Intraspecific diversity poorly predicts invasibility and invasiveness: a
meta-analysis of experimental invasions
Identifying the biotic factors underlying invasion success is critical
to understand the dynamics of biological invasions; and while some
studies suggest that intraspecific diversity may play an important role,
there has not been a systematic evaluation of the evidence. We performed
a meta-analysis on 34 experimental studies and 106 effect sizes to test
two hypotheses: (1) higher intraspecific diversity in a resident
population decreases the likelihood of it being successfully invaded by
other species, and (2) higher intraspecific diversity in an invading
population increases its ability to invade another species or community.
We found small effects in the direction of our hypotheses, but these
were not significant and were influenced by taxon and study duration.
The lack of significant findings are somewhat unexpected, given the
well-understood mechanisms analogous to those offered for interspecific
diversity. These include sampling effects and complementarity, in which
diversity is expected to maximize resource use and increase density,
thereby reducing niche availability and subsequent invasibility.
Additionally, we found evidence of publication bias for studies of
invader intraspecific diversity. We recommend that future research focus
on a wider diversity of organisms, include longer term experiments, and
measure genetic dissimilarity to better understand the role of