Host-parasite coevolution. The mite pockets of lizards.
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Animals↗
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Results for “coevolution”
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Phylogenetic trees support the coevolution of parasites and their hosts.
The close correspondence often observed between the taxonomy of parasites and their hosts has led to Fahrenholz's rule, which postulates that parasites and their hosts speciate in synchrony. This leads to the prediction that phylogenetic trees of parasites and their hosts should be topologically identical. We report here a test of this prediction which involves the construction of phylogenetic trees for rodents and their ectoparasites using protein electrophoretic data. We find a high degree of concordance in the branching patterns of the trees which suggests that there is a history of cospeciation in this host-parasite assemblage. In several cases where the branching patterns were identical in the host and parasite phylogenies, the branch lengths were also very similar which, given the assumptions of molecular clock theory, strongly suggests that the speciation of these hosts and ectoparasites was roughly contemporaneous and causally related.
Animals↗
Antagonistic coevolution between the sexes in a group of insects.
In coevolutionary 'arms races' between the sexes, the outcome of antagonistic interactions may remain at an evolutionary standstill. The advantage gained by one sex, with any evolutionary exaggeration of arms, is expected to be matched by analogous counteradaptations in the other sex. This fundamental coevolutionary process may thus be hidden from the evolutionist's eye, and no natural examples are known. We have studied the effects of male and female armament (clasping and anti-clasping morphologies) on the outcome of antagonistic mating interactions in 15 species of water strider, using a combination of experimental and phylogenetic comparative methods. Here we present, by assessing the independent effects of both species-specific level of arms escalation and small imbalances in the amounts of arms between the sexes within species, the consequences of a sexual arms race. Evolutionary change in the balance of armament between males and females, but not in the species-specific level of escalation, has resulted in evolutionary change in the outcome of sexually antagonistic interactions such as mating rate.
Animals↗
Gene flow in the endophyte Neotyphodium and implications for coevolution with Festuca arizonica.
Arizona fescue (Festuca arizonica) often harbours asymptomatic, asexual endophytic fungi from the genus Neotyphodium. In agronomic grasses, Neotyphodium endophytes are often credited with a wide range of mutualistic benefits to its host many of which are related to fungal production of alkaloids for herbivore deterrence. Neotyphodium in the native grass Arizona fescue, however, usually produces alkaloids at levels too low to deter herbivores, and in general, does not behave mutualistically. This study uses microsatellite markers to examine rates of gene flow among four Arizona populations of Neotyphodium. Haplotypic diversity was generally low; only one population contained more than two haplotypes. Haplotypes carrying multiple loci for some or all of the microsatellite loci were also found, indicating a vegetative hybridization event between Neotyphodium and the grass choke pathogen from the genus Epichloë. Gene flow between Neotyphodium populations is very low, and likely much lower than the pollen mediated gene flow of its host. These differing rates of gene flow are predicted to create trait mismatching between endophyte and host and may explain the low, or lack of, alkaloid production by Neotyphodium in Arizona fescue and other native grass species.
Arizona↗
Coevolution in bicoid-dependent promoters and the inception of regulatory incompatibilities among species of higher Diptera.
To what extent and in what way do gene promoters and their transacting regulatory proteins coevolve? In this and in earlier publications we show that the Bicoid-dependent promoters of the segmentation genes hunchback and tailless in species of higher Diptera (Drosophila, Musca, Calliphora, and Lucilia) are different with respect to the copy number, spacing, sequence, and orientation of Bicoid binding sites. At the same time there are significant amino acid differences in the Bicoid homeodomain. To test these interspecific differences, we used a series of functional assays, starting with the analysis of Bicoid binding affinities of individual sites, through to transgene rescue experiments, to compare within-species with between-species mixtures of Bicoid homeodomains and hunchback or tailless promoters. We observed that components taken from different species interact with less efficiency compared with those taken from within the same species. Our interpretation is that such interspecific incompatibilities are a consequence of interactive genetic elements coevolving one with another, hence maintaining functional compatibility within each species. At the same time such a process allows differences to accumulate between species regarding the precise molecular basis whereby the common function is effected.
Animals↗
The coevolution of ritual and society: new 14C dates from ancient Mexico.
