Morphological interpretation of darwinism

The development of evolutionary theory requires the resolution of the problem of relationships between random and regular processes in historical development of biological systems. According to the theory of natural selection, ecological factors play a leading role in evolution. Variations are nondirectional, unpredictable, and provide chaotic diversity of variants, only some of which are potentially useful. However, based on random processes, new variants that are useful for organisms and remain adaptive significance in various ecological situations are infrequent. At the same time, morphology demonstrates certain evolutionary patterns. The morphological approach takes into account the role in evolution of structural features of organism and social systems and evolutionary significance of “constructive technologies,” which distinguish morphological interpretation of evolutionary processes. The constructive and evolutionary patterns revealed in biological systems provide the basis for morphological interpretation of the principle of natural selection: both natural and artificial selection is interaction between social systems (populations, ecosystems, biogeocoenoses) and organisms composing them.     

Collagen matrix as a tool in studying fibroblastic cell behavior

Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes.     

Neutrale Mutationen und evolutionäre Fortentwicklung

Neutral mutation and evolutionary progress The process and causes of regressive evolution are still under debate. Contrary to DARWIN'S original assumption, Neo-Darwinian proponents make selection responsible for reduction. Biologically functionless structures like eye and pigmentation in cave animals deliver excellent material to study this problem. Comparison of regressive (eye, pigmentation, aggression, dorsal light reaction) and constructive traits (gustatory equipment, egg yolk content, feeding behavior) in epigean and cave fish (Astyanax fasciatus, Characidae) reveal a high variability of the regressive features in the cave forms. Contrary to this, the constructive traits are characterized by a low variability in epigean and cave fish. This difference is attributed to the lack of selection on regressive structures. The existence of an intermediate cave population between epigean and true cave fish of A. fasciatus makes possible the study of evolutionary rates. It is shown that the regressive traits do not evolve more quickly than the constructive ones do. On the contrary, constructive traits like egg yolk content are even more rapid because they are of great biological value in the cave biotope. Especially energy economy is claimed by Neo-Darwinists to play a decisive role as a selective force. Comparison of the development of epi- and hypogean larvae of A. fasciatus shows that the formation of a smaller and less differentiated eye in the cave specimens has no effect on body growth. Furthermore, even behavioral traits like aggressiveness, schooling, dorsal light reaction, or negative phototaxis, which all are not performed in darkness by the epigean ancestor, become genetically reduced in the cave fish. The principles of regressive evolution, loss of selection and increase in variability, play a central role in evolution in general. When biota with empty niches are colonized, stabilizing selection relaxes from the special adaptations to the niche inhabited before by the invading species. Variability may arise in these and is permitted as long as fitness is guaranteed. Such processes characterize adaptive radiation. Examples are given by the species flocks on isolated islands or in chemically abnormal lakes like those of the East African Rift Valley. Only secondarily, on the basis of the arisen variability, does directional selection promote the newly developing species into different niches. The loss of stabilizing selection is an important factor for the evolutionary process to be open for evolutionary progress.     

