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The major histocompatibility complex (MHC) has a central role in the specific immune defence of vertebrates. Exon 3 of MHC class I genes encodes the domain that binds and presents peptides from pathogens that trigger immune reactions. Here we develop a fast population screening method for detecting genetic variation in the MHC class I genes of birds. We found evidence of at least 15 exon 3 sequences in the investigated great reed warbler individual. The organisation of the great reed warbler MHC class I genes suggested that a locus-specific screening protocol is impractical due to the high similarity between alleles across loci, including the introns flanking exon 3. Therefore, we used motif-specific PCR to amplify two subsets of alleles (exon 3 sequences) that were separated with by DGGE. The motif-specific primers amplify a substantial proportion of the transcribed class I alleles (2–12 alleles per individual) from as many as six class I loci. Although not exhaustive, this gives a reliable estimate of the class I variation. The method is highly repeatable and more sensitive in detecting genetic variation than the RFLP method. The motif-specific primers also allow us to avoid screening pseudogenes. In our study population of great reed warblers, we found a high level of genetic variation in MHC class I, and no less than 234 DGGE genotypes were detected among 248 screened individuals. [ABSTRACT FROM AUTHOR]

Atlantic salmon accumulate high levels of contaminants such as polychlorinated biphenyls (PCBs) in their lipids during the adult growth phase spent at sea. The lipids are later utilized during migration for swimming and biological adaptations. We hypothesize that migrating salmons' biotransformation processes are affected by the high levels of built-up PCBs compared to salmon that in a pre-migrational stage. For these analyses we sampled adult Atlantic salmon during migration in the Swedish River Mörrum and measured the 21 most common PCB congeners ( summation operatorPCB) and lipid levels in muscle tissue, aryl hydrocarbon receptor (AHR2) and cytochrome P4501A1 (CYP1A1) transcript levels as well as ethoxyresorufin-O-deethylase activity (EROD) in liver. We also determined which AHR2 genotypes the salmon carried. We show that EROD activity is correlated to CYP1A1 level but not to summation operatorPCB concentration. summation operatorPCB concentration does not predict levels of neither the AHR2 nor CYP1A1 genes. We find no associations between specific AHR2 transcription levels and AHR2 genotypes or a correlation between AHR2 and CYP1A1 transcription levels, which is in direct contrast to pre-migrational adult salmon from the Baltic Sea. When we compare River Mörrum to salmon we have previously sampled in the Baltic Sea we show that migrating salmon have significantly lower lipid levels in their muscles; higher muscle concentrations of summation operatorPCB on a lipid basis; and significantly lower CYP1A1 and EROD levels compared to salmon from the Baltic Sea. Also, transcript levels of three out of four AHR2 genes are significantly different. In conclusion, migrating Swedish Atlantic salmon carry higher concentrations of PCBs in their lipids compared to salmon in the Baltic Sea, but have lower activation of biotransformation genes and enzymes. Our results indicate that accumulated pollutants from the Baltic Sea are deactivated inside the migrating salmon's lipid tissues and increase in concentration when migration is initiated thereby limiting their impact on biotransformation processes.

The microarray technology has revolutionized biological research in the last decade. By monitoring the expression of many genes simultaneously, microarrays can elucidate gene function, as well as scan entire genomes for candidate genes encoding complex traits. However, because of high costs of sequencing and design, microarrays have largely been restricted to a few model species. Cross-species microarray (CSM) analyses, where microarrays are used for other species than the one they were designed for, have had varied success. We have conducted a CSM analysis by hybridizing genomic DNA from the common whitethroat (Sylvia communis) on a newly developed Affymetrix array designed for the zebra finch (Taeniopygia guttata), the Lund-zf array. The results indicate a very high potential for the zebra finch array to act as a CSM utility in other passerine birds. When hybridizing zebra finch genomic DNA, 98% of the gene representatives had higher signal intensities than the background cut-off, and for the common whitethroat, we found the equivalent proportion to be as high as 96%. This was surprising given the fact that finches and warblers diverged 25-50 million years ago, but may be explained by a relatively low sequence divergence between passerines (89-93%). Passerine birds are widely used in studies of ecology and evolution, and a zebra finch array that can be used for many species may have a large impact on future research directions., (© 2007 The Authors.)

