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Sequencing streams: a molecular approach for monitoring macroinvertebrate biodiversity and metacommunity dynamics in an agricultural landscape

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Title: Sequencing streams: a molecular approach for monitoring macroinvertebrate biodiversity and metacommunity dynamics in an agricultural landscape
Author: Gleason, Jennifer Erin
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: Cottenie, KarlHanner, Robert
Abstract: Freshwater habitats are under increased pressures from human-induced landscape changes, an aquatic biodiversity is declining at unprecedented rates. There are potentially millions of undescribed invertebrate taxa, and this massive proportion of unknown diversity can impede our understanding of community composition and the conservation of freshwater habitats. Aquatic macroinvertebrates are commonly used bioindicators of environmental condition, yet these groups present significant challenges for morphological identification. The incorporation of molecular identification (e.g., DNA metabarcoding) can provide greater resolution to detect patterns in taxonomic richness and species distributions. In this thesis, I evaluated the efficacy of metabarcoding environmental DNA (eDNA) to capture the local community composition of aquatic macroinvertebrates in streams by comparing eDNA and tissue metabarcoding. I observed a significant lack of overlap between these two methods, suggesting that eDNA likely captures a different community altogether. Consequently, I used a bulk tissue approach to describe aquatic macroinvertebrate diversity in streams across a gradient of agricultural activity in Ontario, Canada. I observed over 1600 Operational Taxonomic Units (OTUs; a proxy for species) from 149 invertebrate families and described unprecedented taxonomic turnover amongst adjacent patches in the same stream. Samples collected only ten meters apart shared few OTUs and were largely comprised of rare taxa, suggesting that assembly of these communities is extremely variable, even at small distances. I built upon these results by incorporating DNA metabarcoding in a metacommunity ecology framework to describe the environmental and spatial factors which influence aquatic macroinvertebrate community composition. I found evidence that both environmental filtering and dispersal-based processes work in tandem to influence stream communities, though there was also a strong influence of stochastic assembly given the proportions of unexplained variation and extremely high turnover between streams. A temporal influence was also revealed since stream communities were more strongly influenced by agricultural activity in the spring. In general, agricultural land use influenced aquatic macroinvertebrate composition, yet these effects may be mitigated by a larger riparian buffer. This thesis demonstrates the utility of DNA metabarcoding for both biomonitoring and ecological applications and stresses the importance of integrative approaches for freshwater conservation and sustainable agricultural practices.
Date: 2022-05
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Related Publications: Gleason, J. E., Elbrecht, V., Braukmann, T. W. A., Hanner, R. H., & Cottenie, K. (2021). Assessment of stream macroinvertebrate communities with eDNA is not congruent with tissue-based metabarcoding. Molecular Ecology, 30, 3239-3251. doi: 10.1111/mec.15597.Gleason, J.E., Hanner, R. H., & Cottenie, K. (2022). Hidden diversity - DNA metabarcoding reveals hyper-diverse benthic invertebrate communities. bioRxiv. doi: 10.1101/2022.02.28.481642.Gleason, J.E., Hanner, R. H., & Cottenie, K. (2022). Metabarcoding metacommunities: time, space, and land use interact to structure aquatic macroinvertebrate communities in streams. bioRxiv. doi: 10.1101/2022.05.01.490210.

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