Competition drives the evolution of emergent neutrality in the dietary niches of mammalian herbivores

Codron, Daryl; Bousman, C. Britt; Buschke, Falko T.; Clauss, Marcus; Lewis, Chanel; Merwe, Runé van der; Mescht, Aileen C. van der; Brink, James S.

doi:10.1016/j.quaint.2021.11.002

Cited by 6 publications

(6 citation statements)

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“…The bimodal distribution of grazers and browsers in our study matches that in a recent synthesis ( 18 ). However, eudicot consumption was prevalent in our data; at the species level, there were few strict grazers.…”

Section: Discussionsupporting

confidence: 91%

“…2 A ), and the overall distribution of populations along this spectrum ( SI Appendix , Fig. S4 ) resembles that reported elsewhere ( 18 ). However, many species’ positions on this spectrum contrasted with their standard categorizations.…”

Section: Resultssupporting

confidence: 83%

“…Constraints on coexistence should be acute for big, wide-ranging consumers that occur at low densities and require large quantities of substitutable resources ( 4 , 7 ). In these respects, the diverse large-herbivore assemblages in African savannas command attention ( 2 , 16 – 18 ). Identifying the factors that structure these assemblages is especially important given their precarious conservation status and key functional roles in ecosystems ( 19 , 20 ).…”

mentioning

confidence: 99%

“…Support for size-based partitioning of forage height and patch size is likewise variable ( 46 – 48 ). Last, although the grazer–browser spectrum is a robust generality ( 35 ), species cluster bimodally along it ( 18 ), suggesting high niche overlap within grazer and browser guilds. One recent study ( 18 ) theorized that competition promotes stabilizing dietary differences between clusters, while equalizing effects of competitive similarity enable coexistence within them ( 10 ).…”

mentioning

confidence: 99%

“…Last, although the grazer–browser spectrum is a robust generality ( 35 ), species cluster bimodally along it ( 18 ), suggesting high niche overlap within grazer and browser guilds. One recent study ( 18 ) theorized that competition promotes stabilizing dietary differences between clusters, while equalizing effects of competitive similarity enable coexistence within them ( 10 ). However, such clumpy patterns along a niche axis might reflect cryptic niche differences, rather than ecological equivalence, within clusters ( 49 ).…”

mentioning

confidence: 99%

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The generality of cryptic dietary niche differences in diverse large-herbivore assemblages

Pansu

Hutchinson

Anderson

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Ecological niche differences are necessary for stable species coexistence but are often difficult to discern. Models of dietary niche differentiation in large mammalian herbivores invoke the quality, quantity, and spatiotemporal distribution of plant tissues and growth forms but are agnostic toward food plant species identity. Empirical support for these models is variable, suggesting that additional mechanisms of resource partitioning may be important in sustaining large-herbivore diversity in African savannas. We used DNA metabarcoding to conduct a taxonomically explicit analysis of large-herbivore diets across southeastern Africa, analyzing ∼4,000 fecal samples of 30 species from 10 sites in seven countries over 6 y. We detected 893 food plant taxa from 124 families, but just two families—grasses and legumes—accounted for the majority of herbivore diets. Nonetheless, herbivore species almost invariably partitioned food plant taxa; diet composition differed significantly in 97% of pairwise comparisons between sympatric species, and dissimilarity was pronounced even between the strictest grazers (grass eaters), strictest browsers (nongrass eaters), and closest relatives at each site. Niche differentiation was weakest in an ecosystem recovering from catastrophic defaunation, indicating that food plant partitioning is driven by species interactions, and was stronger at low rainfall, as expected if interspecific competition is a predominant driver. Diets differed more between browsers than grazers, which predictably shaped community organization: Grazer-dominated trophic networks had higher nestedness and lower modularity. That dietary differentiation is structured along taxonomic lines complements prior work on how herbivores partition plant parts and patches and suggests that common mechanisms govern herbivore coexistence and community assembly in savannas.

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Section: Discussionsupporting

confidence: 91%

Section: Resultssupporting

confidence: 83%