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Results for “evolutionary potentiation”

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PubMed2001

Patterns of genetic architecture for life-history traits and molecular markers in a subdivided species.

Understanding the utility and limitations of molecular markers for predicting the evolutionary potential of natural populations is important for both evolutionary and conservation genetics. To address this issue, the distribution of genetic variation for quantitative traits and molecular markers is estimated within and among 14 permanent lake populations of Daphnia pulicaria representing two regional groups from Oregon. Estimates of population subdivision for molecular and quantitative traits are concordant, with QST generally exceeding GST. There is no evidence that microsatellites loci are less informative about subdivision for quantitative traits than are allozyme loci. Character-specific comparison of QST and GST support divergent selection pressures among populations for the majority of life-history traits in both coast and mountain regions. The level of within-population variation for molecular markers is uninformative as to the genetic variation maintained for quantitative traits. In D. pulicaria, regional differences in the frequency of sex may contribute to variation in the maintenance of expressed within-population quantitative-genetic variation without substantially impacting diversity at the genic level. These data are compared to an identical dataset for 17 populations of the temporary-pond species, D. pulex.

Animals↗
PubMed2006

Assessment of protein folding potentials with an evolutionary method.

Many different protein folding potentials have been developed in the last decades, based upon knowledge of experimentally determined protein structures. Decoy-based techniques are frequently used to assess these force fields, but other methods can explore different features in the performance of the interaction schemes, thus helping in their evaluation. Here, we propose an evolutionary strategy to efficiently assess folding potentials. We apply it to three potentials with different characteristics, taken from the bibliography. A search for minimum energy protein topologies, treated as arrangements of rigid protein fragments, is performed. The method, applied to a set of helix bundle proteins, shows the different behavior of the studied potentials, providing a reasonably fast tool to evaluate their advantages and limitations.

Algorithms↗
PubMed2003

Low potential for climatic stress adaptation in a rainforest Drosophila species.

The ability of sensitive rainforest species to evolve in response to climate change is largely unknown. We show that the Australian tropical rainforest fly Drosophila birchii exhibits clinal variation in desiccation resistance, but the most resistant population lacks the ability to evolve further resistance even after intense selection for over 30 generations. Parent-offspring comparisons indicate low heritable variation for this trait but high levels of genetic variation for morphology. D. birchii also exhibits abundant genetic variation at microsatellite loci. The low potential for resistance evolution highlights the importance of assessing evolutionary potential in targeted ecological traits and species from threatened habitats.

Adaptation, Physiological↗
PubMed2001

Family- and population-level responses to atmospheric CO2 concentration: gas exchange and the allocation of C, N, and biomass in Plantago lanceolata (Plantaginaceae).

To ascertain the inheritance of responses to changing atmospheric CO(2) content, we partitioned response to elevated CO(2) in Plantago lanceolata between families and populations in 18 families in two populations. Plants were grown in 35 Pa and 71 Pa partial pressure of CO(2) (pCO(2)) in open-top chambers. We measured above- and belowground mass, carbon (C), nitrogen (N), hexose sugar, and gas exchange properties in both CO(2) treatments. Families within populations differed in mass, mass allocation, root : shoot ratios, aboveground percentage N, C : N ratio, and gas exchange properties. The CO(2) × family interaction is the main indicator of potential evolutionary responses to changing CO(2). Significant CO(2) × family interactions were observed for N content, C : N ratio, and photosynthetic rate (A: instantaneous light-saturated carbon assimilation capacity), intercellular CO(2) concentration, transpiration rate (E), and water use efficiency (WUE = A/E), but not for stomatal conductance. Families differed significantly in acclimation across time. The ratio of A in elevated vs. ambient growth CO(2), when measured at a common internal CO(2) partial pressure was 0.79, indicating down-regulation of A under CO(2) enrichment. Mass, C : N ratio, percentage, C (%C), and soluble sugar all increased significantly but overall %N did not change. Increases in %C and sugar were significant and were coincident with redistribution of N aboveground. The observed variation among populations and families in response to CO(2) is evidence of genetic variation in response and therefore of the potential for novel evolutionary trajectories with rising atmospheric CO(2).

Journal Article↗
PubMed2005

Establishing order at the systems level in mammalian brain evolution.

