TY - JOUR
T1 - Trophic ecology of large herbivores in a reassembling African ecosystem
AU - Pansu, Johan
AU - Guyton, Jennifer A.
AU - Potter, Arjun B.
AU - Atkins, Justine L.
AU - Daskin, Joshua H.
AU - Wursten, Bart
AU - Kartzinel, Tyler R.
AU - Pringle, Robert Mitchell
N1 - Funding Information:
Princeton University; National Geographic Society, Grant/Award Number: 9459-14 ; National Science Foundation, Grant/Award Number: DEB-1355122, DEB-1457697 and IOS-1656527 ; Greg Carr Foundation;
Funding Information:
We thank the Mozambican government and Gorongosa National Park for permission to conduct this research. We thank M. Stalmans, R. Branco, J. Denlinger, M. Jordan, A. Marchington, M. Marchington, P. Naskrecki, G. Carr, and the park rangers and staff for scientific and logistical support. We thank J. Montenoise, C. Buoncore, A. Getraer, F. Mequicene, R. Long, and P. Branco for help in the field. M. Stalmans and T. Castigo assisted in the collection of plant vouchers. M. Bison shared R code. Satellite imagery was provided by the DigitalGlobe Foundation. Support for this research was provided by the Innovation Fund for New Ideas in Natural Sciences from the Office of the Dean of Research of Princeton University, the Greg Carr Foundation, the Cameron Schrier Foundation, National Geographic Grant 9459-14 to J.A.G., and US National Science Foundation awards DEB-1355122, DEB-1457697, and IOS-1656527 to R.M.P.
Publisher Copyright:
© 2018 The Authors. Journal of Ecology © 2018 British Ecological Society
PY - 2019/5
Y1 - 2019/5
N2 - 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. 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 prewar baseline: medium-sized ungulates now outnumber larger bodied species, and several apex carnivores remain locally extinct. 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. 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. 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 predation pressure. Future work should test these conjectures and analyse how the taxonomic dietary niche axis studied here interacts with other mechanisms of diet partitioning to affect community reassembly following wildlife declines.
AB - 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. 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 prewar baseline: medium-sized ungulates now outnumber larger bodied species, and several apex carnivores remain locally extinct. 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. 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. 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 predation pressure. Future work should test these conjectures and analyse how the taxonomic dietary niche axis studied here interacts with other mechanisms of diet partitioning to affect community reassembly following wildlife declines.
KW - community assembly
KW - herbivory
KW - individual specialization
KW - intraspecific niche variation
KW - molecular diet analysis
KW - restoration ecology
KW - species coexistence
KW - trophic rewilding
UR - http://www.scopus.com/inward/record.url?scp=85059271821&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85059271821&partnerID=8YFLogxK
U2 - 10.1111/1365-2745.13113
DO - 10.1111/1365-2745.13113
M3 - Article
AN - SCOPUS:85059271821
SN - 0022-0477
VL - 107
SP - 1355
EP - 1376
JO - Journal of Ecology
JF - Journal of Ecology
IS - 3
ER -