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PubMed2002

Identification of G protein-coupled receptors for Drosophila PRXamide peptides, CCAP, corazonin, and AKH supports a theory of ligand-receptor coevolution.

G-protein coupled receptors (GPCRs) are ancient, ubiquitous sensors vital to environmental and physiological signaling throughout organismal life. With the publication of the Drosophila genome, numerous "orphan" GPCRs have become available for functional analysis. Here we characterize two groups of GPCRs predicted as receptors for peptides with a C-terminal amino acid sequence motif consisting of -PRXamide (PRXa). Assuming ligand-receptor coevolution, two alternative hypotheses were constructed and tested. The insect PRXa peptides are evolutionarily related to the vertebrate peptide neuromedin U (NMU), or are related to arginine vasopressin (AVP), both of which have PRXa motifs. Seven Drosophila GPCRs related to receptors for NMU and AVP were cloned and expressed in Xenopus oocytes for functional analysis. Four Drosophila GPCRs in the NMU group (CG14575 [corrected], CG8795, CG9918, CG8784) are activated by insect PRXa pyrokinins, (-FXPRXamide), Cap2b-like peptides (-FPRXamide), or ecdysis triggering hormones (-PRXamide). Three Drosophila GPCRs in the vasopressin receptor group respond to crustacean cardioactive peptide (CCAP), corazonin, or adipokinetic hormone (AKH), none of which are PRXa peptides. These findings support a theory of coevolution for NMU and Drosophila PRXa peptides and their respective receptors.

Amino Acid Sequence↗
PubMed2006

A common mode of attraction of larvae and adults of insect predators to the sex pheromone of their prey (Hemiptera: Matsucoccidae).

The attraction of several adult predators, genera Elatophilus, Hemerobius and Sympherobius, to the sex pheromones of pine bast scales, Matsucoccus Cockerell, has already been demonstrated. Here, the hypothesis that the larvae of these predators are similarly attracted to the host prey sex pheromone is tested. The response of predators was tested in field trials using pine tree arenas baited with the sex pheromones of M. josephi Bodenheimer & Harpaz, M. feytaudi Ducasse and M. matsumurae Kuwana. Experiments were conducted in Israel in stands of Pinus halepensis infested by M. josephi and in Portugal in stands of P. pinaster infested by M. feytaudi, respectively. The selectivity of larvae for the three sex pheromones was tested in Petri dish arenas in the laboratory. In the field, the larval stages exhibited similar modes of attraction to those of the conspecific adults: Elatophilus hebraicus Pericart in Aleppo pine forest, E. crassicornis Reuter and Hemerobius stigma Stephens in the maritime pine forests. Laboratory choice tests confirmed the kairomonal selectivity of larvae. Both forest and laboratory tests demonstrated the response of a coccinellid of the genus Rhyzobius to the sex pheromones of M. feytaudi and M. matsumurae. A unique chemical communication system among several taxa of predators of Matsucoccus spp. was highlighted that may be attributed to their coevolution on a geological time scale.

Animal Communication↗
PubMed1993

Evolution of sequence repetition and gene duplications in the TATA-binding protein TBP (TFIID).

Analysis of TBP gene sequences from a variety of species for clustering of short sequence motifs and for over- and underrepresentation of short sequence motifs suggests involvement of slippage in the recent evolution of the TBP N-terminal domains in metazoans, Acanthamoeba and wheat. AGC, GCA and CAG are overrepresented in TBP genes of other species, suggesting that opa arrays were amplified from motifs overrepresented in ancestral species. The phylogenetic distribution of recently slippage-derived sequences in TBP is similar to that observed in the large subunit ribosomal RNAs, suggesting a propensity for certain evolutionary lineages to incorporate slippage-generated motifs into protein-coding as well as ribosomal RNA genes. Because length increase appears to have taken place independently in lineages leading to vertebrates, insects and nematodes, TBP N-terminal domains in these lineages are not homologous. All gene duplications in the TBP gene family appear to have been recent events despite strong protein sequence similarity between TRF and P. falciparum TBP. The enlargement of the TBP N-terminal domain may have coincided with acquisition of new functions and may have accompanied molecular coevolution with domains of other proteins, resulting in the acquisition of new or more complex mechanisms of transcription regulation.

Acanthamoeba↗
PubMed2003

Evolution of virulence in a plant host-pathogen metapopulation.

