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PubMed2005

The coevolutionary dynamics of obligate ant social parasite systems--between prudence and antagonism.

In this synthesis we apply coevolutionary models to the interactions between socially parasitic ants and their hosts. Obligate social parasite systems are ideal models for coevolution, because the close phylogenetic relationship between these parasites and their hosts results in similar evolutionary potentials, thus making mutual adaptations in a stepwise fashion especially likely to occur. The evolutionary dynamics of host-parasite interactions are influenced by a number of parameters, for example the parasite's transmission mode and rate, the genetic structure of host and parasite populations, the antagonists' migration rates, and the degree of mutual specialisation. For the three types of obligate ant social parasites, queen-tolerant and queen-intolerant inquilines and slavemakers, several of these parameters, and thus the evolutionary trajectory, are likely to differ. Because of the fundamental differences in lifestyle between these social parasite systems, coevolution should further select for different traits in the parasites and their hosts. Queen-tolerant inquilines are true parasites that exert a low selection pressure on their host, because of their rarity and the fact that they do not conduct slave raids to replenish their labour force. Due to their high degree of specialisation and the potential for vertical transmission, coevolutionary theory would predict interactions between these workerless parasites and their hosts to become even more benign over time. Queen-intolerant inquilines that kill the host queen during colony take-over are best described as parasitoids, and their reproductive success is limited by the existing worker force of the invaded host nest. These parasites should therefore evolve strategies to best exploit this fixed resource. Slavemaking ants, by contrast, act as parasites only during colony foundation, while their frequent slave raids follow a predator prey dynamic. They often exploit a number of host species at a given site, and theory predicts that their associations are best described in terms of a highly antagonistic coevolutionary arms race.

Animals↗
PubMed2004

Molecular constraints to interspecies transmission of viral pathogens.

The successful replication of a viral pathogen in a host is a complex process involving many interactions. These interactions develop from the coevolution of pathogen and host and often lead to a species specificity of the virus that can make interspecies transmissions difficult. Nevertheless, viruses do sporadically cross species barriers into other host populations, including humans. In zoonotic infections, many of these interspecies transfer events are dead end, where transmission is confined only to the animal-to-human route but sometimes viruses adapt to enable spread from human to human. A pathogen must overcome many hurdles to replicate successfully in a foreign host. The viral pathogen must enter the host cell, replicate with the assistance of host factors, evade inhibitory host products, exit the first cell and move on to the next, and possibly leave the initial host and transmit to another. Each of these stages may require adaptive changes in the pathogen. Although the factors that influence each stage of the replication and transmission of most agents have not been resolved, the genomics of both hosts and pathogens are now at hand and we have begun to understand some of the molecular changes that enable some viruses to adapt to a new host.

Animals↗
PubMed2006

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↗
PubMed1995

Coevolution of RNA helix stability and Shine-Dalgarno complementarity in a translational start region.

The initiation region of the coat-protein gene of RNA bacteriophage MS2 adopts a well-defined hairpin structure with the start codon occupying the loop position, while the Shine-Dalgarno (SD) sequence is part of the stem. In a previous study, we introduced mutations in this hairpin that changed its thermodynamic stability. The resulting phages evolved to regain the wild-type stability by second-site compensatory substitutions. Neither the original nor the suppressor mutations were in the SD region. In the present analysis, we have made changes in the SD region that shorten or extend its complementarity to the 3' end of 16S rRNA and monitored their evolution to a stable pseudorevertant species. Phages in which the SD complementarity was decreased evolved an initiator hairpin of lower stability than wild type while those in which the complementarity was extended evolved a hairpin with an increased stability. We conclude that weaker SD sequences still allow maximal translation if the secondary structure of the ribosome-landing site is destabilized accordingly. Alternatively, translation-initiation regions with a stronger secondary structure still allow maximal expression, if the SD complementarity is extended. These findings support a previously published model in which the SD interaction helps the ribosome to melt the structure in a translation-initiation region.

