bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple paternity and population genetic structure in natural populations of the poeciliid fish, Heterandria formosa
Authors: Soucy S. , Travis J. 
Published: October 2003

Abstract
Heterandria formosa Agassiz, exhibits internal fertilization, internal brooding of embryos, sperm storage and an extreme level of superfetation. In this study we used microsatellite markers to examine variation among seven populations that exhibited significant variance in their histories of population density. We found that the populations were genetically distinct and that the heterozygosity increased as population density increased. We also examined paternity in three of those populations and found that the number of sires per female and the number of sires per brood increased with population density. Overall, the rates of multiple paternity are quite low relative to other species. The correlations with population density suggest that contact rates play a critical role in the breeding system in this species but the low rates of multiple paternity suggest that females may exert control over fertilization of their ova.
Coevolution between hosts and parasites with partially overlapping geographic ranges
Authors: Nuismer S. L. , Thompson J. N. , Gomulkiewicz R. 
Published: October 2003

Abstract
Many host species interact with a specific parasite within only a fraction of their geographical range. Where host and parasite overlap geographically, selection may be reciprocal constituting a coevolutionary hot spot. Host evolution, however, may be driven primarily by selection imposed by alternative biotic or abiotic factors that occur outside such hot spots. To evaluate the importance of coevolutionary hot spots for host and parasite evolution, we analyse a spatially explicit genetic model for a host that overlaps with a parasite in only part of its geographical range. Our results show that there is a critical amount of overlap beyond which reciprocal selection leads to a coevolutionary response in the host. This critical amount of overlap depends upon the explicit spatial configuration of hot spots. When the amount of overlap exceeds this first critical level, host–parasite coevolution commonly generates stable allele frequency clines rather than oscillations. It is within this region that one of the primary predictions of the geographic mosaic theory is realized, and local maladaptation is prevalent in both species. Past a further threshold of overlap between the species oscillations do evolve, but allele frequencies in both species are spatially synchronous and local maladaptation is absent in both species. A consequence of such transitions between coevolutionary dynamics is that parasite adaptation is inversely proportional to the fraction of its host's range that it occupies. Hence, as the geographical range of a parasite increases, it becomes increasingly maladapted to the host. This suggests a novel mechanism through which the geographical range of parasites may be limited.
Age-related decline in humoral immune function in Collared Flycatchers
Authors: Cichoń M. , Sendecka J. , Gustafsson L. 
Published: October 2003

Abstract
Although immune function usually declines with age in humans and captive animals, little is known about whether immune function deteriorates with age in natural populations. Here we present evidence for such an age-related deterioration in humoral immune function from a wild population of the Collared Flycatcher (Ficedula albicollis). In this study, young (1-year old), mid-age (3-year old) and old (5–6-year old) females were challenged with a nonpathogenic antigen, sheep red blood cells (SRBC), while provisioning their nestlings. The level of antibodies against SRBC was measured thereafter. Old females showed markedly lower humoral immune response and produced fledglings of lower body mass in comparison with the other two age classes. Moreover, the age classes differed in the relationship between immune response and fledgling body mass with mid-age females showing a significant positive relationship while the relationship was negative but nonsignificant among young and old females. The results are discussed in light of existing theories of optimal resource allocation, ageing and the theory of terminal investment.
A molecular phylogeny of enteric bacteria and implications for a bacterial species concept
Authors: Wertz J. E. , Goldstone C. , Gordon D. M. , Riley M. A. 
Published: October 2003

Abstract
A molecular phylogeny for seven taxa of enteric bacteria (Citrobacter freundii, Enterobacter cloacae, Escherichia coli, Hafnia alvei, Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia plymuthica) was made from multiple isolates per taxa taken from a collection of environmental enteric bacteria. Sequences from five housekeeping genes (gapA, groEL, gyrA, ompA, and pgi) and the 16s rRNA gene were used to infer individual gene trees and were concatenated to infer a composite molecular phylogeny for the species. The isolates from each taxa formed tight species clusters in the individual gene trees, suggesting the existence of ‘genotypic’ clusters that correspond to traditional species designations. These sequence data and the resulting gene trees and consensus tree provide the first data set with which to assess the utility of the recently proposed core genome hypothesis (CGH). The CGH provides a genetically based approach to applying the biological species concept to bacteria.
Sexual variation in heritability and genetic correlations of morphological traits in house sparrow (Passer domesticus)
Authors: Jensen H. , Sæther B.-E. , Ringsby T. H. , Tufto J. , Griffith S. C. , Ellegren H. 
Published: October 2003

