[Theoretical analysis of the coevolution of proteins in the phage-bacterium system. A model of the temperate phage-bacterium system].
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Bacterial Proteins↗
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Results for “coevolution”
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Mycoplasma-like organisms (MLO), pathogens of the plant yellows diseases, as a model of coevolution between prokaryotes, insects and plants.
There is no satisfactory theory to explain how parasites whose effect is to kill or to weaken their hosts have been able to survive evolution. A good explanation may be found in the study of mycoplasma-like organisms (MLO). We show here the existence of natural cycles of MLO between symptomless wild plants and unaffected vectors. Such natural cycles may be the basis of a coevolutionary process by which the prokaryotes and the whole cycle have persisted to our time. Disease outbreaks occur with intrusion of a cultivated plant (direct mode) or an imported insect (indirect mode). From an evolutionary point of view, the natural cycle constitutes a protection for the host plants and natural vectors against the introduction of foreign plants or vectors as competitors in their ecological niche. A role of MLO and other parasites in evolution could be to provide stability to ecosystems, which is necessary for new characters to emerge.
Animals↗
[Theoretical analysis of protein coevolution in the phage-bacterium system. The problem].
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Adsorption↗
[Theoretical analysis of protein coevolution in the phage-bacteria system. A deterministic model of the separate microevolutionary stage].
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Adsorption↗
A special relationship: the coevolution of human beings and domesticated animals.
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Agriculture↗
Trypanosomes, tsetse and trypanotolerance: coevolution in tropical Africa.
Trypanotolerance reaches varying degrees of stability in wild and domestic animals according to their co-evolutionary contacts with tsetse flies and trypanosomes. In this context, various mechanisms developed by wild and domestic Bovidae to cope with tsetse and trypanosome challenge are discussed.
Adaptation, Physiological↗
[Coevolutive mechanisms between retroviruses and their hosts. The murine mammary tumor model].
Mouse mammary tumor virus (MMTV) is a type B retrovirus that is transmitted as an infectious milk-borne particle and that causes mammary carcinomas by insertional activation of cellular protooncogenes. Germ line infections result in endogenous Mtv proviruses integrated in the genome of most mouse strains. These endogenous proviruses have been integrated into the genomes of mice for only the past 3-5 million years. The open reading frame present in the 3' long terminal repeat (LTR) of the provirus encodes a superantigen (SAg) which is able to stimulate a large proportion of T cells sharing a common T-cell receptor beta chain variable domain (v beta). Expression of this SAg is critical to the MMTV life cycle. After expression of the SAg in B cells a significant number of T cells are recruited to respond to these MMTV infected cells. As a consequence both the T cells expressing the relevant TCR V beta domain and the infected B cells become activated and start dividing. This would facilitate integration of MMTV and amplify the number of virus infected lymphocytes. Most likely during lactation the mammary glands become receptive to viral infection. The presence of endogenous Mtvs induces an early clonal deletion of reactive T cells. For this reason it has been argued that the presence of these proviruses confers a selective advantage to the mouse population by protecting the host from infection with an exogenous MMTV coding for a cross-reactive SAg. However, recent results discussed herein suggest that Mtv proviruses may also be detrimental to the mouse population by participating in recombinations with exogenous MMTVs, giving rise to highly tumorigenic recombinant particles. These results are discussed in the light of recent reports suggesting the involvement of viral sequences with a high homology to MMTV in human mammary tumorigenesis.
Animals↗
Coevolving protein residues: maximum likelihood identification and relationship to structure.
