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PubMed2003

Genetic dimension of the coevolution of virulence-resistance in Drosophila -- parasitoid wasp relationships.

Variations observed in parasite virulence and host resistance may be the outcome of coevolutionary processes. Recent theoretical developments have led to a 'geographic mosaic theory' of coevolution according to which there are some localities where reciprocal selection occurs (hot spots) and others where it is strongly reduced (cold spots). Studies of host-parasitoid systems back this up, revealing a geographical variation of traits subjected to antagonistic selection governed by variations in the strength of the ecological interactions. A more detailed analysis of the genetic basis of these geographic variations in a model system -- the interaction between Drosophila melanogaster and its specific parasitoid Leptopilina boulardi -- suggests that cold spots and hot spots are also driven by the amount of genetic variation available for the trait considered. Our approach, based on isolating reference strains, has been found to predict the result of sympatric interactions and it will be helpful in identifying the selective forces responsible for the coevolution. In this model, host resistance to a standardised reference strain is a weak predictor of the outcome of interactions in the field, and the main parameter accounting for the geographic variations is the number of host species available, with less parasitoid virulence towards D. melanogaster being found in areas displaying a more diversified host community.

Animals↗
PubMed1993

Simian immunodeficiency viruses from central and western Africa: evidence for a new species-specific lentivirus in tantalus monkeys.

Although up to 50% of African green monkeys (AGMs) are infected by simian immunodeficiency viruses (SIV) in their natural habitat, they remain asymptomatic carriers of these lentiviruses. They provide an attractive model to study not only the origin but also the link among genetic variation, host-virus adaptation, and pathogenicity of primate lentiviruses. SIVagm have been isolated from three species of AGM: the vervet (Cercopithecus pygerythrus), the grivet (Cercopithecus aethiops), and the sabaeus (Cercopithecus sabaeus) monkey. We studied four new SIVagm isolates from a fourth AGM species, the tantalus monkey (Cercopithecus tantalus), caught in the Central African Republic, and four new isolates from feral sabaeus monkeys from Senegal. Antigenic properties and partial env sequences were used to evaluate the diversity among these isolates. Alignment of env sequences in SIVagm isolated from tantalus and sabaeus monkeys permitted detailed mapping of the variable and conserved domains in the external glycoprotein. Genetic distances indicated that SIVagm isolates from tantalus monkeys are the most divergent among SIVagm in feral AGMs in Africa. The fact that AGMs are infected by four distinct lentiviruses, each specific for a single AGM species, supports the hypothesis of a coevolution of these viruses and their natural hosts and suggests that SIV transmission is a rare event among separated AGM species in the wild.

Amino Acid Sequence↗
PubMed1977

Blood corpuscles and blood hemoglobins: a possible example of coevolution.

A model which equates oxygen transport to hemoglobin concentration and molecular weight is used to demonstrate that high concentrations of hemoglobin will augment oxygen transport only if the molecular weight of the hemoglobin is low. The evolution of corpuscles is a necessary counterpart to having high concentrations of the low molecular weight hemoglobins. corpuscles prevent loss of the small molecules by way of excretory filters and prevent the development of exceedingly high plasma osmotic pressures.

Biological Evolution↗
PubMed2002

Developmental genetics and evolution of symbiotic structures in nitrogen-fixing nodules and arbuscular mycorrhiza.

