Coevolution Theory Research Articles

Double-layer evolutionary model for N-player iterated prisoner’s dilemma

Concerning the problem that cooperation in N-player Iterated Prisoner's Dilemma (NIPD) is hard to emerge when N is great, this paper researched the status of game both in the free competition mode and in the agreement competition mode. And imitating the strategy "Tit for Tat" in 2-IPD, it promoted the strategy "Simulated TFT". And combining the theories of co-evolution, it built up a double-layer evolutionary model, DL-NIPD, in which players and their aggregations, groups, can evolve in their own-layer respectively. Analysis of the numerical experiment results indicates that, under the free competition case, cooperation is usually easier to emerge in a small group of player than in a larger one, while depending on the straight-agreement and competition of groups, DL-NIPD can get a high rate of cooperation under any N.

Red leaf color as a warning signal against insect herbivory: Honest or mimetic?

The co-evolution theory for red leaf colors considers redness as a handicap signal against herbivory. We have examined whether the assumed signal is honest and, accordingly, costly, by seeking a correlation between anthocyanin and total phenolic levels in 11 plants exhibiting variation in the expression of the red character either between individuals or between modules on the same individual. Selection of total phenolics as a variable was based on their assumed anti-herbivore function and on their common biosynthetic origin with anthocyanins. Plants with young or senescing red leaves were tested. Confirming evidence was found in senescing leaves, where in three out of the four studied species a significant and strongly positive correlation between signal strength (redness) and actual defensive potential (total phenolics) was found, rendering the signal both honest and costly. In young, developing leaves a significant, yet weakly positive correlation was found only in three out the seven examined species. Accordingly, the handicap signal hypothesis may be questioned in the case of young leaves. Hence, young leaf redness fits more to the alternative hypotheses that red leaf color is less easily perceived by folivorous insect photoreceptors or that red leaf color undermines insect camouflage. These hypotheses do not demand an increased chemical defensive potential.

Natural variation in Pristionchus pacificus insect pheromone attraction involves the protein kinase EGL-4

The geographical mosaic theory of coevolution predicts that different local species interactions will shape population traits, but little is known about the molecular factors involved in mediating the specificity of these interactions. Pristionchus nematodes associate with different scarab beetles around the world, with Pristionchus pacificus isolated primarily from the oriental beetle in Japan. In particular, the constituent populations of P. pacificus represent a rare opportunity to study multiple specialized interactions and the mechanisms that influence population traits at the genetic level. We identified a component of the cGMP signaling pathway to be involved in the natural variation for sensing the insect pheromone ETDA, using targeted introgression lines, exogenous cGMP treatment, and a null egl-4 allele. Our data strongly implicate egl-4 as one of several loci involved in behavioral variation in P. pacificus populations. That EGL-4 homologs have been independently implicated for behavioral variations in other invertebrate models suggests that EGL-4 may act as a modulator for interspecies behavioral repertoires across large phylogenetic distances.

Coevolution in the tumor microenvironment

The progression of carcinomas to high-grade malignancies is accompanied by profound histological changes in the tumor-associated stroma. Although previous studies have suggested that mesenchymal cells of the stroma undergo genetic alterations during this progression, a new study now provides evidence that strongly contradicts this theory of stromal cell coevolution.

The black hole mass–stellar velocity dispersion correlation: bulges versus pseudo-bulges

We investigate the correlation between the supermassive black holes (SMBHs) mass (Mbh) and the stellar velocity dispersion ( ) in two types of host galaxies: the early-type bulges (disk galaxies with classical bulges or elliptical galaxies) and pseudobulges. In the form log(Mbh=M ) = + log( =200 km s 1 ), the best-fit results for the 39 early-type bulges are the slope = 4:06 0:28 and the normalization = 8:28 0:05; the best-fit results for the 9 pseudobulges are = 4:5 1:3, = 7:50 0:18. Both relations have intrinsic scatter in logMbh of .0.27 dex. The Mbh- relation for pseudobulges is different from the relation in the early-type bulges over the 3 significance level. The contrasting relations indicate the formation and growth histories of SMBHs depend on their host type. The discrepancy between the slope of the Mbh- relations using different definition of velocity dispersion vanishes in our sample, a uniform slope will constrain the coevolution theories of the SMBHs and their host galaxies more effectively. We also find the slope for the “core” elliptical galaxies at the high mass range of the relation appears steeper ( ’ 5-6), which may be the imprint of their origin of dissipationless mergers.