Base Sequence↗
PubMed2004

A reconciliation analysis of host switching in plant-fungal symbioses.

Plant-fungal symbioses include many familiar antagonistic and mutualistic associations and some model cases of coevolution. The relationship between coevolution at the different evolutionary scales has remained an open question. Widespread host specificity and documented host switches offer conflicting indications of what to expect from comparisons of plant and fungal phylogenies. This study sought to establish the role of plant phylogeny in determining fungal phylogeny and the relative contributions of codivergence and host switching by comparing tree topologies for 15 plant-fungal symbioses. Second it attempted to characterize the relationship between phylogenetic congruence and switching. Trees were estimated from published sequences and reconciliation analysis was applied in the form of cophylogeny mapping using "jungles". This provided an exhaustive account of all possible switches capable of reconciling two associated phylogenies. A continuum of cophylogenetic dynamics was identified, ranging from mostly codivergence (e.g., Exobasidium) to mostly switching, (e.g., Erysiphe). Surprisingly, congruent solutions do not necessarily have fewer switches when using cophylogeny mapping, but a significant negative relationship between congruence and the distance of switches proved to be a useful indicator. According to reconciliation analysis, the contribution of host phylogeny varies widely across plant-fungal symbioses, making host specificity and coadaptation poor indicators of macroevolutionary trends because they are necessary, but not sufficient, conditions.

Computational Biology↗
PubMed2004

Genotypic vs. condition effects on parasite-driven rare advantage.

Models and empirical studies of coevolution assume host resistance and parasite infectivity are genetically based. However, nongenetic physiological or environmental influences could alter host susceptibility even when the relationship is genetically based. In this experiment we examined the influence of host genotype, host condition at the time of infection (age and reproductive status), and their interaction on resistance of the freshwater snail Potamopyrgus antipodarum) to its dominant trematode parasite (Microphallus sp.). We used a laboratory infection experiment of a clonal snail population to determine the susceptibility of juveniles, brooding adult females, and nonbrooding adult females. We found a significant effect of both life-history state and clonal genotype on the prevalence of infection. However, the relative susceptibility of different clonal genotypes was not altered by condition; genotypes that were rare in the natural population were less infected than those that were common for each life-history state. These results suggest that although host condition affects susceptibility, it does not disrupt the specificity of the match between parasites and common clonal genotypes. Hence these findings support the Red Queen hypothesis for the maintenance of sex under genetically based host-parasite interactions.

Analysis of Variance↗
PubMed2005

Coevolution and biogeography among Nematodirinae (Nematoda: Trichostrongylina) Lagomorpha and Artiodactyla (Mammalia): exploring determinants of history and structure for the northern fauna across the holarctic.

Nematodes of the subfamily Nematodirinae are characteristic components of a Holarctic fauna. The topology of a generic-level phylogenetic hypothesis, patterns of diversity, and geographic distributions for respective nematode taxa in conjunction with data for host occurrence are consistent with primary distributions determined across Beringia for species of Murielus, Rauschia, Nematodirus, and Nematodirella. Ancestral hosts are represented by Lagomorpha, with evidence for a minimum of 1 host-switching-event and subsequent radiation in the Artiodactyla. Diversification may reflect vicariance of respective faunas along with episodic or cyclical range expansion and isolation across Beringia during the late Tertiary and Quaternary. Secondarily, species of Nematodirus attained a distribution in the Neotropical region with minimal diversification of an endemic fauna represented by Nematodirus molini among tayassuids, Nematodirus lamae among camelids and Nematodirus urichi in cervids during the Pleistocene. Nematodirines are a core component of an Arctic-Boreal fauna of zooparasitic nematodes (defined by latitude and altitude) adapted to transmission in extreme environments characterized by seasonally low temperatures and varying degrees of desiccation. The history and distribution of this fauna is examined in the context of biotic and abiotic determinants for geographic colonization and host switching with an exploration of predicted responses of complex host-parasite systems to ecological perturbation under a regime of global climate change.

