bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential gene exchange between parapatric morphs of Littorina saxatilis detected using AFLP markers
Authors: Wilding C. S. , Butlin R. K. , Grahame J. 
Published: March 2003

Abstract
Speciation requires the acquisition of reproductive isolation, and the circumstances under which this could evolve are of great interest. Are new species formed after the acquisition of generalized incompatibility arising between physically separated populations, or may they arise as a result of the action of disruptive selection beginning with the divergence of a rather restricted set of gene loci? Here we apply the technique of amplified fragment length polymorphism (AFLP) analysis to an intertidal snail whose populations display a cline in shell shape across vertical gradients on rocky shores. We compare the FST values for 306 AFLP loci with the distribution of FST estimated from a simulation model using values of mutation and migration derived from the data. We find that about 5% of these loci show greater differentiation than expected, providing evidence of the effects of selection across the cline, either direct or indirect through linkage. This is consistent with expectations from nonallopatric speciation models that propose an initial divergence of a small part of the genome driven by strong disruptive selection while divergence at other loci is prevented by gene flow. However, the pattern could also be the result of differential introgression after secondary contact.
Multiple infection dynamics has pronounced effects on the fitness of RNA viruses
Authors: Miralles R. , Ferrer R. , Solé R. V. , Moya A. , Elena S. F. 
Published: March 2003

Abstract
Several factors play a role during the replication and transmission of RNA viruses. First, as a consequence of their enormous mutation rate, complex mixtures of genomes are generated immediately after infection of a new host. Secondly, differences in growth and competition rates drive the selection of certain genetic variants within an infected host. Thirdly, but not less important, a random sampling occurs at the moment of viral infectious passage from an infected to a healthy host. In addition, the availability of hosts also influences the fate of a given viral genotype. When new hosts are scarce, different viral genotypes might infect the same host, adding an extra complexity to the competition among genetic variants. We have employed a two-fold approach to analyse the role played by each of these factors in the evolution of RNA viruses. First, we have derived a model that takes into account all the preceding factors. This model employs the classic Lotka-Volterra competition equations but it also incorporates the effect of mutation during RNA replication, the effect of the stochastic sampling at the moment of infectious passage among hosts and, the effect of the type of infection (single, coinfection or superinfection). Secondly, the predictions of the model have been tested in an in vitro evolution experiment. Both theoretical and experimental results show that in infection passages with coinfection viral fitness increased more than in single infections. In contrast, infection passages with superinfection did not differ from the single infection. The coinfection frequency also affected the outcome: the larger the proportion of viruses coinfecting a host, the larger increase in fitness observed.
Population divergence of developmental thermal optima in Swedish common frogs, Rana temporaria
Authors: Ståhlberg F. , Olsson M. , Uller T. 
Published: March 2003

Abstract
Growth rate, like any other trait, should be under balancing selection in natural populations, with selection adjusting mean growth rate in a population in relation to its site-specific costs and benefits. In the present study, we tested for differences in thermal growth optima between a northern and a southern region of Rana temporaria by rearing tadpoles in three different temperatures in the laboratory (10, 15 and 20 °C). Because of the rapid increase in post-melt temperature at high latitudes, spawn and tadpoles from the northern region experience significantly higher minimum, mean and maximum temperature throughout the period of pre-metamorph development. Frogs up north also enjoys a shorter breeding season and activity season overall. This suggests that growth and development should be maximized at a relatively higher temperature in the north as a result of directional selection. In accordance with this prediction we found that tadpoles from the northern region grew faster at relatively higher temperature than frogs in the south, whereas the opposite was true at relatively lower temperatures. North tadpoles also had a higher mortality and poorer physiological performance than south tadpoles at low temperatures. In summary, our results conclusively support the hypothesis that frogs in the north are adapted to relatively warmer developmental conditions than frogs in the south.
Origins of clonal diversity in the hypervariable asexual ostracode Cypridopsis vidua
Authors: Cywinska A. , Hebert P. D. N. 
Published: March 2003

