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PubMed1998

Evaluating gene flow using selected markers: a case study.

The extent to which an organism is locally adapted in an environmental pocket depends on the selection intensities inside and outside the pocket, on migration, and on the size of the pocket. When two or more loci are involved in this local adaptation, measuring their frequency gradients and their linkage disequilbria allows one to disentangle the forces-migration and selection-acting on the system. We apply this method to the case of a local adaptation to organophosphate insecticides in the mosquito Culex pipiens pipiens in southern France. The study of two different resistance loci allowed us to estimate with support limits gene flow as well as selection pressure on insecticide resistance and the fitness costs associated with each locus. These estimates permit us to pinpoint the conditions for the maintenance of this pocket of adaptation as well as the effect of the interaction between the two resistance loci.

Animals↗
PubMed2004

Towards evidence-based clinical practice guidelines in Saudi Arabia.

The objective of this review is to provide a brief background on clinical practice guidelines CPGs and tools to assess and locally adapt CPGs. Over the last 2 decades, CPGs have become an increasingly popular tool for synthesis of clinical information, so as to change clinical practice and improve quality of health care. Such a quantitative growth in the number of guidelines available in different specialties is a source of concern since there is evidence that recommendations produced by different groups can be conflicting, invalid, unreliable, and even harmful. Various critical appraisal instruments were designed and tested to assess whether developers have minimized the biases inherent in creating guidelines and addressed the requirements for effective implementation. We recommend using the AGREE instrument which was developed by the Appraisal of Guideline Research and Evaluation AGREE collaboration. It is the most well-developed guideline appraisal instrument available, and it has been shown to have good reliability and validity. There is a growing recognition that it is not possible for national guidelines to be produced on every clinical problem of concern. The cost is huge and few practices have the resources or skills to develop their own valid evidence-based guidelines. Several developed countries encourage local adaptation of international good quality guidelines to avoid duplication of work and cost involved in guidelines development. Therefore wherever possible, Saudi guidelines should be based on existing good quality guidelines. The methodology for local adaptation of CPGs to meet the local needs and resources are explained in this review.

Cooperative Behavior↗
PubMed1977

Tubular localization of adaptation to dietary phosphate in rats.

The renal tubule of rats adapts its transport capacity for inorganic phosphate (Pi) in response to changes in dietary Pi intake. Tubular localization of this adaptation was studied in rats pair-fed for 10 days a low (LPD), i.e., 0.2 g/100 g, or a high (HPD), i.e., 1.8 g/100 g, phosphorus diet. Free-flow micropunctures under acute Pi infusion were made at elevated but similar filtered loads of Pi: LPD, 6.07 +/- 0.29 (n, 32); HPD 5.34 +/- 0.24 (n, 33) micromol/kidney per min. Fractional excretion of Pi (FEPi) for the whole kidney was: LPD, 0.26 +/- 0.02 (n, 32); HPD, 0.67 +/- 0.02 (n, 33) (P less than 0.001). The fraction of filtered Pi found at various puncture sites suggests that part of the adaptation to dietary Pi occurs in the early proximal tubule. An effect in the later portion of the proximal convoluted tubule cannot be excluded in the present experiments. Furthermore, dietary Pi affects markedly the difference in Pi delivery between distal tubule and final urine. This could be due to a greater adaptive response of deep nephrons. Alternatively, the results could also indicate that an adaptation with a secretory component takes place along the terminal part of the nephrons.

Adaptation, Physiological↗
PubMed2004

Barriers to sympatry between avian sibling species (Paridae: Baeolophus) in local secondary contact.