Animals↗
PubMed2004

Wolbachia transfer from Rhagoletis cerasi to Drosophila simulans: investigating the outcomes of host-symbiont coevolution.

Wolbachia is an endosymbiont of diverse arthropod lineages that can induce various alterations of host reproduction for its own benefice. Cytoplasmic incompatibility (CI) is the most common phenomenon, which results in embryonic lethality when males that bear Wolbachia are mated with females that do not. In the cherry fruit fly, Rhagoletis cerasi, Wolbachia seems to be responsible for previously reported patterns of incompatibility between populations. Here we report on the artificial transfer of two Wolbachia variants (wCer1 and wCer2) from R. cerasi into Drosophila simulans, which was performed with two major goals in mind: first, to isolate wCer1 from wCer2 in order to individually test their respective abilities to induce CI in the new host; and, second, to test the theoretical prediction that recent Wolbachia-host associations should be characterized by high levels of CI, fitness costs to the new host, and inefficient transmission from mothers to offspring. wCer1 was unable to develop in the new host, resulting in its rapid loss after successful injection, while wCer2 was established in the new host. Transmission rates of wCer2 were low, and the infection showed negative fitness effects, consistent with our prediction, but CI levels were unexpectedly lower in the new host. Based on these parameter estimates, neither wCer1 nor wCer2 could be naturally maintained in D. simulans. The experiment thus suggests that natural Wolbachia transfer between species might be restricted by many factors, should the ecological barriers be bypassed.

Animals↗
PubMed1995

Molecular evolution of transfer RNA from two precursor hairpins: implications for the origin of protein synthesis.

In this paper we are going to present a model for the coevolution of major components of the protein synthesis machinery in a primordial RNA world. We propose that the essential prerequisites for RNA-based protein synthesis, i.e., tRNA-like molecules, ribozymic charging catalysts, small-subunit(SSU) rRNA, and large-subunit(LSU) rRNA, evolved from the same ancestral RNA molecule. Several arguments are considered which suggest that tRNA-like molecules were derived by tandem joining of template-flanking hairpin structures involved in replication control. It is further argued that the ancestors of contemporary group I tRNA introns catalyzed such hairpin joining reactions, themselves also giving rise to the ribosomal RNAs. Our model includes a general stereochemical principle for the interaction between ribozymes and hairpin-derived recognition structures, which can be applied to such seemingly different processes as RNA polymerization, aminoacylation, tRNA decoding, and peptidyl transfer, implicating a common origin for these fundamental functions. These and other considerations suggest that generation and evolution of tRNA were coupled to the evolution of synthetases, ribosomal RNAs, and introns from the beginning and have been a consequence arising from the original function of tRNA precursor hairpins as replication and recombination control elements.

Animals↗
PubMed1987

cDNA sequence of a human skeletal muscle ADP/ATP translocator: lack of a leader peptide, divergence from a fibroblast translocator cDNA, and coevolution with mitochondrial DNA genes.

We have characterized a 1400-nucleotide cDNA for the human skeletal muscle ADP/ATP translocator. The deduced amino acid sequence is 94% homologous to the beef heart ADP/ATP translocator protein and contains only a single additional amino-terminal methionine. This implies that the human translocator lacks an amino-terminal targeting peptide, a conclusion substantiated by measuring the molecular weight of the protein synthesized in vitro. A 1400-nucleotide transcript encoding the skeletal muscle translocator was detected on blots of total RNA from human heart, kidney, skeletal muscle, and HeLa cells by hybridization with oligonucleotide probes homologous to the coding region and 3' noncoding region of the cDNA. However, the level of this mRNA varied substantially among tissues. Comparison of our skeletal muscle translocator sequence with that of a recently published human fibroblast translocator cognate revealed that the two proteins are 88% identical and diverged about 275 million years ago. Hence, tissues vary both in the level of expression of individual translocator genes and in differential expression of cognate translocator genes. Comparison of the base substitution rates of the ADP/ATP translocator and the oxidative phosphorylation genes encoded by mitochondrial DNA revealed that the mitochondrial DNA genes fix 10 times more synonymous substitutions and 12 times more replacement substitutions; yet, these nuclear and cytoplasmic respiration genes experience comparable evolutionary constraints. This suggests that the mitochondrial DNA genes are highly prone to deleterious mutations.

