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At least 613 records · Page 34Linked to original sources
PubMed1999

Quantitative genetics in conservation biology.

Most of the major genetic concerns in conservation biology, including inbreeding depression, loss of evolutionary potential, genetic adaptation to captivity and outbreeding depression, involve quantitative genetics. Small population size leads to inbreeding and loss of genetic diversity and so increases extinction risk. Captive populations of endangered species are managed to maximize the retention of genetic diversity by minimizing kinship, with subsidiary efforts to minimize inbreeding. There is growing evidence that genetic adaptation to captivity is a major issue in the genetic management of captive populations of endangered species as it reduces reproductive fitness when captive populations are reintroduced into the wild. This problem is not currently addressed, but it can be alleviated by deliberately fragmenting captive populations, with occasional exchange of immigrants to avoid excessive inbreeding. The extent and importance of outbreeding depression is a matter of controversy. Currently, an extremely cautious approach is taken to mixing populations. However, this cannot continue if fragmented populations are to be adequately managed to minimize extinctions. Most genetic management recommendations for endangered species arise directly, or indirectly, from quantitative genetic considerations.

Animals↗
PubMed2003

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe.

The capercaillie inhabits a continuous range in large parts of the Palearctic boreal forest, but is patchily distributed in temperate Europe. An ongoing population decline, largely related to human land use changes, has been most pronounced in central and western Europe, where some local populations have become extinct. In this study, we document the genetic differentiation of capercaillie populations at different stages along a gradient of spatial structuring from high connectivity (continuous range in the boreal forest) to a metapopulation systems (Alps) and recent (central Europe) and historic (Pyrenees) isolation. Four hundred and sixty individuals from 14 sample sites were genotyped at 10 polymorphic microsatellite loci to assess genetic structure and variation of capercaillie populations across its European range. As expected, differentiation was least pronounced within the continuous range in the boreal forest. Within the metapopulation system of the Alps, differentiation was less than among the isolated populations of central Europe (Black Forest, Fichtelgebirge, Thuringia, Vosges). In the long-isolated population of the Pyrenees, and the recently isolated populations of central Europe, genetic diversity was significantly reduced compared with the Alps and boreal forest. Our results agree with the concept of a gradual increase in genetic differentiation from connectivity to isolation, and from recent to historic isolation. Anthropogenic habitat deterioration and fragmentation thus not only leads to range contractions and extinctions, but may also have significant genetic and evolutionary consequences for surviving populations. To maintain high levels of genetic variation in species in fragmented habitats, conservation should aim at securing connectivity between spatially distinct populations.

Animals↗
PubMed1976

[Several methodologic problems of evolutionary histology in light of the findings of molecular genetics].

The paper elucidates certain methodological problems of evolutionary histology. The principal attention is given to the necessary synthesis of modern molecular biology and genetics and evolutionary histology. Modern data on the levels of the organization of the living matter and their significance for the rightness of the A.A. Zavarzin's theory of parallel lines in the tissue evolution are presented. The hypothesis of an application of the theory of parallel lines in the hereditary variability by N.I. Vavilov to the analysis of regularities of the tissue evolution is set forth. The hypothesis is proposed that mutation changes of similar genes in representatives of different types of animals underlie the regularities of the tissue evolution discovered by A.A. Zavarzin, and epigenomic changes of regulation systems occurring most frequently in the process of ontogenesis of organisms lie in the basis of the divergent evolution of tissues after N.G. Chlopin.

Biological Evolution↗
PubMed2002

Advice to an aging scientist.

Fifty years ago, Peter Medawar and George Williams developed two now-classic theories for the evolution of senescence. In the past 20 years, evolutionary biologists studying aging have developed explicit mathematical models of these theories, used these models to derive explicit predictions, and tested these predictions using a variety of approaches. But, we argue here, our singular focus on these models may have hindered progress in evolutionary studies of aging. Research in this area has not kept pace with dramatic advances in evolutionary theory and molecular genetics. Progress in evolutionary studies of aging will depend on a bold, integrative approach, incorporating evolutionary and molecular advances from other fields, along with the powerful statistical and mathematical tools now available. We discuss several specific examples where we may gain new insight into the causes of aging by looking to other evolutionary phenomena, including sexual conflict and the evolution of social behavior. In addition, we present new results which suggest that the analysis of gene networks may lend particular insight into the genetic underpinnings of the aging process.

Aging↗
PubMed2001

New molecular markers for phlebotomine sand flies.

