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Results for “Evolutionary adaptability”

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PubMed2004

Maternal diet and other factors affecting offspring sex ratio: a review.

Mammals usually produce approximately equal numbers of sons and daughters, but there are exceptions to this general rule, as has been observed in ruminant ungulate species, where the sex-allocation hypothesis of Trivers and Willard has provided a rational evolutionary underpinning to adaptive changes in sex ratio. Here, we review circumstances whereby ruminants and other mammalian species, especially rodents and primates, appear able to skew the sex ratio of their offspring. We also discuss some of the factors, both nutritional and nonnutritional, that potentially promote such skewing. Work from our laboratory, performed on mice, suggests that age of the mother and maternal diet, rather than the maternal body condition per se, play directive roles in controlling sex ratio. In particular, a diet high in saturated fats but low in carbohydrate leads to the birth of significantly more male than female offspring in mature laboratory mice, whereas when calories are supplied mainly in the form of carbohydrate rather than fat, daughters predominate. As the diets fed to the mice in these experiments were nutritionally complete and because litter sizes did not differ between treatments, dietary inadequacy seems not to be the cause for sex-ratio distortion. A number of mechanisms, all of which are testable, are discussed to provide an explanation for the phenomenon. We conclude the review by discussing potential implications of these observations to human medicine and agriculture.

Animal Nutritional Physiological Phenomena↗

PubMed1985

Evidence for the activation of female reproduction by males in a marsupial, the gray short-tailed opossum (Monodelphis domestica).

Although social factors are known to influence reproduction in a number of eutherian mammals, the effect of these factors on marsupial reproduction has not heretofore been studied. In this study, the temporal pattern of births and of the appearance of vaginal estrus following pairing with a male were examined in the gray short-tailed opossum, a small Brazilian didelphid. Although the estrous cycle is approximately 32 days long in this species, 75% of conceptions occurred within 9 days and 91.6% within 13 days following pairing. When sensory contact was permitted although mating was prevented, females tended to show vaginal estrus 3 to 7 days following pairing with a male. These findings are discussed with respect to possible mechanism, adaptive significance, and evolutionary perspective.

Animals↗

PubMed1997

Physiological effects of hunting red deer (Cervus elaphus).

When red deer (Cervus elaphus) were hunted by humans with hounds the average distance travelled was at least 19 km. This study of 64 hunted red deer provides the first empirical evidence on their state at the time of death. Blood and muscle samples obtained from hunted deer after death were compared with samples from 50 non-hunted red deer that had been cleanly shot with rifles. The effects on deer of long hunts were (i) depletion of carbohydrate resources for powering muscles, (ii) disruption of muscle tissue, and (iii) elevated secretion of beta-endorphin. High concentrations of cortisol, typically associated with extreme physiological and psychological stress, were found. Damage to red blood cells occurred early in the hunts; possible mechanisms are discussed. Taken together, the evidence suggests that red deer are not well-adapted by their evolutionary or individual history to cope with the level of activity imposed on them when hunted with hounds.

Animals↗

PubMed2006

Overconfidence in wargames: experimental evidence on expectations, aggression, gender and testosterone.

Overconfidence has long been noted by historians and political scientists as a major cause of war. However, the origins of such overconfidence, and sources of variation, remain poorly understood. Mounting empirical studies now show that mentally healthy people tend to exhibit psychological biases that encourage optimism, collectively known as 'positive illusions'. Positive illusions are thought to have been adaptive in our evolutionary past because they served to cope with adversity, harden resolve, or bluff opponents. Today, however, positive illusions may contribute to costly conflicts and wars. Testosterone has been proposed as a proximate mediator of positive illusions, given its role in promoting dominance and challenge behaviour, particularly in men. To date, no studies have attempted to link overconfidence, decisions about war, gender, and testosterone. Here we report that, in experimental wargames: (i) people are overconfident about their expectations of success; (ii) those who are more overconfident are more likely to attack; (iii) overconfidence and attacks are more pronounced among males than females; and (iv) testosterone is related to expectations of success, but not within gender, so its influence on overconfidence cannot be distinguished from any other gender specific factor. Overall, these results constitute the first empirical support of recent theoretical work linking overconfidence and war.

Adolescent↗

PubMed1980

Studies on the genetics of feeding behaviour in the cave fish Astyanax mexicanus f. anoptichthys. An example of apparent monofactorial inheritance by polygenes.