Canoes and cultural evolution

Over the last 30 years, the idea that the processes producing cultural stability and change are analogous in important respects to those of biological evolution has become increasingly popular. Biological evolution is characterized by changing frequencies of genes in populations through time as a result of such processes as natural selection; likewise, cultural evolution refers to the changing distributions of cultural attributes in populations, which are affected by processes such as natural selection but also by others that have no analogue in genetic evolution. The fundamental, mathematically based theory that justified and spelled out the necessary modifications to standard population genetics theory to make it relevant to culture was laid out by Cavalli-Sforza and Feldman (1) and Boyd and Richerson (2) in the 1980s, on the basis of earlier papers, and Richard Dawkins (3) had already introduced the idea to the popular imagination with his concept of the “meme” as analogous to the gene. In the intervening period, the development of what has come to be called “dual inheritance theory” or “gene–culture coevolution theory” has continued, and it has been accompanied by a slowly growing number of empirical case studies that apply these ideas to understanding patterned variation in cultural data. The article by Rogers and Ehrlich (4) in this issue of PNAS makes a significant contribution to this growing field by showing how different cultural evolutionary processes can be identified and distinguished from one another and how they differentially affect different kinds of cultural traits; it will certainly become a widely cited classic case study, and the dataset of descriptive traits of canoes from different Polynesian groups is likely to become a test bed for future cultural evolutionary studies.

Increasing productivity accelerates host–parasite coevolution

Host-parasite coevolution is believed to influence a range of evolutionary and ecological processes, including population dynamics, evolution of diversity, sexual reproduction and parasite virulence. The impact of coevolution on these processes will depend on its rate, which is likely to be affected by the energy flowing through an ecosystem, or productivity. We addressed how productivity affected rates of coevolution during a coevolutionary arms race between experimental populations of bacteria and their parasitic viruses (phages). As hypothesized, the rate of coevolution between bacterial resistance and phage infectivity increased with increased productivity. This relationship can in part be explained by reduced competitiveness of resistant bacteria in low compared with high productivity environments, leading to weaker selection for resistance in the former. The data further suggest that variation in productivity can generate variation in selection for resistance across landscapes, a result that is crucial to the geographic mosaic theory of coevolution.

FINE-SCALE LOCAL ADAPTATION OF WEEVIL MOUTHPART LENGTH AND CAMELLIA PERICARP THICKNESS: ALTITUDINAL GRADIENT OF A PUTATIVE ARMS RACE

Although coevolutionary theory predicts that evolutionary interactions between species are spatially hierarchical, few studies have examined coevolutionary processes at multiple spatial scales. In an antagonistic system involving a plant, the Japanese camellia (Camellia japonica), and its obligate seed predator, the camellia weevil (Curculio camelliae), I elucidated the local adaptation of a camellia defensive armament (pericarp thickness) and a weevil offensive armament (rostrum length) within Yakushima Island (ca. 30 km in diameter), compared to a larger-scale variation in those traits throughout Japan reported in previous studies. Results showed that camellia pericarp thickness and weevil rostrum length vary remarkably within several kilometers on this island. In addition, geographic variation in each camellia and weevil armament was best explained by the armament size of the sympatric participant than by abiotic environmental heterogeneity. However, I also found that camellia pericarp thickness significantly decreased in cool-temperate (i.e., highland) areas, suggesting the contributions of climate on the spatial structuring of the weevil-camellia interaction. Interestingly, relatively thin pericarps occurred not only in the highlands but also in some low-altitude areas, indicating that other factors such as nonrandom or asymmetric gene flow play important roles in the metapopulation processes of interspecific interactions at small spatial scales.

An extension of the coevolution theory of the origin of the genetic code.

