bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amount of introgression in flycatcher hybrid zones reflects regional differences in pre and post‐zygotic barriers to gene exchange
Authors: BORGE T. , LINDROOS K. , NÁDVORNÍK P. , SYVÄNEN A. ‐C. , SæTRE G. ‐P. 
Published: August 2005

AbstractIntrogression is the incorporation of alleles from one species or semispecies into the gene pool of another through hybridization and backcrossing. The rate at which this occurs depends on the frequency of hybridization and the fitness of hybrids and backcrosses compared to ‘pure’ individuals. The collared flycatcher (Ficedula albicollis) and the pied flycatcher (F. hypoleuca) co‐exist and hybridize at low to moderate frequencies in a clinal hybrid zone in Central Europe and on the islands of Gotland and Öland off the Swedish east coast. Data on hatching success suggest that hybrids are less fertile in Central Europe compared to on the islands. Direct fitness estimates using molecular markers to infer paternity are consistent with the demographic data. Applying a tag‐array‐based minisequencing assay to genotype interspecific substitutions and single nucleotide polymorphisms we demonstrate that the amount of introgression from the pied to the collared flycatcher is higher in the two island populations (Gotland and Öland) than in two geographically distinct areas from the Central European hybrid zone (Czech Republic and Hungary). In all areas the amount of introgression from collared to pied flycatchers is very low or seemingly absent. The different patterns of introgression are consistent with regional differences in rates of hybridization and fitness of hybrids. We suggest that barriers to gene exchange may have been partly broken down on the islands due to asymmetric gene flow from allopatry. Alternatively, or in addition, more pronounced reinforcement of prezygotic isolation in Central Europe might have increased post‐zygotic isolation through hitchhiking, since genes affecting pre and post‐zygotic isolation are both sex‐linked in these birds. One of our genetic markers appears to introgress from pied to collared flycatchers at a much higher rate than the other markers. We discuss the possibility that the introgressed marker may be linked to a gene which is under positive selection in the novel genetic background.
Inbreeding depression and heterosis in populations of Schiedea viscosa, a highly selfing species
Authors: WELLER S. G. , SAKAI A. K. , THAI D. A. , TOM J. , RANKIN A. E. 
Published: August 2005

AbstractProgeny from self‐pollinations and intrapopulation crosses were examined in Schiedea viscosa to determine the extent of inbreeding depression in this highly selfing species. Progeny of interpopulation crosses were also investigated to determine whether deleterious alleles have been fixed in populations of S. viscosa. There was no inbreeding depression at early life history stages, including seeds per capsule, seed mass, or germination. Inbreeding depression was detected for the later life history stage of fruit biomass, although not for survival or life span. Heterosis for vegetative biomass and fruit biomass was detected in progeny from crosses between populations. Levels of inbreeding depression in S. viscosa are low relative to out‐crossing species of Schiedea, especially when early life history stages are compared.
Evolution of late-life fecundity in Drosophila melanogaster
Authors: Rauser C. L. , Tierney J. J. , Gunion S. M. , Covarrubias G. M. , Mueller L. D. , Rose M. R. 
Published: August 2005

Abstract
Late-life fecundity has been shown to plateau at late ages in Drosophila analogously to late-life mortality rates. In this study, we test an evolutionary theory of late life based on the declining force of natural selection that can explain the occurrence of these late-life plateaus in Drosophila. We also examine the viability of eggs laid by late-age females and test a population genetic mechanism that may be involved in the evolution of late-life fecundity: antagonistic pleiotropy. Together these experiments demonstrate that (i) fecundity plateaus at late ages, (ii) plateaus evolve according to the age at which the force of natural selection acting on fecundity reaches zero, (iii) eggs laid by females in late life are viable and (iv) antagonistic pleiotropy is involved in the evolution of late-life fecundity. This study further supports the evolutionary theory of late life based on the age-specific force of natural selection.
Why does a grasshopper have fewer, larger offspring at its range limits?
Authors: Hassall M. , Walters R. J. , Telfer M. , Hassall M. R. J. 
Published: August 2005

