\((Y_i)\) are independant random variables with density \(2/(\lambda_\epsilon) exp(-(\beta+n+1)x) (1-exp(-x))^\beta\)
References
Maliet O., Gascuel F., Lambert A. (2018) Ranked tree shapes, non-random
extinctions and the loss of phylogenetic diversity, bioRxiv 224295,
doi: https://doi.org/10.1101/224295