BackgroundThe coevolution theory of the origin of the genetic code suggests that the genetic code is an imprint of the biosynthetic relationships between amino acids. However, this theory does not seem to attribute a role to the biosynthetic relationships between the earliest amino acids that evolved along the pathways of energetic metabolism. As a result, the coevolution theory is unable to clearly define the very earliest phases of genetic code origin. In order to remove this difficulty, I here suggest an extension of the coevolution theory that attributes a crucial role to the first amino acids that evolved along these biosynthetic pathways and to their biosynthetic relationships, even when defined by the non-amino acid molecules that are their precursors.ResultsIt is re-observed that the first amino acids to evolve along these biosynthetic pathways are predominantly those codified by codons of the type GNN, and this observation is found to be statistically significant. Furthermore, the close biosynthetic relationships between the sibling amino acids Ala-Ser, Ser-Gly, Asp-Glu, and Ala-Val are not random in the genetic code table and reinforce the hypothesis that the biosynthetic relationships between these six amino acids played a crucial role in defining the very earliest phases of genetic code origin.ConclusionAll this leads to the hypothesis that there existed a code, GNS, reflecting the biosynthetic relationships between these six amino acids which, as it defines the very earliest phases of genetic code origin, removes the main difficulty of the coevolution theory. Furthermore, it is here discussed how this code might have naturally led to the code codifying only for the domains of the codons of precursor amino acids, as predicted by the coevolution theory. Finally, the hypothesis here suggested also removes other problems of the coevolution theory, such as the existence for certain pairs of amino acids with an unclear biosynthetic relationship between the precursor and product amino acids and the collocation of Ala between the amino acids Val and Leu belonging to the pyruvate biosynthetic family, which the coevolution theory considered as belonging to different biosyntheses.ReviewersThis article was reviewed by Rob Knight, Paul Higgs (nominated by Laura Landweber), and Eugene Koonin.

Reciprocal Relations in Evolutionary Processes

In nature, our biological world consists of many species of biological contents such as DNA, RNA, and proteins, etc. We frequently ask a question: “Which is first, egg or chicken?” In the evolution of life, we also encounter a similar question: “Which is first, RNA, DNA, or protein?” or “How do they co-evolute?” In such biological systems, a theory of co-evolution of biopolymers is necessary. However, we have not yet been able to tame such a tough issue in the problem. Recently, Aita et al.1) have proposed a thermodynamic theory-like interpretation of evolutionary processes such as evolutions of proteins and biopolymers.∗) They found appropriate definitions for the concepts such as free fitness, evolutionary temperature, constant, entropy, force, and flux, etc. Using such quantities in evolutionary processes, they found a linear relationship between the evolutionary force and flux such as the linear response theory in thermodynamics. Their theory suggests that there may exist “a theory of irreversible processes” in evolution of a “single species” in biology. It can be thought of as a generalization of Onsager’s theory2),3) of irreversible processes to that of evolutionary processes. So, as a first step toward such a direction, I would like to postulate a generalization of Onsager’s theory of irreversible processes-like approach1) to the theory of evolutionary/co-evolutionary processes. In this paper, if there is no confusion, I would like to mean “co-evolutionary”(or “co-evolution”) simply by “evolutionary”(or “evolution”). Finally, I would like to give some comments on the relationship between Aita-Husimi’s interpretation,1) Kauffman’s point of view of generalized thermodynamics4) and Fuller’s synergetics philosophy.5),6) They are essentially all the same.

Equality in Exchange Revisited - from an Evolutionary (Genetic and Cultural) Point of View

This paper addresses the legal relevance of recent evolutionary theoretical research on human prosociality and human strong reciprocity and the explanations it offers regarding the existence and scope of what could be called a 'sense of fairness'. To this end, I will draw on the legal example of equality in exchange in contract law on the one hand and on research on human cooperative behaviour on the other hand. I will start by making some remarks on the issue of substantive fairness in legal contract theory and in legal anthropology. I will then briefly sketch some results of some of the experiments commonly used in behavioural economics to shed light on human prosocial behaviour. Recent research not only shows that the economists' canonical assumption that individuals are entirely self-regarding is incorrect, but also indicates that there is a considerable amount of cross-cultural behavioural variability. This should set the stage for an exposition of a particular encompassing evolutionary theoretical framework underlying a particular interpretation of the experimental data. Indeed, I mainly hope to show why evolutionary analysis in law could benefit considerably from incorporating culture - and its accompanying evolutionary theory - more explicitly into its models than at present seems to be the case. I will argue that one has to be able to give a plausible evolutionary account for both the behaviour that is supposed to be regulated and the regulating behaviour itself. Moreover, rather than focusing exclusively on the - indeed likely - universal aspects of the regulated behaviour, this universality has to be connected more explicitly with the - cultural - diversity encountered in the world's legal systems. When approaching regulating behaviour in general as an evolutionary puzzling form of human large-scale cooperation, gene-culture coevolutionary theory and the related concept of cultural group selection promise to go a long way in providing this necessary connection.