AbstractAnalysis of size of offspring reared through three laboratory generations from populations of the field grasshopper Chorthippus brunneus from 27 sites around the British Isles showed that offspring were larger towards the cooler-wetter conditions in the western and northern limits of the range. This variation had a significant genetic component. There was a trade-off between clutch size and offspring size between and within populations. Under favourable thermal and feeding conditions maternal fitness was optimal when individuals produced the largest clutches of the smallest eggs, but under poor conditions maternal fitness was optimal when individuals produced small clutches of very large offspring. Calculation of geometric mean fitness over time indicated that having larger offspring near to the edge of the range could be advantageous as a conservative risk-spreading strategy. As well as geographic variation in egg size, significant environment–genotype interactions in egg size in relation to temperature were observed.
Patterns of diversification of Afrotropical Otiteselline fig waSPS: phylogenetic study reveals a double radiation across host figs and conservatism of host association
Authors: Jousselin E. , Van Noort S. , Rasplus J.-Y. , Greeff J. M. 
Published: August 2005

Abstract
We studied the phylogenetic relationships of Otiteselline fig waSPS associated with Ficus in the Afrotropical region using rDNA sequences. African fig species usually host two species of Otiteselline fig waSPS. Phylogenetic analyses reveal that this pattern of association results from the radiation of two clades of waSPS superimposed on the fig system. Within each clade, wasp species generally cluster according to their host classification. The phylogenies of the two clades are also generally more congruent than expected by chance. Together these results suggest that Otiteselline wasp speciation is largely constrained by the diversification of their hosts. Finally, we show a difference in ovipositor length between the two Otiteselline species coexisting in the same Ficus species, which probably corresponds to ecological differences. The diversification of ecological niches within the fig is probably, with cospeciation, one of the key factors explaining the diversification and maintenance of species of parasites of the fig/pollinator system.
Rapid temporal change in the expression and age-related information content of a sexually selected trait
Authors: Hegyi G. , TÖRÖK J. , Tóth L. , Garamszegi L. Z. , Rosivall B. 
Published: August 2005

Abstract
The expression of sexual signals is often phenotypically plastic and also evolves rapidly. Few studies have considered the possibility that proximate determination – the pathway between genes and trait expression – may also be subject to both phenotypic plasticity and evolutionary change. We examined long-term patterns in size, condition- and age-dependence, repeatability and heritability of forehead patch size, a sexually selected plumage trait in male collared flycatchers. We also estimated survival and sexual selection on the phenotypic value of the trait. Forehead patch size linearly declined during the 15 years, probably due to the significantly negative survival selection. In addition, the expression of genetic variation for the ornament apparently underwent an age-limited change, which implies a change in the information content of the signal to receivers. The persistent lack of condition-dependence makes phenotypic plasticity an unlikely explanation to our results. This raises the possibility of a microevolutionary change of both expression and proximate determination during the study period.
Can maternally transmitted endosymbionts facilitate the evolution of haplodiploidy?
Authors: Engelstädter J. , Hurst G. D. D. 
Published: August 2005

Abstract
Whilst many invertebrate taxa are haplodiploid, the factors underlying the evolution of haplodiploidy remain unresolved. We investigate theoretically whether haplodiploidy might evolve as an outcome of the co-evolution between maternally inherited endosymbionts and their hosts. First, we substantially extend a recently developed model that involves maternally inherited endosymbionts that kill male offspring by eliminating the paternal genome. We also put forward a new hypothesis and develop a model that involves bacteria that induce cytoplasmic incompatibility (CI). Based on these models, we explore the co-evolutionary events that might occur between hosts and symbionts. We find that both with male-killers and CI-inducing endosymbionts, the hosts are likely to develop increased viability of haploid males, which can be considered a preadaptation to haplodiploidy. In addition, populations with haploidizing male-killers can in some cases evolve directly towards a genetic system of paternal genome elimination, a special form of haplodiploidy. These results are combined with consideration of mechanism and ecology to appraise the likelihood of male-killers and CI inducing bacteria being involved in the evolution of haplodiploidy.
No evidence for the ‘Meselson effect’ in parthenogenetic oribatid mites (Oribatida, Acari)
Authors: Schaefer I. , Domes K. , Heethoff M. , Schneider K. , Schön I. , Norton R. A. , Scheu S. , Maraun M. 
Published: August 2005

