Evolution & Development最新文献

The body patterning of trochophore larvae is important for understanding spiralian evolution and the origin of the bilateral body plan. However, considerable variations are observed among spiralian lineages, which have adopted varied strategies to develop trochophore larvae or even omit a trochophore stage. Some spiralians, such as patellogastropod mollusks, are suggested to exhibit ancestral traits by producing equal-cleaving fertilized eggs and possessing “typical” trochophore larvae. In recent years, we developed a potential model system using the patellogastropod Lottia peitaihoensis (= Lottia goshimai). Here, we introduce how the species were selected and establish sources and techniques, including gene knockdown, ectopic gene expression, and genome editing. Investigations on this species reveal essential aspects of trochophore body patterning, including organizer signaling, molecular and cellular processes connecting the various developmental functions of the organizer, the specification and behaviors of the endomesoderm and ectomesoderm, and the characteristic dorsoventral decoupling of Hox expression. These findings enrich the knowledge of trochophore body patterning and have important implications regarding the evolution of spiralians as well as bilateral body plans.

Eremurus was described at the beginning of the 19th century. However, due to limited sampling and the small number of gene markers to date, its phylogeny and evolution are largely unknown. In this study, we analyzed plastomes from 27 species belonging to 2 subgenera and 3 sections of Eremurus, which are found in Central Asia (its center of diversity) and China. We also analyzed nuclear DNA ITS of 33 species, encompassing all subgenera and sections of the genus in Central Asia, southwest Asia and China. Our findings revealed that the genus was monophyletic, although both subgenera Eremurus and Henningia were found to be paraphyletic. Both plastome and nrDNA-based phylogenetic trees had three clades that did not reflect the current taxonomy of the genus. Our biogeographical and time-calibrated trees suggest that Eremurus originated in the ancient Tethyan area in the second half of the Eocene. Diversification of Eremurus occurred from the early Oligocene to the late Miocene. Paratethys Sea retreat and several orogenetic events, such as the progressive uplift of the Qinghai-Tibet Plateau and surrounding mountain belts (Altai, Pamir, Tian Shan), caused serious topographic and climate (aridification) changes in Central Asia that may have triggered a split of clades and speciation. In this transformed Central Asia, speciation proceeded rapidly driven mainly by vicariance caused by numerous mountain chains and specialization to a variety of climatic, topographic and soil conditions that exist in this region.

Understanding general principles about the origin of species remains one of the foundational challenges in evolutionary biology. The genomic divergence between groups of individuals can spawn hybrid inviability and hybrid sterility, which presents a tantalizing developmental problem. Divergent developmental programs may yield either conserved or divergent phenotypes relative to ancestral traits, both of which can be responsible for reproductive isolation during the speciation process. The genetic mechanisms of developmental evolution involve cis- and trans-acting gene regulatory change, protein–protein interactions, genetic network structures, dosage, and epigenetic regulation, all of which also have roots in population genetic and molecular evolutionary processes. Toward the goal of demystifying Darwin's “mystery of mysteries,” this review integrates microevolutionary concepts of genetic change with principles of organismal development, establishing explicit links between population genetic process and developmental mechanisms in the production of macroevolutionary pattern. This integration aims to establish a more unified view of speciation that binds process and mechanism.

Adaptation to different environments can be achieved by physiological shifts throughout development. Hormonal regulators shape the physiological and morphological traits of the evolving animals making them fit for the particular ecological surroundings. We hypothesized that the artificially induced hypersynthesis of calcitonin and parathyroid hormone mutually influencing calcium metabolism could affect bone formation during early ontogeny in fish imitating the heterochrony in craniofacial ossification in natural adaptive morphs. Conducting an experiment, we found that the long-standing treatment of salmonid juveniles with high doses of both hormones irreversibly shifts the corresponding hormone status for a period well beyond the time scale for total degradation of the injected hormone. The hormones program the ossification of the jaw suspension bones and neurocranial elements in a specific manner affecting the jaws position and pharingo-branchial area stretching. These morphological shifts resemble the adaptive variants found in sympatric pelagic and demersal morphs of salmonids. We conclude that solitary deviations in the regulators of calcium metabolism could determine functional morphological traits via transformations in skeletal development.

Organisms construct their own environments and phenotypes through the adaptive processes of habitat choice, habitat construction, and phenotypic plasticity. We examine how these processes affect the dynamics of mean fitness change through the environmental change term of the Price Equation. This tends to be ignored in evolutionary theory, owing to the emphasis on the first term describing the effect of natural selection on mean fitness (the additive genetic variance for fitness of Fisher's Fundamental Theorem). Using population genetic models and the Price Equation, we show how adaptive niche constructing traits favorably alter the distribution of environments that organisms encounter and thereby increase population mean fitness. Because niche-constructing traits increase the frequency of higher-fitness environments, selection favors their evolution. Furthermore, their alteration of the actual or experienced environmental distribution creates selective feedback between niche constructing traits and other traits, especially those with genotype-by-environment interaction for fitness. By altering the distribution of experienced environments, niche constructing traits can increase the additive genetic variance for such traits. This effect accelerates the process of overall adaption to the niche-constructed environmental distribution and can contribute to the rapid refinement of alternative phenotypic adaptations to different environments. Our findings suggest that evolutionary biologists revisit and reevaluate the environmental term of the Price Equation: owing to adaptive niche construction, it contributes directly to positive change in mean fitness; its magnitude can be comparable to that of natural selection; and, when there is fitness G × E, it increases the additive genetic variance for fitness, the much-celebrated first term.

We compare and contrast two theoretical perspectives on adaptive evolution—the orthodox Modern Synthesis perspective, and the nascent Agential Perspective. To do so, we develop the idea from Rasmus Grønfeldt Winther of a ‘countermap’, as a means for comparing the respective ontologies of different scientific perspectives. We conclude that the modern Synthesis perspective achieves an impressively comprehensive view of a universal set of dynamical properties of populations, but at the considerable cost of radically distorting the nature of the biological processes that contribute to evolution. For its part, the Agential Perspective offers the prospect of representing the biological processes of evolution with much greater fidelity, but at the expense of generality. Trade-offs of this sort are endemic to science, and inevitable. Recognizing them helps us to avoid the pitfalls of ‘illicit reification’, i.e. the mistake of interpreting a feature of a scientific perspective as a feature of the non-perspectival world. We argue that much of the traditional Modern Synthesis representation of the biology of evolution commits this illicit reification.

Organisms modify their development and function in response to the environment. At the same time, the environment is modified by the activities of the organism. Despite the ubiquity of such dynamical interactions in nature, it remains challenging to develop models that accurately represent them, and that can be fitted using data. These features are desirable when modeling phenomena such as phenotypic plasticity, to generate quantitative predictions of how the system will respond to environmental signals of different magnitude or at different times, for example, during ontogeny. Here, we explain a modeling framework that represents the organism and environment as a single coupled dynamical system in terms of inputs and outputs. Inputs are external signals, and outputs are measurements of the system in time. The framework uses time-series data of inputs and outputs to fit a nonlinear black-box model that allows to predict how the system will respond to novel input signals. The framework has three key properties: it captures the dynamical nature of the organism–environment system, it can be fitted with data, and it can be applied without detailed knowledge of the system. We study phenotypic plasticity using in silico experiments and demonstrate that the framework predicts the response to novel environmental signals. The framework allows us to model plasticity as a dynamical property that changes in time during ontogeny, reflecting the well-known fact that organisms are more or less plastic at different developmental stages.