In a wild plant-pathogen system, host resistance and pathogen virulence varied markedly among local populations. Broadly virulent pathogens occurred more frequently in highly resistant host populations, whereas avirulent pathogens dominated susceptible populations. Experimental inoculations indicated a negative trade-off between spore production and virulence. The nonrandom spatial distribution of pathogens, maintained through time despite high pathogen mobility, implies that selection favors virulent strains of Melampsora lini in resistant Linum marginale populations and avirulent strains in susceptible populations. These results are consistent with gene-for-gene models of host-pathogen coevolution that require trade-offs to prevent pathogen virulence increasing until host resistance becomes selectively neutral.

Basidiomycota↗
PubMed2004

Old World fossil record of modern-type hummingbirds.

I report on tiny skeletons of stem-group hummingbirds from the early Oligocene of Germany that are of essentially modern appearance and exhibit morphological specializations toward nectarivory and hovering flight. These are the oldest fossils of modern-type hummingbirds, which had not previously been reported from the Old World. The findings demonstrate that early hummingbird evolution was not restricted to the New World. They further suggest that bird-flower coevolution dates back to the early Oligocene and open another view on the origin of ornithophily in Old World plants.

Americas↗
PubMed1994

Phylogeny and classification, origins, and evolution of host associations of lice.

Lice are highly successful ectoparasites. Most species of mammals and birds are infested by at least 1 but up to 6 species of lice. Current opinion is that lice evolved from free-living Psocoptera (booklice, barklice and psocids). It is generally agreed that there are 4 main groups of lice: Anoplura, Amblycera, Ischnocera and Rhyncophthirina. In contrast, there is no agreement on the phylogenetic relationships of these groups and their classification. In particular, there is much debate over the validity of the taxon Mallophaga, which is almost certainly paraphyletic. For many years the sister-group of the Boopiidae, which almost exclusively infest Australasian marsupials, was thought to be a group of lice that now infest marsupials in South America. This, however, is almost certainly incorrect; the sister-group of the Boopiidae probably contains bird-infesting lice from the Menoponidae (Amblycera). Thus, menoponid lice transferred from birds to mammals and from these arose the Boopiidae. Transfers of lice between mammals and birds have occurred on other occasions during the evolution of the lice; 2 of the 4 main groups of lice, the Ischnocera and Amblycera, contain families that infest birds and families that infest mammals. Strict cospeciation and coevolution was thought to predominate among the lice; however, detailed studies indicate this to be incorrect. Consequently, the axiom that lice and their hosts invariably coevolve should be abandoned. Ironically, biologists may learn more about the evolutionary biology of hosts when host-switching has occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The role of helminths in the biological control of mammals.

Biological control of invertebrates has been successful while that of vertebrates has been, with the exception of myxomatosis in rabbits, unsuccessful; reasons for this are discussed. Demographic studies of small mammals suggest that population regulation occurs by several different mechanisms, more than one of which may be acting at the same time. Coevolution is an important phenomenon in host-parasite associations, nevertheless parasites may limit host population abundance. The basis of the regulatory effect on the host population is that parasite-induced host mortality or reduction in fecundity is density-dependent. Increasing evidence of the density-dependent effects of helminths on host survival and reproduction is forthcoming from laboratory studies but has not been confirmed in the field. The theory that a helminth parasite may regulate mammal population abundance has been verified recently in the laboratory. A multidisciplinary research programme aimed at understanding the mechanisms responsible for formation of house mouse (Mus domesticus) plagues and seeking strategies to reduce mouse numbers is discussed. One aspect of the work involves investigation of the potential of the nematode, Capillaria hepatica, as a biological agent in the control of wild mice in the cereal-growing regions of Australia. Biological control of mammals is viewed within the context of integrated pest management. A helminth species which reduces host survival or fecundity at an increasing rate as host abundance increases has a role in host population regulation. There is potential to capitalize on that role and apply the helminth as a biological agent in the control of mammals which have attained pest status.

Animals↗
PubMed1991

Time required for gene frequency change in a deterministic model of gene-culture coevolution, with special reference to the lactose absorption problem.

The time required for gene frequency change under natural selection in a deterministic model of gene-culture coevolution is investigated. A discrete generations model is formulated, and its continuous time approximation is derived. In passing to the continuous time limit, it is assumed that the frequency of the culturally transmitted trait does not change under oblique (between generations) transmission. The system of ordinary differential equations thus obtained are solved, and the dependence on the parameters of horizontal (within generations) transmission and natural selection is examined. The time required is found to be substantially longer when the determination of a phenotypic difference subject to natural selection is partly cultural rather than completely genetic. The predictions are relevant to the possibility of the coevolution of lactose absorbers and milk drinkers in some human populations. Alternative hypotheses are briefly discussed in the light of the theoretical results.

Biological Evolution↗
PubMed1984

Systematic temporal changes in host susceptibility to infection: demographic mechanisms.

