TreePar (version 3.3)

bd.densdep.optim: bd.densdep.optim: Estimating maximum likelihood speciation and extinction rates in phylogenies under a density-dependent speciation model.

Description

bd.densdep.optim estimates the maximum likelihood speciation and extinction rates under a density-dependent speciation model. Speciation rate is a function of the number of species N, lambda(N) = max(0,lambda(1-N/K)), where K is the carying capacity and lambda the speciation rate when N<

Usage

bd.densdep.optim(x,minK,maxK,discrete=TRUE,continuous=FALSE,lambdainit=2,
muinit=1,Kinit=0,Yule=FALSE,muset=0,rho=1,model=-1)

Arguments

x

Vector of speciation times in the phylogeny. Time is measured increasing going into the past with the present being time 0. x can be obtained from a phylogenetic tree using getx(TREE).

minK

Minimal value of K (when discrete=TRUE). Default is minK = (number of species).

maxK

Maximal value of K (when discrete=TRUE). Default is maxK = 1.5(number of species).

discrete

If discrete=TRUE, the likelihood function is maximized with K being an integer and the minimal size being minK and the maximal size being maxK.

continuous

If continuous=TRUE, the likelihood function is maximized with K being a continuous parameter. The function subplex is used for optimization and sometimes gets stuck at a non-optimal K. Thus it is recommended to also calculate with discrete=TRUE.

lambdainit

Initial lambda value for optimization when K is continuous (default is 2).

muinit

Initial mu value for optimization when K is continuous (default is 1).

Kinit

Initial K value for optimization when K is continuous (default is Kinit=0 which automatically sets Kinit=(number of species)+1).

Yule

Yule=FALSE is default. Yule=TRUE fixes mu=0, i.e. no extinction.

muset

muset=0 (default) maximizes over the whole parameter range. muset>0 means that the optimization is done over all mu>muset. muset

rho

rho=1 is default meaning all present-day species are sampled. 0=n has given rise to a sample of size n with probability 1. rho<-1 means that any number n,n+1,..,(-k) of present-day species may have given rise to a sample of size n with probability 1. rho>1 means that exactly rho>n present-day species gave rise to the sample n with probability 1.

model

model=-1 (default) is the density-dependent model. model=0 (only relevant for testing purposes) assumes that lambda is constant for number of species < K, and 0 for number of species >= K. model=0 is used for testing / comparing to constant rate model implemented in bd.shifts.optim.

Value

res

Maximum likelihood speciation rate lambda and extinction rate mu and the saturation value K; the first entry, res[[1]], is the result when K is discrete (0 if discrete=FALSE) and the second entry, res[[2]], is the result when K is continuous (0 if continuous=FALSE). $par is the maximum likelihood estimate of (lambda,mu,K). $value is the -log likelihood value. The likelihood is calculated assuming there were two lineages at the time of the root. The likelihood is NOT conditioned on survival of the two lineages. Likelihood values from bd.shifts.optim are directly comparable (eg. using AIC) for survival = 0. Likelihood values from laser are directly comparable to those obtained by bd.densdep.optim and bd.shifts.optim for survival = 0 after the TreePar output $value is transformed to -$value+sum(log(2:length(x))).

References

R.S. Etienne, B. Haegeman, T. Stadler, T. Aze, P.N. Pearson, A. Purvis, A.B. Phillimore. Diversity-dependence brings molecular phylogenies closer to agreement with the fossil record. Proc. Roy. Soc. B, 279: 1300-1309, 2012.

G. Leventhal, H. Guenthard, S. Bonhoeffer, T. Stadler. Using an epidemiological model for phylogenetic inference reveals density-dependence in HIV transmission. Mol. Biol. Evol., 31(1): 6-17, 2014.

Examples

set.seed(1)
x<-c(10:1)

bd.densdep.optim(x,discrete=FALSE,continuous=TRUE)

# Laser returns same result for Yule model
res <- -bd.densdep.optim(x,Yule=TRUE,discrete=FALSE,continuous=TRUE)[[2]]$value 
res<-res+ sum(log(2:length(x)))
res

# library(laser)
# DDL(x)