make.phylo {paleobuddy}

Phylogeny generating

Description

Generates a phylogeny from a sim object containing speciation and extinction times, parent and status information (see ?sim). Returns a phylo object containing information on the phylogeny, following an "evolutionary Hennigian" (sensu Ezard et al 2011) format (i.e., a bifurcating tree). Takes an optional argument encoding fossil occurrences to return a sampled ancestor tree (see references). This tree consists of the original tree, plus the fossil occurrences added as branches of length 0 branching off of the corresponding species at the time of occurrence. Such trees can be used, as is or with small modifications, as starting trees in phylogenetic inference software that make use of the fossilized birth-death model. Returns NA and sends a warning if the simulation has only one lineage or if more than one species has NA as parent (i.e. there is no single common ancestor in the simulation). In the latter case, please use find.lineages first.

Usage

make.phylo(sim, fossils = NULL, returnRootTime = NULL)

Arguments

sim

A sim object, containing extinction times, speciation times, parent, and status information for each species in the simulation. See ?sim.

fossils

A data frame with a "Species" column and a SampT column, usually an output of the sample.clade function. Species names must contain only one number each, corresponding to the order of the sim vectors.

returnRootTime

Logical indicating if phylo should have information regarding root.time. If set to NULL (default), returned phylogenies will not have root.time if there is at least one extant lineage in the sim object. If there are only extinct lineages in the sim object and it is set to NULL, root.time will be returned. If set to FALSE or TRUE, root.time will be removed or forced into the phylo object, respectively. In this case, we highly recommend users to read about the behavior of some functions (such as APE's axisPhylo) when this argument is forced.

Details

When root.time is added to a phylogeny, packages such as APE can change their interpretation of the information in the phylo object. For instance, a completely extinct phylogeny might be interpreted as extant if there is no info about root.time. This might create misleading interpretations even with simple functions such as ape::axisPhylo. make.phylo tries to accommodate different evo/paleo practices in its default value for returnRootTime by automatically attributing root.time when the sim object is extinct. We encourage careful inspection of output if users force make.phylo to use a specific behavior, especially when using phylogenies generated by this function as input in functions from other packages. For extinct phylogenies, it might usually be important to explicitly provide information that the edge is indeed a relevant part of the phylogeny (for instance adding root.edge = TRUE when plotting a phylogeny with root.time information with ape::plot.phylo. The last example here provides a visualization of this issue.

Value

A phylo object from the APE package. Tip labels are numbered following the order of species in the sim object. If fossil occurrence data was supplied, the tree will include fossil occurrences as tips with branch length 0, bifurcating at its sampling time from the corresponding species' edge (i.e. a sampled ancestor tree). Note that to obtain a true sampled ancestor (SA) tree, one must perform the last step of deleting tips that are not either extant or fossil occurrences (i.e. the tips at true time of extinction).

Note this package does not depend on APE (Paradis et al, 2004) since it is never used inside its functions, but it is suggested since one might want to manipulate the phylogenies generated by this function.

Author(s)

Matheus Januario and Bruno do Rosario Petrucci

References

Ezard, T. H., Pearson, P. N., Aze, T., & Purvis, A. (2012). The meaning of birth and death (in macroevolutionary birth-death models). Biology letters, 8(1), 139-142.

Paradis, E., Claude, J., Strimmer, & K. (2004). APE: Analyses of Phylogenetics and Evolution in R language. Bioinformatics, 20(2), 289-290.

Heath, T. A., Huelsenbeck, J. P., & Stadler, T. (2014). The fossilized birth–death process for coherent calibration of divergence-time estimates. Proceedings of the National Academy of Sciences, 111(29), E2957-E2966.

