Recolonizing native wildlife facilitates exotic plant invasion into Singapore’s rain forests: Data and R script

Halting biological invasions and rewilding extirpated fauna are
conservation interventions to bolster biodiversity, species interactions,
and ecosystems. These actions are often considered separately and the
potential for reintroduced wildlife to facilitate invasive plants has been
largely overlooked. Here, we investigate the role of Singapore’s
recolonizing native wild pigs (Sus scrofa) in facilitating an invasive
weed Miconia crenata into tropical rain forests, which are normally highly
resistant to invasion. We conducted line-transect surveys in 11
Singaporean rain forests and used generalized linear mixed models to
consider the contribution of pigs' soil disturbances, human forest
paths, and other environmental covariates, on the density of M. crenata.
We found that M. crenata was more abundant at forest edges and invasion
into forest interior was facilitated by pigs, paths, and canopy gaps, but
that these effects were all additive, not synergistic (i.e. not
multiplicative). These results highlight how modern invasions are driven
by multiple disturbances as well as propagule pressure (e.g. urban birds
dispersing seeds at forest edges where they establish in pig soil
disturbances). Singapore’s extensive native forest restoration efforts may
have provided plentiful edge and secondary forests that are well suited to
pigs and M. crenata, which in turn undermine the aims of fostering
later-successional native plant communities. To prevent negative
externalities, we suggest that plant restoration and rewilding projects
consider the potential role of wildlife in facilitating non-native plants,
and couple these actions with preliminary screening of unintended
consequences and continued monitoring, as well as limiting human-mediated
weed invasion to minimize propagule sources.