Quantitative Genetics and Genome Structure in a Wild Population: the Use of a Great Reed Warbler Pedigree

Sammanfattning: Long-term studies of birds play an important role in the understanding of quantitative traits in natural populations. The relative ease by which individual birds can be monitored and caught in the wild enable us collect detailed information from individuals throughout their life time, sometimes from several generations in a population. In this thesis I describe the utilization of a great reed warbler (Acrocephalus arundinaceus) pedigree to shed light on the genome structure of passerine birds and the variation in quantitative traits. The significant heritabilities among seven of eight studied traits indicate that the great reed warblers show potential to evolve phenotypically. Moreover, several traits have been subject to moderate forces of natural selection. However, we also find that evolution might be hampered by the high genetic correlation among the morphological traits and the sexual antagonistic selection observed in wing length. In the first paper of the thesis, quantitative genetic parameters were estimated from resemblances between parents and offspring while the utilization the animal model, which takes all relatives in a pedigree into account, has become increasingly common for estimation of such parameters. When comparing the methods we found that heritabilities estimated with the parent-offspring regression were very similar to the estimates from the animal model while a small upward bias of the genetic correlations was observed in the parent-offspring approach. Moreover, the utilization of repeated measures instead of individual mean trait values generates lower estimates of heritability and with lower sampling error. For a better understanding of the evolutionary properties of quantitative traits we need to know more about the genes that affect traits and about the genome structure in general. In the thesis I also describe the construction and applications of a partial linkage map of the great reed warbler genome by using in total 154 informative microsatellite and AFLP markers. This has resulted in a sex-specific partial linkage map containing 115 markers distributed among 22 linkage groups that probably corresponds to different chromosomes in the genome. In a comparative study between the great reed warbler and chicken we found that the genome structure and gene order appear highly conserved between the species. Moreover, the great reed warbler also appears to have considerably lower recombination rate than chicken. The low recombination rate will facilitate the future detection of major genes affecting the quantitative traits of great reed warblers.