Abstract
Prior allozyme studies have indicated that populations of the asexual ostracode, Cypridopsis vidua (Müller), show extraordinary clonal diversity. Based on a joint examination of allozyme variation and sequence divergence at the mitochondrial cytochrome c oxidase I (COI) gene, the present analysis provides new insights concerning the origins of this variation. The results establish that populations of C. vidua in one recently deglaciated region of North America are not only allozymically diverse, but also include several divergent mitochondrial DNA (mtDNA) lineages. The extent of sequence divergence among these lineages is so large as to suggest their diversification over the past 7–8 million years. The patterning of genetic divergence among co-occurring clones makes it apparent that much of the mtDNA and allozyme diversity in local populations owes its origins to recurrent colonization events. However, in situ mutational diversification also appears to explain some variation. The mechanisms enabling the sustained coexistence of such a large array of closely allied genotypes remain unclear, but there is an apparent difference in equilibrium diversity between benthic and planktonic asexual organisms.
A test of the Darwin–Fisher theory for the evolution of male secondary sexual traits in monogamous birds
Authors: Dearborn D. C. , Ryan M. J. 
Published: March 2003

Abstract
The Darwin–Fisher theory proposes that the presence of male secondary sexual traits in monogamous birds is selected for by early season breeding of females that are in good condition. These early breeding females have high fecundity because of their good condition, and they select mates based on secondary sex traits. We tested whether this hypothesis may be responsible for the presence of male sexual ornaments in the great frigatebird, a socially and genetically monogamous seabird. Consistent with the Darwin–Fisher theory, we found that reproductive success declined over the season. However, males with more exaggerated ornaments were not chosen as mates earlier in the season than males with less exaggerated ornaments, and selection gradients on these ornaments were not significantly different from zero.
Paternity analysis in Ophiopogon xylorrhizus Wang et Tai (Liliaceae s.l.): selfing assures reproductive success
Authors: He T. , Smouse P. E. 
Published: March 2003

Abstract
We assessed the utility of codominant allozyme markers for paternity analysis in natural populations of Ophiopogon xylorrhizus (Liliaceae s. l.) by means of likelihood-based approach. In the three independent natural stands of 46 individual plants with 354 seeds of O. xylorrhizus (Liliaceae s. l), we assigned 319 seeds to a single individual with the highest LOD score. Among these, 179 seeds had a significant D-value. An individual (acting either as female or male) mateds with an average of one other individual on average to reproduce, except when it self-pollinated. If an individual that neither donated pollen to other individuals nor selfed, being strictly a pollen acceptor, the number of offspring produced was half that produced by as many offspring as individuals which both provided and accepted pollen (4.1 vs. 9.5). Significant positive relationships were found in all the three stands between the number of self-pollen an individual produced and the number of seeds that individual set. Male outcrossing reproductive success was unevenly varied, both in amount and spatial location. The individuals located in the centre of the stand and the individuals closest to each other had higher male outcrossing reproductive success than those at the edge of the stand. Male selfing reproductive success showed a similar pattern, with an even distribution of female reproductive output. Most mating events were took place within 20 m. The distance between mates mirrored the active ranges of pollinators, and shaped the fine-scale population spatial genetic spatial structure. The results indicate that selfing assures reproductive success in O. xylorrhizus.
Developmental stability and genetic architecture: a comparison within and across thermal regimes in tadpoles
Authors: Olsson M. , Uller T. 
Published: March 2003

