Evolutionary Cascade Research Articles

Convergent evolution of cardiac-glycoside resistance in predators and parasites of milkweed herbivores

The community of plant-feeding insects (herbivores) that specialize on milkweeds (Apocynaceae) form a remarkable example of convergent evolution across levels of biological organization1. In response to toxic cardiac glycosides produced by these plants, the monarch butterfly (Danaus plexippus) and other specialist herbivores have evolved parallel substitutions in the alpha subunit (ATPA) of the Na+/K+-ATPase. These substitutions render the pump insensitive to cardiac glycosides2,3, allowing the monarch and other specialists, from aphids to beetles, to sequester cardiac glycosides, which in turn provide defense against attacks by enemies from the third trophic level4. The evolution of 'target-site-insensitivity' substitutions in these herbivores poses a fundamental biological question: have predators and parasitoids that feed on cardiac-glycoside-sequestering insects also evolved Na+/K+-ATPases that are similarly insensitive to cardiac glycosides (as predicted by Whiteman and Mooney)5? In other words, can plant toxins cause evolutionary cascades that reach the third trophic level? Here we show that at least four enemies of the monarch and other milkweed herbivores have indeed evolved amino-acid substitutions associated with target-site insensitivity to cardiac glycosides. These attackers represent four major animal clades, implicating cardiac glycosides as keystone molecules6 and establishing ATPalpha, which encodes ATPA, as a keystone gene with effects that reverberate within ecological communities7.

Degree of anisogamy is unrelated to the intensity of sexual selection

Males and females often display different behaviours and, in the context of reproduction, these behaviours are labelled sex roles. The Darwin–Bateman paradigm argues that the root of these differences is anisogamy (i.e., differences in size and/or function of gametes between the sexes) that leads to biased sexual selection, and sex differences in parental care and body size. This evolutionary cascade, however, is contentious since some of the underpinning assumptions have been questioned. Here we investigate the relationships between anisogamy, sexual size dimorphism, sex difference in parental care and intensity of sexual selection using phylogenetic comparative analyses of 64 species from a wide range of animal taxa. The results question the first step of the Darwin–Bateman paradigm, as the extent of anisogamy does not appear to predict the intensity of sexual selection. The only significant predictor of sexual selection is the relative inputs of males and females into the care of offspring. We propose that ecological factors, life-history and demography have more substantial impacts on contemporary sex roles than the differences of gametic investments between the sexes.

Predicting Metastasis from Cues of Metastatic Cancer Stem-like Cells-3D-Ultrasensitive Metasensor at a Single-Cell Level.

Metastasis is the primary reason for treatment failure and cancer-related deaths. Hence forecasting the disease in its primary state can advance the prognosis. However, existing techniques fail to reveal the tumor heterogeneity or its evolutionary cascades; hence they are not feasible to predict the onset of metastatic cancer. The key to metastasis originates from the primary tumor cells, evolving by inheriting multistep sequential cue signals. We have identified this specific population, termed metastatic cancer stem-like cells (MCSCs), to foresee cancer's ability to metastasize. An invasive property renders MCSCs nonadherent, summoning a powerful technique to forecast metastasis. Thus, we have generated an ultrasensitive 3D-metasensor to efficiently capture and investigate MCSCs and magnify the vital premetastatic signals from a single cell. We developed 3D-metasensor by an ultrafast laser ionization technique, consisting of self-assembled three-dimensionally organized nanoprobes incorporated with dopant functionalities. This distinct methodology establishes attachment with nonadherent MCSCs, elevates Raman activity, and enables probing of consequent signals (metabolic, proliferation, and metastatic) specifically altered in MCSCs. Extensive analysis using prediction tools-the area under the curve (AUC) and principal component analysis (PCA)-revealed high sensitivity (100%) and specificity (80%) to differentiate the MCSCs from other populations. Further, investigation reveals that the cue signal level from MCSCs of primary cancer is analogous to MCSCs from higher-level tumors, disclosing the relative dependence to estimate the primary tumor's capacity to metastasize. Multiple spectrum evaluation using the metasensor pinpoint the dynamic cues in MCSCs predict the onset of metastasis; thus, exploring these metastasis hallmarks can enhance prognosis and revolutionize therapy strategies.