New (14)C dates from Oaxaca, Mexico, document changes in religious ritual that accompanied the evolution of society from hunting and gathering to the archaic state. Before 4000 B.P. in conventional radiocarbon years, a nomadic egalitarian lifeway selected for unscheduled (ad hoc) ritual from which no one was excluded. With the establishment of permanent villages (4000-3000 B.P.), certain rituals were scheduled by solar or astral events and restricted to initiates/social achievers. After state formation (2050 B.P.), many important rituals were performed only by trained full-time priests using religious calendars and occupying temples built by corvee labor. Only 1,300-1,400 years seem to have elapsed between the oldest known ritual building and the first standardized state temple.
Anthropology, Cultural↗
Feedbacks and the coevolution of plants and atmospheric CO2.
The coupled evolution of land plants, CO2, and climate over the last half billion years has maintained atmospheric CO2 concentrations within finite limits, indicating the involvement of a complex network of geophysiological feedbacks. But insight into this important regulatory network is extremely limited. Here we present a systems analysis of the physiological and geochemical processes involved, identifying new positive and negative feedbacks between plants and CO2 on geological time scales. Positive feedbacks accelerated falling CO2 concentrations during the evolution and diversification of terrestrial ecosystems in the Paleozoic and enhanced rising CO2 concentrations across the Triassic-Jurassic boundary during flood basalt eruptions. The existence of positive feedbacks reveals the unexpected destabilizing influence of the biota in climate regulation that led to environmental modifications accelerating rates of terrestrial plant and animal evolution in the Paleozoic.
Biological Evolution↗
Coevolution between nonhomologous but functionally similar proteins and their conserved partners in the Legionella pathogenesis system.
Legionella pneumophila, the causative agent of Legionnaires' disease, and other pathogenic Legionella species multiply inside protozoa and human macrophages by using the intracellular multiplication (Icm)/defect in organelle trafficking (Dot) type-IV secretion system. The IcmQ protein, which possesses pore-forming activity, and IcmR, which regulates the IcmQ activity, are two essential components of this system. Analysis of the region expected to contain these two genes from 29 Legionella species revealed the presence of a conserved icmQ gene and a large hypervariable gene family [functional homologues of icmR (fir) genes], located at the icmR genomic position. Although hypervariable in their sequence, the fir genes from all 29 Legionella species were found, together with their corresponding icmQ genes, to function similarly during infection. In addition, all FIR proteins we examined were found to interact with their corresponding IcmQ proteins. Detailed bioinformatic, biochemical, and genetic analysis of the interaction between the variable FIR proteins and conserved IcmQ proteins revealed that their interaction depends on a variable region located between two conserved domains of IcmQ. This variable region was also found to be critical for IcmQ self-interaction, and the region probably coevolved with the corresponding FIR protein. A FIR-IcmQ pair was also found in Coxiella burnetii, the only known non-Legionella bacterium that contains an Icm/Dot system, indicating the significance of this protein pair for the function of this type-IV secretion system. We hypothesize that this gene variation, which is probably mediated by positive selection, plays an important role in the evolutionary arms race between the protozoan host cell and the pathogen.
Acanthamoeba castellanii↗
Coevolution of TCR-MHC interactions: conserved MHC tertiary structure is not sufficient for interactions with the TCR.
The specificity for self-MHC that is necessary for T cell function is a consequence of intrathymic selection during which T cell antigen receptors (TCRs) expressed by immature thymocytes are tested for their affinity for self-peptide:self-MHC. The germ-line-encoded segments of the TCR, however, are believed to have an innate specificity for structural features of MHC molecules. We directly tested this hypothesis by generating a transgenic mouse system in which the protein HLA-DM is expressed at the surface of thymic cortical epithelial cells in the absence of classical MHC molecules. The specialized intracellular function of HLA-DM has removed this MHC class II-like protein from the evolutionary forces that have been hypothesized to shape TCR-MHC interactions. Our study shows that a structural mimic of MHC class II is not sufficient to appropriately interact with the TCRs expressed by developing thymocytes. This result emphasizes the unique complementarity of TCR-MHC interactions that are maintained by the evolutionary pressures dictated by positive selection.
Animals↗
Coevolution of tRNA intron motifs and tRNA endonuclease architecture in Archaea.
