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Results for “Evolutionary adaptability”

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PubMed2006

Global use of alcohol, drugs and tobacco.

Humans have always used drugs, probably as part of their evolutionary and nutritional heritage. However, this previous biological adaptation is unlikely to be so in the modern world, in which 2 billion adults (48% of the adult population) are current users of alcohol, 1.1 billion adults (29% of the adult population) are current smokers of cigarettes and 185 million adults (4.5% of the adult population) are current users of illicit drugs. The use of drugs is determined largely by market forces, with increases in affordability and availability increasing use. People with socio-economic deprivation, however measured, are at increased risk of harmful drug use, as are those with a disadvantaged family environment, and those who live in a community with higher levels of substance use. Substance use is on the increase in low-income countries which, in the coming decades, will bear a disproportionate burden of substance-related disability and premature death.

Africa↗

PubMed2005

Hybridization in the recent past.

The question we address in this article is how hybridization in the recent past can be detected in recently evolved species. Such species may not have evolved genetic incompatibilities and may hybridize with little or no fitness loss. Hybridization can be recognized by relatively small genetic differences between sympatric populations because sympatric populations have the opportunity to interbreed whereas allopatric populations do not. Using microsatellite DNA data from Darwin's finches in the Galapagos archipelago, we compare sympatric and allopatric genetic distances in pairs of Geospiza and Camarhynchus species. In agreement with the hybridization hypothesis, we found a statistically strong tendency for a species to be more similar genetically to a sympatric relative than to allopatric populations of that relative. Hybridization has been studied directly on two islands, but it is evidently more widespread in the archipelago. We argue that introgressive hybridization may have been a persistent feature of the adaptive radiation through most of its history, facilitating evolutionary diversification and occasionally affecting both the speed and direction of evolution.

Animals↗

PubMed2003

Molecular basis and evolutionary origins of color diversity in great star coral Montastraea cavernosa (Scleractinia: Faviida).

Natural pigments are normally products of complex biosynthesis pathways where many different enzymes are involved. Corals and related organisms of class Anthozoa represent the only known exception: in these organisms, each of the host-tissue colors is essentially determined by a sequence of a single protein, homologous to the green fluorescent protein (GFP) from Aequorea victoria. This direct sequence-color linkage provides unique opportunity for color evolution studies. We previously reported the general phylogenetic analysis of GFP-like proteins, which suggested that the present-day diversity of reef colors originated relatively recently and independently within several lineages. The present work was done to get insight into the mechanisms that gave rise to this diversity. Three colonies of the great star coral Montastraea cavernosa (Scleractinia, Faviida) were studied, representing distinct color morphs. Unexpectedly, these specimens were found to express the same collection of GFP-like proteins, produced by at least four, and possibly up to seven, different genetic loci. These genes code for three basic colors-cyan, green, and red-and are expressed differently relative to one another in different morphs. Phylogenetic analysis of the new sequences indicated that the three major gene lineages diverged before separation of some coral families. Our results suggest that color variation in M. cavernosa is not a true polymorphism, but rather a manifestation of phenotypic plasticity (polyphenism). The family level depth of its evolutionary roots indicates that the color diversity is adaptively significant. Relative roles of gene duplication, gene conversion, and point mutations in its evolution are discussed.

Animals↗

PubMed2006

A scan for signatures of positive selection in candidate loci for skin pigmentation in humans.

Although the combination of pale skin and intense sun exposure results in an important health risk for the individual, it is less clear if at the population level this risk has possessed an evolutionary meaning. In this sense, a number of adaptive hypotheses have been put forward to explain the evolution of human skin pigmentation, such as photoprotection against sun-induced cancer, sexual selection, vitamin D synthesis or photoprotection of photolabile compounds, among others. It is expected that if skin pigmentation is adaptive, we might be able to see the signature of positive selection on some of the genes involved. In order to detect this signature, we analyze a battery of 81 candidate loci by means of phylogenetic and population genetic tests. Our results indicate that both light and dark skin may possess adaptive value. Of the main loci presenting this signature, TP53BP1 shows clear evidence of adaptive selection in Africans, whereas TYRP1 and SLC24A5 show evidence of adaptive selection in Caucasians. Although we cannot offer a mechanism that based on these genes explains the advantage of light skin, if TP53BP1, and perhaps RAD50, have truly conferred an adaptive value to the African population analyzed, photoprotection against sun-induced skin damage/cancer might be proposed as a mechanism that has driven the evolution of human skin pigmentation.