Foundations of the new phylogenetics

Evolutionary idea is the core of the modern biology. Due to this, phylogenetics dealing with historical reconstructions in biology takes a priority position among biological disciplines. The second half of the 20th century witnessed growth of a great interest to phylogenetic reconstructions at macrotaxonomic level which replaced microevolutionary studies dominating during the 30s-60s. This meant shift from population thinking to phylogenetic one but it was not revival of the classical phylogenetics; rather, a new approach emerged that was baptized The New Phylogenetics. It arose as a result of merging of three disciplines which were developing independently during 60s-70s, namely cladistics, numerical phyletics, and molecular phylogenetics (now basically genophyletics). Thus, the new phylogenetics could be defined as a branch of evolutionary biology aimed at elaboration of "parsimonious" cladistic hypotheses by means of numerical methods on the basis of mostly molecular data. Classical phylogenetics, as a historical predecessor of the new one, emerged on the basis of the naturphilosophical worldview which included a superorganismal idea of biota. Accordingly to that view, historical development (the phylogeny) was thought an analogy of individual one (the ontogeny) so its most basical features were progressive parallel developments of "parts" (taxa), supplemented with Darwinian concept of monophyly. Two predominating traditions were diverged within classical phylogenetics according to a particular interpretation of relation between these concepts. One of them (Cope, Severtzow) belittled monophyly and paid most attention to progressive parallel developments of morphological traits. Such an attitude turned this kind of phylogenetics to be rather the semogenetics dealing primarily with evolution of structures and not of taxa. Another tradition (Haeckel) considered both monophyletic and parallel origins of taxa jointly: in the middle of 20th century it was split into phylistics (Rasnitsyn's term; close to Simpsonian evolutionary taxonomy) belonging rather to the classical realm, and Hennigian cladistics that pays attention to origin of monophyletic taxa exclusively. In early of the 20th century, microevolutionary doctrine became predominating in evolutionary studies. Its core is the population thinking accompanied by the phenetic one based on equation of kinship to overall similarity. They were connected to positivist philosophy and hence were characterized by reductionism at both ontological and epistemological levels. It led to fall of classical phylogenetics but created the prerequisites for the new phylogenetics which also appeared to be full of reductionism. The new rise of phylogenetic (rather than tree) thinking during the last third of the 20th century was caused by lost of explanatory power of population one and by development of the new worldview and new epistemological premises. That new worldview is based on the synergetic (Prigoginian) model of development of non-equilibrium systems: evolution of the biota, a part of which is phylogeny, is considered as such a development. At epistemological level, the principal premise appeared to be fall of positivism which was replaced by post-positivism argumentation schemes. Input of cladistics into new phylogenetics is twofold. On the one hand, it reduced phylogeny to cladistic history lacking any adaptivist interpretation and presuming minimal evolution model. From this it followed reduction of kinship relation to sister-group relation lacking any reference to real time scale and to ancestor-descendant relation. On the other hand, cladistics elaborated methodology of phylogenetic reconstructions based on the synapomorphy principle, the outgroup concept became its part. The both inputs served as premises of incorporation of both numerical techniques and molecular data into phylogenetic reconstruction. Numerical phyletics provided the new phylogenetics with easily manipulated algorithms of cladogram construing and thus made phylogenetic reconstructions operational and repetitive. The above phenetic formula "kinship = similarity" appeared to be a keystone for development of the genophyletics. Within numerical phyletics, a lot of computer programs were elaborated which allow to manipulate with evolutionary scenario during phylogenetic reconstructions. They make it possible to reconstruct both clado- and semogeneses based on the same formalized methods. Multiplicity of numerical approaches indicates that, just as in the case of numerical phenetics, choice of adequate method(s) should be based on biologically sound theory. The main input of genophyletics (= molecular phylogenetics) into the new phylogenetics was due to completely new factology which makes it possible to compare directly such far distant taxa as prokaryotes and higher eukaryotes. Genophyletics is based on the theory of neutral evolution borrowed from microevolutionary theory and on the molecular clock hypothesis which is now considered largely inadequate. The future developments of genophyletics will be aimed at clarification of such fundamental (and "classical" by origin) problems as application of character and homology concepts to molecular structures. The new phylogenetics itself is differentiated into several schools caused basically by diversity of various approaches existing within each of its "roots". Cladistics makes new phylogenetics splitted into evolutionary and parsimonious ontological viewpoints. Numerical phyletics divides it into statistical and (again) parsimonious methodologies. Molecular phylogenetics is opposite by its factological basis to morphological one. The new phylogenetics has significance impact onto the "newest" systematics. From one side, it gives ontological status back to macrotaxa they have lost due to "new" systematics based on population thinking. From another side, it rejects some basical principles of classical phylogenetic (originally Linnean) taxonomy such as recognitions of fixed taxonomic ranks designated by respective terms and definition of taxic names not by the diagnostic characters but by reference to the ancestor. The latter makes the PhyloCode overburdened ideologically and the "newest" systematics self-controversial, as concept of ancestor has been acknowledged non-operational from the very beginning of cladistics. Relation between classical and new phylogenetics is twofold. At the one hand, general phylogenetic hypothesis (in its classical sense) can be treated as a combination of cladogenetic and semogenetic reconstructions. Such a consideration is bound to pay close attention to the uncertainty relation principle which, in case of the phylogenetics, means that the general phylogenetic hypothesis cannot be more certain than any of initial cladogenetic or semogenetic hypotheses. From this standpoint, the new phylogenetics makes it possible to reconstruct phylogeny following epistemological principle "from simple to complex". It elaborates a kind of null hypotheses about evolutionary history which are more easy to test as compared to classical hypotheses. Afterward, such hypotheses are possible to be completed toward the classical, more content-wise ones by adding anagenetic information to the cladogenetic one. At another hand, reconstructions elaborated within the new phylogenetics could be considered as specific null hypotheses about both clado- and semogeneses. They are to be tested subsequently by mean of various models, including those borrowed from "classical" morphology. The future development of the new phylogenetics is supposed to be connected with getting out of plethora of reductionism inherited by it from population thinking and specification of object domain of the phylogenetics. As the latter is a part of an evolutionary theory, its future developments will be adjusted with the latter. Lately predominating neodarwinism is now being replaced by the epigenetic evolutionary theory to which phylistics (one of the modern versions of classical phylogenetics) seems to be more correspondent.     