The Mexican characid Astyanax mexicanus gave rise to a series of cavernicolous populations ("Anoptichthys") not earlier than during the Pleistocene age. When searching for food the blind cave fish swims at an angle of about 45 degrees to the ground. The river fish, however, when having no visual information, stands vertically on its head. With the aid of infrared-videorecording and on the basis of crossing experiments it could be demonstrated that this difference in feeding behaviour is controlled by polygenes, although frequency distributions of the crossings suggest an apparent monofactorial inheritance. The evolutionary processes of adaptive reduction of headstanding and of progressive development of the gustatory equipment are genetically independent and both traits have been achieved by small genetic steps.

Animals↗

PubMed1992

Intestinal physiology in the parasitized host: integration, disintegration, and reconstruction of systems.

As noted in the introduction, the major objective in discussing gut inflammation in the parasitized host is to underscore the difficulty in establishing whether an inflammation-induced change represents a physiological adaptation or maladaptation (Fig. 3). Deciding whether a specific physiological adjustment, even one that contributes to disease, serves a useful function depends on the perspective of the observer who is in possession of information to make a critical judgment. This is like considering adaptations from an evolutionary sense where the significance of a change that evolved as a consequence of natural selection must be interpreted relative to the long-term "goal directedness" of that change, e.g., relative to its contribution to reproductive fitness. Because of the contributions of inflammation to both symptoms of disease and to the development of functional immunity, the parasitized host provides a means whereby both negative and positive effects of mucosal responses can be studied simultaneously. A careful analysis of the consequences of inflammation is important in contemplating the meaning of "neuroimmunophysiology of gastrointestinal mucosa."

Animals↗

PubMed2006

State-dependent learned valuation drives choice in an invertebrate.

Humans and other vertebrates occasionally show a preference for items remembered to be costly or experienced when the subject was in a poor condition (this is known as a sunk-costs fallacy or state-dependent valuation). Whether these mechanisms shared across vertebrates are the result of convergence toward an adaptive solution or evolutionary relicts reflecting common ancestral traits is unknown. Here we show that state-dependent valuation also occurs in an invertebrate, the desert locust Schistocerca gregaria (Orthoptera: Acrididae). Given the latter's phylogenetic and neurobiological distance from those groups in which the phenomenon was already known, we suggest that state-dependent valuation mechanisms are probably ecologically rational solutions to widespread problems of choice.

Animals↗

PubMed1999

The human genus.

A general problem in biology is how to incorporate information about evolutionary history and adaptation into taxonomy. The problem is exemplified in attempts to define our own genus, Homo. Here conventional criteria for allocating fossil species to Homo are reviewed and are found to be either inappropriate or inoperable. We present a revised definition, based on verifiable criteria, for Homo and conclude that two species, Homo habilis and Homo rudolfensis, do not belong in the genus. The earliest taxon to satisfy the criteria is Homo ergaster, or early African Homo erectus, which currently appears in the fossil record at about 1.9 million years ago.

Adaptation, Physiological↗

PubMed2006

Molecular genetic and structural modeling studies of Staphylococcus aureus RNA polymerase and the fitness of rifampin resistance genotypes in relation to clinical prevalence.

The adaptive and further evolutionary responses of Staphylococcus aureus to selection pressure with the antibiotic rifampin have not been explored in detail. We now present a detailed analysis of these systems. The use of rifampin for the chemotherapy of infections caused by S. aureus has resulted in the selection of mutants with alterations within the beta subunit of the target enzyme, RNA polymerase. Using a new collection of strains, we have identified numerous novel mutations in the beta subunits of both clinical and in vitro-derived resistant strains and established that additional, undefined mechanisms contribute to expression of rifampin resistance in clinical isolates of S. aureus. The fitness costs associated with rifampin resistance genotypes were found to have a significant influence on their clinical prevalence, with the most common clinical genotype (H481N, S529L) exhibiting no fitness cost in vitro. Intragenic mutations which compensate for the fitness costs associated with rifampin resistance in clinical strains of S. aureus were identified for the first time. Structural explanations for rifampin resistance and the loss of fitness were obtained by molecular modeling of mutated RNA polymerase enzymes.

DNA, Bacterial↗

PubMed1992

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.