The identification of protein sites undergoing correlated evolution (coevolution) is of great interest due to the possibility that these pairs will tend to be adjacent in the three-dimensional structure. Identification of such pairs should provide useful information for understanding the evolutionary process, predicting the effects of site-directed substitution, and potentially for predicting protein structure. Here, we develop and apply a maximum likelihood method with the aim of improving detection of coevolution. Unlike previous methods which have had limited success, this method allows for correlations induced by phylogenetic relationships and for variation in rate of evolution along branches, and does not rely on accurate reconstruction of ancestral nodes. In order to reduce the complexity of coevolutionary relationships and identify the primary component of pairwise coevolution between two sites, we reduce the data to a two-state system at each site, regardless of the actual number of residues observed at that site. Simulations show that this strategy is good at identifying simple correlations and at recognizing cases in which the data are insufficient to distinguish between coevolution and spurious correlations. The new method was tested by using size and charge characteristics to group the residues at each site, and then evaluating coevolution in myoglobin sequences. Grouping based on physicochemical characteristics allows categorization of coevolving sites into positive and negative coevolution, depending on the correlation between equilibrium state frequencies. We detected a striking excess of negative coevolution (corresponding to charge) at sites brought into proximity by the periodicity of the alpha-helix, and there was also a tendency for sites with significant likelihood ratios to be close in the three-dimensional structure. Sites on the surface of the protein appear to coevolve both when they are close in the structure, and when they are distant, implying a role for folding and/or avoidance of quaternary structure in the coevolution process.
Computer Simulation↗
Do hosts and parasites coevolve? Empirical support from the Schistosoma system.
Coevolution between host and parasite is, in principle, a powerful determinant of the biology and genetics of infection and disease. However, coevolution is difficult to demonstrate rigorously in practice and therefore has rarely been observed empirically, particularly in animal-parasite systems. Research on host-schistosome interactions has the potential for making an important contribution to the study of coevolution or reciprocal adaptation. This may be particularly pertinent because schistosomes represent an indirectly transmitted macroparasite, so often overlooked among both theoretical and empirical studies. Here we present ideas and experiments on host-schistosome interactions, in part reviewed from published work but focusing in particular on preliminary novel data from our ongoing studies of potential host-schistosome evolution and coevolution in the laboratory. The article is split into three main sections: we first focus on the evidence for evolution in the host, then in the parasite, before combining both to illustrate the gathering evidence of host-parasite coevolution in the snail-schistosome system. In particular, we demonstrate that genetic architecture, variability, and selective pressures are present for the evolution of resistance and susceptibility, virulence, and infectivity to occur, the mechanisms allowing such polymorphisms to be maintained, and that hosts and parasites appear to have reciprocal effects on each other's phenotype and genotype.
Adaptation, Biological↗
Coevolutionary clines across selection mosaics.
Much of the dynamics of coevolution may be driven by the interplay between geographic variation in reciprocal selection (selection mosaics) and the homogenizing action of gene flow. We develop a genetic model of geographically structured coevolution in which gene flow links coevolving communities that may differ in both the direction and magnitude of reciprocal selection. The results show that geographically structured coevolution may lead to allele-frequency clines within both interacting species when fitnesses are spatially uniform or spatially heterogeneous. Furthermore, the results show that the behavior and shape of clines differ dramatically among different types of coevolutionary interaction. Antagonistic interactions produce dynamic clines that change shape rapidly through time, producing shifting patterns of local adaptation and maladaptation. Unlike antagonistic interactions, mutualisms generate stable equilibrium patterns that lead to fixed spatial patterns of adaptation. Interactions that vary between mutualism and antagonism produce both equilibrium and dynamic clines. Furthermore, the results demonstrate that these interactions may allow mutualisms to persist throughout the geographic range of an interaction, despite pockets of locally antagonistic selection. In all cases, the coevolved spatial patterns of allele frequencies are sensitive to the relative contributions of gene flow, selection, and overall habitat size, indicating that the appropriate scale for studies of geographically structured coevolution depends on the relative contributions of each of these factors.
Alleles↗
Sexual conflict and sexual selection: lost in the chase.
The emergent field of evolutionary biology that studies disparities between the evolutionary interests of alleles expressed in the two sexes, or sexual conflict, promises to offer novel insights into male-female coevolution and speciation. Our theoretical understanding of basic concepts is, however, still incomplete. In a recent perspective paper, Pizzari and Snook provided a framework for understanding sexually antagonistic coevolution and for distinguishing this process from other models of male-female coevolution and suggested an experimental protocol to test for sexually antagonistic coevolution. Here, I show that the framework is flawed, primarily because it is built upon the mistaken assumption that male and female fitness can evolve independently. Further, while the empirical strategy advocated has indeed offered important insights in the past, it does not allow unambiguous discrimination between competing hypotheses.
Animals↗
Coevolving predator and prey robots: do "arms races" arise in artificial evolution?
