Insect-associated bacterial communities in an alpine stream

Abstract

The roles of macroinvertebrate and microbial communities in stream ecosystems are recognized to be important to energy flow and nutrient cycling. While the linkages of these major groups of aquatic organisms has not been thoroughly investigated, determining how they interact is particularly important for understanding the mechanisms and potential evolutionary relationships that contribute to ecosystem processes, such as organic matter decomposition. We evaluated the microbiomes of several aquatic macroinvertebrate species differing in trophic ecology and belonging to different functional feeding groups at two sites along an Italian Alpine river with different elevation and environmental characteristics, one located above the tree-line and the other in a forested environment. We found that the internal microbial communities of the different insect species significantly varied in taxonomic and functional composition and could be used to classify samples to both species and environment. We demonstrated that functional differences existed between the microbiota of different macroinvertebrate species with variable feeding behaviors, and that species differences were more important, in this context, than environmental or habitat conditions. These results provide new information on how the microbiomes of macroinvertebrates may potentially be influenced by their hosts and habitat conditions in Alpine streams.

Microbial succession from a subsequent secondary death event following mass mortality

“…A Random Forest algorithm was used to identify the highest-ranking predictor taxa among timepoints using highest mean decrease gini scores. This analysis was performed using the randomForest R package using default parameters (1000 trees) [ 2 , 45 – 47 ]. This model works by determining how much a model decreases in accuracy by removing a certain taxon [ 48 ].…”

The effects of taxonomy, diet, and ecology on the microbiota of riverine macroinvertebrates

“…A summary of the most common bacterial phyla identified within the microbiota of terrestrial invertebrates (Colman et al, 2012;Hernández-García et al, 2017;Jones et al, 2013;Mikaelyan et al, 2015;Muturi et al, 2017;Pérez-Cobas et al, 2015;Rizzi et al, 2013;Singhal et al, 2017;Yun et al, 2014) and freshwater invertebrates (Ayayee et al, 2018;Pechal & Benbow, 2016;Receveur et al, 2020), fishes (Desai et al, 2012;X. Li et al, 2013;Roeselers et al, 2011;Sullam et al, 2012;Wu et al, 2012), plants (Srivastava et al, 2017;Tanaka et al, 2012), sediments (Zhang et al, 2019), bacterioplankton (Ayayee et al, 2018;Portillo et al, 2012), and biofilms (Ayayee et al, 2018) is shown in Table 7.…”

“…Additionally, environmental bacteria have shown differential growth across aquatic substrates (Goldfarb et al, 2011); thus, we are seeking to understand whether similar patterns exist within invertebrate microbiota sampled across different microhabitats within a sampling site. Given that previous studies of both terrestrial and aquatic invertebrates have revealed significant differences among diets or functional feeding groups (Ayayee et al, 2018;Colman et al, 2012;Jones et al, 2013;Kim et al, 2017;Knapp et al, 2009;Mikaelyan et al, 2015;Pechal & Benbow, 2016;Receveur et al, 2020;Xiang et al, 2019;Yun et al, 2014), this is a factor that will be investigated in the current study. Additionally, the methodological omission noted in previous aquatic invertebrate studies provides increased motivation.…”

Flow intermittency negatively affects three phylogenetically related shredder stoneflies by reducing CPOM availability in recently intermittent Alpine streams in SW-Italian Alps

“…In addition, the high fine sediment deposition can alter the quantity of energy inputs, as it affects the amount of autotrophic production (Henley et al, 2000;Bona et al, 2016) and allochthonous coarse organic matter availability in Alpine streams (Doretto et al, 2016(Doretto et al, , 2017. In particular, the burial of leaf litter by sediments reduces availability of this resource and alters the composition of the microbial community involved in its degradation (Receveur et al, 2020), with consequent negative effects on shredder invertebrates (Danger et al, 2012).…”

“…Therefore, as flow intermittency events occur in summer, they are expected to impact shredders during the oviposition and early instars, greatly reducing their survival and abundance, but also because recurrent drying events significantly alter organic matter processing, as already observed in Mediterranean streams (e.g., Abril et al, 2016). For instance, surface flow disappearance usually reduces the decomposition rate especially in dry streambed sediments, where the activity of Ingoldian fungi, bacteria and invertebrates are inhibited by emersion (Corti et al, 2011;Receveur et al, 2020). In addition, lower flow velocity reduces the removal of fine sediments, with consequent high fine sediment deposition, which can alter the quality and quantity of resources, in terms of both reduced instream production, due to the abrasion of autotrophic biofilms (Henley et al, 2000;Bona et al, 2016), and allochthonous coarse organic matter availability through burial (Doretto et al, 2016).…”