■地理区域,两个密切相关的分类单元与不同的迁移路线接触,被称为迁徙鸿沟。假设源自迁移鸿沟的杂种相对于亲本种群以中间迁移。很少有研究在野生鸟类中检验这一假设,只有在已经完成迁移回到繁殖地的杂种中。这里,我们利用柳莺(Phylloscopustrochilus)的既定迁徙路线,亚种tchilus和acredula在1号和5号染色体上具有与迁移相关的遗传标记。遗传方法使我们能够分析青少年在第一次秋季迁徙期间的地理分布,预测在意大利的中央航道上,杂种的频率应比沿典型的西南路线的rochilus和acredula的SE路线更为频繁。
■从非洲越冬鸟类中收集血液和羽毛样本(n=69),以及葡萄牙秋季迁徙期间的青少年(n=33),意大利(n=38)和保加利亚(n=32)。通过qPCRSNP测定进行基因分型,在1号染色体(SNP65)和5号染色体(SNP285)上的一个SNP上。这两种SNP都具有在每个亚种中高度固定(>97%)的替代等位基因。
■观察到的两个SNP的组合基因型与已知的迁移途径和三叶草和acredula的越冬分布有关,分别。我们在意大利(5/38)和葡萄牙(2/33)的青少年中发现了杂种(HH)。意大利的杂种比例显着高于亚种同种种群中杂种基因型的背景率(1.5%)。
■我们将个体分配到亚种和杂种的遗传方法使我们能够研究幼鸟首次迁徙时的迁徙方向,与仅限于成功移民的研究相比,这应该更好地反映出先天的移民方向。意大利杂种的过剩,表明他们采用相对于父母群体的中间途径。我们的qPCRSNP基因分型方法对于处理大样本是有效的,因此,将有助于具有已知种群遗传结构的物种的迁移研究。
UNASSIGNED: Geographic regions, where two closely related taxa with different migration routes come into contact, are known as migratory divides. Hybrids originating from migratory divides are hypothesized to migrate intermediately relative to the parental populations. Few studies have tested this hypothesis in wild birds, and only in hybrids that have completed the migration back to the breeding grounds. Here, we make use of the well-established migration routes of willow warblers (Phylloscopus trochilus), for which the subspecies trochilus and acredula have migration-associated genetic markers on chromosomes 1 and 5. The genetic approach enabled us to analyze the geographic distribution of juveniles during their first autumn migration, predicting that hybrids should be more frequent in the central flyway over Italy than along the typical SW routes of trochilus and SE routes of acredula.
UNASSIGNED: Blood and feather samples were collected from wintering birds in Africa (n = 69), and from juveniles during autumn migration in Portugal (n = 33), Italy (n = 38) and Bulgaria (n = 32). Genotyping was carried out by qPCR SNP assays, on one SNP each on chromosome 1 (SNP 65) and chromosome 5 (SNP 285). Both these SNPs have alternative alleles that are highly fixed (> 97%) in each of the subspecies.
UNASSIGNED: The observed combined genotypes of the two SNPs were associated with the known migration routes and wintering distributions of trochilus and acredula, respectively. We found hybrids (HH) among the juveniles in Italy (5/38) and in Portugal (2/33). The proportion of hybrids in Italy was significantly higher than expected from a background rate of hybrid genotypes (1.5%) in allopatric populations of the subspecies.
UNASSIGNED: Our genetic approach to assign individuals to subspecies and hybrids allowed us to investigate migration direction in juvenile birds on their first migration, which should better reflect the innate migratory direction than studies restricted to successful migrants. The excess of hybrids in Italy, suggests that they employ an intermediate route relative to the parental populations. Our qPCR SNP genotyping method is efficient for processing large sample sizes, and will therefore be useful in migration research of species with known population genetic structure.