Coevolution (i.e., the evolution of two or more competing populations with coupled fitness) has several features that may potentially enhance the power of adaptation of artificial evolution. In particular, as discussed by Dawkins and Krebs [3], competing populations may reciprocally drive one another to increasing levels of complexity by producing an evolutionary "arms race." In this article we will investigate the role of coevolution in the context of evolutionary robotics. In particular, we will try to understand in what conditions coevolution can lead to "arms races." Moreover, we will show that in some cases artificial coevolution has a higher adaptive power than simple evolution. Finally, by analyzing the dynamics of coevolved populations, we will show that in some circumstances well-adapted individuals would be better advised to adopt simple but easily modifiable strategies suited for the current competitor strategies rather than incorporate complex and general strategies that may be effective against a wide range of opposing counter-strategies.
Biological Evolution↗
Coevolutionary computation.
This article proposes a general framework for the use of coevolution to boost the performance of genetic search. It combines coevolution with yet another biologically inspired technique, called lifetime fitness evaluation (LTFE). Two unrelated problems--neural net learning and constraint satisfaction--are used to illustrate the approach. Both problems use predator-prey interactions to boost the search. In contrast with traditional "single population" genetic algorithms (GAs), two populations constantly interact and co-evolve. However, the same algorithm can also be used with different types of co-evolutionary interactions. As an example, the symbiotic coevolution of solutions and genetic representations is shown to provide an elegant solution to the problem of finding a suitable genetic representation. The approach presented here greatly profits from the partial and continuous nature of LTFE. Noise tolerance is one advantage. Even more important, LTFE is ideally suited to deal with coupled fitness landscapes typical for coevolution.
Algorithms↗
Evolutionary dynamics of predator-prey systems: an ecological perspective.
Evolution takes place in an ecological setting that typically involves interactions with other organisms. To describe such evolution, a structure is needed which incorporates the simultaneous evolution of interacting species. Here a formal framework for this purpose is suggested, extending from the microscopic interactions between individuals--the immediate cause of natural selection, through the mesoscopic population dynamics responsible for driving the replacement of one mutant phenotype by another, to the macroscopic process of phenotypic evolution arising from many such substitutions. The process of coevolution that results from this is illustrated in the context of predator-prey systems. With no more than qualitative information about the evolutionary dynamics, some basic properties of predator-prey coevolution become evident. More detailed understanding requires specification of an evolutionary dynamic; two models for this purpose are outlined, one from our own research on a stochastic process of mutation and selection and the other from quantitative genetics. Much of the interest in coevolution has been to characterize the properties of fixed points at which there is no further phenotypic evolution. Stability analysis of the fixed points of evolutionary dynamical systems is reviewed and leads to conclusions about the asymptotic states of evolution rather different from those of game-theoretic methods. These differences become especially important when evolution involves more than one species.
Animals↗
Physicochemical optimization in the genetic code origin as the number of codified amino acids increases.
We have assumed that the coevolution theory of genetic code origin (Wong JT, Proc Natl Acad Sci USA 72:1909-1912, 1975) is essentially correct. This theory makes it possible to identify at least 10 evolutionary stages through which genetic code organization might have passed prior to reaching its current form. The calculation of the minimization level of all these evolutionary stages leads to the following conclusions. (1) The minimization percentages increased linearly with the number of amino acids codified in the codes of the various evolutionary stages when only the sense changes are considered in the analysis. This seems to favor the physicochemical theory of genetic code origin even if, as discussed in the paper, this observation is also compatible with the coevolution theory. (2) For the first seven evolutionary stages of the genetic code, this trend is less clear and indeed is inverted when we consider the global optimisation of the codes due to both sense changes and synonymous changes. This inverse correlation between minimization percentages and the number of amino acids codified in the codes of the intermediate stages seems to favor neither the physicochemical nor the stereochemical theories of genetic code origin, as it is in the early and intermediate stages of code development that these theories would expect minimization to have played a crucial role, and this does not seem to be the case. However, these results are in agreement with the coevolution theory, which attributes a role to the physicochemical properties of amino acids that, while important, is nevertheless subordinate to the mechanism which concedes codons from the precursor amino acids to the product amino acids as the primary factor determining the evolutionary structuring of the genetic code. The results are therefore discussed in the context of the various theories proposed to explain genetic code origin.
