bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differentiation trees, a junk DNA molecular clock, and the evolution of neoteny in salamanders
Authors: Martin C. Cristofre , Gordon Richard 
Published: December 2004

AbstractObligate neotenic salamanders die if forced to metamorphose. We suggest that this can be explained by assuming: 1) their “excess” DNA is “junk” DNA; 2) the “adult” specifying portion of the DNA becomes junk DNA and is available for repeated duplication. This suggests a “new” junk DNA molecular clock. We obtain remarkable agreement in “predicting” the amount of DNA per nucleus in present day non‐obligate neotene salamanders from this molecular clock. These observatons are consistent with the idea that the development of these animals is describable in terms of differentiation trees whose branches (gene cascades) corresponding to adult somatic tissues accumulate deleterious mutations over evolutionary time. We show that the amount of DNA per nucleus increases linearly with the phylogenetic age of salamander families. The lack of constraints by natural selection, on unused adult branches, may account for the large amount of so‐called “junk DNA” in obligate neotenic salamanders. The effects of this excess DNA, via increased cell size, suggest a positive feedback, ecophysiological explanation for such junk DNA: adaptation to cool water environments is enhanced by the lower metabolism associated with more DNA, larger cells and slower developmental time.
Rapid evolution of courtship song pattern in Drosophila willistoni sibling species
Authors: Ritchie M. G. , Gleason J. M. 
Published: December 2004

AbstractCourtship behaviours may provide a more reliable means of identifying reproductively isolated taxa than traits such as morphology or many genetic markers. Here we describe the courtship songs of the Drosophila willistoni sibling species group, which consists of several species and subspecies. We find that song pattern is species‐specific, despite significant differences among strains within species. D. paulistorum has the most variable song pattern, which reflects this species' traditional subdivision into semispecies. All the other species could be unambiguously identified by song. The major differences among these species was in the interpulse interval, as has been found in other studies of fly song. However, the interpulse intervals of the species studied here were often multimodal. This was partly due to the presence of multiple song types within the courtship repertoire, but it also reflected changes in interpulse interval within a song type by some males. Unusually, some species had distinctively patterned variation in interpulse interval. Song must have evolved rapidly within the species complex, probably due to sexual selection.
Sexual selection in the barn swallow Hirundo rustica. VI. Aerodynamic adaptations
Authors: Møller A. P. , De Lope F. , Saino N. 
Published: December 2004

AbstractSecondary sexual characters are assumed to be costly to produce and maintain, and this will select for morphological modifications that reduce the magnitude of such costs. Here we test whether a feather ornament, the sexually exaggerated outermost tail feathers of male barn swallows Hirundo rustica, a trait currently subject to a directional female mate preference, and other aspects of the morphology used for flight have been modified to increase aerodynamic performance. This was done by making comparisons among sexes within populations, among individuals varying in tail length within populations, and among populations from different parts of Europe. Male barn swallows experienced reduced drag from their elongated tail feathers by morphological modifications of the ornamental feathers as compared to females. Morphological features of the outermost tail feathers were unrelated to tail length in both males and females within populations. Wing and tail morphology (length of central tail feathers and wings, wing span, wing area, wing loading, and aspect ratio) was modified in males compared to females. Barn swallows with long tails had morphological tail and wing modifications that reduced the cost of a large ornament, and similar modifications were seen among populations. The costs of the exaggerated secondary sexual character were therefore reduced by the presence of cost‐reducing morphological modifications. The assumptions of reliable signalling theory, that signals should be costly, but more so to low than to high quality individuals, were not violated because long‐tailed male barn swallows had the largest cost‐reducing morphological characters.
Malformed offspring, sibling matings, and selection against inbreeding in the sand lizard (Lacerta agilis)
Authors: Olsson M. , Gullberg A. , Tegelström H. 
Published: December 2004

AbstractWe demonstrated that sand lizards (Lacerta agilis) are more likely to have malformed offspring when they mate with siblings. Offspring with malformations, such as deformed limbs and heads, have zero survival in a natural population. Normal‐looking siblings of malformed hatchlings also had a reduced survival in the wild, compared to offspring from clutches in which all siblings appeared normal. The proportion of malformed hatchlings in the natural population was ca. 10%, in spite of differences in juvenile dispersal between males and females. Male juveniles disperse significantly further from their natal sites than do female juveniles.
Resource allocation: a conflict in the fig/fig wasp mutualism?
Authors: Anstett M.‐C. , Bronstein J. L. , Hossaert‐McKey M. 
Published: December 2004