Members of the three kingdoms of life contain tRNA genes with introns. The introns in pre-tRNAs of Bacteria are self-splicing, whereas introns in archaeal and eukaryal pre-tRNAs are removed by splicing endonucleases. We have studied the structures of the endonucleases of Archaea and the architecture of the sites recognized in their pre-tRNA substrates. Three endonuclease structures are known in the Archaea: a homotetramer in some Euryarchaea, a homodimer in other Euryarchaea, and a heterotetramer in the Crenarchaeota. The homotetramer cleaves only the canonical bulge-helix-bulge structure in its substrates. Variants of the substrate structure, termed bulge-helix-loops, appear in the pre-tRNAs of the Crenarcheota and Nanoarcheota. These variant structures can be cleaved only by the homodimer or heterotetramer forms of the endonucleases. Thus, the structures of the endonucleases and their substrates appear to have evolved together.
Archaeal Proteins↗
Coevolution of generalist feeding ecologies and gyrencephalic mushroom bodies in insects.
Here we demonstrate the independent acquisition of strikingly similar brain architectures across divergent insect taxa and even across phyla under similar adaptive pressures. Convoluted cortical gyri-like structures characterize the mushroom body calyces in the brains of certain species of insects; we have investigated in detail the cellular and ecological correlates of this morphology in the Scarabaeidae (scarab beetles). "Gyrencephalic" mushroom bodies with increased surface area and volume of calycal synaptic neuropils and increased intrinsic neuron number characterize only those species belonging to generalist plant-feeding subfamilies, whereas significantly smaller "lissencephalic" mushroom bodies are found in more specialist dung-feeding scarab beetles. Such changes are not unique to scarabs or herbivores, because the mushroom bodies of predatory beetles display similar morphological disparities in generalists vs. specialists. We also show that gyrencephalic mushroom bodies in generalist scarabs are not associated with an increase in the size of their primary input neuropil, the antennal lobe, or in the number of antennal lobe glomeruli but rather with an apparent increase in the density of calycal microglomeruli and the acquisition of calycal subpartitions. These differences suggest changes in calyx circuitry facilitating the increased demands on processing capability and flexibility imposed by the evolution of a generalist feeding ecology.
Adaptation, Biological↗
The emergence of humans: the coevolution of intelligence and longevity with intergenerational transfers.
Two striking differences between humans and our closest living relatives, chimpanzees and gorillas, are the size of our brains (larger by a factor of three or four) and our life span (longer by a factor of about two). Our thesis is that these two distinctive features of humans are products of coevolutionary selection. The large human brain is an investment with initial costs and later rewards, which coevolved with increased energy allocations to survival. Not only does this theory help explain life history variation among primates and its extreme evolution in humans; it also provides new insight into the evolution of longevity in other biological systems. We introduce and apply a general formal demographic model for constrained growth and evolutionary tradeoffs in the presence of life-cycle transfers between age groups in a population.
Animals↗
Coevolution of head, neck, and tail domains of myosin heavy chains.
Myosins, a large family of actin-based motors, have one or two heavy chains with one or more light chains associated with each heavy chain. The heavy chains have a (generally) N-terminal head domain with an ATPase and actin-binding site, followed by a neck domain to which the light chains bind, and a C-terminal tail domain through which the heavy chains self-associate and/or bind the myosin to its cargo. Approximately 140 members of the myosin superfamily have been grouped into 17 classes based on the sequences of their head domains. I now show that a phylogenetic tree based on the sequences of the combined neck and tail domains groups 144 myosins, with a few exceptions, into the same 17 classes. For the nine myosin classes that have multiple members, phylogenetic trees based on the head domain or the combined neck/tail domains are either identical or very similar. For class II myosins, very similar phylogenetic trees are obtained for the head, neck, and tail domains of 47 heavy chains and for 29 essential light chains and 19 regulatory light chains. These data strongly suggest that the head, neck, and tail domains of all myosin heavy chains, and light chains at least of class II myosins, have coevolved and are likely to be functionally interdependent, consistent with biochemical evidence showing that regulated actin-dependent MgATPase activity of Dictyostelium myosin II requires isoform specific interactions between the heavy chain head and tail and light chains.
Animals↗
Coevolution of transcriptional and allosteric regulation at the chorismate metabolic branch point of Saccharomyces cerevisiae.