Abstract
We investigated homogeneity of growth and development as indices of developmental stability in sibling tadpoles from two sampling regions of the common frog, Rana temporaria. One region is characterized by relatively warm breeding ponds with a short activity season (`north'), and one by relatively cool breeding ponds and a long activity season (`south'). Tadpoles from the two regions were raised in three different temperatures selected to mimic the natural variation throughout the range. The results show that (1) north tadpoles respond with a relatively greater increase in growth with increased temperature than south tadpoles, (2) mean growth rate and its coefficient of variation were negatively correlated in the temperature regime in which a population was primarily under selection in the wild, whereas no such correlation was found at temperatures more seldom encountered in the natural populations, (3) phenotypic and genetic correlations between morphological traits within individuals were positive and were relatively higher in north than south tadpoles in the warm treatment, but higher for south tadpoles in the cold treatment and (4) across thermal environments, south tadpoles showed significant genetic correlations, whereas the correlations for north tadpoles were not significantly different from zero. South tadpoles showed only positive genetic correlations (n=30), whereas 14 of 30 correlation coefficients were negative in north tadpoles. In conclusion, developmental stability for growth and morphometry was higher at `optimal' conditions and decreased at the tail ends of the reaction norms within regions, with marked differences reflecting selection history between regions.
Physiological consequences of immune response by Drosophila melanogaster (Diptera: Drosophilidae) against the parasitoid Asobara tabida (Hymenoptera: Braconidae)
Authors: Hoang A. 
Published: March 2003

Abstract
Parasites can exert a wide range of negative effects on their hosts. Consequently, hosts that can resist infection should have a selective advantage over nonresistant conspecifics. Yet, host populations remain susceptible to some parasites. Could genetic heterogeneity in the host's ability to resist parasites reflect costs of mounting an immune response? Previous work on Drosophila melanogaster establishes that maintaining the ability to mount an immune response decreases larval competitive ability. Moreover, mounting an immune response decreases fitness.  I report on the impact of mounting an immune response on fitness of D. melanogaster survived parasitism by Asobara tabida. I used isofemale lines to determine whether genotype influences the costs of immune response. I examined fitness consequences both to larvae and adults. Survivors of parasitism show no measurable decrease in larval fitness (development time) but have decreased adult fitness (population growth rates), probably because of their smaller size.
A genotypic trade-off between the number and size of clonal offspring in the stoloniferous herb Potentilla reptans
Authors: Stuefer J. F. , Van Hulzen J.B. , During H. J. 
Published: March 2003

Abstract
A negative, genetic correlation between the total number and average size of progeny is a classical life-history trade-off that can greatly affect the fitness of organisms in their natural environments. This trade-off has been investigated for animals and for sexually reproducing plants. However, evidence for a genetical size-number trade-off for clonal progeny in plants is still scarce. This study provides experimental evidence for such a trade-off in the stoloniferous herb Potentilla reptans, and it studies phenotypic plasticity to light availability for the involved traits. Genotypes of P. reptans were collected from distinctively different environments, clonally replicated and exposed to high light and to shaded conditions. We found a significant negative correlation between the average size and the total number of offspring across genotypes for both light environments. Shading reduced ramet numbers, but hardly affected average ramet size.
Human longevity and early reproduction in pre-industrial Sami populations
Authors: Helle S. , Käär P. , Jokela J. 
Published: March 2003

Abstract
Senescence is predicted to be associated with the intensity and timing of reproduction at an earlier age. Here, we examine the phenotypic association between reproduction and post-reproductive survival in three pre-industrial human populations that lived in Northern Scandinavia during 1640–1870. In both sexes longevity was independent of the total number of born or adult children, whereas early reproduction was negatively associated with the longevity of females and males. Our results thus do not support the view that reproductive investment as such has a negative impact on longevity, but suggest that survival costs are associated with the scheduling of reproduction. We discuss, however, an alternative point of view suggesting that less intense selection for early reproduction, extended parental care, and social structure allowing kin selection through the effects of close relatives are factors that have selected for the long post-reproductive life span in humans.
Timing of the population dynamics of bullhead Cottus gobio (Teleostei: Cottidae) during the Pleistocene
Authors: Volckaert F. A. M. , Hänfling B. , Hellemans B. , Carvalho G. R. 
Published: March 2003