The present paper presents a new view of mammalian brain evolution based upon the finding of a level of neural organization at which phylogenetic constraints appear to play a channeling role. It is proposed that the subdivisions of a neural system exhibit the same complement (i.e. the same number of homologous subdivisions) within all species of a particular mammalian order, irrespective of the brain size, phenotype or life history. Specific examples from monotremes, cetaceans, rodents, carnivores and primates are given to provide an empirical basis for the presented hypothesis. The conclusion reached is that the presented evolutionary pattern shows a far higher relative frequency of occurrence than do other potential evolutionary explanations of systems level evolution in the mammalian nervous system.

Animals↗
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

Opportunity for natural selection in a Basque population and its secular trend: evolutionary implications of epidemic mortality.

Analysis of the interaction between mortality patterns and opportunity for natural selection could help to elucidate potential evolutionary implications of epidemic mortality. In this paper secular trends are studied in relation to Crow's index (It) and its components of mortality (Im) and fertility (If), using parish records for family reconstitution in a Basque population. A principal components analysis (91% of the variance accounted for) showed marked quantitative and qualitative variations of Im and If depending on the stage of demographic transition of the population analyzed: In pretransitional societies the opportunity for natural selection is determined mainly by differential prereproductive mortality, whereas in posttransitional societies selection resulting from differential fertility plays a key role. The highest values for the mortality component (range 0.81-1.26) and for the relative contribution of Im, to It (range 47.1-57.2%) were observed in periods with a high incidence of infectious diseases and when the most severe mortality crises were detected (1830-1859, 1860-1889, and 1890-1919). A differential incidence of epidemic mortality was also found at prereproductive ages (before 16 years) and at reproductive ages (16-45 years), which provides strong support for the idea of the long-term genetic consequences of mortality crises.

Adolescent↗
PubMed2005

Developmental plasticity and the origin of species differences.

Speciation is the origin of reproductive isolation and divergence between populations, according to the "biological species concept" of Mayr. Studies of reproductive isolation have dominated research on speciation, leaving the origin of species differences relatively poorly understood. Here, I argue that the origin of species differences, and of novel phenotypes in general, involves the reorganization of ancestral phenotypes (developmental recombination) followed by the genetic accommodation of change. Because selection acts on phenotypes, not directly on genotypes or genes, novel traits can originate by environmental induction as well as mutation, then undergo selection and genetic accommodation fueled by standing genetic variation or by subsequent mutation and genetic recombination. Insofar as phenotypic novelties arise from adaptive developmental plasticity, they are not "random" variants, because their initial form reflects adaptive responses with an evolutionary history, even though they are initiated by mutations or novel environmental factors that are random with respect to (future) adaptation. Change in trait frequency involves genetic accommodation of the threshold or liability for expression of a novel trait, a process that follows rather than directs phenotypic change. Contrary to common belief, environmentally initiated novelties may have greater evolutionary potential than mutationally induced ones. Thus, genes are probably more often followers than leaders in evolutionary change. Species differences can originate before reproductive isolation and contribute to the process of speciation itself. Therefore, the genetics of speciation can profit from studies of changes in gene expression as well as changes in gene frequency and genetic isolation.

Animals↗
PubMed2003

Phylogenetic insights into the evolution of parasitism in hymenoptera.

The Hymenoptera are one of the four megadiverse orders of insects, with over 100000 described species and several times this number still waiting to be described. A major part of this diverse group is formed of large lineages of parasitoid wasps. Some of these lineages have in turn given rise to subgroups that have gone on to diversify into other lifestyles, such as gall-forming on, and pollination of, plants, as well as a broad array of food-collecting behaviors associated with social living in colonies. Thus, the Hymenoptera demonstrate the large evolutionary potential of parasitism as a lifestyle, in contrast to early assertions that parasitism tends to lead to evolutionary 'dead ends' driven by overspecialization. Phylogenetic approaches have already led to a number of important insights into the evolution of parasitism in Hymenoptera. A series of examples are discussed in this review, including the origin of parasitism in the order, the development of koinobiosis in some groups, coevolution with symbiotic viruses, and the evolution in some groups away from parasitism and into such habits as gall formation, pollination of figs, nest building and sociality. The potential for comparative analysis of hymenopteran habits is large, but progress is still in its early stages due to the paucity of available well-supported phylogenies, and the still limited accumulation of basic biological data for many taxa.

Animals↗
PubMed2006

Bayesian estimation of the timing and severity of a population bottleneck from ancient DNA.