Genome wide identification, classification and functional characterization of heat shock transcription factors in cultivated and ancestral cottons (Gossypium spp.)

Heat shock transcription factors (HSF) have been demonstrated to play a significant transcriptional regulatory role in plants and considered as an integral part of signal transduction pathways against environmental stresses especially heat stress. Despite of their importance, HSFs have not yet been identified and characterized in all cotton species. In this study, we report the identification of 42, 39, 67, and 79 non-redundant HSF genes from diploid cottons G. arboreum (A2) and G. raimondii (D5), and tetraploid cottons G. barbadense (AD2) and G. hirsutum (AD1) respectively. The chromosome localization of identified HSFs revealed their random distribution on all the 13 chromosomes of A and D genomes of cotton with few regions containing HSFs in clusters. The genes structure and conserved domain analysis revealed the family-specific conservation of intron/exon organization and conserved domains in HSFs. Various abiotic stress-related cis-regulatory elements were identified from the putative promoter regions of cotton HSFs suggesting their possible role in mediating abiotic stress tolerance. The combined phylogenetic analysis of all the cotton HSFs grouped them into three subfamilies; with 145 HSFs belong to class A, 85 to class B, and 17 to class C subfamily. Moreover, a detailed analysis of HSF gene family in four species of cotton elucidated the role of allopolyploid and hybridization during evolutionary cascade of allotetraploid cotton. Comparatively, existence of more orthologous genes in cotton species than Arabidopsis, advocated that polyploidization produced new cotton specific orthologous gene clusters. Phylogenetic, collinearity and multiple synteny analyses exhibited dispersed, segmental, proximal, and tandem gene duplication events in HSF gene family. Duplication of gene events suggests that HSF gene family of cotton evolution was under strong purifying selection. Expression analysis revealed that GarHSF04 were found to be actively involved in PEG and salinity tolerance in G. arboreum. GhiHSF14 upregulated in heat and downregulated in salinity whilst almost illustrated similar behavior under cold and PEG treatments and GhiHSF21 exhibited down regulation almost across all the stresses in G. hirsutum. Overwhelmingly, present study paves the way to better understand the evolution of cotton HSF TFs and lays a foundation for future investigation of HSFs in improving abiotic stress tolerance in cotton.

Phoretic dispersal influences parasite population genetic structure.

Dispersal is a fundamental component of the life history of most species. Dispersal influences fitness, population dynamics, gene flow, genetic drift and population genetic structure. Even small differences in dispersal can alter ecological interactions and trigger an evolutionary cascade. Linking such ecological processes with evolutionary patterns is difficult, but can be carried out in the proper comparative context. Here, we investigate how differences in phoretic dispersal influence the population genetic structure of two different parasites of the same host species. We focus on two species of host-specific feather lice (Phthiraptera: Ischnocera) that co-occur on feral rock pigeons (Columba livia). Although these lice are ecologically very similar, "wing lice" (Columbicola columbae) disperse phoretically by "hitchhiking" on pigeon flies (Diptera: Hippoboscidae), while "body lice" (Campanulotes compar) do not. Differences in the phoretic dispersal of these species are thought to underlie observed differences in host specificity, as well as the degree of host-parasite cospeciation. These ecological and macroevolutionary patterns suggest that body lice should exhibit more genetic differentiation than wing lice. We tested this prediction among lice on individual birds and among lice on birds from three pigeon flocks. We found higher levels of genetic differentiation in body lice compared to wing lice at two spatial scales. Our results indicate that differences in phoretic dispersal can explain microevolutionary differences in population genetic structure and are consistent with macroevolutionary differences in the degree of host-parasite cospeciation.

Egg chemoattractants moderate intraspecific sperm competition.