Algorithms↗
First evidence of regular common cuckoo, Cuculus canorus, parasitism on eastern olivaceous warblers, Hippolais pallida elaeica.
Coevolution is defined as specialized relationships between species that lead to a reciprocal evolutionary change. A particularly suitable model system for studying coevolution is the interactions between obligate avian brood parasites and their hosts. The common cuckoo (Cuculus canorus, hereafter cuckoo) is a well-known brood parasite, which utilizes a range of smaller passerines as hosts. However, warblers of the genus Hippolais have rarely been reported as being victims of cuckoos, and furthermore, few data exist on the occurrence of antiparasite defenses in these hosts. In this study, we examined possible host-parasite coevolution between cuckoos and eastern olivaceous warblers (Hippolais pallida elaeica, hereafter olivaceous warblers) in three closely situated areas in northwestern Bulgaria. The olivaceous warbler has never been reported to be a regular cuckoo host. However, the present study, carried out in 2001-2003 shows that the olivaceous warbler is regularly and heavily parasitized by the cuckoo in this area. Parasitism rate was high (26.6%, 34/128) and consistent among years, with some variation between areas. The cuckoo egg mimicry was moderately good, and olivaceous warbler rejection rate of such eggs was 50%. Cuckoo eggs laid in olivaceous warbler nests had a whitish to whitish-green ground color, and the majority appeared to be distinctly different from cuckoo eggs found in other host species in the area. The olivaceous warbler proved to be a rather good host for cuckoos as 20.6% (7/34) of cuckoo eggs laid produced fledglings, a breeding success comparable to other suitable hosts in Europe. This is the first in-depth study of brood parasitism in a warbler of the genus Hippolais, and cuckoos parasitizing olivaceous warblers probably represent a previously unknown gens.
Animals↗
The coevolutionary potential of a 'generalist' parasite, the hen flea Ceratophyllus gallinae.
Hosts exert selection pressures on their parasites and it is often assumed that host-parasite coevolution with each host is less intense in a generalist parasite than for a parasite with a narrow host range. Selection pressure on the parasite, however, is rather determined by host specificity, i.e. the relative importance of each host, than simply by the range of hosts. The determination of host specificity requires an assessment of the prevalence and intensity of parasite infestation within each host's nests, as well as the local abundance of each host species. Since the hen flea, Ceratophyllus gallinae, is a rather generalist parasite of birds it could be concluded that there has been weak coevolution with each of its hosts. By reviewing the literature on the prevalence and intensity of hen flea infestations in bird nests we estimated the number of individuals produced in the nest of each host species. The comparative analysis shows (1) that the prevalence of infestation is highest in hole-nesting avian families, (2) that prevalence and intensity of infestation among bird families are highly correlated, and (3) that hole-nesting Paridae have the highest intensities of infestation and harbour the majority of the flea population. These results underline the fleas' potential for coevolution with Paridae despite their extensive host range.
Animals↗
Rapid evolution of reproductive barriers driven by sexual conflict.
A growing amount of experimental data indicates extremely rapid evolution of traits and proteins related to fertilization in many diverging taxa. These data come from studies of sperm or pollen competition between closely related species, and from molecular studies of fertilization proteins. The positive selection for evolutionary novelty that appears to be acting on fertilization systems seems paradoxical because successful reproduction requires the close matching of female and male traits. It has been suggested that perpetual coevolution between the sexes can result from sexual conflict in mating. Sexual conflict occurs when characteristics that enhance the reproductive success of one sex reduce the fitness of the other sex. Numerous examples of sexual conflict resulting from sensory exploitation, polyspermy and the cost of mating have been discussed in detail. The potential for coevolution due to such conflict has been evaluated experimentally. Here I develop a simple mathematical model describing coevolutionary dynamics of male and female traits involved in reproduction. The model shows that continual change in such traits at a constant speed is expected whenever females (or eggs) experience fitness loss from having too many compatible males (or sperms). The plausibility of runaway coevolution increases with increasing population size. Rapid evolution of reproductive barriers driven by sexual conflict may explain increased speciation rates after colonization of new habitats ('adaptive radiation') and high species richness in resource-rich environments.
Animals↗