Conclusions

We analyzed stomach contents of wild-caught Campylomormyrus fish using hybrid capture and subsequent HTS DNA metabarcoding. Despite of the highly degraded nature of the dietary material, this approach provided a picture of the overall diet of this genus and revealed dietary diversity, relative to divergent phenotypical traits (EOD and snout). Although standard metabarcoding is technically less demanding and may be preferred for analysis of stomach samples if DNA quality is sufficient (Deagle et al. 2006; Jarman et al. 2004), hybrid capture provides an alternative for samples of progressed digestion and associated high DNA fragmentation. Generally, hybrid capture and subsequent HTS has been found superior to direct PCR amplification, when small fragment sizes are encountered, as in aDNA (e.g., Paijmans et al. 2016) and sedaDNA (e.g., Krueger et al. 2021). Our results confirmed that Campylomormyrus species can exploit multiple food niches in their habitats (fauna at the bottom, at the water surface, and in the water column) to feed on benthic invertebrates, allochthonous invertebrates, and vegetation. alpha and beta dietary diversity were significantly associated with differences in EOD duration and snout length. Divergence in these traits may constitute functional adaptations to exploiting different food sources and substrates and may underly the radiation and sympatric coexistence of the numerous species of this genus.