Adaptation, Biological↗

PubMed2001

Evaluation of methods for determination of a reconstructed history of gene sequence evolution.

With whole-genome sequences being completed at an increasing rate, it is important to develop and assess tools to analyze them. Following annotation of the protein content of a genome, one can compare sequences with previously characterized homologous genes to detect novel functions within specific proteins in the evolution of the newly sequenced genome. One common statistical method to detect such changes is to compare the ratios of nonsynonymous (K(a)) to synonymous (K(s)) nucleotide substitution rates. Here, the effects of several parameters that can influence this calculation (sequence reconstruction method, phylogenetic tree branch length weighting, GC content, and codon bias) are examined. Also, two new alternative measures of adaptive evolution, the point accepted mutations (PAM)/neutral evolutionary distance (NED) ratio and the sequence space assessment (SSA) statistic are presented. All of these methods are compared using two sequence families: the recent divergence of leptin orthologs in primates, and the more ancient divergence of the deoxyribonucleoside kinase family. The examination of these and other measures to detect changes of gene function along branches of a phylogenetic tree will become increasingly important in the postgenomic era.

Algorithms↗

PubMed2026

Trade-Offs Associated with Virulence of Soybean Cyst Nematode on the Broad-Spectrum Resistance Source PI 437654.

The soybean cyst nematode (SCN; Heterodera glycines) poses a major challenge to soybean production, intensified by the declining effectiveness of natural resistance against this pathogen. Although the use of resistant soybean varieties can be effective, their widespread and repeated use ultimately results in the emergence of virulent nematode populations that can successfully attack these resistant hosts. To assess for potential trade-offs between virulence and fitness, we investigated the hatch response, penetration rate, and reproductive potential of SCN adapted to overcome the broad-spectrum resistance source PI 437654. The hatching process is a critical phase in the life cycle of the SCN, influencing its ability to infect hosts and complete its life cycle. Our results indicated that SCN populations exhibit preferential and heightened hatch responses to their adapted host compared to alternative hosts, regardless of their virulence profile. Additionally, we found that SCN populations adapted to overcome broad-spectrum resistance showed reduced reproductive success on susceptible hosts compared to unadapted populations. This reduction in reproductive success was not attributed to differences in hatch response or penetration rates. The results from our study highlight the potential trade-offs associated with SCN virulence adaptation and emphasize the importance of considering these evolutionary dynamics in developing sustainable management strategies.

Disease Control and Pest Management↗

PubMed1994

Biodiversity at the molecular genetic level: experiences from disparate macroorganisms.

Genetic variation is the basis of adaptive flexibility in populations and is the ultimate evolutionary basis of much species and community-level diversity. Accordingly, the preservation and maintenance of genetic diversity has a high priority in many conservation programmes. This paper discusses how genetic diversity is measured at the molecular level, including some newer measures made possible with restriction site or DNA sequence data as well as the development of a phylogenetic approach to assessing the significance of genetic variation within a species. These measures of genetic diversity are then used to re-examine the validity of the 50/500 rule of conservation biology; a rule that states that populations should have no fewer than 50 individuals for short-term maintenance of genetic variation and no fewer than 500 individuals for long-term maintenance. Both the 50 and 500 parts of this rule are found to be invalid and frequently misleading. Instead of invoking 'universal' rules, conservation biologists should recognize the role of biodiversity in management policies. Not all species are the same, and we need more research and a willingness to try novel approaches rather than naively apply a 'rule' that has no demonstrable generality.

Animals↗

PubMed2001

Using human immunodeficiency virus type 1 sequences to infer historical features of the acquired immune deficiency syndrome epidemic and human immunodeficiency virus evolution.

In earlier work, human immunodeficiency virus type 1 (HIV-1) sequences were analysed to estimate the timing of the ancestral sequence of the main group of HIV-1, the virus that is responsible for the acquired immune deficiency syndrome pandemic, yielding a best estimate of 1931 (95% confidence interval of 1915-1941). That work will be briefly reviewed, outlining how phylogenetic tools were extended to incorporate improved evolutionary models, how the molecular clock model was adapted to incorporate variable periods of latency, and how the approach was validated by correctly estimating the timing of two historically documented dates. The advantages, limitations, and assumptions of the approach will be summarized, with particular consideration of the implications of branch length uncertainty and recombination. We have recently undertaken new phylogenetic analysis of an extremely diverse set of human immunodeficiency virus envelope sequences from the Democratic Republic of the Congo (the DRC, formerly Zaire). This analysis both corroborates and extends the conclusions of our original study. Coalescent methods were used to infer the demographic history of the HIV-1 epidemic in the DRC, and the results suggest an increase in the exponential growth rate of the infected population through time.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Comparison of self-sustained sequence-replication reaction systems.

