Freshwater habitats are of high conservation value and provide a wide range of ecosystem services. Effective management requires regular monitoring. However, conventional methods based on direct observation or specimen collection are so invasive, expensive and labour-intensive that frequent monitoring is uncommon. Here, we test whether the evaluation of environmental DNA (eDNA) from water based on a simple protocol can be used for assessing biodiversity. We use universal metazoan primers for characterizing water eDNA across horizontal and vertical spatial dimensions in two reservoirs with known species diversity for two key taxa. eDNA obtained directly from 42 samples × 15 ml water (total = 630 ml) per reservoir yielded DNA signatures for more than 500 metazoan species, of which 105 could be identified to species/genus based on DNA barcodes. We show that eDNA can be used to assign each water sample to its reservoir of origin, and that eDNA outperforms conventional survey methods in single-sample richness comparisons, while revealing evidence for hundreds of unknown species that are undetected by conventional bioassessment methods. eDNA also confirms the presence of a recently discovered invasive snail species and provides evidence for the continued survival of a rare native species of goby not sighted in that habitat since 2007. eDNA thus promises to be a useful addition to the bioassessment toolbox for freshwater systems.
Studies of ecosystem functions are gaining traction in the scientific community along with a growing consensus that losses in ecosystem functions have widespread consequences. Food webs, which are networks comprising all trophic interactions (represented by links) between taxa present in a community (represented by nodes), are important aspects of ecosystem functioning, yet a clear understanding of the factors and mechanisms influencing their assembly and structure is lacking. In our study, we addressed this fundamental question by investigating the respective roles of (1) environmental filtering and (2) biotic filtering, in governing food web structure. We did this by assessing the relationship between the network structure of five high‐resolution empirical tropical food webs and associated environmental and biotic covariates. Our data suggest that only environmental filtering is important in shaping food webs. Further, we found that the underlying ecological mechanism is a function of bottom‐up influences comprising resource levels, and to a lesser degree, resource type (i.e., terrestrial organic matter) available. Specifically, our data suggest high‐nutrient environments favor greater food web complexity. In the general context of community assembly, our findings add to existing knowledge of the process by demonstrating that environmental conditions previously shown to influence species assemblages can also drive trends in prevailing species interactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.