  Genetic data are often used to infer demographic history and changes or
detect genes under selection. Inferential methods are commonly based on models
making various strong assumptions: demography and population structures are
supposed \textit{a priori} known, the evolution of the genetic composition of a
population does not affect demography nor population structure, and there is no
selection nor interaction between and within genetic strains. In this paper, we
present a stochastic birth-death model with competitive interactions and
asexual reproduction. We develop an inferential procedure for ecological,
demographic and genetic parameters. We first show how genetic diversity and
genealogies are related to birth and death rates, and to how individuals
compete within and between strains. {This leads us to propose an original model
of phylogenies, with trait structure and interactions, that allows multiple
merging}. Second, we develop an Approximate Bayesian Computation framework to
use our model for analyzing genetic data. We apply our procedure to simulated
data from a toy model, and to real data by analyzing the genetic diversity of
microsatellites on Y-chromosomes sampled from Central Asia human populations in
order to test whether different social organizations show significantly
different fertility.