Genetic and molecular mechanisms of development are compared for two major plant-microbe endosymbioses: N(2)-fixing nodules (with rhizobia or actinomycetes Frankia) and arbuscular mycorrhiza (with Glomales fungi). Development from the primordia formed de novo in root tissues is common for all known types of N(2)-fixing nodules. However, their structure varies greatly with respect to: (i) tissue topology (location of vascular bundles is peripherical in legumes or central in non-legumes); (ii) position of nodule primordium (inner or outer cortex in legumes, pericycle in non-legumes); (iii) stability of apical meristem (persistent in the indeterminate nodules, transient in the determinate ones). In addition, legumes vary in ability to form compartments harboring endosymbiotic rhizobia and located intercellularly (infection threads) and intracellularly (symbiosomes). Using pea (Pisum sativum) symbiotic mutants, the nodule developmental program is dissected into a range of spatially and temporarily differentiated steps comprising four sub-programs (development of endosymbiotic compartments; nodule histogenesis; autoregulation of nodulation; bacteroid differentiation). The developmental mutations are suggested in some cases to reverse the endosymbiotic system into the morphologically simpler forms some of which may correspond to the ancestral stages of nodule evolution. The origin of legume-rhizobial and actinorhizal symbioses is suggested to be based on a set of preadaptations many of which had been evolved in angiosperms during coevolution with arbuscular mycorrhizal fungi (e.g., inter- and intracellular maintenance of symbionts, their control via defence-like reactions and recognition of chitin-like molecules). An analysis of parallel morphological variation in symbiotic mutants and wild-growing legume species enables us to reconstruct the major stages of evolution for N(2)-fixing symbioses.

Actinomycetales↗
PubMed1992

Evolution of thymidine and thymidylate kinases: the possibility of independent capture of TK genes by different groups of viruses.

Phylogenetic analysis of viral and cellular thymidine and thymidylate kinases was performed using computer-assisted methods. Multiple alignments and tentative phylogenetic trees were generated for the two families of these enzymes, which include a) thymidine kinases (TK) of mammals, poxviruses, African swine fever virus, E. coli, and bacteriophage T4; and b) thymidylate kinases (ThyK) of yeast and poxviruses and distantly related herpesvirus proteins with both enzymatic activities. Analysis of the alignment of the TKs of the first family highlighted three strongly conserved segments. Two of these corresponded to the A and B motifs of the purine NTP-binding pattern. The third, C-terminal segment, showing the highest conservation, encompassed a modified Zn finger motif. It is speculated that this motif might be involved in TK oligomerization. Phylogenetic trees constructed by three different methods suggested that cellular TK genes could be captured independently by T4 bacteriophage, African swine fever virus, fowlpox virus, and the other poxviruses. The observed tree topologies appear to contradict the popular virus-host coevolution schemes and to imply that different subdivisions of poxviruses diverged at earlier stages of evolution than their hosts did. It was shown that deoxynucleoside monophosphate kinase of bacteriophage T4 is related to the ThyK family. Phylogenetic analysis suggested that ThyK genes probably have been acquired independently by phage T4, poxviruses, and herpes-viruses.

Amino Acid Sequence↗
PubMed1998

Resistance of eels (Gymnothorax) to the venom of sea kraits (Laticauda colubrina): a test of coevolution.

Eels of the genus Gymnothorax from the Pacific are selectively preyed upon by banded sea kraits (Laticauda colubrina) and have been reported to sustain massive doses of sea krait venom without ill effect. By contrast, the present study found that Gymnothorax moringa from the Caribbean, where no sea snakes occur, are sensitive to sea krait venom, with doses as low as 0.01 mg dry wt of venom/kg wet wt of eel resulting in signs of envenomation, and doses as small as 0.1 mg/kg proving to be lethal. These observations suggest that the resistance of Pacific Gymnothorax to sea krait venom results from coevolution of predator and prey, rather than from a general hardiness of Gymnothorax. This theory is supported further by literature reports of sensitivity to sea snake venom by other taxa of non-coevolved eels that either are allopatric with sea snakes (Anguilla), or are sympatric with them but occupy different habitats and are not preyed upon by them (Heteroconger).

Animals↗
PubMed2002

Coevolution of costly mate choice and condition-dependent display of good genes.