Base Sequence↗
PubMed1999

Evolutionary relationships among the protostrongylidae (Nematoda: Metastrongyloidea) as inferred from morphological characters, with consideration of parasite-host coevolution.

The phylogeny of nematodes in the family Protostrongylidae (Nematoda: Metastrongyloidea) was reconstructed by cladistic analysis of 28 binary and multistate characters derived from comparative morphology. Analyses were hierarchical, and examined (1) relationships among genera, including 13 ingroup taxa and Metastrongylidae as an outgroup (single tree, 78 steps, consistency index [CI] = 0.705); and (2) relationships among genera and species groups, including 21 ingroup taxa and Metastrongylus apri as an outgroup (single tree, 76 steps, CI = 0.582). In the species-level tree, Protostrongylidae was divided into 2 major clades, 1 containing the subfamilies Muelleriinae (including the recently described Umingmtakstrangylus pallikuukensis), Elaphostrongylinae, and the Varestrongylinae (excluding Pneumocaulus kadenazii). Varestrongylus was paraphyletic as it included Pneumostrongylus calcaratus. The second major clade consisted of a paraphyletic group containing Protostrongylus spp. and Spiculocaulus leuckarti and, basal to this subclade, several other individual protostrongylid lineages. The various subclades generally correspond to the subfamilial divisions of the Protostrongylidae. The Neostrongylinae, however, is not supported as Neostrongylus and Orthostrongylus are not sister groups. Based on a large number of hypothesized synapomorphies, the elaphostrongylines appear to be a highly derived group of protostrongylids, a feature potentially correlated with their habitat localization in muscular and nervous tissues. The generic-level tree retained most of the primary structure revealed among the species but excluded the varestrongylines from the Muelleriinae + Elaphostrongylinae subclade. Artiodactyles of the family Cervidae are considered basal hosts for protostrongylids; secondary colonization in Caprini, Rupicaprini, and among lagomorphs is postulated.

Animals↗
PubMed2003

A model for the coevolution of immunity and immune evasion in vector-borne diseases with implications for the epidemiology of malaria.

We describe a model of host-parasite coevolution, where the interaction depends on the investments by the host in its immune response and by the parasite in its ability to suppress (or evade) its host's immune response. We base our model on the interaction between malaria parasites and their mosquito hosts and thus describe the epidemiological dynamics with the Macdonald-Ross equation of malaria epidemiology. The qualitative predictions of the model are most sensitive to the cost of the immune response and to the intensity of transmission. If transmission is weak or the cost of immunity is low, the system evolves to a coevolutionarily stable equilibrium at intermediate levels of investment (and, generally, at a low frequency of resistance). At a higher cost of immunity and as transmission intensifies, the system is not evolutionarily stable but rather cycles around intermediate levels of investment. At more intense transmission, neither host nor parasite invests any resources in dominating its partner so that no resistance is observed in the population. These results may help to explain the lack of encapsulated malaria parasites generally observed in natural populations of mosquito vectors, despite strong selection pressure for resistance in areas of very intense transmission.

Animals↗
PubMed2026

Tree Killer, Qu'est-ce Que C'est? Insights From Forest Pathogen Genomes.

