Ecological interaction and phylogeny, studying functionality on composed networks

We study a class of composed networks that are formed by two tree networks, T P and T A , whose end points touch each other through a bipartite network B P A . We explore this network using a functional approach. We are interested in how much the topology, or the structure, of T X ( X = A or P ) determines the links of B P A . This composed structure is a useful model in evolutionary biology, where T P and T A are the phylogenetic trees of plants and animals that interact in an ecological community. We make use of ecological networks of dispersion of fruits, which are formed by frugivorous animals and plants with fruits; the animals, usually birds, eat fruits and disperse their seeds. We analyse how the phylogeny of T X determines or is correlated with B P A using a Monte Carlo approach. We use the phylogenetic distance among elements that interact with a given species to construct an index κ that quantifies the influence of T X over B P A . The algorithm is based on the assumption that interaction matrices that follows a phylogeny of T X have a total phylogenetic distance smaller than the average distance of an ensemble of Monte Carlo realisations. We find that the effect of phylogeny of animal species is more pronounced in the ecological matrix than plant phylogeny.