In this first application of the approximate Bayesian computation approach using the serial coalescent, we demonstrated the estimation of historical demographic parameters from ancient DNA. We estimated the timing and severity of a population bottleneck in an endemic subterranean rodent, Ctenomys sociabilis, over the last 10,000 y from two cave sites in northern Patagonia, Argentina. Understanding population bottlenecks is important in both conservation and evolutionary biology. Conservation implications include the maintenance of genetic variation, inbreeding, fixation of mildly deleterious alleles, and loss of adaptive potential. Evolutionary processes are impacted because of the influence of small populations in founder effects and speciation. We found a decrease from a female effective population size of 95,231 to less than 300 females at 2,890 y before present: a 99.7% decline. Our study demonstrates the persistence of a species depauperate in genetic diversity for at least 2,000 y and has implications for modes of speciation in the incredibly diverse rodent genus Ctenomys. Our approach shows promise for determining demographic parameters for other species with ancient and historic samples and demonstrates the power of such an approach using ancient DNA.

Animals↗
PubMed2003

Inbreeding and the genetic variance in floral traits of Mimulus guttatus.

The additive genetic variance, V(A), is frequently used as a measure of evolutionary potential in natural plant populations. Many plants inbreed to some extent; a notable observation given that random mating is essential to the model that predicts evolutionary change from V(A). With inbreeding, V(A) is not the only relevant component of genetic variation. Several nonadditive components emerge from the combined effects of inbreeding and genetic dominance. An important empirical question is whether these components are quantitatively significant. We use maximum likelihood estimation to extract estimates for V(A) and the nonadditive 'inbreeding components' from an experimental study of the wildflower Mimulus guttatus. The inbreeding components contribute significantly to four of five floral traits, including several measures of flower size and stigma-anther separation. These results indicate that inbreeding will substantially alter the evolutionary response to natural selection on floral characters.

Analysis of Variance↗
PubMed1995

The consensus sequence of a major Alu subfamily contains a functional retinoic acid response element.

Alu repeats are interspersed repetitive DNA elements specific to primates that are present in 500,000 to 1 million copies. We show here that an Alu sequence encodes functional binding sites for retinoic acid receptors, which are members of the nuclear receptor family of transcription factors. The consensus sequences for the evolutionarily recent Alu subclasses contain three hexamer half sites, related to the consensus AGGTCA, arranged as direct repeats with a spacing of 2 bp, which is consistent with the binding specificities of retinoic acid receptors. An analysis was made of the DNA binding and transactivation potential of these sites from an Alu sequence that has been previously implicated in the regulation of the keratin K18 gene. These Alu double half sites are shown to bind bacterially synthesized retinoic acid receptors as assayed by electrophoretic mobility shift assays. These sites are further shown to function as a retinoic acid response element in transiently transfected CV-1 cells, increasing transcription of a reporter gene by a factor of approximately 35-fold. This transactivation requires cotransfection with vectors expressing retinoic acid receptors, as well as the presence of all-trans-retinoic acid, which is consistent with the known function of retinoic acid receptors as ligand-inducible transcription factors. The random insertion of potentially thousands of Alu repeats containing retinoic acid response elements throughout the primate genome is likely to have altered the expression of numerous genes, thereby contributing to evolutionary potential.

Animals↗
PubMed2006

The evolutionary consequences of ecological interactions mediated through phenotypic plasticity.

Phenotypic plasticity describes the capacity of a genotype to exhibit a range of phenotypes in response to variation in the environment. Environmental variation encompasses both abiotic and biotic components of the environment, including interactions among organisms. The strength and outcome of many ecological interactions, ranging from antagonism to mutualism, are mediated through the phenotypically plastic responses of one or more players in the interaction. Herein, three broadly defined, non-mutually exclusive, evolutionary consequences of ecological interactions mediated through phenotypic plasticity are discussed. (1) The predictable plastic response of one partner can favor behaviors, physiological responses, and life history traits of an interacting partner that manipulate, circumvent, or ameliorate the response of that partner. (2) Phenotypic plasticity can generate substantial spatial and temporal variation within and among populations. Such phenotypic variation can depend on the density and identity of interacting players in an ecological community, and can ultimately affect the evolutionary outcome of ecological interactions. (3) Phenotypic plasticity affects the strength and direction of natural selection. Ecological interactions mediated through phenotypic plasticity are ubiquitous in nature, and the potential evolutionary consequences of these interactions illustrate the complexity inherent in understanding evolution in a community context.

Adaptation, Physiological↗
PubMed2003

Genetic variation and founder effects in the parasitoid wasp, Diaeretiella rapae (M'intosh) (Hymenoptera: Braconidae: Aphidiidae), affecting its potential as a biological control agent.