Abstract
It has been hypothesized that in ancient apomictic, nonrecombining lineages the two alleles of a single copy gene will become highly divergent as a result of the independent accumulation of mutations (Meselson effect). We used a partial sequence of the elongation factor-1α (ef-1α) and the heat shock protein 82 (hsp82) genes to test this hypothesis for putative ancient parthenogenetic oribatid mite lineages. In addition, we tested if the hsp82 gene is fully transcribed by sequencing the cDNA and we also tested if there is evidence for recombination and gene conversion in sexual and parthenogenetic oribatid mite species. The average maximum intra-specific divergence in the ef-1α was 2.7% in three parthenogenetic species and 8.6% in three sexual species; the average maximum intra-individual genetic divergence was 0.9% in the parthenogenetic and 6.0% in the sexual species. In the hsp82 gene the average maximum intra-individual genetic divergence in the sexual species Steganacarus magnus and in the parthenogenetic species Platynothrus peltifer was 1.1% and 1.2%, respectively. None of the differences were statistically significant. The cDNA data indicated that the hsp82 sequence is transcribed and intron-free. Likelihood permutation tests indicate that ef-1α has undergone recombination in all three studied sexual species and gene conversion in two of the sexual species, but neither process has occurred in any of the parthenogenetic species. No evidence for recombination or gene conversion was found for sexual or parthenogenetic oribatid mite species in the hsp 82 gene. There appears to be no Meselson effect in parthenogenetic oribatid mite species. Presumably, their low genetic divergence is due to automixis, other homogenizing mechanisms or strong selection to keep both the ef-1α and the hsp82 gene functioning.
The influence of environmental factors, the pollen : ovule ratio and seed bank persistence on molecular evolutionary rates in plants
Authors: Whittle C.-A. 
Published: August 2005

Abstract
One of the main goals of molecular evolutionary biology is to determine the factors that influence the evolutionary rate of selectively neutral DNA, but much remains unknown, especially for plants. Key factors that could alter the mutation rate include environmental tolerances (because they reflect a plants vulnerability to changes in habitat), the pollen : ovule ratio (as it is associated with the number of mitotic divisions) and seed longevity (because this influences the number of generations per unit time in plants). This is the first study to demonstrate that seed bank persistence and drought tolerance are positively associated with molecular evolutionary rates in plants and that pollen : ovule ratio, shade tolerance and salinity tolerance have no detectable relationship. The implications of the findings to our understanding of the impact of environmental agents, the number of cell divisions and cell aging on neutral DNA sequence evolution are discussed.
Fitness consequences of variable maternal provisioning in quacking frogs (Crinia georgiana)
Authors: Dziminski M. A. , Roberts J. D. 
Published: August 2005

Abstract
Variable maternal provisioning may evolve when there is variation in the quality of offspring environments. The frog Crinia georgiana has high variability in egg size both within and between clutches, independent of female phenotype. It breeds in ponds with high spatial and temporal variation in habitat quality. Egg size strongly affected offspring fitness in good and poor quality offspring environments, whether the egg size difference was from between or within clutches. Since there is a trade-off in egg size and number, these fitness consequences translate to strong effects on maternal fitness. In the variable and unpredictable offspring environment of C. georgiana, the maintenance of variable maternal provisioning both within and between clutches is likely to be an evolved response to the offspring environment.
Does genetic diversity hinder parasite evolution in social insect colonies?
Authors: Hughes W. O. H. , Boomsma J. J. 
Published: August 2005