Abstract
Estimates of genetic components are important for our understanding of how individual characteristics are transferred between generations. We show that the level of heritability varies between 0.12 and 0.68 in six morphological traits in house sparrows (Passer domesticus L.) in northern Norway. Positive and negative genetic correlations were present among traits, suggesting evolutionary constraints on the evolution of some of these characters. A sexual difference in the amount of heritable genetic variation was found in tarsus length, wing length, bill depth and body condition index, with generally higher heritability in females. In addition, the structure of the genetic variance-covariance matrix for the traits differed between the sexes. Genetic correlations between males and females for the morphological traits were however large and not significantly different from one, indicating that sex-specific responses to selection will be influenced by intersexual differences in selection differentials. Despite this, some traits had heritability above 0.1 in females, even after conditioning on the additive genetic covariance between sexes and the additive genetic variances in males. Moreover, a meta-analysis indicated that higher heritability in females than in males may be common in birds. Thus, this indicates sexual differences in the genetic architecture of birds. Consequently, as in house sparrows, the evolutionary responses to selection will often be larger in females than males. Hence, our results suggest that sex-specific additive genetic variances and covariances, although ignored in most studies, should be included when making predictions of evolutionary changes from standard quantitative genetic models.
Large size in an island-dwelling bird: intraspecific competition and the Dominance Hypothesis
Authors: Robinson-Wolrath S. I. , Owens I. P. F. 
Published: October 2003

Abstract
Differences between island- and mainland-dwelling forms provide several classic ecological puzzles. Why, for instance, are island-dwelling passerine birds consistently larger than their mainland counterparts? We examine the ‘Dominance hypothesis’, based on intraspecific competition, which states that large size in island passerines evolves through selection for success in agonistic encounters. We use the Heron Island population of Capricorn silvereyes (Zosterops lateralis chlorocephalus), a large-bodied island-dwelling race of white-eye (Zosteropidae), to test three assumptions of this hypothesis; that (i) large size is positively associated with high fitness, (ii) large size is associated with dominance, and (iii) the relationship between size and dominance is particularly pronounced under extreme intraspecific competition. Our results supported the first two of these assumptions, but provided mixed evidence on the third. On balance, we suggest that the Dominance Hypothesis is a plausible mechanism for the evolution of large size of island passerines, but urge further empirical tests on the role of intraspecific competition on oceanic islands versus that on mainlands.
Conflicting selection pressures on seed size: evolutionary ecology of fruit size in a bird-dispersed tree, Olea europaea
Authors: Alcántara J. M. , Rey P. J. 
Published: October 2003

Abstract
Recent evidence indicates that fruit size has evolved according to dispersers’ size. This is hypothesized to result from a balance between factors favouring large seeds and dispersers setting the maximum fruit size. This hypothesis assumes that (1) the size of fruits that can be consumed by dispersers is limited, (2) fruit and seed size are positively correlated, and (3) the result of multiple selection pressures on seed size is positive. Our studies on the seed dispersal mutualism of Olea europaea have supported the first and second assumptions, but valid tests of the third assumption are still lacking. Here we confirm the third assumption. Using multiplicative fitness components, we show that conflicting selection pressures on seed size during and after dispersal reverse the negative pattern of selection exerted by dispersers.
Temperature dependent larval resource allocation shaping adult body size in Drosophila melanogaster
Authors: Bochdanovits Z. , de Jong G. 
Published: October 2003

