ultimately losing its ability to serve as a model for bacterial evolution. Here we address a more fundamental issue: is there a Tree of Life that results from bacterial evolution without considering such lateral gene transfers? Unlike eukaryotic speciation events, lineage separation in bacteria is a gradual process that occurs over tens of millions of years, whereby genetic isolation is established on a gene-by-gene basis. As a result, groups of closely related bacteria, while showing robust genetic isolation as extant lineages, were not created by an unambiguous series of lineage-splitting events. Rather, a temporal fragmentation of the speciation process results in cognate genes showing different genetic relationships. We argue that lineage divergence in bacteria does not produce a tree-like framework, and inferences drawn from such a framework have the potential to be incorrect and misleading. Therefore, the Tree of Life is an inappropriate paradigm for bacterial evolution regardless of the extent of gene transfer between distantly related taxa. (shrink)

Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction form the building blocks of the (Neo-)Darwinian research program, and several of these have been called “Darwinian principles.” Here, we suggest that caution should be taken in calling these principles Darwinian because of the important role played by reticulate evolutionary mechanisms and processes in also bringing about these phenomena. Reticulate mechanisms and processes include symbiosis, symbiogenesis, lateral gene transfer, infective heredity mediated by genetic and organismal mobility, and hybridization. Because (...) the “Darwinian principles” are brought about by both vertical and reticulate evolutionary mechanisms and processes, they should be understood as foundational for a more pluralistic theory of evolution, one that surpasses the classic scope of the Modern and the Neo-Darwinian Synthesis. Reticulate evolution moreover demonstrates that what conventional (Neo-)Darwinian theories treat as intra-species features of evolution frequently involve reticulate interactions between organisms from very different taxonomic categories. Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction therefore cannot be understood as “traits” or “properties” of genes, organisms, species, or ecosystems because the phenomena are irreducible to specific units and levels of an evolutionary hierarchy. Instead, these general principles of evolution need to be understood as common goods that come about through interactions between different units and levels of evolutionary hierarchies, and they are exherent rather than inherent properties of individuals. (shrink)

Summary The common view has been that Darwin regarded species as artificial and arbitrary constructions of taxonomists, not as distinct natural units. However, in his transmutation notebooks he clearly subscribed to the reality of species, on the basis of the criterion of non-interbreeding. A consequence of this biological species concept was his identification of the acquisition of reproductive isolation as the mark of the completion of speciation. He developed in the notebooks a theory of geographic speciation on the grounds of (...) (a) an empirical correlation between barriers and the geographical distributions of allied species, (b) the analogy of artificial isolation in the formation of new domesticated varieties, and (c) the logical consequence of blending inheritance. A brief discussion of Darwin's species concept in later writings concludes the paper. (shrink)

A founder event occurs when a new population is established from a small number of individuals drawn from a large ancestral population. Mayr proposed that genetic drift in an isolated founder population could alter the selective forces in an epistatic system, an observation supported by recent studies. Carson argued that a period of relaxed selection could occur when a founder population is in an open ecological niche, allowing rapid population growth after the founder event. Selectable genetic variation can actually increase (...) during this founder‐flush phase due to recombination, enhanced survival of advantageous mutations, and the conversion of non‐additive genetic variance into additive variance in an epistatic system, another empirically confirmed prediction. Templeton combined the theories of Mayr and Carson with population genetic models to predict the conditions under which founder events can contribute to speciation, and these predictions are strongly confirmed by the empirical literature. Much of the criticism of founder speciation is based upon equating founder speciation to an adaptive peak shift opposed by selection. However, Mayr, Carson and Templeton all modeled a positive interaction of selection and drift, and Templeton showed that founder speciation is incompatible with peak‐shift conditions. Although rare, founder speciation can have a disproportionate importance in adaptive innovation and radiation, and examples are given to show that “rare” does not mean “unimportant” in evolution. Founder speciation also interacts with other speciation mechanisms such that a speciation event is not a one‐dimensional process due to either selection alone or drift alone. BioEssays 30:470–479, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Speciation is a central but elusive issue in evolutionary biology. Over the past sixty years, the subject has been studied within a framework conceived by Ernst Mayr and Theodosius Dobzhansky and subsequently developed further by numerous other workers. In this “isolation” theory, the evolution of reproductive isolation is a key element of speciation; natural selection is given only secondary importance while gene flow is considered prohibitive to the process. In this paper, I argue that certain elements in this approach have (...) produced confusion and irreconcilability among students of speciation. The more prominent debates in speciation (i.e., the species definition, sympatry/allopatry, and the role of reinforcement) all derive from an inherent conflict between the “isolation” theory and Darwin's “selection” view on species and speciation (in which disruptive selection is crucial). New data, mainly from field ecology, molecular population genetics, laboratory studies with Drosophila and computer analysis, all suggest that the isolation theory may no longer be the most desirable vantage point from which to explore speciation. Instead, environmental selection in large populations, often unimpeded by ongoing gene flow, appears to be the decisive element. The traditional preoccupation with reproductive isolation has created gaps in our knowledge of several crucial issues, mainly regarding the role of environmental selection and its connection with mate selection. BioEssays 22:1134–1141, 2000. © 2000 John Wiley & Sons, Inc. (shrink)