Abstract
Polyandry is often difficult to explain because benefits of the behaviour have proved elusive. In social insects, polyandry increases the genetic diversity of workers within a colony and this has been suggested to improve the resistance of the colony to disease. Here we examine the possible impact of host genetic diversity on parasite evolution by carrying out serial passages of a virulent fungal pathogen through leaf-cutting ant workers of known genotypes. Parasite virulence increased over the nine-generation span of the experiment while spore production decreased. The effect of host relatedness upon virulence appeared limited. However, parasites cycled through more genetically diverse hosts were more likely to go extinct during the experiment and parasites cycled through more genetically similar hosts had greater spore production. These results indicate that host genetic diversity may indeed hinder the ability of parasites to adapt while cycling within social insect colonies.
Temporal dynamics of genotypic diversity reveal strong clonal selection in the aphid Myzus persicae
Authors: Vorburger C. 
Published: August 2005

Abstract
Parthenogenetic organisms often harbour substantial genotypic diversity. This diversity may be the result of recurrent formations of new clones, or it may be maintained by environmental heterogeneity acting on ecological differences among clones. In aphids, both processes may be important because obligate and cyclical parthenogens can form mixed populations. Using microsatellites, I analysed the temporal dynamics of clonal diversity in such a population of the aphid Myzus persicae over a 1-year period. The frequency distribution of clonal genotypes was very skewed, with many rare and few common clones. The relative frequencies of common clones underwent strong and rapid changes indicative of intense clonal selection. Differences in their host associations suggest that these shifts may partly be caused by changes in the abundance of annual host plants. Other selective factors of potential importance are also discussed. New, sexually produced genotypes made a minor contribution to clonal diversity, consistent with the observed heterozygote excess characteristic of predominantly asexual populations in M. persicae.
Host resistance and parasite virulence in greenfinch coccidiosis
Authors: Hõrak P. , Saks L. , Karu U. , Ots I. 
Published: August 2005

Abstract
The question why different host individuals within a population differ with respect to infection resistance is of fundamental importance for understanding the mechanisms of parasite-mediated selection. We addressed this question by infecting wild-caught captive male greenfinches with intestinal coccidian parasites originating either from single or multiple hosts. Birds with naturally low pre-experimental infection retained their low infection status also after reinfection with multiple strains, indicating that natural infection intensities confer information about the phenotypic ability of individuals to resist novel strains. Exposure to novel strains did not result in protective immunity against the subsequent infection with the same strains. Infection with multiple strains resulted in greater virulence than single-strain infection, indicating that parasites originating from different host individuals are genetically diverse. Our experiment thus demonstrates the validity of important but rarely tested assumptions of many models of parasite-mediated selection in a wild bird species and its common parasite.
Sexual reproduction advances autumn leaf colours in mountain birch (Betula pubescens ssp. czerepanovii)
Authors: Sinkkonen A. 
Published: August 2005

Abstract
Autumnal change in leaf colour of deciduous trees is one of the most fascinating displays in nature. Current theories suggest that autumn leaf colours are adaptations to environmental stress. Here I report that the number of ripening female catkins altered timing of yellow autumn leaf colours in mountain birch. The tree's autumnal colour change was brought forward if the tree matured plenty of female catkins. Since yellow colour pigments in leaves are unmasked as leaf nitrogen is re-translocated, sexual reproduction may alter resource allocation at times of leaf senescence. Thus, our current view on the reasons for leaf senescence has to be re-examined, and a novel evolutionary explanation is needed for the appearance of yellow autumn leaf colours.
Frost Injury as a Possible Inciting Factor in Bud and Shoot Necroses of Fraxinus excelsior L.
Authors: Pukacki P. M. , Przybył K. 
Published: August 2005

