Patterns of polymorphism in the MHC class II of a non-passerine bird,the great snipe (<Emphasis Type="Italic">Gallinago media</Emphasis>)

The genomic organisation of the major histocompatibility complex (MHC) seems to vary considerably between different bird species. In order to understand this variation it is important to gather information from different species. We have, for the first time, investigated MHC class II polymorphism in a wader species, the great snipe (Gallinago media). Eleven alleles were found in five sequenced individuals; these come from at least three different loci, but RFLP data suggest that a larger number of genes may be present. For MHC genes, amino acid substitutions followed the, for MHC genes, general pattern of high non-synonymous substitution rates in peptide-binding regions, suggesting that the sequenced alleles may be expressed. The number of genes, lengths of introns and exon sequences of the great snipe MHC seem to be intermediate between those of chicken and passerine birds.     

Characterization of MHC class II B polymorphism in bottlenecked New Zealand saddlebacks reveals low levels of genetic diversity

The major histocompatibility complex (MHC) is integral to the vertebrate adaptive immune system. Characterizing diversity at functional MHC genes is invaluable for elucidating patterns of adaptive variation in wild populations, and is particularly interesting in species of conservation concern, which may suffer from reduced genetic diversity and compromised disease resilience. Here, we use next generation sequencing to investigate MHC class II B (MHCIIB) diversity in two sister taxa of New Zealand birds: South Island saddleback (SIS), Philesturnus carunculatus, and North Island saddleback (NIS), Philesturnus rufusater. These two species represent a passerine family outside the more extensively studied Passerida infraorder, and both have experienced historic bottlenecks. We examined exon 2 sequence data from populations that represent the majority of genetic diversity remaining in each species. A high level of locus co-amplification was detected, with from 1 to 4 and 3 to 12 putative alleles per individual for South and North Island birds, respectively. We found strong evidence for historic balancing selection in peptide-binding regions of putative alleles, and we identified a cluster combining non-classical loci and pseudogene sequences from both species, although no sequences were shared between the species. Fewer total alleles and fewer alleles per bird in SIS may be a consequence of their more severe bottleneck history; however, overall nucleotide diversity was similar between the species. Our characterization of MHCIIB diversity in two closely related species of New Zealand saddlebacks provides an important step in understanding the mechanisms shaping MHC diversity in wild, bottlenecked populations.     

Factors affecting avian cross-species microsatellite amplification

Compilation and analysis of information from the literature regarding cross-species microsatellite amplification and polymorphism success, and relating this to source-target species genetic distance as estimated by pairwise cytochrome b ( cytb ) divergence, enabled an in-depth investigation of factors affecting avian cross-species microsatellite amplification. Source-target species cytb distances provided accurate estimates of cross-species microsatellite amplification/polymorphism success rates not only in birds, but also in taxa where microsatellites cross-amplify across contrasting levels of taxonomic classification (frogs and cetaceans). As cytb is one of the most commonly sequenced DNA regions, pairwise cytb genetic distances should therefore be useful for predicting cross-species microsatellite success across a range of taxonomic groups. While the most important factor affecting cross-species microsatellite amplification/polymorphism success was a negative association with source-target species genetic distance, associations with additional features affecting cross-species amplification/polymorphism success included: decreasing PCR annealing temperature significantly increasing the chance of successful cross-species amplification, and a significant positive association between source species polymorphism and the proportion of target species in which a locus revealed polymorphism. No association between cross-species amplification and repeat motif (di-, tri-, or tetranucelotide) or repeat structure (perfect, imperfect, or compound) was observed. A set of nine loci which cross-amplified across an unusually broad range of passerine bird species were also identified, and could serve as a good starting point for cross-species amplification testing in passerine species for which insufficient loci are available.     