Simple mathematical models are developed to examine the influence of variability in host susceptibility to infection, on the dynamics of host-parasite population interactions. When hosts differ in their innate susceptibility (at birth), to infection by a specific parasite, the average susceptibility of the host population as a whole may show systematic changes through time. Such patterns may arise as a result of demographic factors associated with the interaction between host and parasite populations, in the absence of inheritance mechanisms (a genetic component) or acquired resistance (an immunological component). The general significance of this observation is discussed in terms of the coevolution of host-parasite associations.

Animals↗
PubMed2003

Coevolution in variable mutualisms.

Many mutualistic interactions are probably not mutualistic across all populations and years. This article explores consequences of this observation with a series of genetic models that consider how variable mutualisms coevolve. The first models, previously introduced in a general coevolutionary context, consider two coevolving species whose fitness interactions change between beneficial and antagonistic in response to independent spatial or temporal variation in the abiotic or biotic environment. The results demonstrate that both temporal and spatial variability in fitness interactions can cause partner species with tightly matched traits favored by unconditional mutualisms to be vulnerable to evolutionary invasion by alternative types. A new model presented here shows that an additional mutualistic species can have a similar effect and can even cause fitness interactions between the other two species to evolve. Under some conditions, the pairwise interactions can change unidirectionally from mutualistic to antagonistic, with virtually no evolutionary change in either partner species. In other cases, fitness interactions between the species pair can oscillate between mutualism and antagonism as a result of coevolution in the third species. Taken as a whole, these theoretical results suggest that many features of mutualistic coevolution can best be understood by considering spatial, temporal, and community-dependent patterns of fitness interactions.

Biological Evolution↗
PubMed1992

Genome canalization: the coevolution of transposable and interspersed repetitive elements with single copy DNA.

Transposable and interspersed repetitive elements (TIREs) are ubiquitous features of both prokaryotic and eukaryotic genomes. However, controversy has arisen as to whether these sequences represent useless 'selfish' DNA elements, with no cellular function, as opposed to useful genetic units. In this review, we selected two insect species, the Dipteran Drosophila and the Lepidopteran Bombyx mori (the silkmoth), in an attempt to resolve this debate. These two species were selected on the basis of the special interest that our laboratory has had over the years in Bombyx with its well known molecular and developmental biology, and the wealth of genetic data that exist for Drosophila. In addition, these two species represent contrasting repetitive element types and patterns of distribution. On one hand, Bombyx exhibits the short interspersion pattern in which Alu-like TIREs predominate while Drosophila possesses the long interspersion pattern in which retroviral-like TIREs are prevalent. In Bombyx, the main TIRE family is Bm-1 while the Drosophila group contains predominantly copia-like elements, non-LTR retroposons, bacterial-type retroposons and fold-back transposable elements sequences. Our analysis of the information revealed highly non-random patterns of both TIRE biology and evolution, more indicative of these sequences acting as genomic symbionts under cellular regulation rather than useless or selfish junk DNA. In addition, we extended our analysis of potential TIRE functionality to what is known from other eukaryotic systems. From this study, it became apparent that these DNA elements may have originated as innocuous or selfish sequences and then adopted functions. The mechanism for this conversion from non-functionality to specific roles is a process of coevolution between the repetitive element and other cellular DNA often times in close physical proximity. The resulting interdependence between repetitive elements and other cellular sequences restrict the number of evolutionarily successful mutational changes for a given function or cistron. This mutual limitation is what we call genome canalization. Well documented examples are discussed to support this hypothesis and a mechanistic model is presented for how such genomic canalization can occur. Also proposed are empirical studies which would support or invalidate aspects of this hypothesis.

Animals↗
PubMed1991

Co-evolution of parasites and adaptive immune responses.

The interplay between evolving host populations and evolving parasite populations is dominated by two key genetically based elements, namely the virulence of parasites and the resistance of their hosts. Here, Graham Mitchell gives a personal overview of ideas on the coevolution of parasite-host relationships and the contributions to immunology that are likely to emerge from systematic studies on this relationship.

Adaptation, Biological↗
PubMed1987

Evolutionary changes of sequences and factors that direct transcription termination of human and mouse ribsomal genes.

We have analyzed the sequences required for termination of human rDNA transcription. The human ribosomal transcription unit is shown to extend about 350 nucleotides into the 3'-terminal spacer and ends immediately upstream of a region with a distinct sequence heterogeneity. This heterogeneous region contains a cluster of conserved 10-base pair sequence elements which exert a striking homology to the proximal part of the 18-base pair murine rDNA transcription termination signal sequence, termed SalI box. Exonuclease III protection assays and in vitro transcription experiments with both homologous and heterologous human-mouse minigene constructs, and extracts from HeLa or Ehrlich ascites cells, reveal a functional analogy of the human sequence to the mouse SalI box. It mediates binding of a nuclear protein which functions as a transcription termination factor. The murine signal sequence is recognized by the human factor but not vice versa. The different sequence specificities and electrophoretic properties of the functionally equivalent protein factors suggest that a molecular coevolution has taken place between the termination signal sequences and the genes coding for the termination factors.

