Ephemeroptera, Plecoptera And Trichoptera Taxa Research Articles

Analyzing multiple stressor effects on EPT taxa in a mesocosm experiment with DNA metabarcoding

Multiple stressors diversely and often adversely affect stream ecosystems around the globe. Therefore, understanding multiple stressor effects on different organisms is essential for a better ecosystem understanding, an accurate water quality assessment and improved ecosystem management. However, while multiple stressor effects should be assessed at species level this taxonomic resolution is often not achieved e.g. for stream macroinvertebrates. Due to their high abundance and diversity, species-level identification is often not feasible with morphology‑based approaches. DNA metabarcoding represents an alternative approach for studying multiple stressor interactions at species level. In an outdoor experiment over 10,000 specimens from the insect orders Ephemeroptera, Plecoptera and Trichoptera (EPT), which are routinely used as bioindicators, and their responses to stressors were studied. In the experiment salinity, fine sediment deposition and flow velocity were manipulated in a full‑factorial design in 64 mesocosms with two microhabitats each (streambed and leaf litter), resulting in eight replicates per treatment. DNA metabarcoding revealed 122 EPT Operational Taxonomic Units (OTUs), from which the most abundant 27 alone showed 14 different response patterns to the applied stressors. The high taxonomic resolution achieved by DNA metabarcoding revealed species specific stressor responses that were hidden at a lower taxonomic resolution. As a prominent example, Rhithrogena semicolorata responded negatively to fine sediment deposition and flow velocity reduction, while Ecdyonurus torrentis (both Heptageniidae, Ephemeroptera) was insensitive to experimental manipulation, highlighting different stressor responses among species within the same family (Fig. 1, Beermann et al. 2020). Even for well-studied organisms such as EPT taxa, this study shows that DNA metabarcoding has the potential to depict response patterns at species or OTU level despite high specimen abundance. Consequently, DNA metabarcoding promises to be a rewarding method when investigating and assessing multiple stressor effects on stream water quality.

Applying the umbrella index across aquatic insect taxon sets for freshwater assessment

Abstract Biological surrogates in conservation biology are valuable for rapid biodiversity and environmental surveys, and as an early warning of potential threats. However, these surrogates need to be simple and inexpensive to apply. The umbrella index was applied here to quantify the selection of surrogate species for biodiversity assessments, but requires interrogation for application in areas rich in threatened endemic species. Aquatic larvae of Ephemeroptera, Plecoptera and Trichoptera (EPT), as well as the adult Odonata, are all highly responsive to changes in freshwater condition. Using the umbrella index, we evaluated the performance of the surrogate species approach for aquatic insect conservation in a region (Greater Cape Floristic Region) with an exceptional level of rare and endemic species, across multiple rivers with different disturbance levels. Due to a lack of species level information, EPT taxa were calculated using morphospecies within families, and Odonata were identified to species level. The umbrella index identified eight EPT species and seven Odonata species as potential surrogates. Both these groups co-occurred with high percentages of their own overall groups (EPT surrogates for overall EPT, and Odonata surrogates for overall Odonata), as well as for the other group (EPT surrogates for overall Odonata, and Odonata surrogates for overall EPT). The index was surprisingly flexible, and performed well in an area with so many species of conservation concern, as well as across spatial scales greater than a single river, with varying degrees of disturbance. Both EPT and Odonata showed promise as potential biodiversity surrogates, and for future conservation planning. Ideally, conservationists should aim to use taxa that are easy to identify to species level, with known sensitivities to human disturbance. However, when this is not a possibility, the umbrella index is still applicable and accurate for morphospecies (family level sensitivities).