Extremely high MHC class I variation in a population of a long-distance migrant,the Scarlet Rosefinch (<Emphasis Type="Italic">Carpodacus erythrinus</Emphasis>)

Although the number of studies focusing on the major histocompatibility complex (MHC) in non-model vertebrates is increasing, results are often contradictory, and the structure of MHC is still poorly understood in wild species. Here, we describe the structure and diversity of exon 3 of MHC class I in a passerine bird, the Scarlet Rosefinch (Carpodacus erythrinus). Using capillary electrophoresis single-strand conformation polymorphism, we identified 82 different MHC class I variants in one Rosefinch population nesting at one site in the Czech Republic. Thus far, this is the highest intra-populational MHC class I variation observed in birds. We have not found support for ‘minimal essential’ MHC in this species since individuals exhibited between three and nine different exon 3 sequences, indicating that there may be at least five amplified MHC class I genes. By cloning, we obtained and analysed 29 exon sequences and found that all of them could be translated into potentially functional proteins. We also show that strong positive selection appears to be acting mainly, but not only, on previously described antigen-binding sites in MHC class I genes. Furthermore, our results indicate that recombination has played an important role in generating genetic diversity of these genes in the Scarlet Rosefinch; we discuss the significance of this extremely high genetic diversity in light of the life history traits of this species, such as long-distance migration. The sequence data described in this paper are accessible in GenBank data library under accession numbers FJ392762–FJ392790.     

Rapid parallel evolution of aberrant traits in the diversification of the Gulf of Guinea white-eyes (Aves, Zosteropidae)

Archipelago-endemic bird radiations are familiar to evolutionary biologists as key illustrations of evolutionary patterns. However, such radiations are in fact rare events. White-eyes (Zosteropidae) are birds with an exceptionally high colonization and speciation potential; they have colonized more islands globally than any other passerine group and include the most species-rich bird genus. The multiplication of white-eye island endemics has been consistently attributed to independent colonizations from the mainland; the white-eyes of the Gulf of Guinea archipelago had been seen as a classic case, spanning as great a breadth of phenotypic diversity as the family worldwide. Contrary to this hypothesis, our molecular phylogenetic analysis places the Gulf of Guinea white-eyes in just two radiations, one grouping all five oceanic island taxa and the other grouping continental island and land-bridge taxa. Numerous 'aberrant' phenotypes (traditionally grouped in the genus Speirops) have evolved independently over a short space of time from nonaberrant (Zosterops) phenotypes; the most phenotypically divergent species have separated as recently as 0.22 Ma. These radiations rival those of Darwin's finches and the Hawaiian honeycreepers in terms of the extent of adaptive radiation per unit time, both in terms of species numbers and in terms of phenotypic diversity. Tempo and patterns of morphological divergence are strongly supportive of an adaptive radiation in the oceanic islands driven by ecological interactions between sympatric white-eyes. Here, very rapid phenotypic evolution mainly affected taxa derived from the youngest wave of colonization, in accordance with the model of asymmetric divergence owing to resource competition in sympatry.     

Patterns of variation in MHC class II beta loci of the little greenbul (Andropadus virens) with comments on MHC evolution in birds

We have isolated major histocompatibility complex (MHC) class II beta loci from the little greenbul (Andropadus virens), an African songbird. We utilized preexisting information about conserved regions of the avian MHC to design primers to amplify a pool of sequences representing multiple loci. From this pool, a unique locus spanning 1109 bp that we designate as Anvi-DAB1 was cloned and sequenced. We designed locus-specific primers based on this sequence information and amplified six alleles from seven individuals. Compared to other A. virens MHC sequences obtained from genomic DNA or cDNA, the variability of sequences from Anvi-DAB1 was low and the ratio of nonsynonymous to synonymous substitution was much less than one, suggesting that Anvi-DAB1 may either be a pseudogene or a nonclassical MHC locus. Phylogenetic analysis revealed that the Anvi-DAB1 locus was highly divergent when compared with other passerine or A. virens genomic or transcribed MHC sequences. The use of conserved MHC primers followed by analysis of cloned sequences allows rapid isolation of MHC loci from exotic species and avoids laborious large-scale cloning and sequencing.     

