title: On the length distribution of external branches in coalescence trees: genetic diversity within species.
abstract: Let Z(n) denote the length of an external branch, chosen at random from a Kingman n-coalescent. Based on a recursion for the distribution of Z(n), we show that nZ(n) converges in distribution, as n tends to infinity, to a non-negative random variable Z with density x--> 8/(2+x)(3), x>or=0. This result facilitates the study of the time to the most recent common ancestor of a randomly chosen individual and its closest relative in a given population. This time span also reflects the maximum relatedness between a single individual and the rest of the population. Therefore, it measures the uniqueness of a random individual, a central characteristic of the genetic diversity of a population.
authors.affiliation: Institut für Medizinische Informatik und Statistik, Christian-Albrechts-Universität Kiel, 24105 Kiel, Germany. caliebe@math.uni-kiel.de
authors.forename: Amke
authors.initials: A
authors.lastname: Caliebe
authors.forename: Ralph
authors.initials: R
authors.lastname: Neininger
authors.forename: Michael
authors.initials: M
authors.lastname: Krawczak
authors.forename: Uwe
authors.initials: U
authors.lastname: Rösler
mesh_terms: D014644:Genetic Variation / Q000235:genetics*; D005858:Germany; D015233:Models, Statistical; D013045:Species Specificity; D014197:Trees / Q000235:genetics* / Q000502:physiology*