Control of transcription and enzyme activities are two interwoven regulatory systems essential for the function of a metabolic node. Saccharomyces cerevisiae strains differing in enzyme activities at the chorismate branch point of aromatic amino acid biosynthesis were constructed by recombinant DNA technology. Expression of an allosterically unregulated, constitutively activated chorismate mutase encoded by the ARO7(T226I) (ARO7(c)) allele depleted the chorismate pool. The resulting tryptophan limitation caused growth defects, which could be counteracted only by transcriptional induction of TRP2 encoding the competing enzyme anthranilate synthase. ARO7 expression is not transcriptionally regulated by amino acids. Transcriptional activation of the ARO7(c) allele led to stronger growth retardation upon tryptophan limitation. The same effect was achieved by removing the competing enzyme anthranilate synthase, which is encoded by the TRP2 gene, from the transcriptional control. The allelic situation of ARO7(c) being under general control instead of TRP2 resulted in severe growth defects when cells were starved for tryptophan. In conclusion, the specific regulatory pattern acting on enzymatic activities at the first metabolic node of aromatic amino acid biosynthesis is necessary to maintain proper flux distribution. Therefore, the evolution of the sophisticated allosteric regulation of yeast chorismate mutase requires as prerequisite (i) that the encoding ARO7 gene is not transcriptionally regulated, whereas (ii) the transcription of the competing feedback-regulated anthranilate synthase-encoding gene is controlled by availability of amino acids.
Alleles↗
Lumsden-Wilson theory of gene-culture coevolution.
A critique is presented of the Lumsden-Wilson theory [Lumsden, C. J. & Wilson, E. O. (1980) Proc. Natl. Acad. Sci. USA 77, 4382-4386] of the transmission of cultural traits. An analysis of the underlying assumptions and the mathematical nature of the theory clarifies its essentially reductionist and determinist qualities. The mathematical functions governing the transition probability that an individual member of a group of a specified size will switch from one trait to an alternative form of that trait is assumed to be genetically controlled although the single independent variable of this function, the number of individuals characterized by each of the two forms of the trait, is environmentally determined. The model assumes that the cultural properties of a society are simply the sum of the properties of the individuals; that each individual is equally influenced by every other member of the group; and that kinship structures, cultural institutions, and historical factors can be neglected.
Journal Article↗
Niche packing and coevolution in competition communities.
A coevolutionary model of species packing is developed that allows evolutionary adjustment in both niche position and within-phenotype niche width of one-three competing species. The environment is specified as a single resource dimension x and availability of resources along x is given by a gaussian curve that has parameters x[unk](R) and sigma(R). The model predicts that, for S species, the ratio of optimal niche width w[unk] to sigma(R) is roughly independent of sigma(R) and can be approximated by 1/S when the competitors are completely resource limited. Niche separation (d[unk]/w[unk]) increases only moderately with increases in resource diversity sigma(R) and is greater for two than for three competing species. To the extent that the competitors are not completely resource limited, both coevolutionary niche separation and niche width decrease. Many of the general trends in niche width and niche separation predicted by this coevolutionary model parallel those from optimal foraging theory and limiting similarity models of community structure. The coevolutionary model stands out, however, in the singularly high values predicted for niche separation, making coevolved communities highly invasible. Hence, the theory suggests, as some empirical evidence indicates, that coevolved competition communities can only eixst as such on remote islands or in other habitats that might be free from invasion by outside species.
Journal Article↗
Gene-culture coevolution: models for the evolution of altruism with cultural transmission.
Models of sexual haploids under kin selection are constructed. The trait of altruism is transmitted vertically from parent to child, but not in a strictly genetic manner. Two systems of altruism are considered: parent-to-offspring and sib-to-sib. In the former case it is shown that even when Hamilton's conditions for the success of genetically determined altruism are met, genes that increase the transmission of altruism may not invade the population. With sib-to-sib altruism, such genes will always increase initially.
Alleles↗
Gene-culture coevolution of complex social behavior: human altruism and mate choice.
The hypothesis is examined that genes bias the development of complex social behavior in one direction over alternatives. Studies of altruism and political attitudes in twins estimate that approximately 50% of the variance is associated with direct genetic inheritance, virtually 0% with the twin's common family environment, and the remainder with each twin's specific environment. Studies of human marriages show that spouses choose each other on the basis of similarity, assorting on the most genetically influenced of a set of homogeneous attributes. These data imply a genetic canalization of social influences such that, within the constraints allowed by the total spectrum of cultural alternatives, people create environments maximally compatible with their genotypes.
Altruism↗