Anthropogenic stressors have strong impacts on ecosystems. To understand their influence, detailed knowledge about trophic relationships among species is critical. However, this requires both exceptional resolution in dietary assessments and sampling breadth within communities, especially for highly diverse, tropical ecosystems. We used gut content metabarcoding across a broad range of coral reef fishes (8 families, 22 species) in Mo'orea, French Polynesia, to test whether this technique has the potential to capture the structure of a hyperdiverse marine food web. Moreover, we explored whether taxonomic groups (families) and traditional, broad‐scale trophic assignments explained fish diet across four different metrics of quantifying predator–prey interactions. Metabarcoding yielded a large number (4,341) of unique operational taxonomic units (i.e. prey) with high‐resolution taxonomic assignments (i.e. often to the level of genus or species). We demonstrate that across multiple metrics, taxonomic group at the family level is a consistently better, albeit still weak, predictor of empirical trophic relationships than frequently used, broad‐scale functional assignments. Our method also reveals a complex trophic network with fine‐scale partitioning among species, further emphasizing the importance of examining fish diets beyond broad trophic categories. We demonstrate the capacity of metabarcoding to reconstruct diverse and complex food webs with exceptional resolution, a significant advancement from traditional food web reconstruction. Furthermore, this method allows us to pinpoint the trophic niche of species with niche‐based modelling, even across hyperdiverse species assemblages such as coral reefs. In conjunction with complementary techniques such as stable isotope analysis, applying metabarcoding to whole communities will provide unparalleled information about energy and nutrient fluxes and inform their susceptibility to disturbances even in the world's most diverse ecosystems.
Oligotrophic tropical coral reefs are built on efficient internal energy and nutrient cycling, facilitated by tight trophic interactions. In the competition for available prey, some small fishes have evolved to feed on apparently barren sand patches that connect hard‐substratum patches in many reef habitats. One strategy for obtaining prey from a particulate matrix is to sift out small prey items from the sediment (often called ‘winnowing’). Yet, the trophic link between small winnowing consumers and their prey are poorly resolved, let alone the morphological specialisations that enable this foraging behaviour. We used aquarium‐based feeding experiments to quantify the impact of winnowing by two sand‐dwelling goby species ( After 4 days of sifting through the sand matrix, the two species significantly reduced meiobenthic prey abundance by 30.7% ± 9.2 Our results provide important background on the trophic link between the meiobenthos and winnowing gobies on coral reefs. The revealed specialisations of the goby feeding apparatus facilitate sand‐sifting foraging behaviour and access to an otherwise inaccessible trophic niche of microscopic prey. By having evolved a specialised strategy to obtain nutritious and highly abundant prey from seemingly barren sand, we suggest that winnowing gobies act as an important conduit for sand‐derived energy to higher trophic levels.
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- Award ID(s):
- 1701665
- NSF-PAR ID:
- 10369702
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 36
- Issue:
- 8
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- p. 1936-1948
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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