Females often choose their mates, instead of mating at random, even when a father contributes nothing but genes to his offspring. Costly female preferences for males with exaggerated traits that reduce viability, such as the peacock's tail, are particularly puzzling. Such preferences can evolve if directly favoured by natural selection or when the exaggerated trait, although maladaptive per se, indicates high overall quality of the male's genotype. Two recent analyses suggested that the advantage to mate choice based on genetic quality is too weak to explain extreme cases of exaggeration of display traits and the corresponding preferences. We studied coevolution of a female mate-preference function and a genotype-dependent male display function where mutation supplies variation in genotype quality and mate preference is costly. Preference readily evolves, often causing extreme exaggeration of the display. Mate choice and trait expression can approach an equilibrium, or a limit cycle, or exaggeration can proceed forever, eventually causing extinction.

Animals↗
PubMed2003

Genomics of helicobacter 2003.

Research on Helicobacter pylori has been driven by the field of genomics since the release of the first of two complete genome sequences in 1997. In this review we highlight progress made in the last year. New bioinformatics tools and methods promise better functional and strain comparative analyses of individual genes. Sequence-based methods of strain comparison documented the coevolution of H. pylori with human populations. Several comprehensive analyses of the bacterial transcriptome were undertaken as well as two sophisticated studies of the transcriptional response of specific host tissues in response to H. pylori infection using different mouse models of H. pylori diseases. Some progress was made in developing genetic tools for mutational analysis of the genes required for infection. Finally, proteomic approaches were refined to delineate surface exposed and secreted proteins that represent potential antigens. In summary, while we do not have the full story of H. pylori, significant progress in deciphering the genome into functional biology has been made.

Genetic Variation↗
PubMed2002

No accident: genetic codes freeze in error-correcting patterns of the standard genetic code.

The standard genetic code poses a challenge in understanding the evolution of information processing at a fundamental level of biological organization. Genetic codes are generally coadapted with, or 'frozen' by, the protein-coding genes that they translate, and so cannot easily change by natural selection. Yet the standard code has a significantly non-random pattern that corrects common errors in the transmission of information in protein-coding genes. Because of the freezing effect and for other reasons, this pattern has been proposed not to be due to selection but rather to be incidental to other evolutionary forces or even entirely accidental. We present results from a deterministic population genetic model of code-message coevolution. We explicitly represent the freezing effect of genes on genetic codes and the perturbative effect of changes in genetic codes on genes. We incorporate characteristic patterns of mutation and translational error, namely, transition bias and positional asymmetry, respectively. Repeated selection over small successive changes produces genetic codes that are substantially, but not optimally, error correcting. In particular, our model reproduces the error-correcting patterns of the standard genetic code. Aspects of our model and results may be applicable to the general problem of adaptation to error in other natural information-processing systems.

Animals↗
PubMed1989

Evolution of RNA genomes: does the high mutation rate necessitate high rate of evolution of viral proteins?

RNA genomes have been shown to mutate much more frequently than DNA genomes. It is generally assumed that this results in rapid evolution of RNA viral proteins. Here, an alternative hypothesis is proposed that close cooperation between positive-strand RNA viral proteins and those of the host cells required their coevolution, resulting in similar amino acid substitution rates. Constraints on compatibility with cellular proteins should determine, at any time, the covarion sets in RNA viral proteins. These ideas may be helpful in rationalizing the accumulating data on significant sequence similarities between proteins of positive-strand RNA viruses infecting evolutionarily distant hosts as well as between viral and cellular proteins.

Biological Evolution↗
PubMed2005

A role for habitat area in the geographic mosaic of coevolution between red crossbills and lodgepole pine.

