bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of floral display in Eichhornia paniculata (Pontederiaceae): genetic correlations between flower size and number
Authors: Worley A. C. , Barrett S. C. H. 
Published: March 2003

Abstract
The evolution of floral display is thought to be constrained by trade-offs between the size and number of flowers and inflorescences. We grew in the glasshouse 60 maternal families from each of two Brazilian populations of the annual herb, Eichhornia paniculata. We measured flower size, daily flower number, and total flower number per inflorescence, and two indices of module size, leaf area and age at flowering. We also assessed the size and number of inflorescences produced over 6 weeks. All floral traits exhibited significant heritable variation, some of which was due to genetic variation in module size. Genetic (maternal family) correlations between daily and total flower number did not differ from 1.0, indicating that display size (daily flower number) cannot evolve independently from total flower number per inflorescence. Genetic correlations between flower size and daily flower number ranged from negative to positive (r=–0.78 to +0.84), depending on population and inflorescence. Positive correlations occurred when variation in investment per inflorescence was high so that some families produced both larger and more flowers. These correlations became zero when we controlled for variation in module size. Families that flowered later produced fewer, larger inflorescences (r=–0.33, –0.85). These data support theoretical predictions regarding the combined effects of variation in resource acquisition and allocation on traits involved in trade-offs, and they emphasize the hierarchical organization of floral displays. Our results imply that patterns of resource allocation among inflorescences influence evolutionary changes in flower size and number per inflorescence.
Insularity and adaptation in coupled victim–enemy associations
Authors: Hochberg M. E. , Møller A. P. 
Published: March 2003

Abstract
Employing a mathematical model we show how insularity, genotypic interactions and victim life-history/demography can influence adaptation in a simple enemy–victim interaction where genotypes migrate between a large source and a smaller, initially unoccupied, isolated habitat. We find that when there are explicit costs to heightened enemy virulence and victim resistance, large/close islands resemble their immigration sources, whereas small and/or distant islands tend to be occupied only by the least defended victims and least virulent enemies. In a model with no explicit cost to genotypic identity, frequencies do not differ on average between source and island. Despite these trends in genotype frequencies, for a range of realistic conditions, both cost and cost-free genotypic interactions yield an increase in the frequency of resistant encounters as a function of isolation. Moreover, in models with explicit costs, maximal island to island variation in genotypic frequencies is found on islands of intermediate distance from the source. In contrast, the model without explicit costs produces more variable communities, attaining maximum variability in genotypic frequencies at the most isolated islands. We hypothesize that adaptive patterns in mainland–island comparisons may differ substantially from those generated by centre-periphery comparisons in continental systems.
The evolutionary significance of parasitism: do parasite-driven genetic dynamics occur ex silico?
Authors: Little T. J. 
Published: March 2003

Abstract
It has long been recognized that reciprocal antagonism might lock host and parasite populations into a process of constant change, adapting and reacting in open-ended coevolution. A significant body of theory supports this intuition: dynamic genetic polymorphisms are a common outcome of computer simulations of host–parasite coevolution. These in silico experiments have also shown that dynamical interactions could be responsible for high levels of genetic diversity in host populations, and even be the principle determinant of rates of genetic recombination and sexuality. The evolutionary significance of parasitism depends on the strength and prevalence of parasite-mediated selection in nature. Here I appraise whether parasitism is a pervasive agent of evolutionary change by detailing empirical evidence for selection. Although there is considerable evidence of genetic variation for resistance, and hence the potential for selection, direct observation of parasite-driven genetic change is lacking.
Evolutionary aspects of the metapopulation dynamics of Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni
Authors: Charbonnel N. , Angers B. , Rasatavonjizay R. , Bremond P. , Jarne P. 
Published: March 2003

Abstract
Combining genetic and demographic data is a powerful approach to study adaptation process and evolutionary forces acting in natural populations. We focus on the freshwater snail Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni. Twenty-one populations sampled in the south of Madagascar were genotyped at six microsatellite loci. Demographic parameters and parasitic prevalence were estimated monthly over the year preceding the genetic sampling. Our results indicate that populations experience recurrent bottlenecks and size fluctuations, which strongly depresses the genetic diversity within population. The recolonization of depleted sites involves genetically differentiated immigrants. We detected frequent migration events along rivers and rare migration events between watersheds. This explains the high level of differentiation observed among populations. The negative regression observed between the prevalence of S. mansoni and the genetic diversity of B. pfeifferi populations indicates that host consanguinity may affect prevalence through the genetic mechanisms involved in resistance. Coevolutionary outcomes are also influenced by the relative migration rates of snails and flukes, but the parasite local adaptation may be prevented by rare long distance dispersal in snails and the phylogeographical patterns of colonization of both hosts and snails.
Local adaptation, evolutionary potential and host–parasite coevolution: interactions between migration, mutation, population size and generation time
Authors: Gandon S. , Michalakis Y. 
Published: March 2003