The toxicity induced by several environmental pollutants is mediated by the aryl hydrocarbon receptor (AHR), which controls the expression of many biotransformation genes, such as cytochrome P4501A1 (CYP1A1). Previous studies have indicated that fish populations can evolve tolerance to persistent chlorinated pollutants by down-regulating the AHR pathway. Here, we measure to what extent tissue loads of polychlorinated biphenyl (PCB) congeners and AHR genotypes contribute to biotransformation capacity in wild, foraging Atlantic salmon (Salmo salar L.) from the Baltic Sea. In muscle, the sum of the 21 most common PCB congeners (ZPCB) was correlated with three extracted AHR agonists (PCBs 77/110, 118/123/149, and 105/132/153). Both the AHR agonists as well as sigmaPCB were correlated with lipid content. The sigmaPCB, controlled for the effects of sex and lipid content in muscle tissue, did not predict mRNA transcript levels of the measured AHRs (AHR2alpha, AHR2gamma, and AHR2delta) or CYP1A1 in liver. However, all AHR2 mRNA transcript levels were positively correlated with CYP1A1 level. In turn, the CYP1A1 level was negatively correlated with concentration of the muscle-tissue antioxidant astaxanthin, suggesting that astaxanthin is depleted when biotransformation processes (CYP1A1) are activated. No correlation was found between ethoxyresorufin-O-deethylase activity and sigmaPCB, CYP1A1, or antioxidant levels. In 5'-flanking regions of the AHR2 genes, we identified multiple allelic variants that were used for genotyping. The mRNA transcript level of AHR2alpha was significantly associated with the AHR2alpha 5'-flanking region genotype and with the interaction of the genotype and individual PCB level. These results suggest that in wild Atlantic salmon from the Baltic Sea, active production of AHR2 mRNA by means of PCB exposure may be affected by genetic polymorphisms at the AHR2 loci.

Malaria parasites are a widespread and species-rich group infecting many wild populations of mammals, birds and reptiles. Studies on humans have demonstrated that genetic factors play a key role in the susceptibility and outcome of malaria infections. Until the present study, it has not been examined whether genetic variation in hosts is important for the outcome of malaria infections in natural avian populations. We investigated associations between major histocompatibility complex (MHC) genes and prevalence of three different avian malaria parasites (Haemoproteus payevskyi (GRW1), Plasmodium sp. (GRW2) and Plasmodium sp. (GRW4)) in a long-term study of great reed warblers Acrocephalus arundinaceus. We hypothesized that the MHC genes could either give full protection against a malaria infection, or confer protection against lethal malaria and direct the infection towards being milder. We found a positive association between numbers of MHC class I alleles (a measure of level of heterozygosity) and prevalence of the GRW2 parasite, suggesting the latter scenario. There was also a positive association between a specific MHC allele (B4b), previously shown to be under frequency-dependent selection in the study population, and prevalence of GRW2. These associations suggest that individuals carrying either a large number of MHC alleles or a specific MHC allele are protected against lethal malaria infections.

The existence and nature of indirect genetic benefits to mate choice remain contentious. Major histocompatibility complex (MHC) genes, which play a vital role in determining pathogen resistance in vertebrates, may be the link between mate choice and the genetic inheritance of vigour in offspring. Studies have shown that MHC-dependent mate choice can occur in mammal and fish species, but little work has focused on the role of the MHC in birds. We tested for MHC-dependent mating patterns in the Seychelles warbler (Acrocephalus sechellensis). There was no influence of MHC class I exon 3 variation on the choice of social mate. However, females were more likely to obtain extra-pair paternity (EPP) when their social mate had low MHC diversity, and the MHC diversity of the extra-pair male was significantly higher than that of the cuckolded male. There was no evidence that females were mating disassortatively, or that they preferred males with an intermediate number of MHC bands. Overall, the results are consistent with the 'good genes' rather than the 'genetic compatibility' hypothesis. As female choice will result in offspring of higher MHC diversity, MHC-dependent EPP may provide indirect benefits in the Seychelles warbler if survival is positively linked to MHC diversity.