Host–parasite ‘Red Queen’ dynamics archived in pond sediment

Antagonistic interactions between hosts and parasites are a key structuring force in natural populations, driving coevolution. However, direct empirical evidence of long-term host-parasite coevolution, in particular 'Red Queen' dynamics--in which antagonistic biotic interactions such as host-parasite interactions can lead to reciprocal evolutionary dynamics--is rare, and current data, although consistent with theories of antagonistic coevolution, do not reveal the temporal dynamics of the process. Dormant stages of both the water flea Daphnia and its microparasites are conserved in lake sediments, providing an archive of past gene pools. Here we use this fact to reconstruct rapid coevolutionary dynamics in a natural setting and show that the parasite rapidly adapts to its host over a period of only a few years. A coevolutionary model based on negative frequency-dependent selection, and designed to mimic essential aspects of our host-parasite system, corroborated these experimental results. In line with the idea of continuing host-parasite coevolution, temporal variation in parasite infectivity changed little over time. In contrast, from the moment the parasite was first found in the sediments, we observed a steady increase in virulence over time, associated with higher fitness of the parasite.

Redescription of a weevil Paramecops sinaitus (Coleoptera: Curculionidae: Molytinae) from the Sinai and an ecological study of its interaction with the Sinai milkweed Asclepias sinaica (Gentianales: Asclepiadaceae)

We collected specimens of Paramecops sinaitus (Pic, 1930) (Curculionidae: Molytinae) from south Sinai in Egypt, which enabled us to make the first complete description of this species. We also include some taxonomic remarks on the genus. Paramecops solenostemmatis (Peyerimhoff, 1930) is a synonym of Paramecops sinaitus. We propose the new combination Paramecops sogdianus (Nasreddinov, 1978), based on Perihylobius sogdianus Nasreddinov, 1978, which would make Perihylobius and Paramecops synonymous. Like other Paramecops species, P. sinaitus appears to share a close interaction with Asclepiads, in this case the Sinai milkweed Asclepias sinaica (Boiss.) Muschl., 1912 (Asclepiadaceae). We investigated the oviposition behaviour of female weevils to test whether it is linked to larval performance, as predicted by coevolutionary theory. We found that female oviposition preference was positively related to plant size and to the volume of the seed follicles in which the eggs were laid. The survival of eggs was negatively related to plant size, perhaps due to plant differences in the production of defensive cardenolides. Larval survival was not related to plant size but increased with follicle volume, probably as a result of competition for food. Paramecops is relatively sedentary and nocturnal in its behaviour. Night-time observations of behaviour showed that weevils were more active at lower temperatures.

Can chemical communication be cryptic? Adaptations by herbivores to natural enemies exploiting prey semiochemistry