The Y chromosome in the XY sex-determination system is often shorter than its X counterpart, a condition attributed to degeneration after Y recombination ceases. Contrary to the traditional view of continuous, gradual degeneration, our study reveals stabilization within large mating populations. In these populations, we demonstrate that both mutant and active alleles on the Y chromosome can reach equilibrium through a mutation-selection balance. However, the emergence of a new species, particularly through the founder effect, can disrupt this equilibrium. Specifically, if (...) the male founders of a new species carry only a mutant allele for a particular Y-linked gene, this allele becomes fixed, leading to the loss of the corresponding active gene on the Y chromosome. Our findings suggest that the rate of Y-chromosome degeneration may be linked to the frequency of speciation events associated with single-male founder events. (shrink)

Intellectual and professional reforms in evolutionary studies between 1935 and 1950 included substantial expansion, diversification, and realignment of community infrastructure. Theodosius Dobzhansky, Julian Huxley and Alfred Emerson organized the Society for the Study of Speciation at the 1939 AAAS Columbus meeting as one response to concerns about ‘isolation’ and ‘lack of contact’ among speciation workers worried about ‘dispersed’ and ‘scattered’ resources in this newly robust ‘borderline’ domain. Simply constructed, the SSS sought neither the radical reorganization of specialities nor the creation (...) of some new discipline. Instead, it was designed to facilitate: to simplify exchange of information and to provide a minimally invasive avenue for connecting disparate researchers. Emerson served as SSS secretary and was its principal agent. After publishing one block of publications, however, the SSS became ‘quiescent’. Anxious to promote his own agenda, Ernst Mayr tried to manoeuvre around Emerson in an effort to revitalize the project. After meeting impediments, he moved his efforts elsewhere. The SSS was too short-lived to merit a claim for major impact within the community; however, it reveals important features of community activity during the synthesis period and stands in contrast to later efforts by George Simpson, Dobzhansky, and Mayr. (shrink)

The crucial phase of speciation is argued to be the evolution of mating cross-incompatibility (prezygotic incompatibility) between the genotypes distinguishing the prospective species populations. Based on this idea, a single-locus model of speciation is presented, which is shown to be biologically plausible and may help to settle the controversy as to the biological significance of single-locus modes of speciation. The model involves three alleles, two of which characterize in homozygous state the prospective species populations and in heterozygous state their hybrids. (...) The third allele represents a mutant which is equivalent to one of the first two alleles with the exception that it inhibits mating with carriers of the third allele. This third allele is fixed in one population and immigrates into a second population which contains the mutant inhibiting matings with members of the former population. Migration in the reverse direction does not occur. Proceeding from a widely applicable concept of fitness and mating preference it is shown that postzygotic incompatibility (hybrid or heterozygote disadvantage) alone suffices to trigger evolutionary replacement of the extant mating relations in the population receiving immigrants by any arbitrary degree of prezygotic incompatibility. This corroborates Wallace's hypothesis and emphasizes the potential biological relevance of speciation by reinforcement (parapatric speciation) at single gene loci. (shrink)

Studying cartoons about the economic crisis and focusing on a pair of scissors as a symbol, I prove how they first turn into unambiguous metaphor for the economic crisis and then experience an evolution in order to adapt to new communication contexts. Along these processes, they undergo more complex changes such as coadaptation and speciation. This has allowed for the scissors meme as a symbol of economic cutbacks to permeate society, and for its metaphorical use to occupy many disparate communication (...) scenarios, unlike other symbolic elements that were also used, but turned out to be less cognitively efficient and therefore offered fewer evolutionary possibilities. (shrink)

Using ideas from evolution and postformal stages of hierarchical complexity, a hypothetical scenario, premised on genetic engineering advances, portrays the development of a new humanoid species, Superions. How would Superions impact and treat current humans? If the Superion scenario came to pass, it would be the ultimate genocidal terrorism of eliminating an entire species, Homo Sapiens. We speculate about defenses Homo Sapiens might mount. The tasks to relate two species (systems) constitutes a postformal, Metasystematic task. Developing a system of discourse (...) to prevent destruction requires postformal Paradigmatic-stage tasks. Implications are twofold: species survival and sufficient evolution to survive. (shrink)