Aryl hydrocarbon receptor (AhR) genes encode proteins involved in mediating the toxic responses induced by several environmental pollutants. Here, we describe the identification of the first two AhR1 (alpha and beta) genes and two additional AhR2 (alpha and beta) genes in the tetraploid species Atlantic salmon (Salmo salar L.) from a cosmid library screening. Cosmid clones containing genomic salmon AhR sequences were isolated using a cDNA clone containing the coding region of the Atlantic salmon AhR2gamma as a probe. Screening revealed 14 positive clones, from which four were chosen for further analyses. One of the cosmids contained genomic AhR sequences that were highly similar to the rainbow trout (Oncorhynchus mykiss) AhR2alpha and beta genes. SMART RACE amplified two complete, highly similar but not identical AhR type 2 sequences from salmon cDNA, which from phylogenetic analyses were determined as the rainbow trout AhR2alpha and beta orthologs. The salmon AhR2alpha and beta encode proteins of 1071 and 1058 residues, respectively, and encompass characteristic AhR sequence elements like a basic-helix-loop-helix (bHLH) and two PER-ARNT-SIM (PAS) domains. Both genes are transcribed in liver, spleen and muscle tissues of adult salmon. A second cosmid contained partial sequences, which were identical to the previously characterized AhR2gamma gene. The last two cosmids contained partial genomic AhR sequences, which were more similar to other AhR type 1 fish genes than the four characterized salmon AhR2 genes. However, attempts to amplify the corresponding complete cDNA sequences of the inserts proved very difficult, suggesting that these genes are non-functional or very weakly transcribed in the examined tissues. Phylogenetic analyses of the conserved regions did, however, clearly indicate that these two AhRs belong to the AhR type 1 clade and have been assigned as the Atlantic salmon AhR1alpha and AhR1beta genes. Taken together, these findings demonstrate that multiple AhR genes are present in Atlantic salmon genome, which likely is a consequence of previous genome duplications in the evolutionary past of salmonids. Plausible explanations for the high incidence of AhR genes in fish and more specifically in salmonids, like rapid divergences in specialized functions, are discussed.

The aryl hydrocarbon receptor (AhR) mediates the toxicity of several environmental contaminants, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin, and other halogenated hydrocarbons in vertebrates. This receptor initiates the transcription of several biotransformation enzymes, which in turn are responsible for causing severe harm to biological tissue. Here we describe the isolation and complete characterization of the first two AhR genes from the teleost fish Atlantic salmon (Salmo salar). The predicted amino acid sequences contain regions characteristic of other vertebrate AhRs including basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains but show little similarity to other vertebrate AhRs across the C-terminal half. Furthermore, they do not contain distinct Q-rich domains as found in the mammalian AhR, which is in line with previously described fish AhR genes. The salmon cDNAs encode 1106 and 1107 putative residues, respectively, approximately 50 amino acids longer than previously characterized AhR genes. Phylogenetic analyses demonstrated that the two salmon AhR sequences cluster within the AhR subfamily of the bHLH-PAS family, in a clade containing fish AhR2 genes. Although the two AhR2 forms are 92% identical at the amino acid level, the distribution of sequence differences and the presence of both forms in 30 tested individuals suggest that they are not allelic but derived from separate loci. Interestingly, they are not orthologs of the rainbow trout (Oncorhynchus mykiss) AhR2 alpha and beta genes and the new salmon loci are therefore here designated AhR2 gamma and AhR2 delta. In line with this, PCR with DNA from rainbow trout revealed a new trout AhR locus that was more similar to the two salmon genes than to the trout AhR2 alpha and beta genes, suggesting that the rainbow trout possesses at least three distinct AhR2 genes. The presence of multiple AhR genes in these species is probably a consequence of the genome duplications that occurred in the early evolution of fish and later also specifically in the salmonid lineage. Reverse transcription-PCR analyses revealed that both AhR2 gamma and AhR2 delta are transcribed in the liver, spleen and muscles of adult salmon.

The extreme polymorphism found at some major histocompatibility complex (MHC) loci is believed to be maintained by balancing selection caused by infectious pathogens. Experimental support for this is inconclusive. We have studied the interaction between certain MHC alleles and the bacterium Aeromonas salmonicida, which causes the severe disease furunculosis, in Atlantic salmon (Salmo salar L.). We designed full-sibling broods consisting of combinations of homozygote and heterozygote genotypes with respect to resistance or susceptibility alleles. The juveniles were experimentally infected with A. salmonicida and their individual survival was monitored. By comparing full siblings carrying different MHC genotypes the effects on survival due to other segregating genes were minimized. We show that a pathogen has the potential to cause very intense selection pressure on particular MHC alleles; the relative fitness difference between individuals carrying different MHC alleles was as high as 0.5. A co-dominant pattern of disease resistance/susceptibility was found, indicative of qualitative difference in the immune response between individuals carrying the high- and low-resistance alleles. Rather unexpectedly, survival was not higher among heterozygous individuals as compared with homozygous ones.