Examples

###
# we can start with a simple phylogeny

# set a simulation seed
set.seed(1) 

# simulate a BD process with constant rates
sim <- bd.sim(n0 = 1, lambda = 0.3, mu = 0.1, tMax = 10, 
             nExtant = c(2, Inf))

# make the phylogeny
phy <- make.phylo(sim)

# plot it
if (requireNamespace("ape", quietly = TRUE)) {
  # store old par settings
  oldPar <- par(no.readonly = TRUE) 
  
  # change par to show phylogenies
  par(mfrow = c(1, 2))
  
  ape::plot.phylo(phy)
  
  # we can also plot only the molecular phylogeny
  ape::plot.phylo(ape::drop.fossil(phy))
  
  # reset par
  par(oldPar)
}

###
# this works for sim generated with any of the scenarios in bd.sim

# set seed
set.seed(1)

# simulate
sim <- bd.sim(n0 = 1, lambda = function(t) 0.2 + 0.01*t, 
             mu = function(t) 0.03 + 0.015*t, tMax = 10, 
             nExtant = c(2, Inf))

# make the phylogeny
phy <- make.phylo(sim)

# plot it
if (requireNamespace("ape", quietly = TRUE)) {
  # store old par settings
  oldPar <- par(no.readonly = TRUE) 
  
  # change par to show phylogenies
  par(mfrow = c(1, 2))
  
  # plot phylogeny
  ape::plot.phylo(phy)
  ape::axisPhylo()
  
  # we can also plot only the molecular phylogeny
  ape::plot.phylo(ape::drop.fossil(phy))
  ape::axisPhylo()
  
  # reset par 
  par(oldPar)
}

### 
# we can use the fossils argument to generate a sample ancestors tree

# set seed
set.seed(1)

# simulate a simple birth-death process
sim <- bd.sim(n0 = 1, lambda = 0.2, mu = 0.05, tMax = 10, 
              nExtant = c(2, Inf))

# make the traditional phylogeny
phy <- make.phylo(sim)

# sample fossils
fossils <- sample.clade(sim, 0.1, 10)

# make the sampled ancestor tree
saTree <- make.phylo(sim, fossils)

# plot them
if (requireNamespace("ape", quietly = TRUE)) {
  # store old par settings
  oldPar <- par(no.readonly = TRUE) 
  
  # visualize longevities and fossil occurrences
  draw.sim(sim, fossils)
  
  # change par to show phylogenies
  par(mfrow = c(1, 2))

  # phylogeny
  ape::plot.phylo(phy, main = "Phylogenetic tree")
  ape::axisPhylo()
  
  # sampled ancestor tree
  ape::plot.phylo(saTree, main = "Sampled Ancestor tree")
  ape::axisPhylo()
  
  # reset par
  par(oldPar)
}

### 
# finally, we can test the usage of returnRootTime

# set seed
set.seed(1)

# simulate a simple birth-death process with more than one
# species and completely extinct:
sim <- bd.sim(n0 = 1, lambda = 0.5, mu = 0.5, tMax = 10, nExtant = c(0, 0))

# make a phylogeny using default values
phy <- make.phylo(sim)

# force phylo to not have root.time info
phy_rootless <- make.phylo(sim, returnRootTime = FALSE)

# plot them
if (requireNamespace("ape", quietly = TRUE)) {
  # store old par settings
  oldPar <- par(no.readonly = TRUE) 
  
  # change par to show phylogenies
  par(mfrow = c(1, 3))
  
  # if we use the default value, axisPhylo works as intended
  ape::plot.phylo(phy, root.edge = TRUE, main = "root.time default value")
  ape::axisPhylo()
  
  # note that without root.edge, we have incorrect times,
  # as APE assumes tMax was the time of first speciation
  ape::plot.phylo(phy, main = "root.edge not passed to plot.phylo")
  ape::axisPhylo()
  
  # if we force root.time to be FALSE, APE assumes the tree is
  # ultrametric, which leads to an incorrect time axis
  ape::plot.phylo(phy_rootless, main = "root.time forced as FALSE")
  ape::axisPhylo()
  # note time scale in axis
  
  # reset par
  par(oldPar)
}