Gene duplication and gene conversion in class II MHC genes of New Zealand robins (Petroicidae)

In contrast to mammals, the evolution of MHC genes in birds appears to be characterized by high rates of gene duplication and concerted evolution. To further our understanding of the evolution of passerine MHC genes, we have isolated class II B sequences from two species of New Zealand robins, the South Island robin (Petroica australis australis), and the endangered Chatham Island black robin (Petroica traversi). Using an RT-PCR based approach we isolated four transcribed class II B MHC sequences from the black robin, and eight sequences from the South Island robin. RFLP analysis indicated that all class II B loci were contained within a single linkage group. Analysis of 3-untranslated region sequences enabled putative orthologous loci to be identified in the two species, and indicated that multiple rounds of gene duplication have occurred within the MHC of New Zealand robins. The orthologous relationships are not retained within the coding region of the gene, instead the sequences group within species. A number of putative gene conversion events were identified across the length of our sequences that may account for this. Exon 2 sequences are highly diverse and appear to have diverged under balancing selection. It is also possible that gene conversion involving short stretches of sequence within exon 2 adds to this diversity. Our study is the first report of putative orthologous MHC loci in passerines, and provides further evidence for the importance of gene duplication and gene conversion in the evolution of the passerine MHC.Nucleotide sequence data reported in this paper are available in the GenBank database under the accession numbers AY258333–AY258335, AY428561–AY428570, and AY530534–AY530535     

Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations

The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans‐species evolution).     

Genetic variation and bill size dimorphism in a passerine bird, the reed bunting Emberiza schoeniclus

In passerine birds morphological differentiation in bill size within species is not commonly observed. Bill size is usually associated with a trophic niche, and strong differences in it may reflect the process of genetic differentiation and, possibly, speciation. We used both mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic variation between two subspecies of reed bunting, Emberiza schoeniclus schoeniclus and E.s. intermedia , along their distributional boundary in western Europe. These two subspecies are characterized by a high dimorphism in bill size and, although breeding populations of the two subspecies are found very close to each other in northern Italy, apparently no interbreeding occurs. The observed morphological pattern between the two subspecies may be maintained by geographically varying selective forces or, alternatively, may be the result of a long geographical separation followed by a secondary contact. MtDNA sequences of cytochrome b and ND5 (515 bp) showed little variation and did not discriminate between the two subspecies, indicating a divergence time of less than 500 000 years. The analysis of four microsatellite loci suggested a clear, although weak, degree of genetic differentiation in the large- and small-billed populations, as indicated by F _ST and R _ST values and genetic distances. The correlation between bill size and genetic distance between populations remained significant after accounting for the geographical distances between sampling localities. Altogether, these results indicate a very recent genetic differentiation between the two bill morphs and suggest that a strong selection for large bills in the southern part of the breeding range is probably involved in maintaining the geographical differentiation of this species.     

Genetic diversity of MHC class I loci in six non-model frogs is shaped by positive selection and gene duplication

Comparative studies of major histocompatibility complex (MHC) genes across vertebrate species can reveal the evolutionary processes that shape the structure and function of immune regulatory proteins. In this study, we characterized MHC class I sequences from six frog species representing three anuran families (Hylidae, Centrolenidae and Ranidae). Using cDNA from our focal species, we amplified a total of 79 unique sequences spanning exons 2-4 that encode the extracellular domains of the functional alpha chain protein. We compared intra- and interspecific nucleotide and amino-acid divergence, tested for recombination, and identified codon sites under selection by estimating the rate of non-synonymous to synonymous substitutions with multiple codon-based maximum likelihood methods. We determined that positive (diversifying) selection was acting on specific amino-acid sites located within the domains that bind pathogen-derived peptides. We also found significant signals of recombination across the physical distance of the genes. Finally, we determined that all the six species expressed two or three putative classical class I loci, in contrast to the single locus condition of Xenopus laevis. Our results suggest that MHC evolution in anurans is a dynamic process and that variation in numbers of loci and genetic diversity can exist among taxa. Thus, the accumulation of genetic data for more species will be useful in further characterizing the relative importance of processes such as selection, recombination and gene duplication in shaping MHC loci among amphibian lineages.     

Evidence of gene orthology and trans‐species polymorphism,but not of parallel evolution,despite high levels of concerted evolution in the major histocompatibility complex of flamingo species