We sequenced exon 2 of the MHC class II B gene in Atlantic salmon from the Baltic Sea and identified 17 different exon 2 alleles among 22 different restriction fragment length polymorphism haplotypes. The sequences differed at between 1 and 34 bases. Two different tests were used to estimate the importance of recombination in the generation of new alleles. Recombination events appear to have occurred between three and nine times. Only two pairs of sequences differed by less than five nucleotides, minimizing the importance of point mutations for generating new alleles. Phylogenetic analysis showed that sequences did not cluster according to populations, and genetic distances between populations were small compared to those obtained by allele frequency data. These results, together with the similarity found between exon 2 sequences from Baltic salmon and Norwegian salmon, indicate that all of the identified alleles were present in the ancient salmon population colonizing the Baltic rivers after the last glaciation.

We have tested the importance of genetic variation in the major histocompatibility complex (MHC) class IIB in Atlantic salmon (Salmo salar) for survival after challenge with a highly virulent bacterial pathogen. Forty juvenile full siblings from each of 120 families were infected with the bacterium Aeromonas salmonicida, which causes high mortality in salmon due to furunculosis. Fishes from high-resistance (HR, < 35% mortality) and low-resistance (L,R, > 80% mortality) families were screened for their MHC class IIB genotypes using the denaturing gradient gel electrophoresis (DGGE) technique. The exon 2 sequences, encoding the major part of the peptide-binding region, were established for each DGGE fragment. One allele, e, containing a missense single base substitution was significantly more prevalent in HR families than in LR families. An odds-ratio test showed that broods carrying this allele had a 12-fold higher chance of being HR than broods without the e allele. A second allele, i, showed significantly higher frequencies in uninfected and surviving individuals than in infected dead individuals. A third allele, j, tended to more prevalent both in LR families and in individuals that had died of the infection. There was no correlation between MHC heterozygosity and resistance to A. salmonicida. Our results support the hypothesis that MHC polymorphism is maintained through pathogen-driven selection acting by means of frequency-dependent selection rather than heterozygous advantage.

Humans express an array of Mhc genes, while the chicken has an Mhc that is relatively small and compact with fewer expressed genes. Here we ask whether the "minimal essential Mhc" of the chicken is representative for birds. We investigated the RFLP genotypes in 55 great reed warblers Acrocephalus arundinaceus and 10 willow warblers Phylloscopus trochilus to obtain an overview of the number of class II B genes. There were 13-17 bands per individual in the great reed warblers and 25-30 in the willow warblers, and every individual had a unique RFLP genotype. The high number of RFLP bands indicates that both species have a large number of class II B genes although some may be pseudogenes. Seven different class II B sequences were detected in a great reed warbler cDNA library. There was considerable sequence divergence between the cDNA sequences in exon 2 (peptide-binding region, PBR), whereas they were very similar in exon 3. The cDNA sequences were easily alignable to a classical chicken class II B sequence, and balancing selection was acting in the PBR. One of the cDNA sequences had two deletions and is likely nonfunctional. Finally, the polymorphic class I and class II B RFLP fragments seemed to be linked in the five studied great reed warbler families. These and previous results suggest that birds of the order Passeriformes in general have more Mhc class I and II B genes than birds of the order Galliformes. This difference could be caused by their phylogenetic past, and/or by variance in the selection pressure for maintaining a high number of Mhc genes.

Human gliomas express TGF-beta but, so far the expression of downstream mediators has been investigated in only a few cell lines. We have examined tissue specimens of 23 gliomas: 3 astrocytomas grade II (AST), 8 anaplastic astrocytomas grade III (AAST), and 12 glioblastoma multiforme grade IV (GBM). We analyzed the mRNA expression of TGF-beta1, TGF-beta2, TGF-beta3, the TGF-beta receptors type I (TbetaR-I) and type II (TbetaR-II), Smad2, Smad3, and Smad4. mRNA expression of IL-10 and CD95 (FAS/APO-1) were also studied. We detected increased mRNA levels of the 3 TGF-beta isoforms, correlating with the degree of malignancy. TGF-beta3 mRNA was increased, particularly in AST and AAST, while TGF-beta1 and TGF-beta2 mRNAs were strongly expressed in GBM. TGF-beta normally up-regulates the TGF-beta receptors, and TbetaR-I and TbetaR-II showed stronger expression in all gliomas when compared to normal tissues. However, the mRNA expression of Smad2, Smad3, and Smad4 was decreased in GBM. IL-10 mRNA expression was detected in glioma tissues but not in glioma cell lines. No marked increase in the expression of soluble CD95 splicing variants was found in the gliomas compared with normal tissue. However, total CD95 mRNA was elevated among GBM tissues., (Copyright 2000 Wiley-Liss, Inc.)