Amino Acid Sequence↗

PubMed2026

The Baltic Sea: A Unique and Sensitive Ecosystem.

The Baltic Sea is a young, semi-enclosed brackish ecosystem shaped by postglacial history; restricted exchange with the North Sea; and strong gradients in salinity, temperature, and oxygen. These conditions have produced a species-poor but highly productive and ecologically important system. This review synthesizes evidence that Baltic populations persist not only through phenotypic plasticity but also through rapid evolutionary change, local adaptation, hybridization, and demographic history. Population genomic studies reveal sharp genetic differentiation between Baltic and Atlantic populations in many taxa, often across the Danish Straits, and fine-scale structuring within the Baltic itself. Case studies of eelgrass, bladderwrack, blue mussels, Baltic clam, cod, flounder, and herring illustrate how clonality, hybrid swarm formation, reproductive isolation, and habitat-specific selection shape resilience and vulnerability. Rapid warming, hypoxia, eutrophication, overfishing, and low functional redundancy increase ecosystem sensitivity. Long-term resilience will depend on protecting locally adapted populations and integrating genomic knowledge into ecosystem-based management and conservation.

Journal Article↗

PubMed2001

Natural image statistics and neural representation.

It has long been assumed that sensory neurons are adapted, through both evolutionary and developmental processes, to the statistical properties of the signals to which they are exposed. Attneave (1954)Barlow (1961) proposed that information theory could provide a link between environmental statistics and neural responses through the concept of coding efficiency. Recent developments in statistical modeling, along with powerful computational tools, have enabled researchers to study more sophisticated statistical models for visual images, to validate these models empirically against large sets of data, and to begin experimentally testing the efficient coding hypothesis for both individual neurons and populations of neurons.

Animals↗

PubMed2003

Evolution of aptamers with a new specificity and new secondary structures from an ATP aptamer.

Small changes in target specificity can sometimes be achieved, without changing aptamer structure, through mutation of a few bases. Larger changes in target geometry or chemistry may require more radical changes in an aptamer. In the latter case, it is unknown whether structural and functional solutions can still be found in the region of sequence space close to the original aptamer. To investigate these questions, we designed an in vitro selection experiment aimed at evolving specificity of an ATP aptamer. The ATP aptamer makes contacts with both the nucleobase and the sugar. We used an affinity matrix in which GTP was immobilized through the sugar, thus requiring extensive changes in or loss of sugar contact, as well as changes in recognition of the nucleobase. After just five rounds of selection, the pool was dominated by new aptamers falling into three major classes, each with secondary structures distinct from that of the ATP aptamer. The average sequence identity between the original aptamer and new aptamers is 76%. Most of the mutations appear to play roles either in disrupting the original secondary structure or in forming the new secondary structure or the new recognition loops. Our results show that there are novel structures that recognize a significantly different ligand in the region of sequence space close to the ATP aptamer. These examples of the emergence of novel functions and structures from an RNA molecule with a defined specificity and fold provide a new perspective on the evolutionary flexibility and adaptability of RNA.

Adenosine Triphosphate↗

PubMed2006

Representing the richness of avian spatial cognition: properties of a lateralized homing pigeon hippocampus.

Brain organization and its relationship to behavior in any extant species is a reflection of a long evolutionary history of adaptive change. Therefore, it follows that the relationship between the hippocampus and spatial cognition in any species or taxonomic group would be characterized by features adapted to its spatial ecology. Birds are the animal world's supreme navigators, and aspects of their navigational ability are dependent on the integrity of the hippocampal formation. Using the homing pigeon as a model species, we review an accumulating body of data indicating that the avian hippocampus is functionally lateralized. The spatial response properties of left hippocampal neurons, as recorded in freely moving pigeons in a laboratory environment, differ from the response properties of right hippocampal neurons. Left hippocampal lesions generally disrupt navigational behavior under field conditions more than right lesions, while right lesions are more likely to disrupt goal localization behavior under laboratory conditions. We propose that the available data are consistent with a hypothesis of a left hippocampus more involved in navigational processes, and a right hippocampus more involved in representing the locations of events. We also discuss the extent to which the observed hippocampal lateralization should be viewed as an intrinsic property of the hippocampus itself or imposed by the lateralized properties of visual inputs originating in other brain regions. Whatever the nature of the observed hippocampal lateralization, it is likely one adaptive variation in hippocampal organization that supports the extraordinary spatial behavior of birds.

