Abstract
Statistical properties of the site frequency spectrum associated with
Lambda-coalescents are our objects of study. In particular, we derive
recursions for the expected value, variance, and covariance of the spectrum,
extending earlier results of Fu (1995) for the classical Kingman coalescent.
Our focus is on estimating coalescent parameters introduced by certain
Lambda-coalescents for datasets to large for full likelihood methods. The
recursions for the expected values we obtain can be used to find the parameter
values which give the best fit to the observed frequency spectrum. The expected
values are also used to approximate the probability a (derived) mutation arises
on a branch subtending a given number of leaves (DNA sequences), allowing us to
apply a pseudo-likelihood inference to estimate coalescence parameters
associated with certain subclasses of Lambda coalescents. The properties of the
pseudo-likelihood approach are investigated on real and simulated datasets. Our
results for two subclasses of Lambda coalescents show that one can distinguish
these subclasses from the Kingman coalescent, as well as between the
Lambda-subclasses. In addition, our results yield further support for multiple
merger coalescents as an appropriate `null' model at the mitochondrial DNA
level for high-fecundity Atlantic cod (Gadus morhua).
Users
Please
log in to take part in the discussion (add own reviews or comments).