The major histocompatibility complex (MHC) is a cornerstone in the study of adaptive genetic diversity. Intriguingly, highly polymorphic MHC sequences are often not more similar within species than between closely related species. Divergent selection of gene duplicates, balancing selection maintaining trans‐species polymorphism (TSP) that predate speciation and parallel evolution of species sharing similar selection pressures can all lead to higher sequence similarity between species. In contrast, high rates of concerted evolution increase sequence similarity of duplicated loci within species. Assessing these evolutionary models remains difficult as relatedness and ecological similarities are often confounded. As sympatric species of flamingos are more distantly related than allopatric species, flamingos represent an ideal model to disentangle these evolutionary models. We characterized MHC Class I exon 3, Class IIB exon 2 and exon 3 of the six extant flamingo species. We found up to six MHC Class I loci and two MHC Class IIB loci. As all six species shared the same number of MHC Class IIB loci, duplication appears to predate flamingo speciation. However, the high rate of concerted evolution has prevented the divergence of duplicated loci. We found high sequence similarity between all species regardless of codon position. The latter is consistent with balancing selection maintaining TSP, as under this mechanism amino acid sites under pathogen‐mediated selection should be characterized by fewer synonymous codons (due to their common ancestry) than under parallel evolution. Overall, balancing selection maintaining TSP appears to result in high MHC similarity between species regardless of species relatedness and geographical distribution.     

Characterization of MHC class I and II genes in a subantarctic seabird,the blue petrel, <Emphasis Type="Italic">Halobaena caerulea</Emphasis> (Procellariiformes)

The great polymorphism observed in the major histocompatibility complex (MHC) genes is thought to be maintained by pathogen-mediated selection possibly combined with MHC-disassortative mating, guided by MHC-determined olfactory cues. Here, we partly characterize the MHC class I and II B of the blue petrel, Halobaena caerulea (Procellariiformes), a bird with significant olfactory abilities that lives under presumably low pathogen burdens in Subantarctica. Blue petrels are long-lived, monogamous birds which suggest the necessity of an accurate mate choice process. The species is ancestral to songbirds (Passeriformes; many MHC loci), although not to gamefowls (Galliformes; few MHC loci). Considering the phylogenetic relationships and the low subantarctic pathogen burden, we expected few rather than many MHC loci in the blue petrel. However, when we analysed partial MHC class I and class II B cDNA and gDNA sequences we found evidence for as many as at least eight MHC class I loci and at least two class II B loci. These class I and II B sequences showed classical MHC characteristics, e.g. high nucleotide diversity, especially in putative peptide-binding regions where signatures of positive selection was detected. Trans-species polymorphism was found between MHC class II B sequences of the blue petrel and those of thin-billed prion, Pachyptila belcheri, two species that diverged ∼25 MYA. The observed MHC allele richness in the blue petrel may well serve as a basis for mate choice, especially since olfactory discrimination of MHC types may be possible in this species.     

Diversity of North American map and sawback turtles (Testudines: Emydidae: Graptemys)

Map turtles of the genus Graptemys are native to North America, where a high degree of drainage endemism is believed to have shaped current diversity. With 14 species and one additional subspecies, Graptemys represents the most diverse genus in the family Emydidae. While some Graptemys species are characterized by pronounced morphological differences, previous phylogenetic analyses have failed yet to confirm significant levels of genetic divergence for many taxa. As a consequence, it has been debated whether Graptemys is taxonomically inflated or whether the low genetic divergence observed reflects recent radiations or ancient hybridization. In this study, we analysed three mtDNA blocks (3228 bp) as well as 12 nuclear loci (7844 bp) of 89 specimens covering all species and subspecies of Graptemys. Our analyses of the concatenated mtDNA sequences reveal that the widespread G. geographica constitutes the sister taxon of all other Graptemys species. These correspond to two clades, one comprised of all broad‐headed Graptemys species and another clade containing the narrow‐headed species. Most species of the broad‐headed clade are reciprocally monophyletic, except for G. gibbonsi and G. pearlensis, which are not differentiated. By contrast, in the narrow‐headed clade, many currently recognized species are not monophyletic and divergence is significantly less pronounced. Haplotype networks of phased nuclear loci show low genetic divergence among taxa and many shared haplotypes. Principal component analyses using coded phased nuclear DNA sequences revealed eight distinct clusters within Graptemys that partially conflict with the terminal mtDNA clades. This might be explained by male‐mediated gene flow across drainage basins and female philopatry within drainage basins. Our results support that Graptemys is taxonomically oversplit and needs to be revised.     

c-mos variation in songbirds: molecular evolution, phylogenetic implications, and comparisons with mitochondrial differentiation