Abstract
Geographical variation in Drosophila melanogaster body size is a long-standing problem of life-history evolution. Adaptation to a cold climate invariably produces large individuals, whereas evolution in tropical regions result in small individuals. The proximate mechanism was suggested to involve thermal evolution of resource processing by the developing larvae. In this study an attempt is made to merge proximate explanations, featuring temperature sensitivity of larval resource processing, and ultimate approaches focusing on adult and pre-adult life-history traits. To address the issue of temperature dependent resource allocation to adult size vs. larval survival, feeding was stopped at several stages during the larval development. Under these conditions of food deprivation, two temperate and two tropical populations reared at high and low temperatures produced different adult body sizes coinciding with different probabilities to reach the adult stage. In all cases a phenotypic trade-off between larval survival and adult size was observed. However, the underlying pattern of larval resource allocation differed between the geographical populations. In the temperate populations larval age but not weight predicted survival. Temperate larvae did not invest accumulated resources in survival, instead they preserved larval biomass to benefit adult weight. In other words, larvae from temperate populations failed to re-allocate accumulated resources to facilitate their survival. A low percentage of the larvae survived to adulthood but produced relatively large flies. Conversely, in tropical populations larval weight but not age determined the probability to reach adulthood. Tropical larvae did not invest in adult size, but facilitated their own survival. Most larvae succeeded in pupating but then produced small adults. The underlying physiological mechanism seemed to be an evolved difference in the accessibility of glycogen reserves as a result of thermal adaptation. At low rearing temperatures and in the temperate populations, glycogen levels tended to correlate positively with adult size but negatively with pupation probability. The data presented here offer an explanation of geographical variation in body size by showing that thermal evolution of resource allocation, specifically the ability to access glycogen storage, is the proximate mechanism responsible for the life-history trade-off between larval survival and adult size.
Foundress re-emergence and fig permeability in fig tree–wasp mutualisms
Authors: Moore J. C. , Dunn A. M. , Compton S. G. , Hatcher M. J. 
Published: October 2003

Abstract
Some female pollinating fig wasps (foundresses) re-emerge from figs after oviposition/pollination. We investigated why this occurs in the mutualism between the gynodioecious Ficus montana and Liporrhopalum tentacularis. Re-emergence increased with foundress density in figs and some foundresses oviposited in two male figs, indicating that they re-emerge because of oviposition site limitation. Re-emergence was independent of fig diameter, indicating that permeability is not because of fig age at entry. Rather, as some foundresses also pollinate two female figs we suggest permeability is selected for because it increases pollinator production and/or efficiency (although, potentially opposing these hypotheses, we also found between-tree differences in permeability in male figs). In addition, we show that re-emergence is much more common than previously suspected, and more common from gynodioecious than monoecious fig species. We argue that our findings in F. montana could explain this pattern of incidence.
Evolution of cultural communication systems: the coevolution of cultural signals and genes encoding learning preferences
Authors: Lachlan R. F. , Feldman M. W. 
Published: October 2003

Abstract
In several communication systems that rely on social learning, such as bird song, and possibly human language, the range of signals that can be learned is limited by perceptual biases – predispositions – that are presumably based on genes. In this paper, we examine the coevolution of such genes with the culturally transmitted communication traits themselves, using deterministic population genetic models. We argue that examining how restrictive genetic predispositions are is a useful way of examining the evolutionary origin and maintenance of learning. Under neutral cultural evolution, where no cultural trait has any inherent advantage over another, there is selection in favour of less restrictive genes (genes that allow a wider range of signals to recognized). In contrast, cultural conformity (where the most common cultural trait is favoured) leads to selection in favour of more restrictive genes.
Association with host mitochondrial haplotypes suggests that feminizing microsporidia lack horizontal transmission
Authors: Ironside J. E. , Dunn A. M. , Rollinson D. , Smith J. E. 
Published: October 2003

