  Software ecosystems are collections of projects that are developed and evolve
together in the same environment. Existing literature investigates software
ecosystems as isolated entities whose boundaries do not overlap and assumes
they are self-contained. However, a number of software projects are distributed
in more than one ecosystem. As different aspects, e.g., success, security
vulnerabilities, bugs, etc., of such cross-ecosystem packages can affect
multiple ecosystems, we investigate the presence and characteristics of these
cross-ecosystem packages in 12 large software distributions. We found a small
number of packages distributed in multiple packaging ecosystems and that such
packages are usually distributed in two ecosystems. These packages tend to
better support with new releases certain ecosystems, while their evolution can
impact a multitude of packages in other ecosystems. Finally, such packages
appear to be popular with large developer communities.
