# dendropy.simulate.popgensim: Population Genetics Simulations¶

Population genetic simlations.

dendropy.simulate.popgensim.pop_gen_tree(tree=None, taxon_namespace=None, ages=None, num_genes=None, pop_sizes=None, num_genes_attr='num_genes', pop_size_attr='pop_size', rng=None)[source]

This will simulate and return a tree with edges decorated with population sizes and leaf nodes decorated by the number of genes (samples or lineages) in each leaf.

If tree is given, then this is used as the tree to be decorated. Otherwise, a Yule tree is generated based on the given taxon_namespace. Either tree or taxon_namespace must be given.

The timing of the divergences can be controlled by specifying a vector of ages, ages. This should be sequences of values specifying the ages of the first, second, third etc. divergence events, in terms of time from the present, specified either in generations (if the pop_sizes vector is given) or population units (if the pop_size vector is not given). If an ages vector is given and there are less than num_pops-1 of these, then an exception is raised.

The number of gene lineages per population can be specified through the ‘num_genes’, which can either be an scalar integer or a list. If it is an integer, all the population get the same number of genes. If it is a list, it must be at least as long as num_pops.

The population sizes of each edge can be specified using the pop_sizes vector, which should be a sequence of values specifying the population sizes of the edges in postorder. If the pop_size vector is given, then it must be at least as long as there are branches on a tree, i.e. 2 * num_pops + 1, otherwise it is an error. The population size should be the effective haploid population size; i.e., number of gene copies in the population: 2 * N in a diploid population of N individuals, or N in a haploid population * of N individuals.

If pop_size is 1 or 0 or None, then edge lengths of the tree are in haploid population units; i.e. where 1 unit of time equals 2N generations for a diploid population of size N, or N generations for a haploid population of size N. Otherwise edge lengths of the tree are in generations.

This function first generates a tree using a pure-birth model with a uniform birth rate of 1.0. If an ages vector is given, it then sweeps through the internal nodes, assigning branch lengths such that the divergence events correspond to the ages in the vector. If a population sizes vector is given, it then visits all the edges in postorder, assigning population sizes to the attribute with the name specified in ‘pop_size_attr’ (which is persisted as an annotation). During this, if an ages vector was not given, then the edge lengths are multiplied by the population size of the edge so the branch length units will be in generations. If an ages vector was given, then it is assumed that the ages are already in the proper scale/units.