The role of deterministic and stochastic processes in community assembly is a key question in community ecology. We evaluated the effect of an abiotic filter (hydroperiod) on the partitioned diversity of three taxonomic groups (birds, vegetation, macroinvertebrates) from prairie pothole wetlands in Alberta, Canada, which naturally vary in water permanence. We observed that alpha and gamma diversity were higher in permanent than temporary wetlands (16–25% and 34–47% respectively, depending on the taxon). This suggests an influence of deterministic constraints on the number of species a wetland can support. Taxa which cannot persist in shallow, temporary wetlands are excluded by the deterministic constraints that a shortened hydroperiod imposes. In contrast, we observed that beta diversity was significantly higher (2–12%) in temporary wetlands than permanent ones, and temporary wetlands supported more unique combinations of community composition than permanent wetlands, despite having a smaller regional species pool. This observation contradicts prior mesocosm studies that found beta diversity mirrored the pattern in gamma diversity along an environmental filtering gradient. We conclude that deterministic processes are more influential in more stable permanent wetlands, whereas stochastic processes play a more important role in assembly in dynamic temporary wetlands that must disassemble and re‐establish annually. Considering three distinct taxonomic groups differing in their relative mobility, our large‐scale field study demonstrates that both stochastic and deterministic processes act together to influence the assembly of multiple communities and that the relative importance of the two processes varies consistently along a gradient of environmental filtering.

Freshwater habitats are particularly sensitive to changes caused by anthropogenic stress, including habitat degradation, pollution and alteration of water inputs and flow (Dudgeon et al., 2006).Bioindicators are species or taxonomic groups that respond predictably to environmental changes (Cairns & Pratt, 1993) and are often used to evaluate the degree of disturbance or habitat impairment (Norris & Hawkins, 2000). Aquatic macroinvertebrates are commonly used bioindicators in both lentic and lotic systems (Bonada, Prat, Resh, & Statzner, 2006;Cairns & Pratt, 1993); however, they present challenges to traditional morphological identification as some immature stages cannot be reliably identified. The difficulty of identifying juvenile or damaged specimens can result in a significant

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Globally, many aquatic ecosystems experience periodic desiccation that imposes stress on biota. The Northern Prairie Pothole Region (NPPR) in Alberta, Canada, contains abundant wetlands that fill with spring snowmelt and then draw down throughout the summer. They are often assigned a pond‐permanence class based on the duration of ponded water. These dynamic wetlands are home to diverse and productive communities of macroinvertebrates. We expected that pond permanence structures macroinvertebrate communities in NPPR wetlands. In addition to exploring the taxonomic composition of macroinvertebrate communities, we aimed to characterise these communities by functional groups to test for associations between pond permanence and desiccation strategies, feeding groups or behavioural guilds. We sampled aquatic macroinvertebrates from 87 wetlands in the NPPR that spanned a range of pond‐permanence classes. We identified macroinvertebrates to the lowest practical taxonomic level, usually family. We then performed multivariate analyses (multiresponse permutation procedures, non‐metric multidimensional scaling) to identify differences in community composition and functional groups among permanence classes. Community composition of macroinvertebrates was statistically distinct among pond‐permanence classes, with the extremes of temporarily‐ and permanently‐ ponded wetlands differing most. Notably, macroinvertebrates in temporarily‐ ponded wetlands were not unique taxa specially adapted to low‐permanence wetlands, but rather a subset of the community found in more permanent wetlands. In other words, macroinvertebrates at the family level exhibit a nested pattern of diversity best predicted by the permanence of ponded water in wetlands.

Freshwater ecosystems provide essential ecosystem services and support biodiversity; however, their water quality and biological communities are influenced by adjacent agricultural land use. Aquatic macroinvertebrates are commonly used as bioindicators of stream conditions in freshwater biomonitoring programs. Sorting benthic samples for molecular identification is a time-consuming process, and this study investigates the potential of ethanol-collected environmental DNA (eDNA) for metabarcoding macroinvertebrates, especially for common bioindicator groups. The objective of this study was to compare macroinvertebrate composition between paired bulk tissue and ethanol eDNA samples, as eDNA could provide a less time-consuming and non-destructive method of sampling macroinvertebrates. We collected benthic samples from streams in Ontario, Canada, and found that community composition varied greatly between sampling methods and that few taxa were shared between paired tissue and ethanol samples, suggesting that ethanol eDNA is not an acceptable substitute. It is unclear why we did not detect all the organisms that were preserved in the ethanol, or the origin of the DNA we did detect. Furthermore, we also detected no difference in community composition for bioindicator taxa due to surrounding land use or water chemistry, suggesting sites were similar in ecological condition.