Range limits and secondary contact zones often occur at ecotones between major associations of habitat and climate. Therefore, understanding processes that limit sympatry between species in such areas provides an important framework for testing biogeographic and evolutionary hypotheses. Theoretical and empirical work has shown that the evolution of species borders is influenced by a complexity of factors, including gene flow from central to peripheral populations and the ability of species to adapt locally to environmental conditions. However, few studies have used bioclimatic models, combined with molecular and morphological data, to predict geographic range limits in the context of gene flow across a secondary contact zone. In this study, I applied these methods to test specific hypotheses about barriers to sympatry between closely related species where they approach and contact each other. Specifically, I examined the importance of historical isolation, local adaptation, and symmetry of gene flow in limiting sympatry and range expansion of ecologically distinct species across environmental gradients. Molecular (mitochondrial DNA, allozymes), morphological, and bioclimatic data were obtained for two avian sibling species (Baeolophus inornatus and B. ridgwayi) that exist in recent, narrow secondary contact in northern California. These species are broadly allopatric and occupy rangewide associations of oak and pinyon-juniper woodlands, respectively, although B. inornatus also inhabits mixed or juniper woodlands locally. Patterns of molecular variation generally were congruent with morphological and bioclimatic data, and support prior evidence for a history of isolation, adaptation, and divergence in distinctive, species-specific vegetation-climate associations. However, molecular and morphological clines fall east of the limit of oaks, and individuals of B. inornatus in this juniper-associated contact zone experience bioclimates that are more similar to B. ridgwayi than to B. inornatus in oak habitat. Thus, B. inornatus is able to adapt and expand locally into the range of its close relative, but not vice versa. These data support the hypothesis that gene flow is asymmetrical where peripheral populations meet at range boundaries. Physiological differences between species may play an important role in influencing these patterns. Empirical studies that highlight the importance of local adaptation and patterns of gene flow in which closely related species contact across ecotones are central to understanding limits on geographic ranges, sympatry, and introgression-a cornerstone of biogeographic and speciation theory.

Analysis of Variance↗
PubMed2006

Local maladaptation in the soft scale insect Saissetia coffeae (Hemiptera: Coccidae).

Local adaptation has often been documented in herbivorous insects. The potential for local maladaptation in phytophagous insects, however, has not been widely considered. I performed a two-generation reciprocal cross-transplant experiment with the generalist soft scale insect Saissetia coffeae (Hemiptera: Coccidae) on two common species of host plants in rain forest habitat in Costa Rica. In this system, S. coffeae showed significant local maladaptation at the level of the host species. Lineages originally collected from Witheringia enjoyed a strong advantage over those collected from Lomariopsis when both sets of lineages were placed on Lomariopsis; however, when both sets of lineages were raised on Witheringia, their fitnesses were statistically indistinguishable. While some aspects of the biology of S. coffeae may impair its ability to adapt to local selection pressures, scale insects are often locally adapted on fine spatial scales, and local maladaptation is therefore especially surprising. Other documented cases of local maladaptation in parasites appear to be due to evolution on the part of the host. The possibility that hosts or natural enemies may place local genotypes at a disadvantage, producing a pattern of local maladaptation, is one that deserves more consideration in the context of plant-insect interactions.

Adaptation, Physiological↗
PubMed2006

The direction aftereffect is driven by adaptation of local motion detectors.

The processing of motion information by the visual system can be decomposed into two general stages; point-by-point local motion extraction, followed by global motion extraction through the pooling of the local motion signals. The direction aftereffect (DAE) is a well known phenomenon in which prior adaptation to a unidirectional moving pattern results in an exaggerated perceived direction difference between the adapted direction and a subsequently viewed stimulus moving in a different direction. The experiments in this paper sought to identify where the adaptation underlying the DAE occurs within the motion processing hierarchy. We found that the DAE exhibits interocular transfer, thus demonstrating that the underlying adapted neural mechanisms are binocularly driven and must, therefore, reside in the visual cortex. The remaining experiments measured the speed tuning of the DAE, and used the derived function to test a number of local and global models of the phenomenon. Our data provide compelling evidence that the DAE is driven by the adaptation of motion-sensitive neurons at the local-processing stage of motion encoding. This is in contrast to earlier research showing that direction repulsion, which can be viewed as a simultaneous presentation counterpart to the DAE, is a global motion process. This leads us to conclude that the DAE and direction repulsion reflect interactions between motion-sensitive neural mechanisms at different levels of the motion-processing hierarchy.