Interactions among eggs and sperm are often assumed to generate intraspecific variation in reproductive fitness, but the specific gamete‐level mechanisms underlying competitive fertilization success remain elusive in most species. Sperm chemotaxis–the attraction of sperm by egg‐derived chemicals—is a ubiquitous form of gamete signaling, occurring throughout the animal and plant kingdoms. The chemical cues released by eggs are known to act at the interspecific level (e.g., facilitating species recognition), but recent studies have suggested that they could have roles at the intraspecific level by moderating sperm competition. Here, we exploit the experimental tractability of a broadcast spawning marine invertebrate to test this putative mechanism of gamete‐level sexual selection. We use a fluorescently labeled mitochondrial dye in mussels to track the real‐time success of sperm as they compete to fertilize eggs, and provide the first direct evidence in any species that competitive fertilization success is moderated by differential sperm chemotaxis. Furthermore, our data are consistent with the idea that egg chemoattractants selectively attract ejaculates from genetically compatible males, based on relationships inferred from both nuclear and mitochondrial genetic markers. These findings for a species that exhibits the ancestral reproductive strategy of broadcast spawning have important implications for the numerous species that also rely on egg chemoattractants to attract sperm, including humans, and have potentially important implications for our understanding of the evolutionary cascade of sexual selection.

Evolutionary cascades induced by large frugivores

Large, fruit-eating vertebrates have been lost from many of the world's ecosystems. The ecological consequences of this defaunation can be severe, but the evolutionary consequences are nearly unknown because it remains unclear whether frugivores exert strong selection on fruit traits. I assessed the macroevolution of fruit traits in response to variation in the diversity and size of seed-dispersing vertebrates. Across the Indo-Malay Archipelago, many of the same plant lineages have been exposed to very different assemblages of seed-dispersing vertebrates. Phylogenetic analysis of >400 plant species in 41 genera and five families revealed that average fruit size tracks the taxonomic and functional diversity of frugivorous birds and mammals. Fruit size was 40.2-46.5% smaller in the Moluccas and Sulawesi (respectively), with relatively depauperate assemblages of mostly small-bodied animals, than in the Sunda Region (Borneo, Sumatra, and Peninsular Malaysia), with a highly diverse suite of large and small animals. Fruit color, however, was unrelated to vertebrate diversity or to the representation of birds versus mammals in the frugivore assemblage. Overhunting of large animals, nearly ubiquitous in tropical forests, could strongly alter selection pressures on plants, resulting in widespread, although trait-specific, morphologic changes.

Plastomes on the edge: the evolutionary breakdown of mycoheterotroph plastid genomes.

Contents 48 I. 48 II. 50 III. 53 54 References 54 SUMMARY: We examine recent evidence for ratchet-like genome degradation in mycoheterotrophs, plants that obtain nutrition from fungi. Initial loss of the NADH dehydrogenase-like (NDH) complex may often set off an irreversible evolutionary cascade of photosynthetic gene losses. Genes for plastid-encoded subunits of RNA polymerase and photosynthetic enzymes with secondary functions (Rubisco and ATP synthase) can persist initially, with nonsynchronous and quite broad windows in the relative timing of their loss. Delayed losses of five core nonbioenergetic genes (especially trnE and accD, which respectively code for glutamyl tRNA and a subunit of acetyl-CoA carboxylase) probably explain long-term persistence of heterotrophic plastomes. The observed range of changes of mycoheterotroph plastomes is similar to that of holoparasites, although greater diversity of both probably remains to be discovered. These patterns of gene loss/retention can inform research programs on plastome function.