Abstract
The amphipod crustacean Gammarus duebeni hosts two feminizing microsporidian parasites, Nosema granulosis and Microsporidium sp. Samples of G. duebeni were collected from three sites on the Scottish island of Great Cumbrae and screened for microsporidia using polymerase chain reaction. Associations between the prevalence of the two feminizing parasites and haplotypes of the host mitochondrial gene cytochrome oxidase I (COI) were investigated. The prevalence of both parasites varied significantly among the host's COI haplotypes, suggesting that horizontal transmission is rare or absent in the life cycles of the feminizing microsporidia and that all transmission must therefore be vertical. Life cycles in which all transmission is vertical are common among bacterial parasites but have never before been demonstrated in Eukaryotic parasites.
Evolutionary history of asexual hybrid loaches (Cobitis: Teleostei) inferred from phylogenetic analysis of mitochondrial DNA variation
Authors: Janko K , Kotlík P , Ráb P 
Published: October 2003

Abstract
Reconstruction of the evolutionary history of asexual lineages undermines their suitability as models for the studies of evolutionary consequences of sexual reproduction. Using molecular tools we addressed the origin, age and maternal ancestry of diploid and triploid asexual lineages arisen through the hybridization between spiny loaches Cobitis elongatoides, C. taenia and C. tanaitica. Reconstructions of the phylogenetic relationships among mitochondrial DNA (mtDNA) haplotypes, revealed by sequence analyses, suggest that both hybrid complexes (C. elongatoides-taenia and C. elongatoides-tanaitica) contained several asexual lineages of independent origin. Cobitis elongatoides was the exclusive maternal ancestor of all the C. elongatoides-tanaitica hybrids, whereas within the C. elongatoides-taenia complex, hybridization was reciprocal. In both complexes the low haplotype divergences were consistent with a recent origin of asexual lineages. Combined mtDNA and allozyme data suggest that the triploids arose through the incorporation of a haploid sperm genome into unreduced ova produced by diploid hybrids.
Migratory costs and contemporary evolution of reproductive allocation in male chinook salmon
Authors: Kinnison M. T. , Unwin M. J. , Quinn T. P. 
Published: October 2003

Abstract
Energetically demanding migrations may impact the resources available for reproductive trait development and activity, and hence favour evolution of new investment strategies for remaining resources. We conducted a large-scale experiment to evaluate the proximate cost of migration on male reproductive investment in chinook salmon (Oncorhynchus tshawytscha) and contemporary evolution of reproductive allocation. Experimentally induced differences in migratory costs (17 km inland and 17 m elevation vs. 100 km and 430 m) influenced dorsal hump size and upper jaw length, two traits influencing male mating success that are developed during migration. Longer migration also reduced tissue energy reserves available for competition and length of breeding life. Corresponding shifts in the balance between natural and sexual selection appear to have been responsible for heritable population divergence in secondary sexual trait investment, in approximately 26 generations, following colonization of spawning sites with different migratory demands.
Relationship between fluctuating asymmetry and fitness within and between stressed and unstressed populations of the wolf spider Pirata piraticus
Authors: Hendrickx F. , Maelfait J.-P. , Lens L. 
Published: October 2003

Abstract
Although developmental instability, measured as fluctuating asymmetry (FA), is expected to be positively related to stress and negatively to fitness, empirical evidence is often lacking or contradictory when patterns are compared at the population level. We demonstrate that two important properties of stressed populations may mask such relationships: (i) a stronger relationship between FA and fitness, resulting in stronger selection against low quality (i.e. developmental unstable) individuals and (ii) the evolution of adaptive responses to environmental stress. In an earlier study, we found female wolf spiders Pirata piraticus from metal exposed populations to be characterized by both reduced clutch masses and increased egg sizes, the latter indicating an adaptive response to stress. By studying the relationship between these two fitness related traits and levels of FA at individual level, we here show a significant negative correlation between FA and clutch mass in metal stressed populations but not in unstressed reference populations. As a result, levels of population FA may be biased downward under stressful conditions because of the selective removal of developmentally unstable (low quality) individuals. We further show that females that produced larger eggs in stressed populations exhibited lower individual FA levels. Such interaction between individual FA and fitness with stress may confound the effect of metal stress on FA, resulting in an absence of relationships between FA, fitness and stress at the population level.
Ser/Thr phosphorylation of hematopoietic specific protein 1 (HS1)
Authors: Ruzzene Maria , Brunati Anna M. , Sarno Stefania , Marin Oriano , Donella‐Deana Arianna , Pinna Lorenzo A. 
Published: October 2003