Predators and parasites commonly use chemical cues associated with herbivore feeding and reproduction to locate prey. However, we currently know little about mechanisms by which herbivores may avoid such natural enemies. Pheromones are crucial to many aspects of herbivore life history, so radical alterations of these compounds could be disadvantageous despite their exploitation by predators. Instead, minor modifications in pheromone chemistry may facilitate partial escape while maintaining intraspecific functionality. We tested this hypothesis using Ips pini, an endophytic beetle that develops in the phloem tissue of pine trees. Its predominant predators in the Great Lakes region of North America are Thanasimus dubius and Platysoma cylindrica, both of which are highly attracted to I. pini's pheromones. However, there are significant disparities between prey and predator behaviors that relate to nuances of pheromone chemistry. Thanasimus dubius is most attracted to the (+) stereoisomer of ipsdienol, and P. cylindrica is most attracted to the (-) form; Ips pini prefers racemic mixtures intermediate between each predator's preferences. Further, a component that is inactive by itself, lanierone, greatly synergizes the attraction of I. pini to ipsdienol, but has a weak or no effect on its predators. A temporal component adds to this behavioral disparity: lanierone is most important in the communication of I. pini during periods when its predators are most abundant. The difficulties involved in tracking prey are further compounded by spatial and temporal variation in prey signaling on a local scale. For example, the preferences of I. pini vary significantly among sites only 50 km apart. This chemical crypsis is analogous to morphological forms of camouflage, such as color and mimicry, that are widely recognized as evasive adaptations against visually searching predators. Presumably these relationships are dynamic, with predators and prey shifting responses in microevolutionary time. However, several factors may delay predator counter adaptations. The most important appears to be the availability of alternate prey, specifically I. grandicollis, whose pheromone ipsenol is highly attractive to the above predators but not cross-attractive with I. pini. Consistent with this view, the specialist parasitoid, Tomicobia tibialis, has behavioral preferences for pheromone components that closely correspond with those of I. pini. These results are discussed in terms of population dynamics and coevolutionary theory.

Question 6: Coevolution Theory of the Genetic Code: A Proven Theory

The coevolution theory proposes that primordial proteins consisted only of those amino acids readily obtainable from the prebiotic environment, representing about half the twenty encoded amino acids of today, and the missing amino acids entered the system as the code expanded along with pathways of amino acid biosynthesis. The isolation of genetic code mutants, and the antiquity of pretran synthesis revealed by the comparative genomics of tRNAs and aminoacyl-tRNA synthetases, have combined to provide a rigorous proof of the four fundamental tenets of the theory, thus solving the riddle of the structure of the universal genetic code.

The impact of herbivore–plant coevolution on plant community structure

Coevolutionary theory proposes that the diversity of chemical structures found in plants is, in large part, the result of selection by herbivores. Because herbivores often feed on chemically similar plants, they should impose selective pressures on plants to diverge chemically or bias community assembly toward chemical divergence. Using a coevolved interaction between a group of chrysomelid beetles and their host plants, I tested whether coexisting plants of the Mexican tropical dry forest tend to be chemically more dissimilar than random. Results show that some of the communities are chemically overdispersed and that overdispersion is related to the tightness of the interaction between plants and herbivores and the spatial scale at which communities are measured. As coevolutionary specialization increases and spatial scale decreases, communities tend to be more chemically dissimilar. At fairly local scales and where herbivores have tight, one-to-one interactions with plants, communities have a strong pattern of chemical disparity.

GEOGRAPHIC VARIATION IN THE EVOLUTION AND COEVOLUTION OF A TRITROPHIC INTERACTION

The geographic mosaic theory of coevolution predicts that geographic variation in species interactions will lead to differing selective pressures on interacting species, producing geographic variation in the traits of interacting species (Thompson 2005). We supported this hypothesis in a study of the geographic variation in the interactions among Eurosta solidaginis and its natural enemies. Eurosta solidaginis is a fly (Diptera: Tephritidae) that induces galls on subspecies of tall goldenrod, Solidago altissima altissima and S. a. gilvocanescens. We measured selection on E. solidaginis gall size and shape in the prairie and forest biomes in Minnesota and North Dakota over an 11-year period. Galls were larger and more spherical in the prairie than in the forest. We supported the hypothesis that the divergence in gall morphology in the two biomes is due to different selection regimes exerted by natural enemies of E. solidaginis. Each natural enemy exerted similar selection on gall diameter in both biomes, but differences in the frequency of natural enemy attack created strong differences in overall selection between the prairie and forest. Bird predation increased with gall diameter, creating selection for smaller-diameter galls. A parasitic wasp, Eurytoma gigantea, and Mordellistena convicta, an inquiline beetle, both caused higher E. solidaginis mortality in smaller galls, exerting selection for increased gall diameter. In the forest there was stabilizing selection on gall diameter due to a combination of bird predation on larvae in large galls, and M. convicta- and E. gigantea-induced mortality on larvae in small galls. In the prairie there was directional selection for larger galls due to M. convicta and E. gigantea mortality on larvae in small galls. Mordellistena convicta-induced mortality was consistently higher in the prairie than in the forest, whereas there was no significant difference in E. gigantea-induced mortality between biomes. Bird predation was nonexistent in the prairie so the selection against large galls found in the forest was absent. We supported the hypothesis that natural enemies of E. solidaginis exerted selection for spherical galls in both biomes. In the prairie M. convicta exerts stabilizing selection to maintain spherical galls. In the forest there was directional selection for more spherical galls. Eurytoma gigantea exerted selection on gall shape in the forest in a complex manner that varied among years. We also supported the hypothesis that E. gigantea is coevolving with E. solidaginis. The parasitoid had significantly longer ovipositors in the prairie than in the forest, indicating the possibility that it has evolved in response to selection to reach larvae in the larger-diameter prairie galls.