AbstractConflicts of interest are omnipresent between mutualist species. In the monoecious fig/pollinator wasp mutualism, each female flower produces either a seed or a pollinator offspring (which has fed on a single seed). Pollen from a syconium (i.e. fig, a closed urn‐shaped inflorescence) is only dispersed by female pollinator offspring born in this syconium. Thus the fig tree is selected to produce both seed and pollinator offspring whereas for the pollinator there is no short term advantage in seed production. Using controlled pollination experiments (pollen injection, and foundress introduction), we show that 1) The relative proportion of seeds and pollinator offspring produced (i.e., the effective allocation between female and male function) depends mainly on the number of foundresses that entered the syconium. 2) Many female flowers within every syconium mature neither a seed nor a wasp (from 25% to 33%). 3) All the female flowers within a syconium that are not vacant at maturity have the potential to produce a seed, and at least 80% of them can produce a pollinator. Several hypotheses concerning mechanisms that govern the partitioning between seed and wasp production are discussed, and their evolutionary consequences are considered.
Evolution of a colour pattern: history, development, and selection
Authors: Price T. , Pavelka M. 
Published: December 2004

AbstractPatterns of melanin pigmentation in birds are extremely varied. Nevertheless it is easy to think of many patterns that are never observed, and others that frequently recur in diverse and distantly related species. Using as our model the avian genus Phylloscopus we ask how the restricted range of observed patterns might be attributable to a restricted range of variants produced by developmental perturbations. The patterns we consider consist of unmelanized patches on the wings, crown and rump on otherwise pigmented upperparts. We use reaction‐diffusion models to show that gross features of the pattern can be simply predicted from considerations of embryo shape. We suggest that birds are expected to have more patterned heads, because the head region is relatively larger than other regions in the developing embryo. A comparative analysis across many species of birds and a phylogenetic analysis within the genus Phylloscopus show that the component elements of the pattern have repeatedly been lost and gained during evolution. A shift in a threshold reading could explain the appearance and disappearance of the unmelanized patches, perhaps through changes in the sensitivity of melanocytes to epidermal signals. Such threshold shifts would make the transition between patterned and unpatterned forms particularly easy once the patterns have been exposed to selection in some distant ancestor. This partitioning of the roles of selection and development implies that many features of the patterns reflect developmental mechanisms in both immediate and more distant ancestors.
Frequency‐dependent selection by pollinators: mechanisms and consequences with regard to behaviour of bumblebees Bombus terrestris (L.) (Hymenoptera: Apidae)
Authors: Smithson A. , Macnair M. R. 
Published: December 2004

Abstract Bombus terrestris , a typical pollinating insect species, was offered artificial flowers of two different corolla colours with the same sucrose solution reward in an array. Common colours were significantly preferred, and the strength of the frequency‐dependent response increased as a result of learning. There were also frequency‐independent biases towards blue flowers, probably because blue flowers appeared more conspicuous to bumblebees than yellow flowers, and the degree of preference for blue was greater when flowers had low nectar rewards. Flower‐to‐flower movements by individual bumblebees between flowers were non‐random, were biased to movements within the same flower colour, and were also dependent on morph frequency. The mechanisms governing flower selection in bumblebees are discussed.Pollinators foraging similarly in a natural situation would induce positive frequency‐dependent selection, assortative mating, and directional selection on different corolla colour morphs of the plant population being visited, resulting in stabilizing selection for a single flower colour.
The evolution of the reptilian hindfoot and the homology of the hooked fifth metatarsal
Authors: Lee M. S. Y. 
Published: December 2004

AbstractThe homology of the fifth metatarsal in turtles and in diapsid reptiles is reassessed in the light of new phylogenetic studies. The two nearest outgroups to turtles — pareiasaurs and procolophonoids — both lack a fifth distal tarsal but retain a normal fifth metatarsal. The fifth distal tarsal was therefore lost at the base of the clade that contains turtles. Thus, the hooked fifth metatarsal in turtles must consist entirely of a modified fifth metatarsal: it does not include contributions from the fifth distal tarsal, as commonly supposed. In diapsids, loss of the fifth distal tarsal appears to have occurred at the base of crown‐clade diapsids, hooking of the fifth metatarsal subsequently occurring within lepidosauromorphs, and in archosauromorphs. If so, the hooked fifth metatarsal in archosauromorphs, and some lepidosauromorphs, consists entirely of a modified fifth metatarsal. In both turtles and diapsids, integration of the elements distal to the mesotarsal joint precedes evolution of the hooked fifth metatarsal, supporting the view that the latter element evolved to perform a lever function (analogous to the “heel bone” of mammals).
Phenotypic plasticity and selection in Drosophila life history evolution. 2. Diet, mates and the cost of reproduction
Authors: Chippindale A. K. , Leroi A. M. , Saing H. , Borash D. J. , Rose M. R. 
Published: December 2004

