Although RNA viruses exhibit a high frequency of host jumps, major differences exist among the different virus families. Astroviruses manifest the capacity to infect a wide range of hosts that exhorts both public health systems and economic production chains. Here we delineate the ecological and adaptive processes that drive the cross-species transmission of Astroviruses. We observe that distinct transmission zones determine the prevailing Astrovirus host and virus diversity, which in turn suggests that no single host group (e.g. bats) can be natural reservoirs, as illustrated through our phylogenetic analysis.