The effects of recent colonization on the aphid parasitoid, Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae: Aphidiidae), in Western Australia were investigated. When compared with populations from the Old World, the results of a microsatellite analysis show that the insects have low allelic length and low allele frequency variation, revealing that these individuals experienced a significant founder effect. Marked genetic differentiation between populations was also revealed, which has potentially important implications for host utilization in this species when introduced to a new geographical area(s). Low genetic variation and gene flow in a founder population could limit evolutionary potential in Australia, including the ability of a population to mount a response to newly introduced hosts, such as the Russian wheat aphid, Diuraphis noxia (Mordvilko). Although the actual importance of genetic diversity in the success of biological control agents is unclear, current theory concerning the potential impact of genetic bottlenecks on additive genetic variance is discussed.

Animals↗
PubMed2001

How closely correlated are molecular and quantitative measures of genetic variation? A meta-analysis.

The ability of populations to undergo adaptive evolution depends on the presence of quantitative genetic variation for ecologically important traits. Although molecular measures are widely used as surrogates for quantitative genetic variation, there is controversy about the strength of the relationship between the two. To resolve this issue, we carried out a meta-analysis based on 71 datasets. The mean correlation between molecular and quantitative measures of genetic variation was weak (r = 0.217). Furthermore, there was no significant relationship between the two measures for life-history traits (r = -0.11) or for the quantitative measure generally considered as the best indicator of adaptive potential, heritability (r = -0.08). Consequently, molecular measures of genetic diversity have only a very limited ability to predict quantitative genetic variability. When information about a population's short-term evolutionary potential or estimates of local adaptation and population divergence are required, quantitative genetic variation should be measured directly.

Animals↗
PubMed2005

Could obsessive-compulsive disorder have originated as a group-selected adaptive trait in traditional societies?

Obsessive-compulsive disorder (OCD) possesses distinctive characteristics inviting evolutionary and anthropological explanations. A genetically based condition with low fecundity persisting through generations is paradoxical. The concept of group selection is an evolutionary principle capable of clarifying the perplexing epidemiology of OCD. Using a group-selection paradigm, the authors propose that OCD reflects an ancient form of behavioural specialization. The majority of compulsions such as checking, washing, counting, needing to confess, hoarding and requiring precision, all carry the potential to benefit society. Focussing primarily on hunting and gathering cultures, the potential evolutionary advantages of OCD are explored.

Adaptation, Biological↗
PubMed2006

Ancient evolutionary origin of diversified variable regions demonstrated by crystal structures of an immune-type receptor in amphioxus.

Although the origins of genes encoding the rearranging binding receptors remain obscure, it is predicted that their ancestral forms were nonrearranging immunoglobulin-type domains. Variable region-containing chitin-binding proteins (VCBPs) are diversified immune-type molecules found in amphioxus (Branchiostoma floridae), an invertebrate that diverged early in deuterostome phylogeny. To study the potential evolutionary relationships between VCBPs and vertebrate adaptive immune receptors, we solved the structures of both a single V-type domain (to 1.15 A) and a pair of V-type domains (to 1.85 A) from VCBP3. The deduced structures show integral features of the ancestral variable-region fold as well as unique features of variable-region pairing in molecules that may reflect characteristics of ancestral forms of diversified immune receptors found in modern-day vertebrates.

Animals↗
PubMed2002

RbcL sequences indicate a single evolutionary origin of multinucleate cells in the red algal tribe Callithamnieae.

In the Ceramiaceae, one of the largest families of the red algae, there are from 1 to 4000 nuclei in each vegetative cell, but each tribe is homogeneous with respect to the uninucleate/multinucleate character state, except for the Callithamnieae. The goals of this study were to analyze rbcL gene sequences to clarify the evolution of taxa within the tribe Callithamnieae and to evaluate the potential evolutionary significance of the development of multinucleate cells in certain taxa. The genus Aglaothamnion, segregated from Callithamnion because it is uninucleate, was paraphyletic in all analyses. Callithamnion (including Aristothamnion) was monophyletic although not robustly so, apparently due to variations between taxa in rate of sequence evolution. Morphological synapomorphies were identified at different depths in the tree, supporting the molecular phylogenetic analysis. The uninucleate character state is ancestral in this tribe. The evolution of multinucleate cells has occurred once in the Callithamnieae. Multiple nuclei in each cell may combine the benefits of small C values (rapid cell cycle) with large cells (permitting morphological elaboration) while maintaining a constant ratio of nuclear volume: cytoplasmic volume.

Biological Evolution↗