Nucleotide sequences from the c-mos proto-oncogene have previously been used to reconstruct the phylogenetic relationships between distantly related vertebrate taxa. To explore c-mos variation at shallower levels of avian divergence, we compared c-mos sequences from representative passerine taxa that span a range of evolutionary differentiation, from basal passerine lineages to closely allied genera. Phylogenetic reconstructions based on these c-mos sequences recovered topologies congruent with previous DNA-DNA hybridization-based reconstructions, with many nodes receiving high support, as indicated by bootstrap and reliability values. One exception was the relationship of Acanthisitta to the remaining passerines, where the c-mos-based searches indicated a three-way polytomy involving the Acanthisitta lineage and the suboscine and oscine passerine clades. We also compared levels of c-mos and mitochondrial differentiation across eight oscine passerine taxa and found that c-mos nucleotide substitutions accumulate at a rate similar to that of transversion substitutions in mitochondrial protein-coding genes. These comparisons suggest that nuclear-encoded loci such as c-mos provide a temporal window of phylogenetic resolution that overlaps the temporal range where mitochondrial protein-coding sequences have their greatest utility and that c-mos substitutions and mtDNA transversions can serve as complementary, informative, and independent phylogenetic markers for the study of avian relationships.     

Non-monophyly and deep genetic differentiation across low-elevation barriers in a Neotropical montane bird (Basileuterus tristriatus; Aves: Parulidae)

Most widespread birds of Neotropical cloud forests exhibit phenotypic variation that is partitioned geographically suggesting allopatric divergence, but little is known about the extent to which such phenotypic differentiation is consistent with genetic variation. We studied geographic patterns of genetic differentiation in the Three-striped Warbler (Basileuterus tristriatus), a polytypic and widespread understory bird of the foothills and mid-elevation zone of the tropical Andes and adjacent mountains of Central and South America. We sequenced mitochondrial DNA for 196 samples covering the entire range of B. tristriatus, as well as 22 samples of its putative closest relatives: the Three-banded (B. trifasciatus) and Santa Marta (B. basilicus) warblers. We found deep genetic structure across the range of B. tristriatus, which consisted of ten major clades including B. trifasciatus, a species that was nested within B. tristriatus. In contrast, B. basilicus was not closely related to B. tristriatus but part of a clade of Myiothlypis warblers. Geographic boundaries among clades were clearly related to lowland gaps separating subspecies groups. The subspecies melanotis of the mountains of Central America was sister to a large clade including B. t. tacarcunae, and the rest of South American clades, including B. trifasciatus. Five clades are found in the northern Andes, where no signs of gene flow were found across barriers such as the Táchira Depression or the Magdalena valley. Our study highlights the importance of valleys in promoting and maintaining divergence in a lower montane forest bird. The substantial genetic and phenotypic differentiation, and the paraphyly uncovered in B. tristriatus, may call for revising its species boundaries.     

On the relative roles of selection and genetic drift in shaping MHC variation

Genes of the major histocompatibility complex (MHC) have provided some of the clearest examples of how natural selection generates discordances between adaptive and neutral variation in natural populations. The type and intensity of selection as well as the strength of genetic drift are believed to be important in shaping the resulting pattern of MHC diversity. However, evaluating the relative contribution of multiple microevolutionary forces is challenging, and empirical studies have reported contrasting results. For instance, balancing selection has been invoked to explain high levels of MHC diversity and low population differentiation in comparison with other nuclear markers. Other studies have shown that genetic drift can sometimes overcome selection and then patterns of genetic variation at adaptive loci cannot be discerned from those occurring at neutral markers. Both empirical and simulated data also indicate that loss of genetic diversity at adaptive loci can occur faster than at neutral loci when selection and population bottlenecks act simultaneously. Diversifying selection, on the other hand, explains accelerated MHC divergence as the result of spatial variation in pathogen‐mediated selective regimes. Because of all these possible scenarios and outcomes, collecting information from as many study systems as possible, is crucial to enhance our understanding about the evolutionary forces driving MHC polymorphism. In this issue, Miller and co‐workers present an illuminating contribution by combining neutral markers (microsatellites) and adaptive MHC class I loci during the investigation of genetic differentiation across island populations of tuatara Sphenodon punctatus. Their study of geographical variation reveals a major role of genetic drift in shaping MHC variation, yet they also discuss some support for diversifying selection.     