Adaptation, Ocular↗
PubMed2003

Perspective: models of speciation: what have we learned in 40 years?

Theoretical studies of speciation have been dominated by numerical simulations aiming to demonstrate that speciation in a certain scenario may occur. What is needed now is a shift in focus to identifying more general rules and patterns in the dynamics of speciation. The crucial step in achieving this goal is the development of simple and general dynamical models that can be studied not only numerically but analytically as well. I review some of the existing analytical results on speciation. I first show why the classical theories of speciation by peak shifts across adaptive valleys driven by random genetic drift run into trouble (and into what kind of trouble). Then I describe the Bateson-Dobzhansky-Muller (BDM) model of speciation that does not require overcoming selection. I describe exactly how the probability of speciation, the average waiting time to speciation, and the average duration of speciation depend on the mutation and migration rates, population size, and selection for local adaptation. The BDM model postulates a rather specific genetic architecture of reproductive isolation. I then show exactly why the genetic architecture required by the BDM model should be common in general. Next I consider the multilocus generalizations of the BDM model again concentrating on the qualitative characteristics of speciation such as the average waiting time to speciation and the average duration of speciation. Finally, I consider two models of sympatric speciation in which the conditions for sympatric speciation were found analytically. A number of important conclusions have emerged from analytical studies. Unless the population size is small and the adaptive valley is shallow, the waiting time to a stochastic transition between the adaptive peaks is extremely long. However, if transition does happen, it is very quick. Speciation can occur by mutation and random drift alone with no contribution from selection as different populations accumulate incompatible genes. The importance of mutations and drift in speciation is augmented by the general structure of adaptive landscapes. Speciation can be understood as the divergence along nearly neutral networks and holey adaptive landscapes (driven by mutation, drift, and selection for adaptation to a local biotic and/or abiotic environment) accompanied by the accumulation of reproductive isolation as a by-product. The waiting time to speciation driven by mutation and drift is typically very long. Selection for local adaptation (either acting directly on the loci underlying reproductive isolation via their pleiotropic effects or acting indirectly via establishing a genetic barrier to gene flow) can significantly decrease the waiting time to speciation. In the parapatric case the average actual duration of speciation is much shorter than the average waiting time to speciation. Speciation is expected to be triggered by changes in the environment. Once genetic changes underlying speciation start, they go to completion very rapidly. Sympatric speciation is possible if disruptive selection and/or assortativeness in mating are strong enough. Sympatric speciation is promoted if costs of being choosy are small (or absent) and if linkage between the loci experiencing disruptive selection and those controlling assortative mating is strong.

Adaptation, Biological↗
PubMed1991

gamma-Aminobutyric acid and mu-opioid receptor localization and adaptation in the basal forebrain.

In conclusion, GABAA receptors containing the alpha 1 subunit are localized on postsynaptic neurons in the ventral pallidum, mainly in the dorsolateral compartment and on presynaptic terminals in the nucleus accumbens. mu-opioid receptors are localized on postsynaptic neurons in both the nucleus accumbens and ventral pallidum, and therefore may be regulating presynaptic release of enkephalin from the accumbens-pallidal projection. Discrete lesions in the dorsomedial core of the nucleus accumbens will upregulate GABAA receptors in the dorsolateral compartment of the nucleus accumbens in a fashion similar to the upregulation of GABAA receptors in the globus pallidus after striatal lesions. However, larger lesions of the lateral core projection to the dorsolateral compartment of the ventral pallidum do not upregulate the GABAA receptors, suggesting that the mechanisms for upregulation of GABAA receptors are specific to the dorsomedial core or a smaller lesion. The uniqueness of the compartments within the nucleus accumbens and the ventral pallidum are supported by these receptor and mRNA analyses.

Acclimatization↗
PubMed2025

Molecular signatures of adaptive introgression and selection in contact zones of closely related pine species (Pinus genus).