Forests are central to planetary health but are increasingly challenged by emerging diseases driven by climate change, global trade, and anthropogenic disturbance. Despite the apparent resilience of long-lived, genetically diverse tree hosts, forest ecosystems have repeatedly experienced landscape-level pathogen-driven transformations. Advances in genomics, transcriptomics, and functional biology have transformed our understanding of how fungal and oomycete pathogens interact with their hosts across a continuum of lifestyles, from saprotrophy and necrotrophy to biotrophy. Here, we synthesize insights from comparative and population genomics and functional studies across diverse forest pathosystems to examine the traits that characterize successful tree pathogens. We highlight how lifestyle plasticity, adaptations to woody tissues, vector-mediated transmission, and biotrophic stealth enable pathogens to colonize perennial hosts and persist over long temporal scales. We further examine how genome plasticity, hybridization, and horizontal gene transfer generate adaptive potential that often outpaces host evolutionary responses under current environmental change. Finally, we discuss emerging genomic tools, including biosurveillance, machine learning-based classification, and genome editing, that are beginning to link genotype to phenotype and inform assessments of disease risk. By integrating genomic, ecological, and evolutionary perspectives, this review outlines general principles governing forest pathogen success and identifies priorities for future research aimed at improving understanding, early detection, and management of forest diseases in a changing world.

Trees↗
PubMed2006

Phylogeography and the geographic cline in the armament of a seed-predatory weevil: effects of historical events vs. natural selection from the host plant.

Japanese camellia (Camellia japonica) and its seed predator, the camellia weevil (Curculio camelliae), provide a notable example of a geographic mosaic of coevolution. In the species interaction, the offensive trait of the weevil (rostrum length) and the defensive trait of the plant (pericarp thickness) are involved in a geographically-structured arms race, and these traits and selective pressures acting on the plant defence vary greatly across a geographical landscape. To further explore the geographical structure of this interspecific interaction, we tested whether the geographical variation in the weevil rostrum over an 800-km range along latitude is attributed to local natural selection or constrained by historical (phylogeographical) events of local populations. Phylogeographical analyses of the mitochondrial DNA sequences of the camellia weevil revealed that this species has experienced differentiation into two regions, with a population bottleneck and subsequent range and/or population expansion within each region. Although these phylogeographical factors have affected the variation in rostrum length, analyses of competing factors for the geographical variation revealed that this pattern is primarily determined by the defensive trait of the host plant rather than by the effects of historical events of populations and a climatic factor (annual mean temperature). Thus, our study suggests the overwhelming strength of coevolutionary selection against the effect of historical events, which may have limited local adaptation.

Animals↗
PubMed1992

Coevolution of the vertebrate integrin alpha- and beta-chain genes.

The integrin receptors are heterodimers whose alpha and beta subunits are encoded by separate, evolutionarily unrelated multigene families. Phylogenetic analysis of DNA sequences from these two gene families showed that they have not always evolved in a parallel fashion. The integrin alpha chains that can form heterodimers with beta 1 do not constitute a monophyletic group, nor do the beta chains which can form heterodimers with alpha V. On the other hand, the vertebrate alpha chains associating with beta 2 are a monophyletic group. In the metal cation-binding region of the alpha chain, an exon exchange took place between human alpha M and alpha X approximately 40-50 Mya, homogenizing this functionally important region in these two alpha chains. When integrin beta chains of different functional classes are compared, nonsynonymous (amino acid altering) nucleotide substitutions that alter amino acid residue charge in the central region of the molecule occur at a rate significantly higher than that expected under random replacement. By contrast, when closely related beta 1 chains are compared, residue charge is conserved in this region. These results pinpoint the central region as a focus of functional divergence among integrin beta chains, perhaps relating to the ability of each beta integrin class to associate with a specific array of alpha integrins. Furthermore, they imply that positive, directional selection on this region has occurred in the evolution of the integrin beta-chain gene family.

Animals↗
PubMed2003

Rapid divergence of the ecdysone receptor in Diptera and Lepidoptera suggests coevolution between ECR and USP-RXR.

