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The rapid advancement of molecular biodiversity monitoring tools, particularly DNA metabarcoding, has improved specimen identification in bulk samples, such as those from Malaise traps, where traditional morphological identification is impractical. While not yet standardized, a typical first step in insect bulk sample analysis is the extraction of DNA from homogenized specimens. While this step yields reliable metabarcoding results, it destroys the specimens, preventing further use in monitoring and taxonomic analysis. Non-destructive lysis, which preserves specimen integrity, is still being evaluated for its effectiveness in accurately assessing bulk sample biodiversity. In this study, we assessed the suitability of non-destructive lysis for Malaise trap samples and compared its performance with homogenization using an established metabarcoding workflow. Five bulk samples were collected with Malaise traps. Samples were first incubated in a lysis buffer containing Proteinase K (non-destructive lysis) and then homogenized. DNA was extracted from both treatments and metabarcoding was performed to compare OTU richness, accumulation, and beta diversity. On average, homogenized samples yielded 3.8% more OTUs than non-destructive lysis samples. Although homogenization provides a more comprehensive and cost-effective assessment of Malaise trap bulk samples, non-destructive lysis still recovered at least 80% of the OTUs identified through homogenization and revealed similar patterns of community change. Even though our results show that both methods yield comparable data on insect biodiversity and can be used for monitoring, we consider non-destructive lysis as not suitable for integration into automated workflows or large-scale biomonitoring due to the much higher costs. Nonetheless, this method remains important in cases where morphological integrity needs to be preserved and additional sampling is not possible.

Abstract While macroinvertebrate dispersal operates at the individual level, predictions of their dispersal capabilities often rely on indirect proxies rather than direct measurements. To gain insight into the dispersal of individual specimens, it is crucial to mark (label) and capture individuals. Isotopic enrichment with 15N is a non‐invasive method with the potential of labelling large quantities of macroinvertebrates. While the analysis of 15N is widely utilised in food web studies, knowledge on the specific utility of isotopic enrichment with 15N for mass labelling of macroinvertebrate individuals across different taxa and feeding types is limited. Previous studies have focused on single species and feeding types, leaving gaps in our understanding of the broader applicability of this method. Therefore, this study aimed to test and compare isotopic mass enrichment across several macroinvertebrate taxa and feeding types. We released 15NH4Cl at five stream reaches in North‐Rhine Westphalia, Germany, and successfully enriched 12 distinct macroinvertebrate taxa (Crustacea and Insecta). Significant enrichment was achieved in active and passive filter feeders, grazers, shredders and predators, and predominantly showed positive correlations with the enrichment of the taxa's main food sources phytobenthos and particulate organic matter. Enrichment levels rose rapidly and peaked at distances between 50 m and 300 m downstream of the isotopic inlet; significant enrichment occurred up to 2000 m downstream of the isotopic inlet in all feeding types. Macroinvertebrate density estimates on the stream bottom averaged to a total of approximately 3.4 million labelled individuals of the 12 investigated taxa, thus showing the high potential of isotopic (15N) enrichment as a non‐invasive method applicable for mass labelling across different macroinvertebrate feeding types. Hence, isotopic enrichment can greatly assist the analysis of macroinvertebrate dispersal through mark‐and‐recapture experiments, as it allows to measure the movement at the level of individual specimens.

Abstract In lotic freshwater ecosystems, the drift or downstream movement of animals (e.g., macroinvertebrates) constitutes a key dispersal pathway, thus shaping ecological and evolutionary patterns. There is evidence that macroinvertebrate drift may be modulated by parasites. However, most studies on parasite modulation of host drifting behavior have focused on acanthocephalans, whereas other parasites, such as microsporidians, have been largely neglected. This study provides new insight into possible seasonal and diurnal modulation of amphipod (Crustacea: Gammaridae) drift by microsporidian parasites. Three 72 h drift experiments were deployed in a German lowland stream in October 2021, April, and July 2022. The prevalence and composition of ten microsporidian parasites in Gammarus pulex clade E varied seasonally, diurnally, and between drifting and stationary specimens of G. pulex. Prevalence was generally higher in drifting amphipods than in stationary ones, mainly due to differences in host size. However, for two parasites, the prevalence in drift samples was highest during daytime suggesting changes in host phototaxis likely related to the parasite’s mode of transmission and site of infection. Alterations in drifting behavior may have important implications for G. pulex population dynamics and microsporidians’ dispersal. The underlying mechanisms are more complex than previously thought.