Using degenerate-primers PCR we isolated and sequenced fragments from the sand fly Lutzomyia longipalpis homologous to two behavioural genes in Drosophila, cacophony and period. In addition we identified a number of other gene fragments that show homology to genes previously cloned in Drosophila. A codon usage table for L. longipalpis based on these and other genes was calculated. These new molecular markers will be useful in population genetics and evolutionary studies in phlebotomine sand flies and in establishing a preliminary genetic map in these important leishmaniasis vectors.

Amino Acid Sequence↗
PubMed1997

Genetically complex cardiovascular traits. Origins, problems, and potential solutions.

Modern molecular genetic analysis tools are making it possible for researchers to investigate, and in many cases actually disclose, mutations and other genetic factors that contribute to disease susceptibility. However, the ease with which these factors can be identified is dictated by not only the number of factors underlying or influencing the trait, but also by the manner in which these factors interact. Traits that are influenced by multiple genetic and nongenetic factors are termed "complex" genetic traits and are receiving a great deal of attention in the current medical literature. Hypertension and blood pressure regulation are considered paradigmatic complex traits. In this paper, the origin, nature, and dilemmas associated with the analysis of complex traits are considered. Basic biochemical and physiological determinants of blood pressure are described in an effort to show how genetic complexity could arise within an individual, and fundamental concepts in population genetics and evolutionary theory are discussed to expose the reasons certain forms of genetic complexity can emerge and be sustained in the population at large. Methods for approaching the genetic dissection of complex traits and diseases are also enumerated, with simple descriptions of the scientific motivation offered for each. Problems plaguing these approaches are also discussed. Finally, areas for future research are outlined with the hope of sparking further debate on the subject.

Blood Pressure↗
PubMed1996

Genetic basis, mode of inheritance and evolutionary changes of migratory directions in palaearctic warblers (Aves: Sylviidae)

The genetic basis, mode of inheritance and recent evolutionary changes of migratory directions in birds are discussed on the basis of published and new experimental evidence. Displacement experiments with wild-caught migrants and orientation tests with hand-reared passerines illustrate that inexperienced young birds possess genetic information about the direction and approximate distance of migration, but not about the geographic location of the winter quarters. Hand-raised blackcaps Sylvia atricapilla from east and west of the Central European migratory divide, when tested under identical conditions, exibited population-specific migratory directions in orientation cages. Cross-breeding of birds from these two populations demonstrated an intermediate mode of inheritance of this behavioural character. New data on the orientation of an F2 generation suggest that the directional information is encoded by only a few major genes. Migratory adaptations may have evolved recently, in some cases rapidly, as is illustrated by the establishment of a new migration route of central European blackcaps to winter quarters in the British Isles. This new route is shown (in a captive breeding experiment) to be based on a novel, genetically programmed westnorthwesterly migratory direction. It must have spread from almost zero to 7-11 % frequency in parts of central Europe within only three decades. The novel direction is also inherited phenotypically intermediately; its rapid evolution may be mediated by assortative mating based on differential arrival times at the breeding grounds. The evolutionary flexibility of migratory adaptations is discussed in relation to changes in the environment, both natural and accelerated by man.

Journal Article↗
PubMed2005

Placing the Floridian marine genetic disjunction into a regional evolutionary context using the scorched mussel, Brachidontes exustus, species complex.

The well-documented Floridian Gulf/Atlantic marine genetic disjunction provides an influential example of presumed vicariant cladogenesis along a continental coastline for major elements of a diverse nearshore fauna. However, it is unclear if this disjunction represents a local anomaly for regionally distributed morphospecies, or if it is merely one of many such cryptic phylogenetic splits that underlay their assumed genetic cohesiveness. We aimed to place the previously characterized scorched mussel Gulf/Atlantic genetic disjunction into a regional phylogenetic perspective by incorporating genotypes of nominal conspecifics sampled throughout the Caribbean Basin as well as those of eastern Pacific potential geminate species. Our results show it to be one of multiple latent regional genetic disjunctions, involving five cryptic Caribbean species, that appear to be the product of a long history of regional cladogenesis. Disjunctions involving three stem lineages clearly predate formation of the Isthmus of Panama and of the Caribbean Sea, although four of the five cryptic species have within-basin sister relationships. Surprisingly, the Atlantic clade was also found to be widespread in the southern Caribbean, and ancestral demography calculations through time for Atlantic coast-specific genotypes are consistent with a northward range extension after the last glacial maximum. Our new data seriously undermine the hypothesis of a Floridian vicariant genesis and imply that the scorched mussel Gulf/Atlantic disjunction represents a case of geographic and temporal pseudocongruence. All five Caribbean Basin cryptic species exhibited an intriguing pattern of predominantly allopatric distribution characterized by distinct geographic areas of ecological dominance, often adjoining those of sister taxa. This pattern of distribution is consistent with allopatric speciation origins, coupled with restricted postspeciation range extensions. Several lines of indirect evidence favor the hypothesis that the predominantly allopatric distributions are maintained over evolutionary time scales, primarily by postrecruitment ecological filters rather than by oceanographic barriers to larval-mediated gene flow.