Understanding how resource abundance limits adaptive evolution and influences species interactions is an important step towards developing insight into the role of microevolutionary processes in establishing macroevolutionary patterns. We examined how variation in resource abundance (forest area of lodgepole pine Pinus contorta ssp. latifolia) influenced patterns of co-adaptation and coevolution between red crossbill (Loxia curvirostra complex) and lodgepole pine populations. First, we found that crossbill abundance increased logarithmically as forest area increased in mountain ranges lacking a preemptive competitor (pine squirrels Tamiasciurus hudsonicus). Second, seed defences against predation by crossbills increased with increases in crossbill density, suggesting that seed defences have likely evolved in proportion to the intensity of selection that crossbills exert. Third, the average bill size of crossbill populations increased with increasing seed defences, which implies that crossbill offenses increased with increases in seed defences. The large bill size on the largest range is the result of coevolution with lodgepole pine with this crossbill population perhaps speciating. Local adaptation of crossbill populations on smaller ranges, however, is more likely the result of resident crossbills representing a subset of the potential colonists (phenotypic sorting) than of local evolution. In the smallest range, migration and possibly more frequent extinction likely impede local adaptation and may result in maladaptation.

Adaptation, Biological↗
PubMed2004

Escalation and trophic specialization drive adaptive radiation of freshwater gastropods in ancient lakes on Sulawesi, Indonesia.

Species flocks in ancient lakes have long been appreciated as ideal model systems for the study of speciation and adaptive processes. We here present data from a new invertebrate model system with intrinsic parameters distinct from those of other documented radiations. The ancient lakes on Sulawesi harbour an endemic species flock of at least 33 species of viviparous snails. Molecular data reveal multiple independent colonizations of the lakes by riverine ancestors. In each colonizing clade, parallel evolution of conspicuous shell morphologies, followed by a differentiation of trophic morphology and the development of habitat specificity can be observed. Extensive shell crushing experiments and strong dentition of the chelae observed in some lacustrine crab species suggest that coevolution with crabs, i.e. escalation, is the most likely cause of initial shell divergence. By contrast, repeated parallel evolution in radula morphology indicates that speciation within lineages is driven by divergent adaptation to different resources among sympatric taxa. The inclusion of coevolutionary processes is unique in this system compared with diversification models developed for vertebrate radiations.

Adaptation, Biological↗
PubMed1996

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↗
PubMed2004

Genes regulated by mating, sperm, or seminal proteins in mated female Drosophila melanogaster.

In Drosophila melanogaster, sperm and accessory gland proteins ("Acps," a major component of seminal fluid) transferred by males during mating trigger many physiological and behavioral changes in females (reviewed in ). Determining the genetic changes triggered in females by male-derived molecules and cells is a crucial first step in understanding female responses to mating and the female's role in postcopulatory processes such as sperm competition, cryptic female choice, and sexually antagonistic coevolution. We used oligonucleotide microarrays to compare gene expression in D. melanogaster females that were either virgin, mated to normal males, mated to males lacking sperm, or mated to males lacking both sperm and Acps. Expression of up to 1783 genes changed as a result of mating, most less than 2-fold. Of these, 549 genes were regulated by the receipt of sperm and 160 as a result of Acps that females received from their mates. The remaining genes whose expression levels changed were modulated by nonsperm/non-Acp aspects of mating. The mating-dependent genes that we have identified contribute to many biological processes including metabolism, immune defense, and protein modification.

Animals↗
PubMed1979

Arms races between and within species.

An adaptation in one lineage (e.g. predators) may change the selection pressure on another lineage (e.g. prey), giving rise to a counter-adaptation. If this occurs reciprocally, an unstable runaway escalation or 'arms race' may result. We discuss various factors which might give one side an advantage in an arms race. For example, a lineage under strong selection may out-evolve a weakly selected one (' the life-dinner principle'). We then classify arms races in two independent ways. They may be symmetric or asymmetric, and they may be interspecific or intraspecific. Our example of an asymmetric interspecific arms race is that between brood parasites and their hosts. The arms race concept may help to reduce the mystery of why cuckoo hosts are so good at detecting cuckoo eggs, but so bad at detecting cuckoo nestlings. The evolutionary contest between queen and worker ants over relative parental investment is a good example of an intraspecific asymmetric arms race. Such cases raise special problems because the participants share the same gene pool. Interspecific symmetric arms races are unlikely to be important, because competitors tend to diverge rather than escalate competitive adaptations. Intraspecific symmetric arms races, exemplified by adaptations for male-male competition, may underlie Cope's Rule and even the extinction of lineages. Finally we consider ways in which arms races can end. One lineage may drive the other to extinction; one may reach an optimum, thereby preventing the other from doing so; a particularly interesting possibility, exemplified by flower-bee coevolution, is that both sides may reach a mutual local optimum; lastly, arms races may have no stable and but may cycle continuously. We do not wish necessarily to suggest that all, or even most, evolutionary change results from arms races, but we do suggest that the arms race concept may help to resolve three long-standing questions in evolutionary theory.