Effect of fasting on the structure and function of the gastrointestinal tract of house sparrows (Passer domesticus)

Starvation is a condition that often affects animals in nature. The gastrointestinal tract is the organ system displaying the most rapid and dramatic changes in response to nutrient deprivation. To date, little is known about starvation phases and effects on the organ morphology and digestive function in small passerine birds. In this study, we determined the phases of starvation and examined the effect of final stage of starvation in the organ morphology and, intestinal histology and enzymatic function in the small intestine. Our results show the three phases of the classical model of fasting in a shorter period of time. The mass of heart, pancreas, stomach, small intestine and liver of long-term fasted birds was reduced between 20 and 47%. The mass decrease in small intestine was correlated with reduction in small intestinal histology: perimeter, mucosal thickness, villus height and width. In contrast, the enzyme activity of sucrase-isomaltase and aminopeptidase-N in enterocytes, all expressed per μg of protein, was higher in long-term fasted birds than fed animals. This suggest that, while autophagy of digestive organs is induced by starvation, consistent with phenotypic plasticity, the activity of sucrase-isomaltase and aminopeptidase-N remains high, probably as an anticipatory strategy to optimize digestion at re-feeding time.     

Ontogenetic systematics: The synthesis of taxonomy, phylogenetics, and evolutionary developmental biology