Animals↗
PubMed2002

A hierarchical model of HIV-1 protease drug resistance.

A hierarchical model of HIV-1 drug therapy may be used to evaluate new inhibitors and test new treatment strategies that address the problem of drug resistance. The model includes an atomic representation of drug-protease interaction, evaluation of viral fitness based on cleavage of polyprotein substrates during viral maturation, evolutionary modelling of drug resistance mutations in the face of selection pressures by drug and a mathematical description of viral population dynamics in infected individuals. These techniques have been used for the design of resistance-evading inhibitors by computational coevolution techniques and for the optimisation of existing protease inhibitors for improving their robustness in the face of resistance mutation.

Catalytic Domain↗
PubMed2002

Multi-objective cooperative coevolution of artificial neural networks (multi-objective cooperative networks).

In this paper we present a cooperative coevolutive model for the evolution of neural network topology and weights, called MOBNET. MOBNET evolves subcomponents that must be combined in order to form a network, instead of whole networks. The problem of assigning credit to the subcomponents is approached as a multi-objective optimization task. The subcomponents in a cooperative coevolutive model must fulfill different criteria to be useful, these criteria usually conflict with each other. The problem of evaluating the fitness on an individual based on many criteria that must be optimized together can be approached as a multi-criteria optimization problems, so the methods from multi-objective optimization offer the most natural way to solve the problem. In this work we show how using several objectives for every subcomponent and evaluating its fitness as a multi-objective optimization problem, the performance of the model is highly competitive. MOBNET is compared with several standard methods of classification and with other neural network models in solving four real-world problems, and it shows the best overall performance of all classification methods applied. It also produces smaller networks when compared to other models. The basic idea underlying MOBNET is extensible to a more general model of coevolutionary computation, as none of its features are exclusive of neural networks design. There are many applications of cooperative coevolution that could benefit from the multi-objective optimization approach proposed in this paper.

Biological Evolution↗
PubMed1992

Rapid evolution of the human gene for cytochrome c oxidase subunit IV.

We have compared the DNA sequences of nine mammalian genes for cytochrome c oxidase subunit IV (COX4 genes)--four expressed genes (human, bovine, rat, and mouse) and five pseudogenes (human, chimpanzee, orangutan, squirrel monkey, and bovine)--and constructed the sequence of the ancestral mammalian COX4 gene. By analyzing these sequences to determine the pattern and rate of nucleotide substitution in each branch of the evolutionary tree, we deduced that the human gene has evolved rapidly since the origin of the primate pseudogene approximately 41 million years ago, and we discuss the suggestion that this results from coevolution of nuclear and mitochondrial genes for cytochrome c oxidase.

Amino Acid Sequence↗
PubMed2002

Heteropopulation males have a fertilization advantage during sperm competition in the yellow dung fly (Scathophaga stercoraria).

Sexual conflict occurs whenever there is not strict genetic monogamy. The sexually antagonistic coevolution that potentially occurs because of this conflict involves adaptation by one sex followed by the counter-adaptation by the other, and may be thought of as an evolutionary arms-race. As a result of these cycles of antagonistic coevolution, females from one population may be less resistant to heteropopulation males, at least after short periods of allopatry, as they will not have evolved any resistance to them. We tested this prediction in yellow dung fly (Scathophaga stercoraria) populations from the UK and Switzerland. Males from each population mated as first and second males to females from each population, and the mean numbers of offspring sired by the last male to mate in each situation were compared. We also compared the fertility and fecundity of single females mated to males from both populations, as well as the fertility and fecundity of the F(1) crosses. Both crosses produced viable and fertile offspring and the offspring sex ratios were not skewed. However, the fecundity of F(1)-cross females was greater than that of the parentals. In the sperm-competition experiment, there was a significant interaction between male and female origin influencing the proportion of offspring sired by the second male to mate, with heteropopulation males always outcompeting conpopulation males. This effect was independent of copula duration and the delay between copulations. In a separate experiment, we tested to see whether this was due to female preference for genetically dissimilar males but found no evidence for paternity biasing based on genetic similarity. Our results therefore seem to be best explained by sexually antagonistic coevolution as females appear less resistant to males with which they have not coevolved.

Adaptation, Physiological↗