Hematopoietic lineage cell‐specific protein 1 (HS1), a tyrosine multiphosphorylated protein implicated in receptor‐mediated apoptosis and proliferative responses, is shown here to become Ser/Thr phosphorylated upon incubation of platelets with radiolabeled inorganic phosphate. The in vivo Ser/Thr phosphorylation of HS1 is enhanced by okadaic acid and reduced by specific inhibitors of casein kinase (CK)2. In vitro, HS1 is an excellent substrate for either CK2 α subunit alone (Km = 47 nm) or CK2 holoenzyme, tested in the presence of polylysine (Km = 400 nm). Phosphorylation reaches a stoichiometry of about 2 mol phosphate per mol HS1 and occurs mainly at threonyl residue(s), mostly located in the N‐terminal region, but also at seryl residue(s) residing in the central core of the molecule (208–402), as judged from experiments with deleted forms of HS1. Ser/Thr phosphorylation of HS1, either induced in vivo by okadaic acid or catalysed in vitro by CK2, potentiates subsequent phosphorylation at tyrosyl residues. These data indicate the possibility that regulation of HS1 may also be under the control of Ser/Thr phosphorylation, and suggest that in quiescent cells CK2 could play a role in inducing constitutive Tyr phosphorylation of HS1 in the absence of stimuli that activate the protein tyrosine kinase pathway.
Melanom‐Stroma‐Interaktionen und ihre Bedeutung für die Melanomprogression
Authors: Ruiter Dirk J. , Herlyn Meenhard 
Published: October 2003

ZusammenfassungDas Melanom der Haut ist ein aggressiv wachsender Tumor, der frühzeitig metastasieren kann. Nicht nur die Melanomzellen selbst, sondern auch das tumorumgebende Mikroenvironment spielt bei der Entstehung und der Progression des Melanoms eine wichtige Rolle. In diesem Mini‐Review werden die strukturellen und funktionellen Aspekte der Interaktion von Melanomzellen und umgebendem Stroma dargestellt, sowie deren klinische Relevanz diskutiert.
Sentinel‐Lymphonodektomie beim malignen Melanom – ein Update
Authors: Kretschmer Lutz , Bertsch Hans Peter , Meller Johannes 
Published: October 2003

ZusammenfassungZehn Jahre nach der Einführung des Sentinel‐Konzeptes in die Behandlungsstrategie des malignen Melanoms gilt es Bilanz zu ziehen. Die komplexe Methode hat sich als hinreichend sensitiv erwiesen, auch wenn bei der histologischen Aufarbeitung ein bestimmter Prozentsatz falsch‐negativer Resultate in Kauf genommen werden muß. Es wird weiterhin kontrovers diskutiert, ob die generelle Durchführung der Sentinel‐Lymphonodektomie bei High‐Risk‐Patienten gerechtfertigt ist. Drei prospektive Studien zur elektiven Lymphknotendissektion konnten nicht beweisen, daß eine Früherkennung und Frühtherapie von Lymphknotenmetastasen zu einem Überlebensvorteil führt. Dagegen fand eine retrospektive Multizenterstudie ein verbessertes Overall‐Survival für Patienten mit histologisch positivem Sentinel, im Vergleich zu Patienten, bei denen klinisch vergrößerte Lymphknotenmetastasen erst im weiteren Verlauf exzidiert wurden. Der pathologische Status des Sentinel‐Lymphknotens gilt heute als unabhängiger Prognosefaktor. Wie jedes invasive Staging‐Verfahren verlangt auch die Sentinel‐Lymphonodektomie nach einer therapeutischen Konsequenz. Leider existiert derzeit keine allgemein anerkannte adjuvante Therapie. Auch ist bislang nicht gezeigt worden, daß Patienten mit positivem Sentinel von einer komplettierenden regionalen Lymphknotendissektion profitieren.