Advances in research on dinosaur gigantism

Animal gigantism is an important evolutionary phenomenon. Cope’s rule postulates that organisms in evolving lineages tend to increase in body size over time, but many animals don’t show these tendencies. Many of the most well-known examples of animal gigantism are found amongst dinosaurs. The carnivorous theropod Spinosaurus aegyptiacus (~14–18 m in length, ~7–21 t in mass), the herbivorous sauropod Argentinosaurus huinculensis (~30–40 m in length, 60–100 t in mass) and the herbivorous ornithopod Shantungosaurus giganteus (~15–19 m in length, ~10–23 t in mass) are amongst the largest terrestrial animals ever to have walked the Earth. Studies on bone histology show that dinosaurs attained giant size using one of three growth strategies: accelerated growth, delayed maturity or a combination of these strategies. Previous studies have mostly focused on explaining why dinosaurs became so large in terms of environmental and biological factors. In the former aspect, latitude, habitat size, temperature conditions and oxygen levels were all found to be related to dinosaur gigantism. In the latter aspect, diet and selective advantages in biomechanics, respiration, digestion and bone development (osteocyte size) were all found to affect dinosaur gigantism. Significant progress has been made in these regards, but a unanimously agreed consensus has yet to be reached. This has been hampered by difficulties including those encountered when comparing giant non-dinosaurian living animals with dinosaurs as well as incomplete knowledge of some dinosaur palaeoenvironments. In recent years, research on sauropod gigantism has advanced more significantly compared to other dinosaur groups. An evolutionary cascade model (ECM) has been developed to understand the uniquely gigantic body size of sauropods. This model comprises of five evolutionary cascades with each one linked to at least one other: “Reproduction”, “Feeding”, “Head and neck”, “Avian-style lung”, and “Metabolism”. All cascades start with observed or inferred basal traits and end in the trait “very high body mass”. Future research that extends EMC-style approaches to all dinosaur groups and integrates them with additional palaeoenvironmental and biological information to produce more holistic evolutionary perspectives will help to bring consensus to our understanding of dinosaur gigantism. This would be especially welcome, particularly if this can deepen knowledge of herbivore-carnivore co-evolution and understanding of tetrapod gigantism more generally.

Foetal Adjustment to Precarious Conditions: Genes Elegantly Bioprocess

The objective of this perspective article was to underline the significance of embryonic and foetal adaptation to risky environmental conditions through internal maternal and own physiology. Mammals including humans are characterized by their evolutionary principles of growth and development. These evolutionary trends are integrated with earth sciences following physics laws and cosmology as both a science and a reality. In a more limited scale, occurrence of day and night has caused the emergence of circadian rhythms in cell biology that are best reflected in circadian patterns of gene expression, transcription and translation. Such an evolutionary cascade orchestrates different types and functions of genes and proteins in mammals [1-3].

How smart is peptide receptor radionuclide therapy of neuroendocrine tumors especially in the salvage setting? The clinician’s perspective

In the recent past there has been a substantial growth in the understanding of cancer biology with a consequent opening of a Pandora’s box of scientific knowledge and advance in the biological perception of the disease. Paradoxically, this indepth, sun-burst-like knowledge has fogged the several established management protocols rather than clearing the doubts. The ‘knowledge’ that the hitherto established and proven therapeutics do not only target cancer cells but also ‘normal’ cells has shifted the attention more onto toxicity. To overcome the toxicity related to the ‘generalized’ treatment approach medical scientists across the world have gleefully (and possibly gullibly) accepted targeted therapy and the ‘theranostic concept’. This evolved approach should eventually, supposedly, tackle the intelligent cancer cells which have successfully challenged ‘Darwin’s Theory of Evolution’ by replacing the normal ‘chosen’ cells of the best creation and evolved creature of nature. Paradoxically survival of the fittest in this instance leads to extinction of the organism! This has generated a new intellectual theocracy whereby new knowledge has been embraced with almost religious zeal and rigorous assessment diminished in the face of fervor as we seek to reverse a biological Darwinian conundrum. As a consequence a note of caution needs to be placed here because the knowledge of the scientific medical community about neoplasia is juvenile, whereas the cancer cells, by the time they are diagnosed, are evolved and are up to 40 years old [1]. In effect they are the adults in the evolutionary cascade, and thereby not only challenging but also winning the natural selection process which decrees that “growth and spread is to the strongest”. In consideration of such (very old) philosophy, direct implementation of the promising but not matured theranostic concept in a patient with aggressive cancer, with a relatively shorter life expectancy, might not have a significant adverse influence on an already poor quality of life. The problem however achieves a different degree of proportionality when the concept is translated to the treatment of an indolent tumor associated with a relatively good overall survival following the initial diagnosis. Neuroendocrine tumors (NETs) are a group of such tumors, whose incidence and prevalence appear to be increasing at an alarming rate, partially due to highly advanced diagnostic methods and raised awareness [2]. Nuclear medicine is the first exponent of the theranostic concept dating back to early 1950s. The classical example is the use of radioiodine for diagnosis and therapy of various benign and malignant thyroid diseases targeting the thyroid cell sodium iodine transporters. A similar analogy is the identification of the overexpression of somatostatin receptors on NETs. This has enabled nuclear medicine physicians to deal with the complex and heterogeneous tumor by addressing the neoplastic overexpression of particular subclasses of somatostatin receptor. Thus somatostatin receptor-based molecular imaging has become established as an essential tool in the management of NET. Alternatively however, peptide receptor radionuclide therapy (PRRT), using peptides such as DOTATATE or DOTATOC, despite the fact that numerous retrospective (often single-center) studies during the last 10 years have provided evidence of success, has led to controversial discussions amongst oncologists, surgeons and gastroenterologists. The critical points of discussion include toxicity (hematotoxicity and nephrotoxicity) rather than the efficacy of the therapy. Objective response rates range from 4% to 30 %with significant increases in progression-free survival (PFS) compared to established approved therapy regimens [3]. V. Prasad (*) :W. Brenner Department of Nuclear Medicine, Campus Virchow-Klinikum, Charite University Hospital, Berlin, Germany e-mail: vikas.prasad@charite.de