Abstract
Local adaptation of parasites to their sympatric hosts has been investigated on different biological systems through reciprocal transplant experiments. Most of these studies revealed a local adaptation of the parasite. In several cases, however, parasites were found to be locally maladapted or neither adapted nor maladapted. In the present paper, we try to determine the causes of such variability in these results. We analyse a host–parasite metapopulation model and study the effect of several factors on the emergence of local adaptation: population sizes, mutation rates and migration rates for both the host and the parasite, and parasite generation time. We show that all these factors may act on local adaptation through their effects on the evolutionary potential of each species. In particular, we find that higher numbers of mutants or migrants do, in general, promote local adaptation. Interestingly, shorter parasite generation time does not always favour parasite local adaptation. When genetic variability is limiting, shorter generation time, via an increase of the strength of selection, decreases the capacity of the parasite to adapt to an evolving host.
Reverse evolution of fitness in Drosophila melanogaster
Authors: Teotónio H. , Matos M. , Rose M. R. 
Published: March 2003

Abstract
The evolution of fitness is central to evolutionary theory, yet few experimental systems allow us to track its evolution in genetically and environmentally relevant contexts. Reverse evolution experiments allow the study of the evolutionary return to ancestral phenotypic states, including fitness. This in turn permits well-defined tests for the dependence of adaptation on evolutionary history and environmental conditions. In the experiments described here, 20 populations of heterogeneous evolutionary histories were returned to their common ancestral environment for 50 generations, and were then compared with both their immediate differentiated ancestors and populations which had remained in the ancestral environment. One measure of fitness returned to ancestral levels to a greater extent than other characters did. The phenotypic effects of reverse evolution were also contingent on previous selective history. Moreover, convergence to the ancestral state was highly sensitive to environmental conditions. The phenotypic plasticity of fecundity, a character directly selected for, evolved during the experimental time frame. Reverse evolution appears to force multiple, diverged populations to converge on a common fitness state through different life-history and genetic changes.
Longevity and resistance to cold stress in cold-stress selected lines and their controls in Drosophila melanogaster
Authors: Norry F. M. , Loeschcke V. R. 
Published: March 2003

Abstract
Thermal environments can influence many fitness-related traits including life span. Here, we assess whether longevity in Drosophila melanogaster can experimentally evolve as a correlated response to cold-stress selection, and whether genotype-by-temperature and sex-by-temperature interactions are significant components of variation in life span. Three replicated S lines were cold-stress selected and compared with their respective unselected controls (Clines) in the 16th generation of thermal selection. Cold-stress resistance exhibited a substantial direct response to selection, and also showed a significant interaction between sex and type of line. Mean longevity exhibited a significant interaction between adult test temperature (14 and 25 °C) and line (with suggestive evidence for increased longevity of S lines when tested at 14 °C), but there was no evidence for increased longevity in S lines at normal temperatures (i.e. 25 °C). Another temperature-dependent effect was sex-specific, with males being the longer lived sex at 25 °C but the less long-lived sex at 14 °C. Additionally, we tested in an exploratory way the relationship between longevity and cold-stress resistance by also measuring resistance to a prefreezing temperature before and after one generation of longevity selection at 14 °C (selection intensity, i = 1.47 for S lines, and 1.42 for C lines). In this longevity selection, we found that cold-stress resistance increased by about 6% in S lines and 18% in C lines. However, taken together, the results indicate no simple relationship between longevity and cold-stress resistance, with genotype-by-sex interactions in both traits. Temperature dependent interaction in longevity is apparent between S and C lines, and sex-specific variation in mean longevity also depends on temperature.
Confidence of paternity and paternal care: covariation revealed through the experimental manipulation of the mating system in the beetle Onthophagus taurus
Authors: Hunt J. , Simmons L. W. 
Published: March 2003