We compared three different molecular methods currently used for screening of Mhc variation in population studies of Atlantic salmon. Restriction fragment length polymorphism (RFLP) of the entire class II gene detected 22 haplotypes. Seventeen exon 2 sequences were obtained from individuals carrying the 22 haplotypes, two of which had not been detected by RFLP. The six alleles (27%) detected by RFLP and not by exon 2 sequencing probably resulted from sequence variation outside exon 2. Within exon 2, RFLP differentiated 88% of the sequences. Alternatively, denaturing gradient gel electrophoresis (DGGE) performed under two run conditions detected 94% of the sequence variation. Both RFLP using different probes, and the two PCR-based methods using three different primer pairs, suggest that there is only a single Mhc class II B gene in the Baltic populations of Atlantic salmon.

The class I genes of the major histocompatibility complex (Mhc) are here investigated for the first time in a passerine bird. The great reed warbler is a rare species in Sweden with a few semi-isolated populations. Yet, we found extensive Mhc class I variation in the study population. The variable exon 3, corresponding to the alpha2 domain, was amplified from genomic DNA with degenerated primers. Seven different genomic class I sequences were detected in a single individual. One of the sequences had a deletion leading to a shift in the reading frame, indicating that it was not a functional gene. A randomly selected clone was used as a probe for restriction fragment length polymorphism (RFLP) studies in combination with the restriction enzyme Pvu II. The RFLP pattern was complex with 21-25 RFLP fragments per individual and extensive variation. Forty-nine RFLP genotypes were detected in 55 tested individuals. To study the number of transcribed genes, we isolated 14 Mhc class I clones from a cDNA library from a single individual. We found eight different sequences of four different lengths (1.3-2.2 kilobases), suggesting there are at least four transcribed loci. The number of nonsynonymous substitutions (dN) in the peptide binding region of exon 3 were higher than the number of synonymous substitutions (dS), indicating balancing selection in this region. The number of transcribed genes and the numerous RFLP fragments found so far suggest that the great reed warbler does not have a "minimal essential Mhc" as has been suggested for the chicken.

The immune and the detoxication systems of animals are characterized by allelic polymorphisms, which underlie individual differences in ability to combat assaults from pathogens and toxic compounds. Previous studies have shown that females may improve offspring survival by selecting mates on the basis of sexual ornaments and signals that honestly reveal health. In many cases the expression of these ornaments appears to be particularly sensitive to oxidative stress. Activated immune and detoxication systems often generate oxidative stress by an extensive production of reactive metabolites and free radicals. Given that tolerance or resistance to toxic compounds and pathogens can be inherited, female choice should promote the evolution of male ornaments that reliably reveal the status of the bearers' level of oxidative stress. Hence, oxidative stress may be one important agent linking the expression of sexual ornaments to genetic variation in fitness-related traits, thus promoting the evolution of female mate choice and male sexual ornamentation, a controversial issue in evolutionary biology ever since Darwin.

Human tumor and normal tissue specimens, which were collected from autopsy material 1-6 days postmortem, were compared with similar tissue specimens collected within 2 h after surgical resection and transport to the pathology department. The end point criteria used to evaluate the quality of the specimens for biological banking purposes were the extractability and yield of high molecular weight DNA and UV absorption ratios at 260:280 after collection and immediate storage of the specimens at -80 degrees C. The data demonstrated that autopsy material was a quality source of DNA, although of not such high quality as surgical biopsy specimens <2 h after resection. The advantages of using autopsy material to supplement surgical specimen collection sent to pathology, as opposed to using specimen collection at surgery wards or formalin-fixed material, as sources of DNA are: (a) large amounts of tumor and normal tissues from a variety of organ sites can be obtained without regard to the patient's health status; (b) a higher percentage of retrieval of incident cases of cancer in prospective designed trials is more likely to be achieved; and (c) the extractable DNA is of sufficiently high enough quality to permit direct analyses by molecular hybridization and sequence methodologies.