The main purpose of the present review is to draw attention to growing problems in the modern systematics and phylogenetics which are presently underestimated by the professional community. The dramatic reduction of the importance of ontogeny and morphology in phylogenetic studies of the second part of the 20th century is considered among the major factors of the modern taxonomic and evolutionary paradigm. The deep contradiction of modern approaches, which either merely consider systematics and phylogeny as genealogy or even in a neotypolgical manner irrespective of the evolutionary idea, is demonstrated. Thus, despite the widespread opinion that the evolutionary theory is the major basis for taxonomy, the processes, which in fact caused the origin and formation of the systematic hierarchy are often considered as redundant for the procedure of classification. In this respect, the classical, but well forgotten statement that evolution is a modification of ontogeny is specially highlighted. Tight relationships between evolution, ontogeny, systematics, and phylogenetics are prima facie obvious, but also presently underestimated, although the field of the evo-devo is continuously growing. Paradoxically, even despite the outburst of various molecular ontogenetic approaches, the commonly accepted evolutionary paradigm still lacks a general theory for changes in the shape of organisms. As a step towards the development of such a theory, a synthesis (or more exactly, resynthesis) of still largely independently developing major biological fields, i.e., ontogenetic and evolutionary studies, on the one hand, and traditional taxonomy, on the other hand, a new concept of ontogenetic systematics is proposed. The new concept is intended for integration of supposedly ??immobile?? traditional taxonomy with the dynamics, but predominantly considered as hypothetical, evolutionary field based on the process of ontogeny, which, in contrast to the evolution itself, can be observed in the real time. Therefore, it is concluded that, for instance, the evolution of the main group of living organisms Metazoa, is primarily the evolution of a very limited number of ontogenetic cycles that were formed as early as the Early Cambrian. A significant underestimation of cyclic properties of ontogeny in the evolution and systematics is shown. Using two model groups, echinoderms of the class Ophiuroidea and dorid nudibranch mollusks (Gastropoda: Doridacea), practical importance of the integrative approach developed here is demonstrated. The ??disruption?? of the ancestral ontogenetic cycle and further formation of a new descendant cycle (which implies some continuity of ancestral and descendant characters) is considered to be a major evolutionary pattern. The model proposed implies either progressive (addition of stages and characters) or regressive (reduction of already existing stages and structures) modification of ancestral taxon, the diagnosis of which corresponds to the model of its ontogenetic cycle. In the extreme cases of disruption of the ancestral ontogenetic cycle, adult characters of descendants are substituted by juvenile ancestral features, demonstrating paedomorphoses in the narrow sense. Within the framework of the approach proposed, the evolutionary and ontogenetic models of ancestral ontogenetic cycles of brittle stars and dorid nudibranchs are developed and discussed. Based on the original material of the extinct Paleozoic ophiuroid group Oegophiurida, the origin of key evolutionary novelties is discussed. A major conclusion of the present review is the high necessity of integration of new molecular data with already well-established taxonomic hierarchy and ontogenetic information as a basis for the development of the general theory of transformations of organisms, i.e., the theory of evolution in its true sense.     

Diversification of inflorescence development in the PCK clade (Poaceae: Panicoideae: Paniceae)

In grasses, inflorescence diversification and its correlation with species evolution are intriguing and not well understood. Part of this problem lies in our lack of comprehension about the inflorescence morphological complexity of grasses. We focused our study on the PCK clade (named for phosphoenol pyruvate carboxykinase), a well-supported monophyletic group for which the relationships among its taxa are not well resolved. Interestingly, the PCK clade has an extensive diversity of adult inflorescence forms. A comparative developmental approach can help us to understand the basis of such morphological differences as well as provide characters that can be used in phylogenetic studies of the group. Using SEM studies, we demonstrate that inflorescence morphology in this clade is even more complex than what is typically observed in adult forms. We describe a number of new characters, and some classical features previously used for taxonomic purposes are redefined on the basis of development. We also define four morphological groups combining adult inflorescence form and development, and we discuss some of the evolutionary aspects of inflorescence diversification in the PCK clade. Taxonomic delimitation among genera in the PCK clade remains confusing and unclear where molecular and morphological studies support different classifications.     

Dynamic multipopulation and density dependent evolutionary games related to replicator dynamics. A metasimplex concept

This paper contains the basic extensions of classical evolutionary games (multipopulation and density dependent models). It is shown that classical bimatrix approach is inconsistent with other approaches because it does not depend on proportion between populations. The main conclusion is that interspecific proportion parameter is important and must be considered in multipopulation models. The paper provides a synthesis of both extensions (a metasimplex concept) which solves the problem intrinsic in the bimatrix model. It allows us to model interactions among any number of subpopulations including density dependence effects. We prove that all modern approaches to evolutionary games are closely related. All evolutionary models (except classical bimatrix approaches) can be reduced to a single population general model by a simple change of variables. Differences between classic bimatrix evolutionary games and a new model which is dependent on interspecific proportion are shown by examples.     