An evolutionary cascade model for sauropod dinosaur gigantism--overview, update and tests.

Sauropod dinosaurs are a group of herbivorous dinosaurs which exceeded all other terrestrial vertebrates in mean and maximal body size. Sauropod dinosaurs were also the most successful and long-lived herbivorous tetrapod clade, but no abiological factors such as global environmental parameters conducive to their gigantism can be identified. These facts justify major efforts by evolutionary biologists and paleontologists to understand sauropods as living animals and to explain their evolutionary success and uniquely gigantic body size. Contributions to this research program have come from many fields and can be synthesized into a biological evolutionary cascade model of sauropod dinosaur gigantism (sauropod gigantism ECM). This review focuses on the sauropod gigantism ECM, providing an updated version based on the contributions to the PLoS ONE sauropod gigantism collection and on other very recent published evidence. The model consist of five separate evolutionary cascades (“Reproduction”, “Feeding”, “Head and neck”, “Avian-style lung”, and “Metabolism”). Each cascade starts with observed or inferred basal traits that either may be plesiomorphic or derived at the level of Sauropoda. Each trait confers hypothetical selective advantages which permit the evolution of the next trait. Feedback loops in the ECM consist of selective advantages originating from traits higher in the cascades but affecting lower traits. All cascades end in the trait “Very high body mass”. Each cascade is linked to at least one other cascade. Important plesiomorphic traits of sauropod dinosaurs that entered the model were ovipary as well as no mastication of food. Important evolutionary innovations (derived traits) were an avian-style respiratory system and an elevated basal metabolic rate. Comparison with other tetrapod lineages identifies factors limiting body size.

Oil at 150$—The tipping point for changing course of civilizations?

The present work offers a systemic perspective on post conventional oil futures. It is based on the model that accounts for a causal relationship between a dominant worldview in a society and the societal choice of technology and institutions, which then constrain and direct dynamics at the level of production and consumption. The Business as usual scenario provides an idea as where the world might be heading under the assumption of a myopic and unchanging worldview. The Western group leads the process of change scenario describes an evolutionary cascade of change in the Western group, which starts with a substantial change in a dominant worldview. Note that this substantial change is not a revolution – although its institutional solutions appear very challenging today, they do not necessarily stand out of the capitalist democracy. Finally, the third scenario is about global governance – a future that would leave least unknowns and least threats to Western civilization.

Biology of the sauropod dinosaurs: the evolution of gigantism.