During the 1930s, Aleksandr Promptov—a student of the founder of Russian population genetics Sergei Chetverikov—developed an elaborate concept of speciation in birds. He conducted field investigations aimed at giving a naturalistic content to the theoretical formulations and laboratory models of evolutionary processes advanced within the framework of population genetics, placing particular emphasis on the evolutionary role of bird behavior. Yet, although highly synthetic in combining biogeographical, taxonomic, genetic, ecological, and behavioral studies, Promptov's speciation concept was ignored by the architects of (...) the 1930s and 1940s evolutionary synthesis, including Theodosius Dobzhnasky, Ernst Mayr, and Julian Huxley. In this article, I argue that the story of Promptov's concept and its reception by other evolutionists challenges the traditional presentation of the synthesis as a singular, international process of the unification of biology, which led to the creation of a universal synthetic theory of evolution. It suggests that during the same time period, within largely the same theoretical framework, there were multiple, intrinsically local, attempts at creating synthetic evolutionary concepts. These concepts were often quite particular—in their taxonomic applicability, in their explanations of various evolutionary factors, and in the range of disciplines unified in the synthesis. Apparently, these concepts ran contrary to the universal aspirations of the synthesis architects, and as a result, they were disregarded, first by the architects and later by historians of the evolutionary synthesis. (shrink)

A biological explanation for the dependence of genome-wide mutation-rate variation on local base context is now becoming clearer. The proportions of G + C relative to A + T—expressed as GC%—is a species-specific DNA character. The frequencies of these single bases correlate with frequencies of corresponding oligonucleotides that are more-sensitive indicators of species specificity. Thus, when k = 3 there are 64 possible trinucleotide sequences and a GC%-rich species has a high frequency of GC-rich 3-mers. Closely related species have similar (...) k-mer patterns. For distantly related species, even if happening to have the same GC% values, k-mer patterns are widely discordant. Conventionally, a base substitution mutation is viewed as a chemical 1-mer phenomenon. However, the selective difference by which the corresponding mutation is scored usually relates to context. Thus, an A to U codon mutation in sickle cell anemia, rather than attracting an anticodon in a structural loop of glutamate tRNA, pairs with the more complementary anticodon loop of valine tRNA. Likewise, a recent statistical analysis of genome-wide mutation-rate variation supports the view that a failure of discordant DNA loops to pair at meiosis can initiate and/or sustain the speciation process. Such disharmony among base patterns may have unknowingly been hinted at by geneticist William Bateson who invoked a music metaphor when considering speciation mechanisms. (shrink)

Pierre Trémaux’s 1865 ideas on speciation have been unjustly derided following his acceptance by Marx and rejection by Engels, and almost nobody has read his ideas in a charitable light. Here we offer an interpretation based on translating the term sol as “habitat”, in order to show that Trémaux proposed a theory of allopatric speciation before Wagner and a punctuated equilibrium theory before Gould and Eldredge, and translate the relevant discussion from the French. We believe he may have influenced Darwin’s (...) revision to the third edition of the Origin on rates of evolution, and suggest that Gould’s dismissal of Trémaux is motivated by concern that others might think punctuated equilibrium theory was tainted by a connection with Trémaux. (shrink)

Genes that exert their function when they are introduced into a foreign genetic background pose many questions to our current understanding of the forces and mechanisms that promote either the maintenance or divergence of gene functions over evolutionary time. The melanoma inducing Xmrk oncogene of the Southern platyfish (Xiphophorus maculatus) is a stable constituent of the genome of this species. It displays its tumorigenic function, however, almost exclusively only after inter‐populational or, even more severely, interspecific hybridization events. The Xiphophorus hybrid (...) melanoma system has gained attention in biomedical research as a genetic model for studying tumor formation. From an evolutionary perspective, a prominent question is: how could this gene persist over millions of years? An attractive hypothesis is that Xmrk, acting as a detrimental gene in a hybrid genome, could be a speciation gene that shields the gene pool of its species from mixing with other closely related sympatric species. In this article, I briefly review our current knowledge of the molecular genetics and biochemical functions of the Xmrk gene and discuss aspects of its evolutionary history and presence with respect to this idea. While Xmrk as a potentially injurious oncogene has clearly survived for millions of years, its role as a speciation gene has to be questioned. BioEssays 30:822–832, 2008. © 2008 Wiley Periodicals, Inc. (shrink)