Biomedical subjects

Charles B Fenster

Publications and source records attributed to Charles B Fenster.

5 recordsLinked to original sources

PubMed2006

Pollination and seed predation by moths on Silene and allied Caryophyllaceae: evaluating a model system to study the evolution of mutualisms.

Nursery pollinators, and the plants they use as hosts for offspring development, function as exemplary models of coevolutionary mutualism. The two pre-eminent examples--fig wasps and yucca moths--show little variation in the interaction: the primary pollinator is an obligate mutualist. By contrast, nursery pollination of certain Caryophyllaceae, including Silene spp., by two nocturnal moth genera, Hadena and Perizoma, ranges from antagonistic to potentially mutualistic, offering an opportunity to test hypotheses about the factors that promote or discourage the evolution of mutualism. Here, we review nursery pollination and host-plant interactions in over 30 caryophyllaceous plants, based on published studies and a survey of researchers investigating pollination, seed predation, and moth morphology and behavior. We detected little direct evidence of mutualism in these moth-plant interactions, but found traits and patterns in both that are nonetheless consistent with the evolution of mutualism and merit further attention.

Animals↗

PubMed2006

Intraspecific hybridization and the recovery of fitness in the native legume Chamaecrista fasciculata.

Genetic incompatibilities and low offspring fitness are characteristic outcomes of hybridization between species. Yet, the creative potential of recombination following hybridization continues to be debated. Here we quantify the outcome of hybridization and recombination between adaptively divergent populations of the North American legume Chamaecrista fasciculata in a large-scale field experiment. Previously, hybrids between these populations demonstrated hybrid breakdown, suggesting the expression of adaptive epistatic interactions underlying population genetic differentiation. However, the outcome of hybridization ultimately rests on the performance of even later generation recombinants. In experiments that compared the performance of recombinant F6 and F2 generations with nonrecombinant F1 and parental genotypes, we observed that increasing recombination had contrasting effects on different life-history components. Lifetime fitness, defined as the product of survivorship and reproduction, showed a strong recovery of fitness in the F6. The overall gain in fitness with increased recombination suggests that hybridization and recombination may provide the necessary genetic variation for adaptive evolution within species. We discuss the mechanisms that may account for the gain in fitness with recombination, and explore the implications for hybrid speciation and phenotypic evolution.

Biological Evolution↗

PubMed2005

Genetic variability in natural populations of Arabidopsis thaliana in northern Europe.

Ten populations of the model plant Arabidopsis thaliana were collected along a north-south gradient in Norway and screened for microsatellite polymorphisms in 25 loci and variability in quantitative traits. Overall, the average levels of genetic diversity were found to be relatively high in these populations, compared to previously published surveys of within population variability. Six of the populations were polymorphic at microsatellite loci, resulting in an overall proportion of polymorphic loci of 18%, and a relatively high gene diversity for a selfing species (HE = 0.06). Of the overall variability, 12% was found within populations. Two of six polymorphic populations contained heterozygous individuals. Both FST and phylogenetic analyses showed no correlation between geographical and genetic distances. Haplotypic diversity patterns suggested postglacial colonization of Scandinavia from a number of different sources. Heritable variation was observed for many of the studied quantitative traits, with all populations showing variability in at least some traits, even populations with no microsatellite variability. There was a positive association between variability in quantitative traits and microsatellites within populations. Several quantitative traits exhibited QST values significantly less than FST, suggesting that selection may be acting to retard differentiation for these traits.

Arabidopsis↗

PubMed2004

Quantitative trait locus analyses and the study of evolutionary process.

The past decade has seen a proliferation of studies that employ quantitative trait locus (QTL) approaches to diagnose the genetic basis of trait evolution. Advances in molecular techniques and analytical methods have suggested that an exact genetic description of the number and distribution of genes affecting a trait can be obtained. Although this possibility has met with some success in model systems such as Drosophila and Arabidopsis, the pursuit of an exact description of QTL effects, i.e. individual gene effect, in most cases has proven problematic. We discuss why QTL methods will have difficulty in identifying individual genes contributing to trait variation, and distinguish between the identification of QTL (or marker intervals) and the identification of individual genes or nucleotide differences within genes (QTN). This review focuses on what ecologists and evolutionary biologists working with natural populations can realistically expect to learn from QTL studies. We highlight representative issues in ecology and evolutionary biology and discuss the range of questions that can be addressed satisfactorily using QTL approaches. We specifically address developing approaches to QTL analysis in outbred populations, and discuss practical considerations of experimental (cross) design and application of different marker types. Throughout this review we attempt to provide a balanced description of the benefits of QTL methodology to studies in ecology and evolution as well as the inherent assumptions and limitations that may constrain its application.

Adaptation, Biological↗

PubMed2003

Quantifying gene flow from spatial genetic structure data in a metapopulation of Chamaecrista fasciculata (Leguminosae).

An extensive allozyme survey was conducted within a natural "meta" population of the native North American annual legume, Chamaecrista fasciculata (Leguminosae) to quantify genetic structure at different spatial scales. Gene flow was then estimated by a recently developed indirect method based on a continuous population model, using pairwise kinship coefficients between individuals. The indirect estimates of gene flow, quantified in terms of neighborhood size, with an average value on the order of 150 individuals, were concordant among different spatial scales (subpopulation, population, metapopulation). This gene-flow value lies within the range of direct estimates previously documented from observations of pollen and seed dispersal for the same metapopulation. Monte Carlo simulations using the direct measures of gene flow as parameters further demonstrated that the observed spatial pattern of allozyme variation was congruent with a model of isolation by distance. Combining previously published estimates of pollen dispersal distances with kinship coefficients from this study, we quantified biparental inbreeding relative to either a single subpopulation or the whole metapopulation. At the level of a neighborhood, little biparental inbreeding was observed and most departure from Hardy-Weinberg genotypic proportions was explained by self-fertilization, whereas both selfing and biparental inbreeding contributed to nonrandom mating at the metapopulation level. Gene flow was also estimated from indirect methods based on a discontinuous population structure model. We discuss these results with respect to the effect of a patchy population structure on estimation of gene flow.

Chamaecrista↗