The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability. There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism.We review the biology of sauropod dinosaurs in detail and posit that sauropod gigantism was made possible by a specific combination of plesiomorphic characters (phylogenetic heritage) and evolutionary innovations at different levels which triggered a remarkable evolutionary cascade. Of these key innovations, the most important probably was the very long neck, the most conspicuous feature of the sauropod bauplan. Compared to other herbivores, the long neck allowed more efficient food uptake than in other large herbivores by covering a much larger feeding envelope and making food accessible that was out of the reach of other herbivores. Sauropods thus must have been able to take up more energy from their environment than other herbivores.The long neck, in turn, could only evolve because of the small head and the extensive pneumatization of the sauropod axial skeleton, lightening the neck. The small head was possible because food was ingested without mastication. Both mastication and a gastric mill would have limited food uptake rate. Scaling relationships between gastrointestinal tract size and basal metabolic rate (BMR) suggest that sauropods compensated for the lack of particle reduction with long retention times, even at high uptake rates.The extensive pneumatization of the axial skeleton resulted from the evolution of an avian-style respiratory system, presumably at the base of Saurischia. An avian-style respiratory system would also have lowered the cost of breathing, reduced specific gravity, and may have been important in removing excess body heat. Another crucial innovation inherited from basal dinosaurs was a high BMR. This is required for fueling the high growth rate necessary for a multi-tonne animal to survive to reproductive maturity.The retention of the plesiomorphic oviparous mode of reproduction appears to have been critical as well, allowing much faster population recovery than in megaherbivore mammals. Sauropods produced numerous but small offspring each season while land mammals show a negative correlation of reproductive output to body size. This permitted lower population densities in sauropods than in megaherbivore mammals but larger individuals.Our work on sauropod dinosaurs thus informs us about evolutionary limits to body size in other groups of herbivorous terrestrial tetrapods. Ectothermic reptiles are strongly limited by their low BMR, remaining small. Mammals are limited by their extensive mastication and their vivipary, while ornithsichian dinosaurs were only limited by their extensive mastication, having greater average body sizes than mammals.

Molecular Darwinian Evolution of Virulence in Yersinia pestis

The genus Yersinia consists of 15 species (www.bacterio.cict.fr/xz/yersinia.html), and only three of them, Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica, are pathogenic to mammals, including humans. The Y. pseudotuberculosis-Y. pestis evolutionary linkage diverged from Y. enterocolitica between 41 and 186 million years ago, while Y. pestis diverged from Y. pseudotuberculosis within the last 1,500 to 20,000 years (1, 65). In accordance with this evolutionary cascade, wide genetic diversity exists between Y. pseudotuberculosis and Y. enterocolitica, while very close genetic similarity is found between Y. pseudotuberculosis and Y. pestis. Y. pseudotuberculosis causes only nonfatal gastrointestinal disease in mammalian hosts, including humans, and the disease is transmitted by the food-borne route. Y. pestis causes plague, which is one of the most deadly diseases (47). Three pandemics of plague have been recorded in human history and have claimed hundreds of thousands of lives (47). Plague is a typical enzootic disease (an infection of the animal population[s] in one or more confined natural foci without the need for external inputs), and epidemics of rodent plague are restricted in various enzootic plague foci especially in Asia, the Americas, and Africa (80). Compared to its progenitor Y. pseudotuberculosis, Y. pestis utilizes a radically different mechanism of transmission in rodent reservoirs that relies primarily upon biting by flea vectors. This review deals with how genetic changes (gene inactivation, loss, and acquisition) and remodeling of gene regulation encourage Y. pestis to switch from an enteric lifestyle to a mammalian blood-borne lifestyle that relies on vector-borne transmission.

The Portuguese as System-builders in the Fifteenth and Sixteenth Centuries: A Case Study on the Role of Technology in the Evolution of the World System

World system evolution may be viewed as a cascade of multilevel, nested, self-similar and Darwinian-type processes poised on the boundary between order and chaos that allows for innovation. A framework developed by Devezas-Modelski opens the door to conceptualizing globalization as part of that evolutionary cascade, and as a process of system-building of which the Portuguese enterprises of the fifteenth and sixteenth centuries provide an illuminating case. Analysis is focused on two components of that cascade: the Portuguese long cycle, and the two (economic) K-waves and their related innovations. In this period preceding the Industrial Revolution, innovations focused on navigation and shipbuilding and formed the technical support for such activities. Quantitative analysis of empirical evidence on Portuguese expeditions and naval-military campaigns, the global network of bases, and of scarce data on the gold and pepper trades in this period supports the notion of long cycles and K-waves as system-building, and the more general conception of globalization as an evolutionary learning process.