Experimentally evolved and phenotypically plastic responses to enforced monogamy in a hermaphroditic flatworm

Sexual selection is considered a potent evolutionary force in all sexually reproducing organisms, but direct tests in terms of experimental evolution of sexual traits are still lacking for simultaneously hermaphroditic animals. Here, we tested how evolution under enforced monogamy affected a suite of reproductive traits (including testis area, sex allocation, genital morphology, sperm morphology and mating behaviour) in the outcrossing hermaphroditic flatworm Macrostomum lignano, using an assay that also allowed the assessment of phenotypically plastic responses to group size. The experiment comprised 32 independent selection lines that evolved under either monogamy or polygamy for 20 generations. While we did not observe an evolutionary shift in sex allocation, we detected effects of the selection regime for two male morphological traits. Specifically, worms evolving under enforced monogamy had a distinct shape of the male copulatory organ and produced sperm with shorter appendages. Many traits that did not evolve under enforced monogamy showed phenotypic plasticity in response to group size. Notably, individuals that grew up in larger groups had a more male‐biased sex allocation and produced slightly longer sperm than individuals raised in pairs. We conclude that, in this flatworm, enforced monogamy induced moderate evolutionary but substantial phenotypically plastic responses.     

Evo-devo and the search for homology (“sameness”) in biological systems

Developmental biology and evolutionary studies have merged into evolutionary developmental biology (“evo-devo”). This synthesis already influenced and still continues to change the conceptual framework of structural biology. One of the cornerstones of structural biology is the concept of homology. But the search for homology (“sameness”) of biological structures depends on our favourite perspectives (axioms, paradigms). Five levels of homology (“sameness”) can be identified in the literature, although they overlap to some degree: (i) serial homology (homonomy) within modular organisms, (ii) historical homology (synapomorphy), which is taken as the only acceptable homology by many biologists, (iii) underlying homology (i.e., parallelism) in closely related taxa, (iv) deep evolutionary homology due to the “same” master genes in distantly related phyla, and (v) molecular homology exclusively at gene level. The following essay gives emphasis on the heuristic advantages of seemingly opposing perspectives in structural biology, with examples mainly from comparative plant morphology. The organization of the plant body in the majority of angiosperms led to the recognition of the classical root–shoot model. In some lineages bauplan rules were transcended during evolution and development. This resulted in morphological misfits such as the Podostemaceae, peculiar eudicots adapted to submerged river rocks. Their transformed “roots” and “shoots” fit only to a limited degree into the classical model which is based on either–or thinking. It has to be widened into a continuum model by taking over elements of fuzzy logic and fractal geometry to accommodate for lineages such as the Podostemaceae.     

A simplified method of tissue processing for immunostaining with good preservation of antigens and morphology

A simple and rapid method of tissue processing has been developed for immunostaining. Human and murine tissues were fixed in a PVA solution, diluted in a special buffer and embedded in paraffin or stored in a stock solution before preparing frozen sections. By indirect immunofluorescence, several antigens (collagen isotypes, laminin and fibronectin) were better demonstrated in the samples processed by the present method than with frozen or deparaffinized sections. In addition, this method allows a histological preservation quite identical to that seen in classical histology.     

Evolutionary profiles derived from the QR factorization of multiple structural alignments gives an economy of information

We present a new algorithm, based on the multidimensional QR factorization, to remove redundancy from a multiple structural alignment by choosing representative protein structures that best preserve the phylogenetic tree topology of the homologous group. The classical QR factorization with pivoting, developed as a fast numerical solution to eigenvalue and linear least-squares problems of the form Ax=b, was designed to re-order the columns of A by increasing linear dependence. Removing the most linear dependent columns from A leads to the formation of a minimal basis set which well spans the phase space of the problem at hand. By recasting the problem of redundancy in multiple structural alignments into this framework, in which the matrix A now describes the multiple alignment, we adapted the QR factorization to produce a minimal basis set of protein structures which best spans the evolutionary (phase) space. The non-redundant and representative profiles obtained from this procedure, termed evolutionary profiles, are shown in initial results to outperform well-tested profiles in homology detection searches over a large sequence database. A measure of structural similarity between homologous proteins, Q(H), is presented. By properly accounting for the effect and presence of gaps, a phylogenetic tree computed using this metric is shown to be congruent with the maximum-likelihood sequence-based phylogeny. The results indicate that evolutionary information is indeed recoverable from the comparative analysis of protein structure alone. Applications of the QR ordering and this structural similarity metric to analyze the evolution of structure among key, universally distributed proteins involved in translation, and to the selection of representatives from an ensemble of NMR structures are also discussed.     

