Time to a single hybridization event in a group of species with unknown   ancestral history
  We consider a stochastic process for the generation of species which combines a Yule process with a simple model for hybridization between pairs of co-existent species. We assume that the origin of the process, when there was one species, occurred at an unknown time in the past, and we condition the process on producing n species via the Yule process and a single hybridization event. We prove results about the distribution of the time of the hybridization event. In particular we calculate a formula for all moments, and show that under various conditions, the distribution tends to an exponential with rate twice that of the birth rate for the Yule process. 
Krzysztof Bartoszek, Graham Jones, Bengt Oxelman, and Serik Sagitov
q-bio.PE