Biology subjects

Hanner, R. H.

Publications and source records attributed to Hanner, R. H..

5 recordsLinked to original sources

bioRxiv2026

Mining association rules for targeted spatiotemporal aquatic environmental DNA (eDNA) sampling

Environmental DNA (eDNA) offers a non-invasive alternative to traditional, more destructive sampling methods for determining species occupancy at ecological sites of interest. Aquatic eDNA sampling entails filtering a known volume of water to capture and detect genetic material shed by organisms. While the influence of individual environmental properties on the presence of target eDNA has been widely studied, it remains unclear how variables like temperature, pH, flow rate and conductivity correlate collectively with site electrofishing counts and eDNA concentrations. Resolving this question is important for two reasons: (1) typically, only eDNA, not physical specimens, is collected and measured, and (2) when methods like electrofishing and eDNA sampling are used in tandem, results often differ. Here unsupervised association rule-based machine learning is employed to discover interesting relationships among sampled covariates within a previously published case study of native brook trout (Salvelinus fontinalis) collected from Hanlon Creek (Guelph, Ontario, Canada) in September 2019. From a dataset of only 126 observations, the mining process revealed over 12000 plausible association rules linking covariates to eDNA concentrations (low/high) and electrofishing outcomes (absence/presence of brook trout). A strict pruning strategy reduced this ruleset to a manageable size of 153 associations, some of which were corroborated by existing literature, and some of which were novel (such as those potentially relating electrical conductivity to microbial and enzymatic activity). The entire workflow is included as a new R package called RulesTools. These results highlight the promise of association rule mining as a tool for guiding eDNA metadata collection, complementing statistical modelling, and informing conservation and management decision-making.

ecology↗

bioRxiv2022

Metabarcoding metacommunities: time, space, and land use interact to structure aquatic macroinvertebrate communities in streams

There is an increasing need to move beyond evaluating the effect of land use on stream communities by only studying local variables, and instead incorporate a metacommunity perspective which integrates environmental and spatial factors across larger spatial scales. The use of molecular tools (DNA metabarcoding) to identify bioindicator groups, such as aquatic macroinvertebrates, can provide greater taxonomic resolution to explore patterns in stream metacommunities. In this study, we collected aquatic macroinvertebrates from streams in southern Ontario which spanned a gradient of agricultural disturbance and used DNA metabarcoding to identify the species composition from these samples. We address a significant knowledge gap in previous stream aquatic macroinvertebrate metacommunity studies by incorporating molecular identification as well as a temporal component. We observed that a combination of local habitat conditions, regional agricultural land use, and spatial position influenced aquatic macroinvertebrate community composition, suggesting there is an interaction between environmental filtering and dispersal processes that structures these communities. However, aquatic macroinvertebrate communities were also highly dissimilar between streams and composed of many rare species, and a large percentage of unexplained variation suggests that there is a strong stochastic component to community assembly. We also observed that there is a seasonal component to metacommunity dynamics, with different water quality variables being significant to community composition in each sampling month. While we expected that an increased percentage of surrounding agricultural land use would result in more homogenous macroinvertebrate communities, we only detected this relationship in May and found evidence that a larger riparian buffer width can mitigate the effects of agricultural land use. We demonstrate the utility of DNA metabarcoding for revealing patterns in metacommunity dynamics that may not be detectable using coarse taxonomic identifications, and reveal the importance of incorporating a seasonal component when evaluating the influence of land use on community composition.

ecology↗

bioRxiv2022

Hidden diversity - DNA metabarcoding reveals hyper-diverse benthic invertebrate communities

Freshwater ecosystems, such as streams, are facing increasing pressures from agricultural land use. Aquatic insects and other macroinvertebrates have historically been used as indicators of ecological condition and water quality in freshwater biomonitoring programs; however, many of these protocols use coarse taxonomic resolution (e.g., family) when identifying macroinvertebrates. The use of family-level identification can mask species-level diversity, as well as patterns in community composition in response to environmental variables. Recent literature stresses the importance of robust biomonitoring to detect trends in insect decline globally, though most of these studies are carried out in terrestrial habitats. Here, we incorporate molecular identification (DNA metabarcoding) into a stream biomonitoring sampling design to explore the diversity and variability of aquatic macroinvertebrate communities at small spatial scales. We sampled twenty southern Ontario streams in an agricultural landscape for aquatic macroinvertebrates and, using DNA metabarcoding, revealed incredibly rich benthic communities which were largely comprised of rare taxa detected only once per stream despite multiple biological replicates. In addition to numerous rare taxa, our species pool estimates indicated that after 240 samples from twenty streams, there was a large proportion of taxa present which remained undetected by our sampling regime. When comparing different levels of taxonomic resolution, we observed that using OTUs revealed over ten times more taxa than family-level identification. A single insect family, the Chironomidae, contained over one third of the total number of OTUs detected in our study. Within-stream dissimilarity estimates were consistently high for all taxonomic groups (invertebrate families, invertebrate OTUs, chironomid OTUs), indicating stream communities are very dissimilar at small spatial scales. While we predicted that increased land use would homogenize benthic communities, this was not supported as within-stream dissimilarity was unrelated to land use.

ecology↗

bioRxiv2019

Phylogeny of Holarctic gall wasps of the genera Diplolepis and Periclistus (Hymenoptera: Cynipidae) based on DNA barcodes

Rose gall wasps Diplolepis induce structurally distinct galls on wild roses, which provide gallers with food and shelter. These galls are attacked by a wide variety of micro-hymenopterans including another cynipid Periclistus that act as inquilines. Both Diplolepis and Periclistus are difficult to distinguish based on adult morphology, instead the structural appearance of galls is often used to distinguish species. Using the mitochondrial gene COI, we built phylogenies of both Diplolepis and Periclistus, while also estimating the ancestral host use of the inducers. Our phylogeny recovered the monophyly of Diplolepis, which have likely diverged from single-or multi-chambered leaf gallers to other plant organs. Periclistus exhibits a divide between the Palearctic and Nearctic clades, and ranges from specialists to generalists in terms of host specificity. The molecular results have largely supported the validity of species described in the literature, with notable exceptions in four species groups. While it is premature to enact any taxonomic changes without additional molecular markers, this incongruence between morphological and molecular data indicates these groups need taxonomic revision and gall morphology alone may be inadequate to delimit species.

zoology↗

bioRxiv2018

Multiple species drive flexible lake food webs with warming

Climate change is rewiring the food webs that determine the fate of diverse ecosystems. Mobile generalist consumers are responding to climate change by rapidly shifting their behaviour and foraging, driving food webs to flex. Although these responsive generalists form a key stabilizing module in food web structure, the extent to which they are present throughout whole food webs is largely unknown. Here, we show that multiple species comprising key trophic roles drive flexible lake food webs with warming. By examining lakes that span a 7{degrees}C air temperature gradient, we found significant reductions in nearshore derived carbon and nearshore habitat use with increased temperature in three of four fish species. We also found evidence that the response of lake trout to increased temperatures may reduce their biomass and cascade to release their preferred prey, the pelagic forage fish cisco. Our results suggest that climate warming will shift lake food webs toward increased reliance on offshore habitats and resources. We argue that species across trophic levels broadly couple lake macrohabitats, suggesting that potentially stabilizing responsive consumers are present throughout food webs. However, climate change appears to limit their ability to responsively forage, critically undermining a repeated stabilizing mechanism in food webs.

ecology↗