Abstract
Theoretical models of paternal care predict that facultative reductions in male care may occur under certain conditions. One important parameter that has been shown to influence the outcome of these models is a male's confidence of paternity. In this study, we tested whether the amount of care provided by horned males in the dimorphic beetle, Onthophagus taurus, varied with his confidence of paternity. Male care results in an increased weight of dung provided in the brood masses produced by the pair. Using the sterile male technique we showed that a horned male's paternity declined with the number of sneak males in the population. The relationship was nonlinear, with paternity declining most rapidly between a frequency of one and three sneaks, and stabilizing thereafter at about 50%. A horned male's paternity was directly related to the number of copulations with the female, relative to the number of copulations achieved by sneaks. Horned males were shown to reduce their care in relation to their declining paternity. Video analysis demonstrated that reductions in male care occurred through a combination of male desertion and a trade-off between caring and paternity assurance behaviours. The number of fights with sneak males was negatively related to the amount of care provided by a horned male. These results suggest that by gauging his expected paternity through the number of fights with sneaks, a horned male is able to assess his paternity and reduce his investment accordingly. Our data thus provide strong empirical support for the proposed link between paternity and paternal care.
Contrasting effects of Wolbachia on cytoplasmic incompatibility and fecundity in the haplodiploid mite Tetranychus urticae
Authors: Perrot-Minnot M.-J. , Cheval B. , Migeon A. , Navajas M. 
Published: March 2003

Abstract
Recent studies on Wolbachia-induced incompatibility in haplodiploid insects and mites have revealed a diversity of cytoplasmic incompatibility (CI) patterns among host species. Here, we report intraspecific diversity in CI expression among four strains of the arrhenotokous mite Tetranychus urticae and in T. turkestani. Variability of CI expression within T. urticae ranged from no CI to complete CI, and included either female embryonic mortality or male conversion types of CI. A fecundity cost attributed to the infection with the high-CI Wolbachia strain was the highest ever recorded for Wolbachia (−80 to −100% decrease). Sequence polymorphism at a 550-bp-portion of Wolbachia wsp gene revealed two clusters distant by 21%, one of which included three Wolbachia strains infecting mite populations sampled from the same host-plant species, but showing distinct CI patterns. These data are discussed in the light of theoretical predictions on the evolutionary pathways followed in this symbiotic interaction.
The origin of a ‘true’ worker caste in termites: phylogenetic evidence is not decisive
Authors: Grandcolas P. , D'Haese C. 
Published: March 2003

Abstract
The phylogenetic study of the origin of a ‘true’ worker caste in termites by Thompson et al. [J. Evol. Biol. 13 (2000) 869] did not take into account all possibilities of character coding and character optimization on the phylogenetic tree. Actually, contrary to the authors' statements, the phylogenetic evidence presented does not permit to answer decisively most of the questions asked concerning the origin and evolution of worker castes in termites. Particular attention was paid to assumptions implied by the coding of the characters of interest, namely concerning the homology between pseudergates and a ‘true’ worker caste and the kind of the cockroach life type.
Evolution of the capacity to evolve
Authors: Carroll R. L. 
Published: March 2003

Abstract
During the past two decades, the fields of molecular biology and genetics have enabled study of far broader and more detailed aspects of evolutionary change than were possible when the evolutionary synthesis was elaborated in the mid-twentieth century. The capacity for complete sequencing of both genes and proteins of all groups of organisms provide, simultaneously, the means to determine both the patterns and processes of evolution throughout the history of life. Increased knowledge of the genome documents the changing nature of its composition, mode of transmission, and the nature of the units of selection. Advances in evolutionary developmental biology demonstrate the conservation of genetic elements throughout multicellular organisms, and explain how control of the timing, position and nature of their expression has produced the extraordinary diversity of living plants and animals. The next generation of evolutionary biologists will benefit greatly from the increased integration of these new fields of research with those that are currently emphasized in the standard textbooks and journals.
Detecting genetic variation in developmental instability by artificial selection on fluctuating asymmetry
Authors: Fuller R. C. , Houle D. 
Published: March 2003

Abstract
Fluctuating asymmetry (FA) is frequently used as a measure of developmental instability (DI). Assuming a genetic basis to DI, many have argued that FA may be a good indicator of genetic quality to potential mates and to human managers of populations. Unfortunately FA is a poor indicator of DI, making it very difficult to verify this assertion. A recent review of the literature suggests that previous studies of the inheritance of FA and DI using half-sib covariances and parent–offspring regression have been unable to put meaningful limits on the heritability of FA and DI because of the extremely low power of the experiments performed. In this study, we consider the power of artificial selection on FA as an alternative approach to studying the inheritance of FA and DI. Using simulations, we investigate the efficacy of selection for both increased and decreased FA for detecting genetic variation. We find that selection for increased FA has much more power to detect the presence of genetic variation than does selection for decreased FA. These results hold when realistic sample sizes are employed. Artificial selection for increased FA is currently the most powerful approach for the detection of genetic variation in DI.
Spatially structured genetic variation in a broadcast spawning bivalve: quantitative vs. molecular traits
Authors: Luttikhuizen P. C. , Drent J. , Van Delden W. , Piersma T. 
Published: March 2003

