Experimentally reduced paternity affects paternal effort and reproductive success in pied flycatchers.

The question of whether, and how, male birds should change their parental effort in response to reduced paternity is a controversial issue among behavioural ecologists. We report a study on pied flycatchers, Ficedula hypoleuca, in which paternity was manipulated through experimentally induced mate switching during the female's fertile period. The paternity of care-giving males ranged from 0 to 100% of the brood.

Expansion of the pig comparative map by expressed sequence tags (EST) mapping.

We have used a PCR-based approach for the genetical and physical mapping of 34 transcripts isolated from a porcine small intestine cDNA library. All but one gene were regionally localized by using a somatic pig-rodent cell hybrid panel, and 12 genes were mapped by linkage analysis of single-stranded conformational polymorphisms developed in 3' untranslated regions of transcripts. For 20 of the transcripts, the human homolog has already been mapped.

Male-driven evolution of DNA sequences in birds.

Assuming that new mutations arise mainly during DNA replication, sequence evolution in mammals has been seen as 'male driven' (ref. 1) because of the many more cell divisions in spermatogenesis than in oogenesis. Molecular support for this idea has been obtained from the observation of higher substitution rates in genes on the Y than on the X chromosome of primates and rodents, which are species with male heterogamety, but has not been confirmed by the reciprocal analysis of organisms with female heterogamety.

Fitness loss and germline mutations in barn swallows breeding in Chernobyl.

The severe nuclear accident at Chernobyl in 1986 resulted in the worst reported accidental exposure of radioactive material to free-living organisms. Short-term effects on human populations inhabiting polluted areas include increased incidence of thyroid cancer, infant leukaemia, and congenital malformations in newborns. Two recent studies have reported, although with some controversy, that germline mutation rates were increased in humans and voles living close to Chernobyl, but little is known about the viability of the organisms affected.

Microsatellite evolution--a reciprocal study of repeat lengths at homologous loci in cattle and sheep.

The application of microsatellites in evolutionary studies requires an understanding of the patterns governing their evolution in different species. The finding that homologous microsatellite loci are longer, i.e.

New tools for sex identification and the study of sex allocation in birds.

The recent development of simple, DNA-based methods for the determination of an individual's sex will make possible large-scale studies of sex allocation and the consequence of gender in birds. Birds provide ideal systems for studying these questions in vertebrates, as so much is known about their biology and determinants of fitness. Until recently, however, little quantitative work has been possible because of the difficulty in determining gender in most cases.

Experimental mate switching in pied flycatchers: male copulatory access and fertilization success.

By making female birds pair successively with different males, and analysing the paternity of the eggs laid, it is possible to examine how a male's success in obtaining fertilizations is determined by the timing of his copulatory access to the female. Such an experiment is reported here with pied flycatchers, Ficedula hypoleucaMate switching was induced at different stages within the female's fertile period by removing the resident male. The paternity of the clutch was analysed by microsatellite DNA typing.

Low frequency of microsatellites in the avian genome.

A better insight into the occurrence of microsatellites in a range of taxa may help to understand the evolution of simple repeats. Previous studies have found the relative abundance of several repeat motifs to differ among mammals, invertebrates, and plants. Absolute numbers of microsatellites also tend to correlate positively with genome size.

AN EXPERIMENTAL STUDY OF PATERNITY AND TAIL ORNAMENTATION IN THE BARN SWALLOW (HIRUNDO RUSTICA).

Previous studies of the socially monogamous barn swallow (Hirundo rustica) have shown that males that most frequently engage in extrapair copulations and whose partners are least involved in copulations with extrapair males are those with long tail ornaments. In this study, through the use of three highly polymorphic microsatellite markers, we analyze the relationships between length of tail ornaments of male barn swallows and proportion of nestlings fathered in own broods, number of offspring fathered in broods of other pairs, and total number of offspring fathered, using both a correlational and an experimental approach. Consistent with our predictions, we show that males with either naturally long or experimentally elongated tails have higher paternity (proportion of biological offspring in own broods), and they produce more biological offspring during the whole breeding season than males with naturally short or experimentally shortened tails.

Genetical and physical assignments of equine microsatellites--first integration of anchored markers in horse genome mapping.

Twenty equine microsatellites were isolated from a genomic phage library, and their genetical and physical localization was sought by linkage mapping and fluorescent in situ hybridization (FISH). Nineteen of the markers were found to be polymorphic with, in most cases, heterozygosities exceeding 50%. The markers were mapped in a Swedish reference family for gene mapping, comprising eight half-sib families from Standardbred and Icelandic horse sires.

