Data from: Effects of mammalian herbivores and termites on performance of native and exotic plantation tree seedlings

Invasion of exotic species is a global challenge and the potential for
adverse effects on local biodiversity is particularly high in protected
areas. Protected African savanna areas support globally important
biodiversity. At the same time, forest plantations are widespread
throughout Africa and exotic tree species frequently invade natural areas.
To evaluate the potential invasiveness of plant species, it is pertinent
to know to what extent, if at all, consumption by native herbivore
assemblages differentially affects exotic and indigenous plants. We
studied how two globally widespread exotic trees Eucalyptus grandis and
Grevillea robusta and two common indigenous trees Milicia excelsa and
Maesopsis eminii responded to natural herbivory by large herbivores and
termites. We experimentally exposed 720 tree seedlings to: (i) no large
herbivores or termites; (ii) termites only; (iii) large herbivores only;
and (iv) both large herbivores and termites. When exposed to large
herbivores and termites, the total survival was much higher for the
exotics with 45% (E. grandis) and 63% (G. robusta) compared to the
indigenous species (both 20%). Exposure to large herbivores affected early
seedling survival of natives more than the exotics. Apart from the
indigenous M. excelsa, survival did not decrease when seedlings were
exposed to termites. Large herbivores retarded seedling growth for all
species. The exotic E. grandis was the only species capable of growth when
exposed to large herbivores. Exposure to termites had only a small, but
significant effect resulting in a 7% size difference in all species.
Synthesis and applications. Our results highlight how browsing might, for
some tree species, adversely affect native seedling survival and growth
more than exotic species in protected African savanna. If exotic species
are to be used in plantations, managers should consider planting tree
species and varieties that are sensitive to ungulate browsing. This will
not compromise economic gain because large herbivores are generally less
common in plantations. Consequently, local ungulates could function as
biological control agents outside plantations and reduce the potential
risk of exotic plants proliferating in protected areas.