Adaptation, Biological↗
PubMed1994

[Dynamics of evolutionary rates of proteins from small ribosomal subunits].

Phylogenetic analysis of small ribosomal subunit proteins was performed. Plausible taxon-specific acceleration of evolutionary rates ("leading") of base substitution of some ribosomal proteins and 16S rRNA sites in different phyletic lines were revealed. The limited number of synchronously changing proteins is discussed in terms of relay-race model of coevolution of ribosome. The analogy with dilemma of Haldane is drawn. Plausible differences in the evolutionary rates of regions with different secondary structure were revealed. Changes in correlation of evolutionary rates of regions with different secondary structure during leading were determined. It is anticipated that S14 with S19 ribosomal proteins and S7 with corresponding site on 16S rRNA change co-evolutionary.

Animals↗
PubMed1995

The phylogeny of tRNAs seems to confirm the predictions of the coevolution theory of the origin of the genetic code.

An extensive analysis of the evolutionary relationships existing between transfer RNAs, performed using parsimony algorithms, is presented. After building up an estimate of the tRNA ancestral sequences, these sequences are then compared using certain methods. The results seem to suggest that the coevolution hypothesis (Wong, J.T., 1975, Proc. Natl. Acad. Sci. USA 72, 1909-1912) that sees the genetic code as a map of the biosynthetic relationships between amino acids is further supported by these results, as compared to the hypotheses that see the physicochemical properties of amino acids as the main adaptative theme that led to the structuring of the genetic code.

Amino Acid Sequence↗
PubMed2006

The evolutionary outcome of sexual conflict.

Inter-locus sexual conflict occurs by definition when there is sexually antagonistic selection on a trait so that the optimal trait value differs between the sexes. As a result, there is selection on each sex to manipulate the trait towards its own optimum and resist such manipulation by the other sex. Sexual conflict often leads additionally to the evolution of harmful behaviour and to self-reinforcing and even perpetual sexually antagonistic coevolution. In an attempt to understand the determinants of these different outcomes, I compare two groups of traits-those related to parental investment (PI) and to mating-over which there is sexual conflict, but which have to date been explored by largely separate research traditions. A brief review suggests that sexual conflict over PI, particularly over PI per offspring, leads less frequently to the evolution of manipulative behaviour, and rarely to the evolution of harmful behaviour or to the rapid evolutionary changes which may be symptomatic of sexually antagonistic coevolution. The chief determinants of the evolutionary outcome of sexual conflict are the benefits of manipulation and resistance, the costs of manipulation and resistance, and the feasibility of manipulation. All three of these appear to contribute to the differences in the evolutionary outcome of conflicts over PI and mating. A detailed dissection of the evolutionary changes following from sexual conflict exposes greater complexity than a simple adaptation-counter-adaptation cycle and clarifies the role of harm. Not all of the evolutionary changes that follow from sexual conflict are sexually antagonistic, and harm is not necessary for sexually antagonistic coevolution to occur. In particular, whereas selection on the trait over which there is conflict is by definition sexually antagonistic, collateral harm is usually in the interest of neither sex. This creates the opportunity for palliative adaptations which reduce collateral harm. Failure to recognize that such adaptations are in the interest of both sexes can hinder our understanding of the evolutionary outcome of sexual conflict.

Animals↗