Ecdysteroid hormones are major regulators in reproduction and development of insects, including larval molts and metamorphosis. The functional ecdysone receptor is a heterodimer of ECR (NR1H1) and USP-RXR (NR2B4), which is the orthologue of vertebrate retinoid X receptors (RXR alpha, beta, gamma). Both proteins belong to the superfamily of nuclear hormone receptors, ligand-dependent transcription factors that share two conserved domains: the DNA-binding domain (DBD) and the ligand-binding domain (LBD). In order to gain further insight into the evolution of metamorphosis and gene regulation by ecdysone in arthropods, we performed a phylogenetic analysis of both partners of the heterodimer ECR/USP-RXR. Overall, 38 USP-RXR and 19 ECR protein sequences, from 33 species, have been used for this analysis. Interestingly, sequence alignments and structural comparisons reveal high divergence rates, for both ECR and USP-RXR, specifically among Diptera and Lepidoptera. The most impressive differences affect the ligand-binding domain of USP-RXR. In addition, ECR sequences show variability in other domains, namely the DNA-binding and the carboxy-terminal F domains. Our data provide the first evidence that ECR and USP-RXR may have coevolved during holometabolous insect diversification, leading to a functional divergence of the ecdysone receptor. These results have general implications on fundamental aspects of insect development, evolution of nuclear receptors, and the design of specific insecticides.

Amino Acid Sequence↗
PubMed2006

Assessing sexual conflict in the Drosophila melanogaster laboratory model system.

We describe a graphical model of interlocus coevolution used to distinguish between the interlocus sexual conflict that leads to sexually antagonistic coevolution, and the intrinsic conflict over mating rate that is an integral part of traditional models of sexual selection. We next distinguish the 'laboratory island' approach from the study of both inbred lines and laboratory populations that are newly derived from nature, discuss why we consider it to be one of the most fitting forms of laboratory analysis to study interlocus sexual conflict, and then describe four experiments using this approach with Drosophila melanogaster. The first experiment evaluates the efficacy of the laboratory model system to study interlocus sexual conflict by comparing remating rates of females when they are, or are not, provided with a spatial refuge from persistent male courtship. The second experiment tests for a lag-load in males that is due to adaptations that have accumulated in females, which diminish male-induced harm while simultaneously interfering with a male's ability to compete in the context of sexual selection. The third and fourth experiments test for a lag-load in females owing to direct costs from their interactions with males, and for the capacity for indirect benefits to compensate for these direct costs.

Animals↗
PubMed2006

Complex host-pathogen coevolution in the Apterostigma fungus-growing ant-microbe symbiosis.

BACKGROUND: The fungus-growing ant-microbe symbiosis consists of coevolving microbial mutualists and pathogens. The diverse fungal lineages that these ants cultivate are attacked by parasitic microfungi of the genus Escovopsis. Previous molecular analyses have demonstrated strong phylogenetic congruence between the ants, the ants-cultivated fungi and the garden pathogen Escovopsis at ancient phylogenetic levels, suggesting coevolution of these symbionts. However, few studies have explored cophylogenetic patterns between these symbionts at the recent phylogenetic levels necessary to address whether these parasites are occasionally switching to novel hosts or whether they are diversifying with their hosts as a consequence of long-term host fidelity. RESULTS: Here, a more extensive phylogenetic analysis of Escovopsis lineages infecting the gardens of Apterostigma ants demonstrates that these pathogens display patterns of phylogenetic congruence with their fungal hosts. Particular clades of Escovopsis track particular clades of cultivated fungi, and closely-related Escovopsis generally infect closely-related hosts. Discordance between host and parasite phylogenies, however, provides the first evidence for occasional host-switches or acquisitions of novel infections from the environment. CONCLUSION: The fungus-growing ant-microbe association has a complex coevolutionary history. Though there is clear evidence of host-specificity on the part of diverse Escovopsis lineages, these pathogens have switched occasionally to novel host fungi. Such switching is likely to have profound effects on how these host and parasites adapt to one another over evolutionary time scales and may impact how disease spreads over ecological time scales.

Agaricales↗