Abstract
Pleistocene genetic structure of the bullhead, Cottus gobio, was evaluated across the western Palearctic using a 771-bp long fragment of the mitochondrial control region in 123 individuals collected at 35 sites (data set I). In total, 59 haplotypes that differed at 73 positions (9.3%) were detected. Data analysis also included sequences from Englbrecht et al. (2000), thus increasing the sampling to a more comprehensive data set of 529 fish and 63 control region sequences of 482 bp (data set II). A minimum spanning and phylogenetic tree identified a seventh clade (Brittany–Loire) in addition to the previously identified six clades. The geographical range of the North Sea and Lower Rhine clades was considerably larger than thought previously. Haplotype diversity was generally low, and the total fixation index high (FST  = 0.49). Among-group differentiation accounted for 41.7% (data set I) of the variation. Contiguous range expansions and restricted gene flow combined with isolation by distance, interspersed with past fragmentation characterize bullhead across its range. New is the knowledge that dated interglacial periods correlated with population expansions; river captures, proglacial lake systems and sea level played a significant role in the dispersal and expansion either in northern or southern direction. Hence it became possible to identify and date the colonization routes and putative palaeorefugia, most of which were located in Central and North-west Europe. Glacial periods resulted in distinct fragmentation events and lineage sorting.
Tempo and mode in evolution: phylogenetic inertia, adaptation and comparative methods
Authors: Blomberg S. P. , Garland T. 
Published: March 2003

Abstract
Before the Evolutionary Synthesis, ‘phylogenetic inertia’ was associated with theories of orthogenesis, which claimed that organisms possessed an endogenous perfecting principle. The concept in the modern literature dates to Simpson (1944), who used ‘evolutionary inertia’ as a description of pattern in the fossil record. Wilson (1975) used ‘phylogenetic inertia’ to describe population-level or organismal properties that can affect the course of evolution in response to selection. Many current authors now view phylogenetic inertia as an alternative hypothesis to adaptation by natural selection when attempting to explain interspecific variation, covariation or lack thereof in phenotypic traits. Some phylogenetic comparative methods have been claimed to allow quantification and testing of phylogenetic inertia. Although some existing methods do allow valid tests of whether related species tend to resemble each other, which we term ‘phylogenetic signal’, this is simply pattern recognition and does not imply any underlying process. Moreover, comparative data sets generally do not include information that would allow rigorous inferences concerning causal processes underlying such patterns. The concept of phylogenetic inertia needs to be defined and studied with as much care as ‘adaptation’.
Proximate mechanisms of variation in the carotenoid-based plumage coloration of nestling great tits (Parus major L.)
Authors: Tschirren B. , Fitze P. S. , Richner H. 
Published: March 2003

Abstract
Many vertebrates use carotenoid-based signals in social or sexual interactions. Honest signalling via carotenoids implies some limitation of carotenoid-based colour expression among phenotypes in the wild, and at least five limiting proximate mechanisms have been hypothesized. Limitation may arise by carotenoid-availability, genetic constraints, body condition, parasites, or detrimental effects of carotenoids. An understanding of the relative importance of the five mechanisms is relevant in the context of natural and sexual selection acting on signal evolution. In an experimental field study with carotenoid supplementation, simultaneous cross-fostering, manipulation of brood size and ectoparasite load, we investigated the relative importance of these mechanisms for the variation in carotenoid-based coloration of nestling great tits (Parus major). Carotenoid-based plumage coloration was significantly related to genetic origin of nestlings, and was enhanced both in carotenoid-supplemented nestlings, and nestlings raised in reduced broods. We found a tendency for ectoparasite-induced limitation of colour expression and no evidence for detrimental effects of carotenoids on growth pattern, mortality and recruitment of nestlings to the local breeding population. Thus, three of the five proposed mechanisms can generate individual variation in the expression of carotenoid-based plumage coloration in the wild and thus could maintain honesty in a trait potentially used for signalling of individual quality.
Effectiveness of a protocol to improve transfusion practice in knee replacement surgery
Authors: Boralessa H. , Boralessa H. , Contreras M. , Lang‐Stevenson A. , DeSilva A. 
Published: March 2003