AbstractLarge numbers of European ash have died in Poland in all age classes during the last ten years. The characteristic symptom occurring on shoots of planted and self‐sown seedlings was bark necroses starting from the shoot apex, necrotic buds, or leaf and twig scars. The results showed that in the bud tissue of cold acclimated European ash extracellular and intracellular ice formation occurred at approximately −9 and −32°C, respectively. In deacclimated plants in spring water supercooling is limited by the heterogenous ice nucleation temperature and consequently the cold tolerance is −9 to −4°C for bud tissues and −13 to −9°C for shoots. Isolations of fungi were performed from dead buds and from necroses occurring on the main stem. Alternaria alternata, Fusarium lateritium and Phomopsis scobina were among the fungi occurring in both these organs at frequencies of more than 7%. Cylindrocarpon heteronemum, Diplodia mutila and Tubercularia vulgaris from necroses were only isolated in frequencies; 3.3, 1.2 and 5.4%, respectively. It seems likely that freezing injury is the inciting factor, which combined with fungal colonization manifests itself as fatal damage to European ash buds and shoots.
THE PARADOX OF BENEFICIAL RETIREMENT
Authors: Smilansky Saul 
Published: August 2005

AbstractMorally, when should one retire from one's job? The surprising answer may be ‘now’. It is commonly assumed that for a person who has acquired professional training at some personal effort, is employed in a task that society considers useful, and is working hard at it, no moral problem arises about whether that person should continue working. I argue that this may be a mistake: within many professions and pursuits, each one among the majority of those positive, productive, hard working people ought to consider leaving his or her job.
FOETAL AND MATERNAL ACID‐BASE BALANCE DURING NORMAL LABOUR
Authors: Beard R. W. , Morris E. David 
Published: August 2005

Summary(1) Twenty‐six patients whose labours have been judged to be normal have had samples of venous blood taken at the same time as samples of foetal scalp capillary blood at different stages of labour.(2) Using the Astrup micromethod, pH, base excess, and Pco2 estimations have been made on this blood. There is an initial improvement in the maternal and foetal values which is slowly reversed as labour progresses.(3) A constant maternal‐foetal acid‐base difference has been shown to exist at all stages of labour.(4) The suitability of foetal scalp capillary blood for these estimations is demonstrated by the similarity of the acid‐base values of foetal scalp blood taken at full cervical dilatation with the head in the pelvic cavity.
TIME: AN IMPORTANT VARIABLE AT CAESAREAN SECTION
Authors: Lumley Judith , Walker Adrian , Marum John , Wood Carl 
Published: August 2005

SummaryBiochemical evidence of fetal asphyxia (relative hypoxia with hypercapnia) and acidaemia has been found in the cord blood of infants delivered by Caesarean section in a series of patients who had been selected to exclude complications of pregnancy which prejudiced the fetal condition before or during anaesthesia. Further, the findings strongly suggest that fetal asphyxia develops progressively, and Apgar scores were lower as the duration of anaesthesia was extended. While changes with time in the general circulation and respiration of the mother could be excluded as the cause of fetal deterioration, local changes in the utero‐placental circulation, due to recumbency or surgical manipulation, and the effect of anaesthetic agents could not.
LAPAROSCOPY IN THE DIAGNOSIS OF TUBAL PATENCY
Authors: Coltart T. M. 
Published: August 2005

SummaryThirty‐six patients with a diagnosis of bilateral tubal occlusion on hysterosalpingography subsequently underwent laparoscopy and injection of dye through the cervix into the uterus. Bilateral tubal patency was demonstrated in 11 patients (31 per cent) and unilateral patency in 7 more (19 per cent). In view of the poor results from tubal plastic procedures it is advocated that laparoscopy be carried out before tubal surgery on all patients with bilateral negative salpingograms, especially to cases with apparent occlusion at the fimbria.
ENDOMETRIAL CARCINOMA AND SYNTHETIC PROGESTOGENS RESULTS OF INTRAUTERINE TREATMENT
Authors: Hustin J. 
Published: August 2005

SummaryEleven patients with endometrial carcinoma have been treated by intrauterine instillations of progestogen in oil during six days prior to hysterectomy. The histological changes in the hysterectomy specimens have been recorded.Good results were attained in all cases, with disappearance of the tumour in three of them. The mode of action of the progestogens is discussed.