The major histocompatibility complex (MHC) has been studied in a multitude of mammals by now, but much less is known about its organisation and variation in other vertebrate species. The mammalian MHC is organised as a single gene cluster, but recent studies on birds suggest that this paradigm of MHC organisation has to be supplemented. The domestic chicken thus possesses two separate gene clusters which both contain MHC class I and class II B genes, and we have shown that the ring-necked pheasant Phasianus colchicus also has two unlinked clusters of class II B genes. We are studying the effect of the MHC on mate choice, survival and reproductive success in natural populations of birds and reptiles. For this reason, we are developing DNA techniques to determine the animals' MHC genotype. The amplification of the hypervariable exon 3 of the class I gene from songbirds and reptiles has provided us with species specific probes that can be used in Southern blot analysis. The first results indicate very extensive variation in all studied species, that is starlings Sturnus vulgaris, great reed warblers Acrocephalus arundinaceus and water pythons Liasis fuscus. The restriction fragment length polymorphism (RFLP) analysis also suggests that the number of MHC genes is significantly larger in these species than in pheasants and domestic chickens.

The major histocompatibility complex (MHC) is an immunologically important cluster of highly variable genes that is known to affect fitness in domesticated mammals and birds. Spur length of male pheasants in southern Sweden correlates with male viability, female mate choice, and offspring survival rate. Here we show by genetic analyses that the MHC genotype is associated with variation in both male spur length and male viability. These are the first data that directly support a 'good genes' hypothesis by Hamilton and Zuk predicting that females discriminate among males on the basis of secondary sexual characters in order to pass on genes for disease resistance that improve fitness in their offspring.

The DNA-fingerprinting technique was used to find the true pedigrees and to detect the overall genetic similarity between mates of great reed warblers (Acrocephalus arundinaceus) at an isolated breeding site in Sweden. The study covered 4 yr preceded by 3 yr when almost all adults and nestlings in the study area had been banded. DNA fingerprinting revealed that the putative father had sired 97% of the young (N = 455). The mate's genetic similarity, revealed as the proportion of bands shared in restriction fragment length polymorphism (RFLP) patterns, was high compared with other species of wild birds. Also, band sharing was higher between mates native to the area than between pairs in which the female was experimentally introduced from a distant breeding site. Hatching success of eggs was negatively correlated with the degree of genetic similarity between the mates, whereas pedigree data, up to the level of great-grandparents, clearly demonstrated an absence of close inbreeding. These are the first data showing a significant fitness cost associated with the choice of a mate that has high genetic similarity, even if it is not a close kin. This cost might be caused by generalized negative consequences of genomewide inbreeding in the present study, possibly accentuated by recent population bottlenecks., (© 1994 The Society for the Study of Evolution.)

We investigated the class II B genes in a free-ranging population of the ring-necked pheasant Phasianus colchicus by a combination of restriction fragment length polymorphism (RFLP), polymerase chain reaction (PCR), and DNA sequencing. Special attention was paid to the variation in the second exon, which encodes the peptide-binding beta 1-domain. The population was introduced, but it still exhibited major histocompatibility complex polymorphism with at least three segregating class II B haplotypes and consequently six genotypes. We found two class II B genes associated with each haplotype. The class II B genes of birds had until then only been molecularly characterized in the domestic chicken. The pheasant genes were highly variable, although one of the amplified sequences was found in two different haplotypes. Taken together, the most polymorphic positions (residues 37 and 38) were not identical in any of the predicted protein sequences, but all except one of the motifs had already been found in the domestic chicken. Structurally important features in mammalian class II B genes were generally conserved also in the pheasant sequences, but the loss of a potential salt bridge constituent (Arg72) in several sequences may suggest a slightly different structure of the adjacent parts of the peptide-binding groove. The pheasant genes are most closely related to the so called B-LBII family in the chicken, indicating that this represents a major line of development among avian class II B genes.

Recent theory on sexual selection suggests that females in species without paternal care choose mates by their secondary sexual characters because these indicate genotypic quality which will be transmitted to the offspring. These ideas are not yet empirically supported as data quantifying the relationship between female mate choice and female reproductive success are lacking. Only in one case, in Colias butterflies, has it been demonstrated unequivocally that females choose 'good genotypes' as mates and there is only one study, on Drosophila, demonstrating that mate choice increases one component of offspring fitness. Spur length of male pheasants (Phasianus colchicus) correlates with various fitness-related properties. We here present the first experimental field data showing that female pheasants select mates on the basis of male spur length and that female mate choice correlates with female reproductive success.