Background and ObjectivesThe available guidelines on red cell transfusion are not clearly defined and therefore have had only a modest impact on transfusion practice. The aims of this study were to assess the rate of compliance with a transfusion algorithm and its effect on transfusion practice.Materials and MethodsA prospective observational study was carried out on 101 patients who underwent primary elective total knee replacement surgery.ResultsOnly 30% of the patients were transfused. An overall compliance rate of 77% was achieved with the transfusion algorithm.ConclusionA transfusion algorithm, together with staff education, is effective in reducing both the number of patients transfused and inappropriate transfusions.
Resuscitation fluids
Authors: Grocott M. P. W. , Hamilton M. A. 
Published: March 2003

Background and Objectives The aim of this review was to summarize the properties of the commonly available resuscitation fluids and highlight where knowledge of the characteristics of individual fluids might guide their use in clinical practice. Some of the current controversies surrounding resuscitation fluids are also discussed. Blood or blood products, or strategies of fluid administration, are not focused upon.Conclusions The clinical trial data does not support the concept of a therapeutic advantage for either crystalloids or colloids, despite claimed theoretical advantages for both classes of fluid. The available colloid solutions have quite distinct profiles of activity, both in terms of their plasma volume expansion profile and other physiological and pharmacological properties. Recent data suggests that physiologically balanced crystalloid and colloid solutions may improve clinical outcomes when compared with saline‐based fluids.
Increased non‐transferrin bound iron in plasma‐depleted SAG‐M red blood cell units
Authors: Marwah S. S. , Blann A. , Harrison P. , Lumley M. A. , Wright J. , McDowell J. , Phillips J. D. , Rea C. , Bareford D. 
Published: March 2003

Background and Objectives Non‐transferrin bound iron (NTBI) is associated with increased morbidity in a number of transfusion‐dependent disease states such as the severe haemoglobinopathies. We hypothesized that this may be related to excess NTBI present in plasma‐depleted red blood cell units that are free of clear haemolysis.Materials and Methods The level of NTBI was determined using the bleomycin assay in samples from 20 stored plasma‐depleted red cell units, at approximate 5‐day intervals up to day 33 after donation. Forty units of fresh‐frozen plasma (FFP) and 40 units of platelet concentrates were used as negative controls, and samples from 12 units of FFP were also serially assessed.Results Median [interquartile range (IQR)] NTBI was 0 µm (0–0·35) in samples taken from units 3–10 days after donation. Thereafter, the levels of NTBI increased, becoming significant (median 3·05; IQR: 0·05–6·7 µm) 17–22 days after donation. After 30 days, NTBI was detectable in all red cell units. NTBI was undetectable in platelet concentrates and FFP.Conclusions Increased levels of NTBI become detectable 17–22 days after donation and increase further with storage time. This excess NTBI may promote bacterial infection in iron‐loaded individuals.
A novel true volumetric method for the determination of residual leucocytes in blood components
Authors: Cassens U. , Greve B. , Tapernon K. , Nave B. , Severin E. , Sibrowski W. , Göhde W. 
Published: March 2003

Background and Objectives Accurate determination of residual leucocytes [white blood cells (WBC)] in blood components is of high clinical importance. To date, several labour‐intensive, time‐consuming or expensive techniques have been used for this purpose.Materials and Methods A method for the determination of residual WBC is described using a novel low‐cost flow‐cytometric cell counter and analyser (CCA). The DNA in WBC was stained using 4′‐6‐diamidino‐2‐phenylindole (DAPI) and WBC were automatically analysed by true volumetric counting of 200‐µl samples (prepared from a 20‐µl undiluted sample).Results Dilution experiments over a range of 0·5–50 WBC/µl showed a linearity of r= 0·998. The detection limit of this method was 0·83 WBC/µl of red blood cell concentrate (RCC) and 0·67 WBC/µl of platelet concentrate (PC), with an accuracy of 95·5%.Conclusion Residual WBC (< 1 WBC/µl) can be accurately counted using the CCA within 2 min and at a total cost of less than € 1 per sample.