Animals↗

PubMed2026

Primula pingwuensis (Primulaceae), a new species in Primula sect. Auganthus from Sichuan, China.

Primula pingwuensis sp. nov., a new species of Primula sect. Auganthus from Sichuan, China, is described. It resembles P. sinensis in having palmately lobed leaves and multi-whorled inflorescences but differs by its multi-branched stems, more densely short-pubescent surfaces, thicker chartaceous leaves, narrower leaf blades, and indistinct translucent nectar guides. A taxonomic key covering all nine known species of Primula sect. Auganthus is compiled herein to support field morphological discrimination. A chloroplast genome-based phylogeny shows that P. pingwuensis is sister to P. rongrong, and this clade is sister to P. fujiangensis. Incongruence between morphology and molecular phylogeny is observed within the section. Leaf-lobing patterns have undergone multiple independent evolutionary transitions during adaptive radiation in karst habitats, indicating that a few morphological traits cannot be used to reliably infer interspecific relationships. The new species is assessed as Data Deficient (DD) following IUCN criteria, owing to the lack of long-term observations of its threat status and population dynamics. This study provides new data for the taxonomy and evolution of Primula sect. Auganthus.

Primula↗

PubMed1998

Evolution of the vertebrate epididymis.

This review examines the structure and function of the extratesticular sperm ducts of vertebrates in terms of their evolutionary development and adaptive significance. The primitive extratesticular duct system of Chondrichthyes is described as an example of the vertebrate archetype. Adaptations of the duct system in higher vertebrates have involved a loss of some structures and specialization of others. The duct system probably evolved as a homeostatic mechanism to facilitate fertilization and some embryological development under conditions protected from the external environment. However, it is argued that the ducts also play an important role in the competition between males to achieve paternity. In vertebrates that practise internal fertilization the ducts are involved in post-testicular maturation and storage of spermatozoa. The biological significance of post-testicular sperm maturation has not been resolved. By contrast, sperm storage is essential in most male vertebrates because of the slow rate of spermatogenesis, particularly in ectotherms. Sperm storage is also important in the competition between males for paternity as it enables a male to mate a 'partner' a number of times during an oestrus in order to reduce the prospect of being cuckolded by another male. The extent of sperm maturation and storage in the epididymis of particular vertebrates depends on the relative roles of the testis and its extragonadal ducts in the competition between males for paternity. These roles depend on a number of factors, including allometric limitations to testis size, metabolic rate and the development of endothermy, and the reproductive strategy of females of the species.

Animals↗

PubMed1995

aDNA analysis in paleopathology: mini-review and prospects.

The epidemiology of human diseases is a major indicator of living conditions. Cardiovascular diseases are said to be a phenomenon of modern industrial societies, but infectious diseases have always been an indicative determinant in historic and prehistoric human populations. The spread of infectious agents is closely related to socioeconomic factors, e.g., nutritional status, population density, and hygienic conditions. Gathering more paleoepidemiological data on infectious diseases would also be helpful in studying human adaptivity and the evolutionary capability of pathogenic microorganisms. Until now, the collection of paleoepidemiological data was restricted to those human diseases that left traces on the skeletal remains, e.g., the terminal stages of syphilis, tuberculosis, and leprosy, or degenerative disorders of the joints. With modern molecular techniques, the spectrum of detectable infectious and heritable human diseases will foreseeably be enlarged. By detecting the infectious agent, or analysing the genetic codes, it will be possible to focus systematically on those diseases that either lead to sudden death or do not affect the skeleton because of their specific course.

DNA Mutational Analysis↗

PubMedDate not supplied

[Erythrocyte in pathology: speculations at the electron microscope].

The article summarizes the results of several years of research devoted to the surface architectonics and ultrastructure of erythrocyte in patients with pathology of different genesis. Diversity of changes in the shape of red blood cells, their surface and ultrastructure obtained by scanning and transmission microscopy is presented. The question is discussed on the non-specific character of erythrocyte transformation, disorganization of surface architectonics and ultrastructure of red blood cells in different pathological processes. The existence of typical morphological changes of erythrocyte in different pathological processes is suggested, considering it to be an evolutionary form of adaptation.

Erythrocyte Membrane↗