The genetical history of an isolated population of the endangered grey wolf Canis lupus: a study of nuclear and mitochondrial polymorphisms.

The grey wolf was thought to have been exterminated in the Scandinavian peninsula when the sudden appearance of a few animals in southern Sweden was reported in 1980. These wolves founded a new Swedish population which currently numbers at least 25 individuals, one of the world's smallest populations of the species. The sudden occurrence of the founder animals caused speculation that these had not appeared by 'natural' means but rather were Swedish zoo animals deliberately released by man.

First gene on the avian W chromosome (CHD) provides a tag for universal sexing of non-ratite birds.

The avian W chromosome shares many features with the mammalian Y chromosome: it is small, mostly heterochromatic, and filled with large repetitive arrays. No gene so far been assigned to the W chromosome in any bird species and, as a practical consequence, a general tag for avian gender identification on the molecular level is lacking. Here I describe the isolation of a chicken homologue to the mouse chromo-helicase-DNA binding (CHD) gene which encodes a protein involved in global regulation of transcriptional activation on the chromatin level.

Sex ratio adjustment in relation to paternal attractiveness in a wild bird population.

When the relative fitness of sons and daughters differs, sex-allocation theory predicts that it would be adaptive for individuals to adjust their investment in different sexes of offspring. Sex ratio adjustment by females in response to the sexual attractiveness of their mate would be an example of this. In vertebrates the existence of this form of sex ratio adjustment is controversial and may be confounded with sex-biased mortality, particularly in sexually size-dimorphic species.

A comprehensive linkage map of the pig based on a wild pig-Large White intercross.

A comprehensive linkage map, including 236 linked markers with a total sex-average map length of about 2300 cM, covering nearly all parts of the pig genome has been established. Linkage groups were assigned to approximately all 18 autosomes, the X chromosome and the X/Y pseudoautosomal region. Several new gene assignments were made including the assignment of linkage group U1 (EAK-HPX) to chromosome 9.

The extension coat color locus and the loci for blood group O and tyrosine aminotransferase are on pig chromosome 6.

A linkage map of pig chromosome 6 was constructed using a wild pig/Large White intercross pedigree. The map comprises 23 polymorphic loci, and the sex-average map length is approximately 170 cM. The study adds three new genes to the chromosome 6 map: the extension (E) coat color locus, and the blood group O (EAO) and tyrosine aminotransferase (TAT) loci.

A wide-range survey of cross-species microsatellite amplification in birds.

The possibility to perform cross-species microsatellite amplification in birds was surveyed by analysing sets of primers developed from the swallow and the pied flycatcher genomes on a panel of 48 different bird species. In total, 162 cases (species/marker combinations) of heterologous amplification were recorded. Ten amplification products were sequenced and all were found to be true homologues of the original loci.

Limited polymorphism at major histocompatibility complex (MHC) loci in the Swedish moose A. alces.

The Swedish moose was analysed for genetic variability at major histocompatibility complex (MHC) class I and class II DQA, DQB and DRB loci using restriction fragment length polymorphism (RFLP) and single strand conformation polymorphism (SSCP) techniques. Both methods revealed limited amounts of polymorphism. Since the SSCP analysis concerned an expressed DRB gene it can be concluded that the level of functional MHC class II polymorphism, at least at the DRB locus, is low in Swedish moose.

Genetic variation at the growth hormone locus in a wild pig intercross; test of association to phenotypic traits and linkage to the blood group D locus.

A polymorphism in the TATA-box of the porcine growth hormone (GH) gene was analysed in a wild pig/Large White intercross, in which 129 markers had been scored previously. Linkage analyses demonstrated that the GH locus belonged to a linkage group on chromosome 12 together with a previously unassigned marker, the erythrocyte antigen D (EAD) locus. The linear order of this linkage group is EAD-GH-S0096-S0090-S0106-arachidonate 12-lipoxygenase (ALOX12)-inhibin beta A (INHBA).

Resolving genetic relationships with microsatellite markers: a parentage testing system for the swallow Hirundo rustica.

Eight polymorphic microsatellite markers from the swallow were isolated and characterized. Extraordinary variability was revealed at the HrU6 locus with 45 different alleles scored among 46 unrelated individuals. The probability that the same genotype combination would occur in two random and unrelated individuals at six selected loci was as low as 1.