Analysis of tRNA abstract shapes of precursor/derivative amino acids in Archaea

Wong's theory of the genetic code's origin states that because of historical constraints, codon assignment depends on the relation between precursor and derivative amino acids, a result of the coevolutionary process between amino acids' biosynthetic pathways and tRNAs. Based on arguments supporting the assumption that natural selection favors more stable and thus functionally constrained structures, we tested whether precursor and derivative tRNAs are equally evolved by measuring their structural parameters, thermostability and molecular plasticity. We also estimated the extent to which precursor and derivative tRNAs differ within Archaea. We used Archaea sequences of both precursor and derivative tRNAs in order to examine the plastic repertoires or sets of suboptimal structures at a defined free energy interval. We grouped secondary structures according to their helix nesting and adjacency using abstract shapes analysis. This clustering enabled us to infer a consensus sequence for all shapes that fit the clover leaf secondary structure [Giegerich, R., et al., Nucleic Acids Res 2004; 32 (16): 4843–51.]. This consensus sequence was then folded in order to retrieve a set of suboptimal structures. For each pair of precursor and derivative tRNAs, we compared these plastic repertoires based on the number of secondary structures, the thermostability of the minimum free energy structure and two structural parameters (base pair propensity ( P) and mean length of helical stem structures ( S)), which were measured for every representative secondary structure [Schultes, E.A., et al., J Mol Evol 1999; 49 (1): 76–83.]. We found that derivative tRNAs have fewer numbers of shapes, higher thermostability and more stable parameters than precursor tRNAs, a fact in full agreement with Wong's coevolution theory of the genetic code.

Dos and don'ts of testing the geographic mosaic theory of coevolution

The geographic mosaic theory of coevolution is stimulating much new research on interspecific interactions. We provide a guide to the fundamental components of the theory, its processes and main predictions. Our primary objectives are to clarify misconceptions regarding the geographic mosaic theory of coevolution and to describe how empiricists can test the theory rigorously. In particular, we explain why confirming the three main predicted empirical patterns (spatial variation in traits mediating interactions among species, trait mismatching among interacting species and few species-level coevolved traits) does not provide unequivocal support for the theory. We suggest that strong empirical tests of the geographic mosaic theory of coevolution should focus on its underlying processes: coevolutionary hot and cold spots, selection mosaics and trait remixing. We describe these processes and discuss potential ways each can be tested.

POLYGENIC TRAITS AND PARASITE LOCAL ADAPTATION

The extent to which parasites are locally adapted to their hosts has important implications for human health and agriculture. A recently developed conceptual framework--the geographic mosaic theory of coevolution--predicts that local maladaptation should be common and largely determined by the interplay between gene flow and spatially variable reciprocal selection. Previous investigation of this theory has predominately focused on genetic systems of infection and resistance characterized by few genes of major effect and particular forms of epistasis. Here we extend existing theory by analyzing mathematical models of host-parasite interactions in which host resistance to parasites is mediated by quantitative traits with an additive polygenic basis. In contrast to previous theoretical studies predicated upon major gene mechanisms, we find that parasite local maladaptation is quite uncommon and restricted to one specific functional form of host resistance. Furthermore, our results show that local maladaptation should be rare or absent in studies that measure local adaptation using reciprocal transplant designs conducted in natural environments. Our results thus narrow the scope over which the predictions of the geographic mosaic theory are likely to hold and provide novel and readily testable predictions about when and where local maladaptation is expected.