AbstractWhile it is commonplace for biologists to use the response to environmental manipulation as a guide to evolutionary responses to selection, the relationship between phenotypic plasticity and genetic change is not generally well‐established. The life‐histories of laboratory Drosophila populations are among the few experimental systems which simultaneously afford information on phenotypic plasticity and evolutionary trajectories. We employed a combination of two replicated selectively differentiated stocks (postponed aging stocks and their controls; 10 populations in total) and two different environmental manipulations (nutrition and mating) to explore the empirical relationship between phenotypic plasticity and evolutionary trajectories. While there are a number of parallels between the results obtained using these two approaches, there are important differences. In particular, as the detail of the biological characterization of either type of response increases, so their disparities multiply. Nonetheless, the combination of environmental manipulation with evolutionary divergence provides valuable information about the biological connections between life‐history, caloric reserves, and reproductive physiology in Drososphila.
Evolution of animal genitalia: morphological correlates of fitness components in a water strider
Authors: Arnqvist G. , Thornhill R. , Rowe L. 
Published: December 2004

AbstractRapid divergence of male genitalia is one of the most general evolutionary trends in animals with internal fertilization, but the mechanisms of genital evolution are poorly understood. The current study represents the first comprehensive attempt to test the main hypotheses that have been suggested to account for genital evolution (the lock‐and‐key, sexual selection and pleiotropy hypotheses) with intraspecific data. We measure multivariate phenotypic selection in a water strider species, by relating five different components of fitness (mating frequency, fecundity, egg hatching rate, offspring survival rate and offspring growth rate) to a suite of genital and non‐genital morphological traits (in total 48). Body size had a series of direct effects in both sexes. Large size in females was positively related to both fecundity and egg hatching rate. There was positive sexual selection for large size in males (mating frequency), which to some extent was offset by a reduced number of eggs laid by females mated to large males. Male genitalic morphology influenced male mating frequency, but the detected directional selection on genitalia was due to indirect selection on phenotypically correlated non‐intromittent traits. Further, we found no assortative mating between male intromittent genitalia and female morphology. Neither did we find any indications of male genitalia conveying information of male genetic quality. Several new insights can be gained from our study. Most importantly, our results are in stark disagreement with the long standing lock‐and‐key hypothesis of genital evolution, as well as with certain models of sexual selection. Our results are, however, in agreement with other models of sexual selection as well as with the pleiotropy hypothesis of genital evolution. Fluctuating asymmetry of bilaterally symmetrical traits, genital as well as non‐genital, had few effects on fitness. Females with low fluctuating asymmetry in leg length produced offspring with a higher survival rate, a pattern most proba bly caused by direct phenotypic maternal effects. We also discuss the relevance of our results to sexual conflict over mating, and the evolution of sexual traits by coevolutionary arms races between the sexes.
The molecular basis of dominance relationships: the case of some recent adaptive genes
Authors: Bourguet D. , Raymond M. 
Published: December 2004

AbstractA controversial debate in evolutionary biology has been to explain why deleterious mutations are usually recessive to their wild‐type allele. For Fisher, dominance of the wild‐type is the result of selection, whereas for Wright it is a mere consequence of the biochemical properties of physiological pathways. Over time, Wright's theory has appeared as the most appropriate, and Kacser and Burns explained why the widespread occurrence of recessive mutants is the inevitable consequence of the kinetic structure of enzyme networks. Does Wright and Kacser and Burns (W‐K‐B)'s theory apply for newly arisen adaptive genes? A survey of more than 70 studies shows that pesticide resistance conferred by mutations decreasing the affinity of the pesticide target‐sites varies from complete recessivity to complete dominance. This review shows that dominance always has a purely physiological explanation that can be roughly, but not simply, predicted by W‐K‐B's theory. Thus, although W‐K‐B's theory remains powerful for predicting the recessivity of deleterious mutations involved in enzymatic pathways, no general theory emerges from the study of other situations, and molecular explanations are to be sought on a case by case basis.
Epigenetic inheritance in evolution
Authors: Jablonka E. , Lamb M. J. 
Published: December 2004

AbstractWe discuss the role of cell memory in heredity and evolution. We describe the properties of the epigenetic inheritance systems (EISs) that underlie cell memory and enable environmentally and developmentally induced cell phenotypes to be transmitted in cell lineages, and argue that transgenerational epigenetic inheritance is an important and neglected part of heredity. By looking at the part EISs have played in the evolution of multicellularity, ontogeny, chromosome organization, and the origin of some post‐mating isolating mechanisms, we show how considering the role of epigenetic inheritance can sometimes shed light on major evolutionary processes.
Loss of genetic diversity and fitness in Common Toad (Bufo bufo) populations isolated by inimical habitat
Authors: Hitchings S. P. , Beebee T. J. C. 
Published: December 2004

