Data from: Trophic ecology of large herbivores in a reassembling African ecosystem

1. Diverse megafauna assemblages have declined or disappeared throughout
much of the world, and many efforts are underway to restore them.
Understanding the trophic ecology of such reassembling systems is
necessary for predicting recovery dynamics, guiding management, and
testing general theory. Yet there are few studies of recovering
large-mammal communities, and fewer still that have characterized food-web
structure with high taxonomic resolution. 2. In Gorongosa National Park,
large herbivores have rebounded from near-extirpation following the
Mozambican Civil War (1977-1992). However, contemporary community
structure differs radically from the pre-war baseline: medium-sized
ungulates now outnumber larger-bodied species, and several apex carnivores
remain locally extinct. 3. We used DNA metabarcoding to quantify diet
composition of Gorongosa’s 14 most abundant large-mammal populations. We
tested five hypotheses: (i) the most abundant populations exhibit greatest
individual-level dietary variability; (ii) these populations also have the
greatest total niche width (dietary diversity); (iii) interspecific niche
overlap is high, with the diets of less-abundant species nested within
those of more-abundant species; (iv) partitioning of forage species is
stronger in more structurally heterogeneous habitats; and (v) selectivity
for plant taxa converges within guilds and digestive types, but diverges
across them. 4. Abundant (and narrow-mouthed) populations exhibited higher
among-individual dietary variation, but not necessarily the greatest
dietary diversity. Interspecific dietary overlap was high, especially
among grazers and in structurally homogenous habitat, whereas niche
separation was more pronounced among browsers and in heterogeneous
habitat. Patterns of selectivity were similar for ruminants—grazers and
browsers alike—but differed between ruminants and non-ruminants. 5.
Synthesis. The structure of this recovering food web was consistent with
several hypotheses predicated on competition, habitat complexity, and
herbivore traits, but it differed from patterns observed in more-intact
assemblages. We propose that intraspecific competition in the
fastest-recovering populations has promoted individual variation and a
more nested food web, wherein rare species use subsets of foods eaten by
abundant species, and that this scenario is reinforced by weak top-down
control. Future work should test these conjectures and analyze how the
taxonomic dietary niche axis studied here interacts with other mechanisms
of diet partitioning to affect community reassembly following wildlife
declines.