The 3SR (self-sustained sequence-replication) reaction is a very efficient method for isothermal amplification of target DNA or RNA sequences in vitro. This method requires three enzymatic activities: reverse transcriptase, DNA-dependent RNA polymerase and Escherichia coli ribonuclease H. We have modified the original protocol by using human immunodeficiency virus (HIV)-1 reverse transcriptase instead of avian myeloblastosis virus (AMV) reverse transcriptase to allow amplification with T7 RNA polymerase but without E. coli ribonuclease H. Comparison of the incorporation kinetics between the conventional three-enzyme 3SR and our two-enzyme 3SR shows differences in the kinetic behaviour. Furthermore, by the new two-enzyme 3SR, the amplified RNA is obtained in a purer form compared with the experiments with three-enzyme 3SR. The aim of our research is to adapt 3SR as a useful tool for darwinian evolutionary experiments.

Base Sequence↗

PubMed1983

Receptive-field properties in reptilian optic tectum: some comparisons with mammals.

The receptive-field properties of single cells in the optic tectum of Iguana iguana were studied using the same procedures as have been used in this laboratory in studying its mammalian homologue, the superior colliculus. Surprisingly, despite some species-specific characteristics, the range of physiological properties of tectal and superior collicular cells appeared to be strikingly similar. This observation is not consistent with the notion that functional differences between these structures evolved as a consequence of the tremendous elaboration of mammalian neocortex and its involvement in sensory processes. The internal organization of visual tectal receptive fields was observed to be very much like that described in mammals. This included a similar distribution of on-off areas, the presence of both spatial summation and spatial inhibition within the excitatory receptive-field borders, suppressive areas just beyond these borders, and a marked tendency for habituation. In addition, many cells showed distinct directional preferences that were strongly influenced by the velocity of movement through the receptive field. Furthermore, the receptive fields of bimodal and trimodal cells showed topographic correspondences as in mammals, although the sizes of the fields were often large, thereby emphasizing the lack of an exact register between modalities. In contrast to the findings in mammals, however, a preference for stationary over moving stimuli was observed in most neurons, and specializations in iguana tectal cells representing the fovea were noted that have not been described in other species. These foveal specializations include a distinct preference for stationary over moving stimuli, the absence of directional selectivity, and the presence of a majority of cells responding at light onset only. It is suggested that the similarities in the organization and response properties of cells of the optic tectum and superior colliculus reflect the retention of ancestral characteristics through various levels of vertebrate evolution. Furthermore, the subtle species differences in the properties of these cells appear to reflect adaptations to specific ecological pressures rather than general evolutionary trends.

Animals↗

PubMed2005

The recent evolution of human L1 retrotransposons.

L1 elements are the most successful retrotransposons in mammals and are responsible for at least 30% of human DNA. Far from being indolent genomic parasites, L1 elements have evolved and amplified rapidly during human evolution. Indeed during just the last 25 million years (MY) five distinct L1 families have emerged and generated tens of thousands of copies. The most recently evolved human specific L1 family is currently active and L1 copies have been accumulating in the human genome at about the same rate per generation as the currently active L1 families in Old World rats and mice. At times during the last 25 MY L1 activity constituted a significant enough genetic load to be subject to negative selection. During these same times, and in apparent response to the host, L1 underwent adaptive evolution. Understanding the molecular basis for these evolutionary changes should help illuminate one of the least understood but most important aspects of L1 biology, namely the extent and nature of the interaction between L1 and its host.

Evolution, Molecular↗

PubMed2005

Molecular phylogeny and evolution of alcohol dehydrogenase (Adh) genes in legumes.

BACKGROUND: Nuclear genes determine the vast range of phenotypes that are responsible for the adaptive abilities of organisms in nature. Nevertheless, the evolutionary processes that generate the structures and functions of nuclear genes are only now be coming understood. The aim of our study is to isolate the alcohol dehydrogenase (Adh) genes in two distantly related legumes, and use these sequences to examine the molecular evolutionary history of this nuclear gene. RESULTS: We isolated the expressed Adh genes from two species of legumes, Sophora flavescens Ait. and Wisteria floribunda DC., by a RT-PCR based approach and found a new Adh locus in addition to homologues of the Adh genes found previously in legumes. To examine the evolution of these genes, we compared the species and gene trees and found gene duplication of the Adh loci in the legumes occurred as an ancient event. CONCLUSION: This is the first report revealing that some legume species have at least two Adh gene loci belonging to separate clades. Phylogenetic analyses suggest that these genes resulted from relatively ancient duplication events.