BACKGROUND: Natural hybridization plays a key role in shaping genetic diversity, local adaptation, and the dynamics of speciation through interspecific gene flow. Hybrid zones serve as valuable natural systems for studying these processes. In this research, we used genotypic data at thousands of nuclear SNPs to investigate genomic outcomes of hybridization and selection across three contact zones of closely related pine species including Scots pine (Pinus sylvestris L.) and dwarf mountain pine (P. mugo T.). Reference allopatric stands of parental species were used to assess introgression dynamics. RESULTS: Individuals from the hybrid zones showed distinct genetic ancestry patterns and were assigned to groups including putative pure species, first-generation hybrids, and advanced backcrosses. Genotypes of the majority of hybrids were shifted towards P. mugo ancestry. Most outlier loci were shared across all sympatric populations, although some were specific to individual contact zones. The identified outliers were mainly associated with regulatory biological processes related to phosphorylation, proteolysis, and transmembrane transport. Signatures of local adaptation varied in different genetic classes in contact zones and they were strongest in pure P. sylvestris and hybrids with a majority of P. sylvestris ancestry. The pattern suggests that it may be driven by adaptation to peat bog habitats situated outside the species’ core ecological niche. CONCLUSIONS: Our findings indicate strong selective pressure acting on multiple genes in groups of hybrids and pure Pinus sylvestris individuals across all studied hybrid zones. In contrast, the weaker signal of selection observed in individuals with P. mugo ancestry suggests that relict populations of this species, which historically spread across postglacial peat bogs, were pre-adapted to such environments. While several outlier loci were shared across different contact zones, others were unique for one of them, indicating that local environmental pressures and adaptive introgression shape the genomic composition of the populations. These results highlight the role of hybridization in generating adaptive diversity and emphasize the evolutionary significance of hybrid zones in pines.

Hybridization, Genetic↗
PubMed1984

Results from a simple laser color perimeter.

Stimulus size, chromaticity, adaptation, luminance and local adaptation are more easily controlled when laser light rapidly scans the appropriate portion(s) of the visual field. Adaptation of a Ferree-Rand perimeter to the use of He-Ne laser light gives chromatic and achromatic thresholds of relatively low variance.

Adaptation, Ocular↗
PubMed2026

Hidden genomic structure and widespread structural polymorphism across environmental gradients in the spiny sea star Marthasterias glacialis.

Genomic regions of reduced recombination can preserve linkage among co-adapted alleles, facilitating local adaptation despite high connectivity. Such regions-often generated by chromosomal inversions-may be especially important in highly dispersive marine taxa yet remain poorly documented in echinoderms. Here, we combined a chromosome-level reference genome with genome-wide ddRAD-seq from 296 Marthasterias glacialis individuals across 19 Atlantic-Mediterranean locations to quantify population structure and scan for recombination-suppressed haploblocks. Genome-wide neutral markers showed significant population differentiation together with evidence of high connectivity, revealed by the presence of inter-ecoregion migrants. Additionally, we identified 16 polymorphic haploblocks with patterns consistent with putative chromosomal inversions spanning 18.6% of the genome. Haploblock haplotypes were strongly environmentally and geographically structured and contained genes with key functions in stress response, osmoregulation and thermal tolerance. Haplotype distributions also paralleled previously described mitochondrial lineages despite nuclear gene flow, consistent with a model of ancient divergence followed by secondary contact. Overall, our results suggest a role for widespread structural polymorphism in adaptive differentiation in Echinodermata, providing a framework for linking echinoderm genome rearrangements to ecological divergence. Marthasterias glacialis thus emerges as a promising system to explore how structural variation contributes to adaptation and genome evolution in highly dispersive organisms.

Animals↗
PubMed1981

Longitudinal spread of adaptation in the rods of the frog's retina.

