tic relationship between virulence and parasite survival, as the evolution of increased survival across different relationships with virulence may have considerably different epidemiological signatures.

1. Introduction
Interactions between the life history of a pathogen and the environment in which it is embedded drive the evolution of virulence. These interactions thus dictate both the experience of disease at the individual host level and the shape of disease dynamics in host populations [1,2]. The nature of the interaction between virulence and transmission has been the object of both theoretical and empirical examination [2,3,4,5,6,7,8]. Free-living survival, here defined as the ability of a pathogen to persist outside of its host, is one of many transmission life-history traits associated with virulence. The relationship between the two varies between host–pathogen types and different environments [4,8,9,10].
Several hypotheses serve as the canon in the evolution of virulence,