Alcohol Dehydrogenase↗

PubMed2006

Mind the gap... in intelligence: re-examining the relationship between inequality and health.

Wilkinson contends that economic inequality reduces the health and life expectancy of the whole population but his argument does not make sense within its own evolutionary framework. Recent evolutionary psychological theory suggests that the human brain, adapted to the ancestral environment, has difficulty comprehending and dealing with entities and situations that did not exist in the ancestral environment and that general intelligence evolved as a domain-specific adaptation to solve evolutionarily novel problems. Since most dangers to health in the contemporary society are evolutionarily novel, it follows that more intelligent individuals are better able to recognize and deal with such dangers and live longer. Consistent with the theory, the macro-level analyses show that income inequality and economic development have no effect on life expectancy at birth, infant mortality and age-specific mortality net of average intelligence quotient (IQ) in 126 countries. They also show that an average IQ has a very large and significant effect on population health but not in the evolutionarily familiar sub-Saharan Africa. At the micro level, the General Social Survey data show that, while both income and intelligence have independent positive effects on self-reported health, intelligence has a stronger effect than income. The data collectively suggest that individuals in wealthier and more egalitarian societies live longer and stay healthier, not because they are wealthier or more egalitarian but because they are more intelligent.

Adult↗

PubMed2004

Historical diversification of migration patterns in a passerine bird.

Migratory strategies of birds require complex orientation mechanisms, morphological adaptations, and life-history adjustments. From an evolutionary perspective, it is important to know how fast this complex combination of traits can evolve. We analyzed mitochondrial control-region DNA sequences in 241 blackcaps (Sylvia atricapilla) from 12 populations with different migratory behaviors. The sample included sedentary populations in Europe and Atlantic archipelagos and migratory populations with different distances of migration, from regional to intercontinental migrations, and different heading directions (due to a migratory divide in central Europe). There was no genetic structure between migratory and sedentary populations, or among populations from different biogeographic areas (Atlantic islands, the Iberian Peninsula, or the continent), however we found evidence of a genetic structure when comparing populations located on either side of the migratory divide. These findings support an independent evolution of highly divergent migratory strategies in blackcaps, occurring after a postglacial colonization of the continent along western and eastern routes. Accordingly, mismatch-distribution analyses suggested an expansion of blackcaps from a very small population size, and time estimates dated such an expansion during the last postglacial period. However, the populations in Gibraltar, located in a putative Mediterranean refuge, appeared to be independent of these processes, showing evidence of restricted gene flow with other populations and demonstrating insignificant historical changes in effective population size. Our results show that the interruption of gene flow between migratory and sedentary populations is not necessary for the maintenance of such a polymorphism, and that even the most divergent migratory strategies of a bird species are susceptible to evolution in response to historical environmental changes.

Animal Migration↗

PubMedDate not supplied

The ecotopes and evolution of triatomine bugs (triatominae) and their associated trypanosomes.

Triatomine bug species such as Microtriatoma trinidadensis, Eratyrus mucronatus, Belminus herreri, Panstrongylus lignarius, and Triatoma tibiamaculata are exquisitely adapted to specialist niches. This suggests a long evolutionary history, as well as the recent dramatic spread a few eclectic, domiciliated triatomine species. Virtually all species of the genus Rhodnius are primarily associated with palms. The genus Panstrongylus is predominantly associated with burrows and tree cavities and the genus Triatoma with terrestrial rocky habitats or rodent burrows. Two major sub-divisions have been defined within the species Trypanosoma cruzi, as T. cruzi 1 (Z1) and T. cruzi 2 (Z2). The affinities of a third group (Z3) are uncertain. Host and habitat associations lead us to propose that T. cruzi 1 (Z1) has evolved in an arboreal, palm tree habitat with the triatomine tribe Rhodniini, in association with the opossum Didelphis. Similarly we propose that T. cruzi (Z2) and Z3 evolved in a terrestrial habitat in burrows and in rocky locations with the triatomine tribe Triatomini, in association with edentates, and/or possibly ground dwelling marsupials. Both sub-divisions of T. cruzi may have been contemporary in South America up to 65 million years ago. Alternatively, T. cruzi 2 (Z2) may have evolved more recently from T. cruzi 1 (Z1) by host transfers into rodents, edentates, and primates. We have constructed a molecular phylogeny of haematophagous vectors, including triatomine bugs, which suggests that faecal transmission of trypanosomes may be the ancestral route. A molecular clock phylogeny suggests that Rhodnius and Triatoma diverged before the arrival, about 40 million years ago, of bats and rodents into South America.

