Data and R scripts for: Ant invasions is associated with lower root density and different root distribution of a foundational savanna tree species

Some invasive ants have worldwide distributions and impose substantial impacts on human society and native biodiversity. Yet we know little about how ants impact soil ecosystems in general, much less how soil ecosystems shift when invasive ants move in. We excavated the coarse roots of a monodominant savanna tree in invaded and uninvaded areas to test the hypothesis that the presence of invasive ants would be associated with changes in root distribution and biomass across the landscape. We found that in the presence of invasive ants, trees had a shifted distribution of lateral coarse roots, with proportionally less root biomass near the surface and far from tree stems. In addition, the density of lateral coarse-root biomass was ~20% lower for trees within invaded landscapes. Our results suggest that soil-nesting invasive ants can drive important changes in rooting strategy for a tree species that serves a foundational role in the biogeochemical cycles of vertisol savannas.

Methods
Biological samples were collected by John Lemboi and John Mosiany at Ol Pejeta Conservancy, and then processed and entered at Mpala Research Centre by JL, JM, and Patrick Milligan. These samples were stored and used to check outliers in the data, and then analyses were conducted in R using scripts included in the zipped files here. PM and Elizabeth Pringle conducted analyses at the University of Nevada, Reno. No other processing was done beyond transformations and manipulations outlined in the R script and associated article.