The role of selection and historical factors in driving population differentiation along an elevational gradient in an island bird

Adaptation to local environmental conditions and the range dynamics of populations can influence evolutionary divergence along environmental gradients. Thus, it is important to investigate patterns of both phenotypic and genetic variations among populations to reveal the respective roles of these two types of factors in driving population differentiation. Here, we test for evidence of phenotypic and genetic structure across populations of a passerine bird (Zosterops borbonicus) distributed along a steep elevational gradient on the island of Réunion. Using 11 microsatellite loci screened in 401 individuals from 18 localities distributed along the gradient, we found that genetic differentiation occurred at two spatial levels: (i) between two main population groups corresponding to highland and lowland areas, respectively, and (ii) within each of these two groups. In contrast, several morphological traits varied gradually along the gradient. Comparison of neutral genetic differentiation (F_ST) and phenotypic differentiation (P_ST) showed that P_ST largely exceeds F_ST at several morphological traits, which is consistent with a role for local adaptation in driving morphological divergence along the gradient. Overall, our results revealed an area of secondary contact midway up the gradient between two major, cryptic, population groups likely diverged in allopatry. Remarkably, local adaptation has shaped phenotypic differentiation irrespective of population history, resulting in different patterns of variation along the elevational gradient. Our findings underscore the importance of understanding both historical and selective factors when trying to explain variation along environmental gradients.     

Isolation by adaptation in Neochlamisus leaf beetles: host-related selection promotes neutral genomic divergence

This study tests how divergent natural selection promotes genomic differentiation during ecological speciation. Specifically, we use adaptive ecological divergence (here, population divergence in host plant use and preference) as a proxy for selection strength and evaluate the correlation between levels of adaptive and genetic differentiation across pairwise population comparisons. Positive correlations would reveal the pattern predicted by our hypothesis, that of 'isolation by adaptation' (IBA). Notably, IBA is predicted not only for selected loci but also for neutral loci. This may reflect the effects of divergent selection on neutral loci that are 'loosely linked' to divergently selected loci or on geneflow restriction that facilitates genetic drift at all loci, including neutral loci that are completely unlinked to those evolving under divergent selection. Here, we evaluate IBA in maple- and willow-associated populations of Neochlamisus bebbianae leaf beetles. To do so, we collected host preference data to construct adaptive divergence indices and used AFLPs (amplified fragment length polymorphisms) and mitochondrial sequences to quantify genetic differentiation. Partial Mantel tests showed significant IBA in 'pooled' analyses of putatively neutral and of putatively selected ('outlier') AFLP loci. This pattern was also recovered in 12% of 'locus-specific' analyses that separately evaluated genetic differentiation at individual neutral loci. These results provided evidence for widespread effects of selection on neutral genomic divergence. Our collective findings indicate that host-related selection may play important roles in the population genomic differentiation of both neutral and selected gene regions in herbivorous insects.     

Isolation and characterization of microsatellite loci in the blue manakin,Chiroxiphia caudata (Aves,Pipridae)

We designed primers for amplifying 11 polymorphic microsatellite loci in the blue manakin, Chiroxiphia caudata, a neotropical passerine bird which inhabits a critically endangered tropical ecosystem, the Brazilian Atlantic forest. Based on genotypes from 24 individuals from a single population, we detected between four and 22 alleles per locus with observed heterozygosities ranging from 0.54 to 0.92. These highly variable loci will be useful for determining levels of population differentiation and assessing the impact of habitat fragmentation on levels of genetic variation in isolated populations of these birds.     

Characterization of the first growth hormone gene sequence for a passerine bird--the pied flycatcher (Ficedula hypoleuca).

While the growth hormone (GH) gene has been characterized in a broad range of vertebrates, surprisingly little is known about this gene in birds. In order to extend knowledge of the GH gene in avian species and non-domestic species, the pied flycatcher (Ficedula hypoleuca) GH gene has been sequenced in this study. The overall average pairwise sequence divergence level was 0.08 among all available avian sequences and 0.27 among other taxa. However, the overall genetic organization of the gene is quite conserved. The similarity of the GH gene sequence of pied flycatchers with those of chicken and duck suggests that the rapid bursts of molecular evolution observed in mammalian and fish GH have not occurred during the divergence of passerine and non-passerine birds.