Matemática, CAP, Universidade Federal de São João del Rei, 36420-000 Ouro Branco, Minas Gerais - Brazil\
    $^2$Departamento de Física and National Institute of Science and Technology for Complex Systems, ICEx, Universidade Federal de Minas Gerais, C. P. 702, 30123-970 Belo Horizonte, Minas Gerais - Brazil 
author:
- 'Marcelo Martins de Oliveira$^1$[^1] and Ronald Dickman$^2$[^2]'
title: 'Phase diagram of the symbiotic two-species contact process'
---

Introduction
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Originally proposed as a toy model for epidemic spreading, the contact process (CP) [@harris-CP] can also be interpreted as a stochastic single species birth-and-death process with a spatial structure [@durrett]. In the CP, each individual can reproduce assexually with rate $\lambda$, or die with unitary rate. When the reproduction rate $\lambda$ is varied, the system undergoes a phase transition between extinction and survival.

Interacting, spatially extended, multi-species processes are a subject of recent interest [@jansen; @iwata; @multisp; @tauber; @tubay; @parasites; @competing]. In particular, multispecies (or multitype) contact processes have been used to model systems with neutral community structure, and have proven useful in understanding abundance distributions and species-area relationships [@weitz; @munoz].

Symbiosis is the “living together of two phylogenetically unrelated species in close association" [@boucher], and is thought to develop as a consequence of 