Animals↗

PubMed2002

Dietary restriction downregulates free radical and lipid peroxide production: plausible mechanism for elongation of life span.

Dietary restriction elongates life span by suppressing age-related diseases in experimental animals. It has received a great deal of attention in connection with the relationship between aging, nutrition, and oxidative stress because oxidative injury in several tissues is a prominent feature in the aging process. Although the oxidative stress theory of aging has currently gained popularity, the premise from which this hypothesis was derived is paradoxical because the same oxygen, that supports life in one hand threatens survival and promotes aging in the other. Until recently, no single experimental paradigm could offer satisfactory mechanistic explanations for this complex issue. Recent investigations using the life-extending dietary restriction regimen could offer satisfactory mechanistic explanations for this apparent self-contradiction to life. The modulation of free radical-induced oxidative stress provided sufficient data to support the notion that dietary restriction's antiaging effect may come from its ability to tightly regulate the oxidative status of an organism. The result is the maintenance of cellular homeostasis, a hallmark of dietary restriction's action in the extension of life span. To date, we reported that dietary restriction (maintained on 60% of ad libitum feeding) suppresses age-related oxidative damage by modulating the amount as well as the fatty acid composition of tissue phospholipids. These remarkable findings have been incorporated into the new "membrane peorxidation cycle" concept. The intervention of this cycle appears to be an evolutionary process that the dietary restricted rats have adapted as a strategy to protect the membrane in an oxidative environment.

Aging↗

PubMed2006

Evolutionary radiation of "stone plants" in the genus Argyroderma (Aizoaceae): unraveling the effects of landscape, habitat, and flowering time.

Recent phylogenetic evidence suggests that the extraordinary diversity of the Cape Floristic Kingdom in South Africa may be the result of widespread evolutionary radiation. Our understanding of the role of adaptive versus neutral processes in these radiations remains largely speculative. In this study we investigated factors involved in the diversification of Argyroderma, a genus within the most spectacular of the Cape radiations, that of the Ruschioid subfamily of the Aizoaceae. We used amplified fragment length polymorphisms and a suite of morphological traits to elucidate patterns of differentiation within and between species of Argyroderma across the range of the genus. We then used a matrix correlation approach to assess the influence of landscape structure, edaphic gradients, and flowering phenology on phenotypic and neutral genetic divergence in the system. We found evidence for strong spatial genetic isolation at all taxonomic levels. In addition, genetic differentiation occurs along a temporal axis, between sympatric species with divergent flowering times. Morphological differentiation, which previous studies suggest is adaptive, occurs along a habitat axis, between populations occupying different edaphic microenvironments. Morphological differentiation is in turn significantly associated with flowering time shifts. Thus we propose that diversification within Argyroderma has occurred through a process of adaptive speciation in allopatry. Spatially isolated populations diverge phenotypically in response to divergent habitat selection, which in turn leads to the evolution of reproductive isolation through divergence of flowering phenologies, perhaps as a correlated response to morphological divergence. Evidence suggests that diversification of the group has proceeded in two phases: the first involving divergence of allopatric taxa on varied microhabitats within a novel habitat type (the quartz gravel plains), and the second involving range expansion of an early flowering phenotype on the most extreme edaphic habitat and subsequent incomplete differentiation of allopatric populations of the early flowering group. These results point to adaptive speciation in allopatry as a likely model for the spectacular diversification of the ice-plant family in the dissected landscapes of the southern African winter rainfall deserts.

Aizoaceae↗

PubMed1998

Innateness, evolution, and genetics of language.

Our goal in this article is to review a debate over the evolution of language and to suggest some keys to its resolution. We begin with a review of some of the theoretical and empirical evidence for the innateness of language that has caused renewed interest in the evolution of language. In a second section we review some prominent theories of the evolution of language, focusing on the controversy over whether language could have been adapted for some purpose. We argue that for evolutionary studies of language to advance, theorists must make more persuasive arguments for the purpose of language, and, furthermore, linguists must continue to develop a detailed theory of syntax. Finally, we suggest ways that behavioral and population genetics could help to inform studies of the evolution of language.

Biological Evolution↗