This is an interesting and potentially useful study. But the term 'failure' indicates that a purpose or an objective has not been met. The conclusion expressed in this paper's title and invasion biology's central dogma are sensible only if establishing a breeding population in order to take and hold territory is actually an objective of castaway organisms. Unless snails (et al) have objectives they cannot be said to have failed. Even if they copulate, we cannot say they have attempted to reproduce unless we can demonstrate that they somehow comprehend that cause and effect relationship. This might be dismissible as semantic quibbling were it not for the fact that "biological invasions" are widely represented and understood as anomalous or even perverse acts of aggression, when they would be more accurately described as the outcomes of normal behavior under unprecedented circumstances. The difference is significant, especially when a species is indicted as essentially "invasive". "Invasive" inescapably implies some kind of monstrosity or moral failing at the taxon level. Is that what we mean to mean?