AbstractMeasures of genetic diversity (including heterozygosity), survival and developmental homeostasis were found to be significantly lower in small, urban populations of the Common Toad (Bufo bufo) than in larger, rural populations of the same region. The autecology and genetic analysis of this relatively sedentary species suggested that the causal mechanism was genetic drift, arising from barriers to migration created by urban development. The pre‐metamorphic survival of larvae cultured in identical conditions increased positively with the mean number of alleles at a locus and the percentage of polymorphic loci. Observed heterozygosity in urban garden and rural populations was correlated inversely with the number of observed physical abnormalities (used as a measure of developmental homeostasis) in the developing tadpoles. Genetic distances between town sites of mean 2.2 km separation were significantly higher than those between rural sites of mean 37 km separation. Genetic data were based on allozyme analysis of 27 loci in 8 urban and 4 rural populations. A subset of these sites (3 urban, 2 rural) were also assessed at 3 minisatellite loci and a positive correlation found between the average number of alleles per locus detected by the two methods. Estimates of Nei's 1972 genetic distance, derived separately from the DNA and protein data, were not, however, correlated. The reduction in genetic diversity and fitness observed in these urban toads provides an example of the effect on population persistence that longer term depletion in numbers and habitat fragmentation can have in the wider environment.
Plasmoredoxin, a novel redox‐active protein unique for malarial parasites
Authors: Becker Katja , Kanzok Stefan M. , Iozef Rimma , Fischer Marina , Schirmer R. Heiner , Rahlfs Stefan 
Published: December 2004

Thioredoxins are a group of small redox‐active proteins involved in cellular redox regulatory processes as well as antioxidant defense. Thioredoxin, glutaredoxin, and tryparedoxin are members of the thioredoxin superfamily and share structural and functional characteristics. In the malarial parasite, Plasmodium falciparum, a functional thioredoxin and glutathione system have been demonstrated and are considered to be attractive targets for antimalarial drug development.Here we describe the identification and characterization of a novel 22 kDa redox‐active protein in P. falciparum. As demonstrated by in silico sequence analyses, the protein, named plasmoredoxin (Plrx), is highly conserved but found exclusively in malarial parasites. It is a member of the thioredoxin superfamily but clusters separately from other members in a phylogenetic tree. We amplified the gene from a gametocyte cDNA library and overexpressed it in E. coli. The purified gene product can be reduced by glutathione but much faster by dithiols like thioredoxin, glutaredoxin, trypanothione and tryparedoxin. Reduced Plrx is active in an insulin‐reduction assay and reduces glutathione disulfide with a rate constant of 640 m−1·s−1 at pH 6.9 and 25 °C; glutathione‐dependent reduction of H2O2 and hydroxyethyl disulfide by Plrx is negligible. Furthermore, plasmoredoxin provides electrons for ribonucleotide reductase, the enzyme catalyzing the first step of DNA synthesis. As demonstrated by Western blotting, the protein is present in blood‐stage forms of malarial parasites.Based on these results, plasmoredoxin offers the opportunity to improve diagnostic tools based on PCR or immunological reactions. It may also represent a specific target for antimalarial drug development and is of phylogenetic interest.
Functional fine‐mapping and molecular modeling of a conserved loop epitope of the measles virus hemagglutinin protein
Authors: Pütz Mike M. , Hoebeke Johan , Ammerlaan Wim , Schneider Serge , Muller Claude P. 
Published: December 2004

Neutralizing and protective monoclonal antibodies (mAbs) were used to fine‐map the highly conserved hemagglutinin noose epitope (H379–410, HNE) of the measles virus. Short peptides mimicking this epitope were previously shown to induce virus‐neutralizing antibodies [El Kasmi et al. (2000) J. Gen. Virol.81, 729–735]. The epitope contains three cysteine residues, two of which (Cys386 and Cys394) form a disulfide bridge critical for antibody binding. Substitution and truncation analogues revealed four residues critical for binding (Lys387, Gly388, Gln391 and Glu395) and suggested the binding motif X7C[KR]GX[AINQ]QX2CEX5 for three distinct protective mAbs. This motif was found in more than 90% of the wild‐type viruses. An independent molecular model of the core epitope predicted an amphiphilic loop displaying a remarkably stable and rigid loop conformation. The three hydrophilic contact residues Lys387, Gln391 and Glu395 pointed on the virus towards the solvent‐exposed side of the planar loop and the permissive hydrophobic residues Ile390, Ala392 and Leu393 towards the solvent‐hidden side of the loop, precluding antibody binding. The high affinity (Kd = 7.60 nm) of the mAb BH216 for the peptide suggests a high structural resemblance of the peptide with the natural epitope and indicates that most interactions with the protein are also contributed by the peptide. Improved peptides designed on the basis of these findings induced sera that crossreacted with the native measles virus hemagglutinin protein, providing important information about a lead structure for the design of more stable antigens of a synthetic or recombinant subunit vaccine.