1. The stimulus-response function of the red rods in the retina of the common frog (Rana temporaria) was determined in different adaptational states by measuring aspartate-isolated receptor responses. 2. Flash stimuli, background adaptations and bleaches were delivered through the same optical channel forming an oblique light-beam striking the receptor side of the isolated and flat-mounted retina at an angle of 10 degrees. 3. When the light was blue-green and optimally polarized the absorbance of the receptor layer was about 2, from which follows that 70-80% of the light was absorbed in the distal third of the rod outer segments, i.e. the exposure was local. Homogeneous exposures of the whole rod outer segments were obtained with orange and red lights. 4. Combinations of homogeneous and local stimuli with homogeneous and local adaptations were used to investigate the longitudinal spread of background, intermediate and opsin adaptation, i.e. the sensitivity-reducing effect of a background light, and the transient and permanent sensitivity losses following a bleach isomerizing 3.5-26% (usually 10%) of the rhodopsin in the retina. 5. The results obtained were related to predictions based both on the assumption that the adaptation effects spread longitudinally within the rod outer segments and the assumption that they are strictly confined to the disks absorbing the adapting lights. 6. These comparisons reveal that all three types of adaptation spread longitudinally. It is for instance clear that the sensitivity loss observed with homogeneous stimuli and local adaptation (as compared to homogeneous adaptation) is larger than that predicted by the non-spreading hypothesis. 7. The longitudinal spread of background adaptation is largely finished within 10 sec after turning on the background light, while an efficient spread of the intermediate adaptation effect may require minutes. 8. A background light decreasing the sensitivity by about one log unit decreases the time from flash to response maximum from 5 to 1 sec (small responses). Corresponding opsin adaptation effects are accompanied by less dramatic changes in response kinetics. 9. Independent of adaptation type - homogeneous or local, background, intermediate or opsin - it was found that local stimuli are less efficient that homogeneous stimuli in light-adapted retinae. This effect can be explained assuming that the sensitivity-reducing effects are pronounced in the distal than in the proximal parts of the rod outer segments. 10. The opsin adaptation effect following 10% local bleaches decreases the sensitivity to both homogeneous and local stimuli 2-3 times more than corresponding homogeneous bleaches. This means that the strength of the opsin effect is not related to the average percentage bleached but to the fraction bleached in the distal part of the rod, or generally to the fraction bleached in the most affected region. 11...

Adaptation, Ocular↗
PubMed1986

Negative afterimages and photopic luminance adaptation in human vision.

Previous studies of the negative afterimage have reported that the process responsible for these aftereffects has a bandpass spatial characteristic. If this finding is correct, then negative afterimages cannot arise from a simple, local, adaptive process. I remeasure the spatial-frequency characteristic of the negative-afterimage process by using an afterimage contrast-matching procedure with retinally stabilized stimuli and find the spatial characteristic to be constant in the low-spatial-frequency region. This finding is consistent with the theory that the negative afterimage results from local luminance adaptation. As a test of the local adaptation explanation of the negative afterimage, the effect of the negative afterimage on the temporal contrast-sensitivity function (CSF) (measured down to 0.062 Hz) is determined. The apparent contrasts of the negative afterimages associated with very slowly (less than 0.5 Hz) flickering, threshold-contrast stimuli are calculated from power-function descriptions of the temporal development of the negative afterimage, and these afterimage contrasts are then subtracted from the temporal CSF's. The resulting curves are constant for temporal frequencies below 1 Hz, indicating that the decline in sensitivity at lower temporal frequencies is due entirely to the negative-afterimage process. Both the spatial and the temporal characteristics of the negative-afterimage process are consistent with its being a component of local luminance adaptation.

Acclimatization↗
PubMed2006

Molecular population genetics and phenotypic diversification of two populations of the thermophilic cyanobacterium Mastigocladus laminosus.