Evolution of craniofacial novelty in parrots through developmental modularity and heterochrony

Parrots (order Psittaciformes) have developed novel cranial morphology. At the same time, they show considerable morphological diversity in the cranial musculoskeletal system, which includes two novel structures: the suborbital arch and the musculus (M.) pseudomasseter. To understand comprehensively the evolutionary pattern and process of novel cranial morphology in parrots, phylogenetic and developmental studies were conducted. Firstly, we undertook phylogenetic analyses based on mitochondrial ribosomal RNA gene sequences to obtain a robust phylogeny among parrots, and secondly we surveyed the cranial morphology of parrots extensively to add new information on the character states. Character mapping onto molecular phylogenies indicated strongly the repeated evolution of both the suborbital arch and the well-developed M. pseudomasseter within parrots. These results also suggested that the direction of evolutionary change is not always identical in the two characters, implying that these characters are relatively independent or decoupled structures behaving as separate modules. Finally, we compared the developmental pattern of jaw muscles among bird species and found a difference in the timing of M. pseudomasseter differentiation between the cockatiel Nymphicus hollandicus (representative of a well-developed condition) and the peach-faced lovebird Agapornis roseicollis (representative of an underdeveloped condition). On the basis of this study, we suggest that in the development of novel traits, modularity and heterochrony facilitate the diversification of parrot cranial morphology.     

Sex in an Evolutionary Perspective: Just Another Reaction Norm

It is common to refer to all sorts of clear-cut differences between the sexes as something that is biologically almost inevitable. Although this does not reflect the status of evolutionary theory on sex determination and sexual dimorphism, it is probably a common view among evolutionary biologists as well, because of the impact of sexual selection theory. To get away from thinking about biological sex and traits associated with a particular sex as something static, it should be recognized that in an evolutionary perspective sex can be viewed as a reaction norm, with sex attributes being phenotypically plastic. Sex determination itself is fundamentally plastic, even when it is termed “genetic”. The phenotypic expression of traits that are statistically associated with a particular sex always has a plastic component. This plasticity allows for much more variation in the expression of traits according to sex and more overlap between the sexes than is typically acknowledged. Here we review the variation and frequency of evolutionary changes in sex, sex determination and sex roles and conclude that sex in an evolutionary time-frame is extremely variable. We draw on recent findings in sex determination mechanisms, empirical findings of morphology and behaviour as well as genetic and developmental models to explore the concept of sex as a reaction norm. From this point of view, sexual differences are not expected to generally fall into neat, discrete, pre-determined classes. It is important to acknowledge this variability in order to increase objectivity in evolutionary research.     

Combined In Situ Zymography, Immunofluorescence, And Staining Of Iron Oxide Particles In Paraffin-embedded, Zinc-fixed Tissue Sections

AbstractSuperparamagnetic iron oxide particles are used as potent contrast agents in magnetic resonance imaging. In histology, these particles are frequently visualized by Prussian blue iron staining of aldehyde-fixed, paraffin-embedded tissues. Recently, zinc salt-based fixative was shown to preserve enzyme activity in paraffin-embedded tissues. In this study, we demonstrate that zinc fixation allows combining in situ zymography with fluorescence immunohistochemistry (IHC) and iron staining for advanced biologic investigation of iron oxide particle accumulation. Very small iron oxide particles, developed for magnetic resonance angiography, were applied intravenously to BALB/c nude mice. After 3 hours, spleens were explanted and subjected to zinc fixation and paraffin embedding. Cut tissue sections were further processed to in situ zymography, IHC, and Prussian blue staining procedures. The combination of in situ zymography as well as IHC with subsequent Prussian blue iron staining on zinc-fixed paraffin-embedded tissues resulted in excellent histologic images of enzyme activity, protease distribution, and iron oxide particle accumulation. The combination of all three stains on a single section allowed direct comparison with only moderate degradation of fluorescein isothiocyanate-labeled substrate. This protocol is useful for investigating the biologic environment of accumulating iron oxide particles, with excellent preservation of morphology.     

