Despite biological invasions are one of the main environmental problems
of the twenty-first century, there is still no theoretical or empirical
agreement on whether a high phylogenetic relatedness between exotic and
native species positively or negatively affect invasion success. To
resolve this conundrum, it has been proposed that the effect might be
scale-dependent, being negative at smaller spatial scales and positive
at larger scales. Here we show that this scale-dependent pattern may be
a sampling artefact associated with species-area effects and a
non-random pattern of species introductions. We support this conclusion
with simulations and empirical data on invaded and non-invaded avian
communities in regions from five continents. We further show that at
smaller-scales ---where these artifacts are negligible--- invasion
success generally increases with the presence of closely-related
species, but that predictive accuracy largely depends on considering the
influence of human-related disturbances in facilitating invasions.