Animals↗
PubMed2004

Heterogeneity of ITS1 sequences in the biting midge Culicoides impunctatus (Goetghebuer) suggests a population in Argyll, Scotland, may be genetically distinct.

Ribosomal DNA (rDNA) internal transcribed spacer 1 (ITS1) is a useful genomic region for understanding evolutionary and genetic relationships. In the current study, variation in ITS1 from eight Culicoides species was analysed by PCR, DNA restriction analysis, cloning, and sequencing. ITS1 variants were essentially homogenized within a species, as sequences were identical or closely related. However, Culicoides impunctatus ITS1 sequences derived from one (Argyll) of five populations contained considerable genomic diversity. The secondary structure of each ITS1 was computed. The structure aided the production of an accurate alignment and the identification of a large indel. A phylogenetic analysis was performed. Some of the sequences from the diverse Argyll C. impunctatus population were more related to Culicoides imicola, a vector of animal pathogens in the Old World, than they were to the other C. impunctatus sequences. Thus, the rDNA ITS1 regions of individuals in the Argyll C. impunctatus population were not conforming to the general theory of rDNA homogenization through molecular drive.

Animals↗
PubMed1994

Somatic and heritable effects of environmental genotoxins and the emergence of evolutionary toxicology.

The genetic effects of environmental pollutants include mutations in somatic cells or germinal cells that are the direct result of exposure to toxicants. Biomarkers that detect such mutagenic effects have been developed and tested in field studies on wildlife populations. However, another class of genetic effects resulting from pollution exposure exists. Specifically, changes in allele frequencies of populations will occur as a result of population bottlenecks, inbreeding, or selection at loci critical for survival in polluted environments. We describe how such genetic alterations can be studied at the population level using the techniques of molecular genetics, and we predict the development of a new field, evolutionary toxicology, that will address such issues.

Animals↗
PubMed2005

Family level inbreeding depression and the evolution of plant mating systems.

Variation in the magnitude of inbreeding depression (ID) among families may have important consequences for mating system evolution. Experimental studies have shown that such variation is a common feature of natural plant populations. Unfortunately, the genetic and evolutionary significance of family level estimates remains obscure. Almost any kind of genetic variation will generate differences in ID among families, and as a consequence, a non-zero variance in family level ID is not sufficient to distinguish genetic architectures with wholly different implications for mating system evolution. Quantitative genetic methods provide a means to extract more information from ID experiments. Estimates of quantitative genetic variance components directly inform questions about the genetic basis of ID and should ultimately allow tests of alternative theories of mating system evolution.

Biological Evolution↗
PubMed1975

Speculations on the evolution of the genetic code.

An evolutionary scheme is postulated in which the bases enter the genetic code in a definite temporal sequence and the correlated amino acids are assigned definite functions in the evolving system. The scheme requires a singlet code (guanine coding for glycine) evolving into a doublet code (guanine-cytosine doublet coding for gly (GG), ala (GC), arg (CG), pro (CC). The doublet code evolves into a triplet code. Polymerization of nucleotides is thought to have been by block polymerization rather than by a template mechanism. The proteins formed at first were simple structural peptides. No direct nucleotide-amino acid stereo-chemical interaction was required. Rather an adaptor-type indirect mechanism is thought to have been functioning since the origin.

Biological Evolution↗
PubMed2005

The evolutionary history of placodes: a molecular genetic investigation of the larvacean urochordate Oikopleura dioica.

The evolutionary origin of vertebrate placodes remains controversial because divergent morphologies in urochordates, cephalochordates and vertebrates make it difficult to recognize organs that are clearly homologous to placode-derived features, including the olfactory organ, adenohypophysis, lens, inner ear, lateral line and cranial ganglia. The larvacean urochordate Oikopleura dioica possesses organs that morphologically resemble the vertebrate olfactory organ and adenohypophysis. We tested the hypothesis that orthologs of these vertebrate placodes exist in a larvacean urochordate by analyzing the developmental expression of larvacean homologs of the placode-marking gene families Eya, Pitx and Six. We conclude that extant chordates inherited olfactory and adenohypophyseal placodes from their last common ancestor, but additional independent proliferation and perhaps loss of placode types probably occurred among the three subphyla of Chordata.

