Functional traits—not nativeness—shape the effects of large mammalian herbivores on plant communities

Large mammalian herbivores (megafauna) have experienced extinctions and
declines since prehistory. Introduced megafauna have partly counteracted
these losses yet are thought to have unusually negative effects compared
to native megafauna. Using a meta-analysis of 3,995 plot-scale plant
abundance and diversity responses from 221 studies, we found no evidence
that megafauna impacts were shaped by nativeness, ‘invasiveness’,
‘feralness’, coevolutionary history, or functional and phylogenetic
novelty. Nor was there evidence that introduced megafauna facilitate
introduced plants more than native megafauna. Instead, we found strong
evidence that functional traits shaped megafauna impacts, with
larger-bodied and bulk-feeding megafauna promoting plant diversity. Our
work suggests that trait-based ecology provides better insight into
interactions between megafauna and plants than concepts of nativeness.