Abstract
Understanding the origin, maintenance and significance of phenotypic variation is one of the central issues in evolutionary biology. An ongoing discussion focuses on the relative roles of isolation and selection as being at the heart of genetically based spatial variation. We address this issue in a representative of a taxon group in which isolation is unlikely: a marine broadcast spawning invertebrate. During the free-swimming larval phase, dispersal is potentially very large. For such taxa, small-scale population genetic structuring in neutral molecular markers tends to be limited, conform expectations. Small-scale differentiation of selective traits is expected to be hindered by the putatively high gene flow. We determined the geographical distribution of molecular markers and of variation in a shell shape measure, globosity, for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea and adjacent North Sea in three subsequent years, and found that shells of this clam are more globose in the Wadden Sea. By rearing clams in a common garden in the laboratory starting from the gamete phase, we show that the ecotypes are genetically different; heritability is estimated at 23%. The proportion of total genetic variation that is between sites is much larger for the morphological additive genetic variation (QST = 0.416) than for allozyme (FST = 0.000–0.022) and mitochondrial DNA cytochrome-c-oxidase-1 sequence variation (ΦST = 0.017). Divergent selection must be involved and intraspecific spatial genetic differentiation in marine broadcast spawners is apparently not constrained by low levels of isolation.
Cerebral and peripheral near‐infrared spectroscopy: an alternative transfusion trigger?
Authors: Torella F. , Haynes S. L. , McCollum C. N. 
Published: March 2003

Background and Objectives To develop a transfusion trigger based on tissue oxygenation, near‐infrared spectroscopy (NIRS) was evaluated in a model of compensated haemorrhage.Patients and Methods Regional haemoglobin oxygen saturation from the cerebral cortex (CsO2) and the gastrocnemius muscle (PsO2) was monitored (using an INVOS 4100 near‐infrared oximeter) in 30 patients during acute normovolaemic haemodilution to a target haemoglobin of 11 g/dl. Arterial oxygen saturation, end‐tidal carbon dioxide tension, mean arterial pressure and haemoglobin concentration were also measured.Results During blood collection, CsO2 and PsO2 fell by a mean (95% CI) of 8 (5·3–10·7)% (P < 0·001) and 5·5 (3·2–7·8)% (P < 0·001), respectively. Arterial pressure and oxygen saturation did not change, whilst the end‐tidal carbon dioxide tension fell by 2·3 (0·8–3·8) mmHg (P = 0·004). Haemoglobin concentration correlated with CsO2 (R = 0·76, P < 0·001) and PsO2 (R = 0·63, P < 0·001), as did the volume of blood removed.Conclusions CsO2 and PsO2 fell predictably during compensated blood loss. With further research, NIRS may be developed into a transfusion trigger.
Validation of flow cytometry to quantify the potency of anti‐D immunoglobulin preparations
Authors: Schäffner G. , Kayser T. , Tönjes A. , Volkers P. 
Published: March 2003

Background and Objectives Flow cytometry has been recommended as an alternative to that of autoanalyser methodology for estimation of anti‐D potency. This investigation was performed to validate the flow cytometry method based on a quality assurance system.Materials and Methods A flow cytometry method based on indirect labelling of Rh(D)‐positive red blood cells was validated using the parameters precision and accuracy and was compared to the autoanalyser data of manufacturers of anti‐D immunoglobulin preparations.Results The experiment first investigated the possible differences between assays from single donors compared with a pooled assay. Red blood cells of four individual donors and their pooled red blood cells were interchangeable. There was no significant difference between donors, on one hand, and between the use of a single donation and the pooled red blood cells, on the other hand (P = 0·695). The two‐sided 95% confidence intervals (CIs) of the difference between single donors and the pool ranged from −4·6% to 4·7%. The intermediate variability was determined by standard deviation (SD) = 48·4 IU/ml [coefficient of variation (CV) = 3·8%]; the repeatability was SD = 34·3 IU/ml (CV = 2·7%). Using a spiking experiment, the second part of the experiment investigated recovery of a known anti‐D potency. The recovery of samples spiked with defined amounts of reference preparation was 97·7–101%, with a mean bias of −1·3 (95% CI: −4·1 to 1·6). The results of the flow cytometry assay, as compared to those of the autoanalyser performed by the manufacturers of anti‐D immunoglobulin preparations for those manufacturers who have their method validated in‐house, ranged from 87 to 129%, indicating good correlation.Conclusions Flow cytometry is a suitable quality control method for polyclonal anti‐D immunoglobulins, which can be standardized in a quality control laboratory using a quality assurance system.