Animals↗
PubMed2026

Consistent and idiosyncratic pleiotropy in shaping genetic correlations.

Pleiotropy, the phenomenon where a single mutation influences multiple phenotypic traits, creates genetic correlations that can constrain evolutionary trajectories. Yet genetic correlations differ in their persistence: some remain stable over long evolutionary timescales, whereas others change rapidly across generations or environments. One explanation is that similar values of genetic correlation, rG, can arise from different pleiotropic architectures: broadly aligned effects across many loci, or disproportionate covariance contributions from a few large effect loci. Motivated by the distinction between vertical and horizontal pleiotropy, here, we develop a bivariate marker effect framework for recombinant mapping populations that separates candidate large covariance contributors from the polygenic background correlation, rD. We define rD as the correlation among marker effects after trimming markers with unusually large covariance contributions. rD is a trait-pair summary of how consistently small and moderate effect markers align across the genome; high rD is expected when many perturbations propagate through shared developmental, physiological, causal, or geometric structure. Applying this framework to high-dimensional yeast single-cell morphology, we show that trait pairs with similar rG can differ substantially in rD, and that a small number of candidate outlier regions can strongly influence some marker effect correlations. We then test whether rD predicts the environmental stability of genetic correlations under geldanamycin-mediated Hsp90 perturbation. Trait pairs with stronger rD show smaller absolute changes in rG. These results suggest that genetic correlations supported by a strong polygenic marker effect background are more environmentally stable than correlations shaped primarily by a few large covariance contributors.

Genetic Pleiotropy↗
PubMed2006

Genetics, development and evolution of adaptive pigmentation in vertebrates.

The study of pigmentation has played an important role in the intersection of evolution, genetics, and developmental biology. Pigmentation's utility as a visible phenotypic marker has resulted in over 100 years of intense study of coat color mutations in laboratory mice, thereby creating an impressive list of candidate genes and an understanding of the developmental mechanisms responsible for the phenotypic effects. Variation in color and pigment patterning has also served as the focus of many classic studies of naturally occurring phenotypic variation in a wide variety of vertebrates, providing some of the most compelling cases for parallel and convergent evolution. Thus, the pigmentation model system holds much promise for understanding the nature of adaptation by linking genetic changes to variation in fitness-related traits. Here, I first discuss the historical role of pigmentation in genetics, development and evolutionary biology. I then discuss recent empirically based studies in vertebrates, which rely on these historical foundations to make connections between genotype and phenotype for ecologically important pigmentation traits. These studies provide insight into the evolutionary process by uncovering the genetic basis of adaptive traits and addressing such long-standing questions in evolutionary biology as (1) are adaptive changes predominantly caused by mutations in regulatory regions or coding regions? (2) is adaptation driven by the fixation of dominant mutations? and (3) to what extent are parallel phenotypic changes caused by similar genetic changes? It is clear that coloration has much to teach us about the molecular basis of organismal diversity, adaptation and the evolutionary process.

Adaptation, Biological↗
PubMed2003

Genetic diversity as an objective in multi-objective evolutionary algorithms.

A key feature of an efficient and reliable multi-objective evolutionary algorithm is the ability to maintain genetic diversity within a population of solutions. In this paper, we present a new diversity-preserving mechanism, the Genetic Diversity Evaluation Method (GeDEM), which considers a distance-based measure of genetic diversity as a real objective in fitness assignment. This provides a dual selection pressure towards the exploitation of current non-dominated solutions and the exploration of the search space. We also introduce a new multi-objective evolutionary algorithm, the Genetic Diversity Evolutionary Algorithm (GDEA), strictly designed around GeDEM and then we compare it with other state-of-the-art algorithms on a well-established suite of test problems. Experimental results clearly indicate that the performance of GDEA is top-level.

Algorithms↗
PubMed1990

Fisher's contributions to genetics and heredity, with special emphasis on the Gregor Mendel controversy.

R. A. Fisher is widely respected for his contributions to both statistics and genetics. For instance, his 1930 text on The Genetical Theory of Natural Selection remains a watershed contribution in that area. Fisher's subsequent research led him to study the work of (Johann) Gregor Mendel, the 19th century monk who first developed the basic principles of heredity with experiments on garden peas. In examining Mendel's original 1865 article, Fisher noted that the conformity between Mendel's reported and proposed (theoretical) ratios of segregating individuals was unusually good, "too good" perhaps. The resulting controversy as to whether Mendel "cooked" his data for presentation has continued to the current day. This review highlights Fisher's most salient points as regards Mendel's "too good" fit, within the context of Fisher's extensive contributions to the development of genetical and evolutionary theory.

Animals↗