Semiotic Mechanisms Underlying Niche Construction

The explanatory value of niche construction can be strengthened by firm footing in semiotic theory. Anthropologists have a unique perspective on the integration of such diverse approaches to human action and evolutionary processes. Here, we seek to open a dialogue between anthropology and biosemiotics. The overarching aim of this paper is to demonstrate that niche construction, including the underlying mechanism of reciprocal causation, is a semiotic process relating to biological development (sensu stricto) as well as cognitive development and cultural change. In making this argument we emphasize the semiotic mechanisms underlying the niche concept. We argue that the “niche” in ecology and evolutionary biology can be consistent with the Umwelt of Jakob von Uexkull. Following John Deely we therefore suggest that investigations into the organism—environment interface constituting niche construction should emphasize the semiotic basis of experience. Peircean signs are pervasive and allow for flexible interpretations of phenomena in relation to the perceptual and cognitive capacities of the behaving organism, which is particularly pertinent for understanding the relation of proximate/ultimate selective forces as co-productive (i.e., reciprocal). Additionally, theoretical work by Kinji Imanishi on the evolution of daily life and Gregory Bateson’s relational view of evolution both support the linkage between proximate and ultimate evolutionary processes of causation necessitated by the niche construction perspective. We will then apply this theoretical framework to two specific examples: 1) hominin evolution, including uniquely human cultural behaviors with niche constructive implications; and 2) the multispecies and anthropocentric niche of human-dog coevolution from which complex cognitive capacities and semiotic relationships emerged. The intended outcome of this paper is the establishment of concrete semiotic mechanisms and theory underlying niche constructive behavior which can then be applied to a broad spectrum of organisms to contextualize the reciprocal relation between proximate and ultimate drivers of behavior.     

Cavefish as a model system in evolutionary developmental biology

The Mexican tetra Astyanax mexicanus has many of the favorable attributes that have made the zebrafish a model system in developmental biology. The existence of eyed surface (surface fish) and blind cave (cavefish) dwelling forms in Astyanax also provides an attractive system for studying the evolution of developmental mechanisms. The polarity of evolutionary changes and the environmental conditions leading to the cavefish phenotype are known with certainty, and several different cavefish populations have evolved constructive and regressive changes independently. The constructive changes include enhancement of the feeding apparatus (jaws, taste buds, and teeth) and the mechanosensory system of cranial neuromasts. The homeobox gene Prox 1, which is expressed in the expanded taste buds and cranial neuromasts, is one of the genes involved in the constructive changes in sensory organ development. The regressive changes include loss of pigmentation and eye degeneration. Although adult cavefish lack functional eyes, small eye primordia are formed during embryogenesis, which later arrest in development, degenerate, and sink into the orbit. Apoptosis and lens signaling to other eye parts, such as the cornea, iris, and retina, result in the arrest of eye development and ultimate optic degeneration. Accordingly, an eye with restored cornea, iris, and retinal photoreceptor cells is formed when a surface fish lens is transplanted into a cavefish optic cup, indicating that cavefish optic tissues have conserved the ability to respond to lens signaling. Genetic analysis indicates that multiple genes regulate eye degeneration, and molecular studies suggest that Pax6 may be one of the genes controlling cavefish eye degeneration. Further studies of the Astyanax system will contribute to our understanding of the evolution of developmental mechanisms in vertebrates.