We investigated the distributions of genetic and phenotypic variation for two Yellowstone National Park populations of the heterocyst-forming cyanobacterium Mastigocladus (Fischerella) laminosus that exhibit dramatic phenotypic differences as a result of environmental differences in nitrogen availability. One population develops heterocysts and fixes nitrogen in situ in response to a deficiency of combined nitrogen in its environment, whereas the other population does neither due to the availability of a preferred nitrogen source. Slowly evolving molecular markers, including the 16S rRNA gene and the downstream internal transcribed spacer, are identical among all laboratory isolates from both populations but belie considerable genetic and phenotypic diversity. The total nucleotide diversity at six nitrogen metabolism loci was roughly three times greater than that observed for the human global population. The two populations are genetically differentiated, although variation in performance on different nitrogen sources among genotypes could not be explained by local adaptation to available nitrogen in the respective environments. Population genetic models suggest that local adaptation is mutation limited but also that the populations are expected to continue to diverge due to low migratory gene flow.

Cyanobacteria↗
PubMed1990

Dark adaptation in locally detached retina.

Nonrhegmatogenous retinal detachments were formed in the eyes of Dutch rabbits by subretinal injection of Hanks' balanced salt solution. The electroretinogram (ERG) was recorded locally from the acutely detached retina, and simultaneously from the surrounding attached retina (vitreal ERG [VERG]), before and after exposure to diffuse intense irradiation. Light adaptation elevated b-wave threshold for both the local ERG (LERG) and VERG by about 3 log units; thresholds for both responses recovered fully within 60-90 min after the irradiation. The normal time course of dark adaptation of the LERG suggests the occurrence of substantial rhodopsin regeneration in the rod photoreceptors of nonrhegmatogenously detached retina. These results differ from reports that visual pigment regeneration is slow in central serous chorioretinopathy, possibly because our detachments were studied within hours of formation, whereas some photoreceptor degeneration may be present in older clinical detachments.

Animals↗
PubMedDate not supplied

[The temperament evaluation of the Memphis, Pisa, Paris, and San Diego autoquestionnaire, Argentine version (TEMPS-A Buenos Aires)].

UNLABELLED: One of the major points of interest in the study of affective temperaments is the possibility of exploring the clinical significance of sub-affective traits as predictors of the development and inter-episodic manifestation of recurrent mood disorders within the bipolar illness spectrum. The TEMPS-A scale is a self-evaluation questionnaire used worldwide to assess the four basic affective temperaments (hyperthymic, depressive, cyclothymic, and irritable), and the anxious temperament. METHOD: The TEMPS-A questionnaire version that includes 110 items has been locally adapted from the version used in Spain, which in turn was produced by following the translation / retro-translation method. A locally-adapted version was produced from the version used in Spain. This local version was subsequently translated into English by a bilingual translator. RESULTS: A satisfactory adaptation of the version used in Spain was achieved, as confirmed by the retro-translation into English, and its subsequent approval by the authors of the scale. CONCLUSIONS: The Argentine version of the TEMPS-A self-evaluation questionnaire for the assessment of affective temperaments can be considered equivalent to the original version, and used as an important instrument for the clinical investigation of affective disorders in our country.

Humans↗
PubMed2006

Quantifying the gender load: can population crosses reveal interlocus sexual conflict?

Six sister populations of Drosophila melanogaster kept under identical environmental conditions for greater than 600 generations were reciprocally crossed to investigate the incidence of population divergence in allopatry. Population crosses directly influenced fitness, mating frequency, and sperm competition patterns. Changes in both female remating rate and the outcome of male sperm competition (P1, P2) in response to foreign males were consistent with intersexual coevolution. Moreover, seven of the 30 crosses between foreign mates resulted in significant reductions in female fitness, whereas two resulted in significant increases, compared to local matings. This tendency for foreign males to reduce female fitness may be interpreted as evidence for either sexually antagonistic coevolution or the disruption of mutualistic interactions. However, instances in which female fitness improved via cohabitation with foreign males may better reveal sexual conflict, signalling release from the cost of interacting with locally adapted males. By this metric, female reproduction in D. melanogaster is strongly constrained by local adaptation by males, a situation that would promote antagonistic coevolution between the sexes. We conclude that sexual selection can promote population differentiation in allopatry and that sexual conflict is likely to have played a role in population differentiation in this study system.

Animals↗