Lednia Research Articles

The unknown unknown: A framework for assessing environmental DNA assay specificity against unsampled taxa.

Taxon-specific quantitative PCR (qPCR) assays are commonly used for environmental DNA sampling-based inference of animal presence. These assays require thorough validation to ensure that amplification truly indicates detection of the target taxon, but a thorough validation is difficult when there are potentially many non-target taxa, some of which may have incomplete taxonomies. Here, we use a previously published, quantitative model of cross-amplification risk to describe a framework for assessing qPCR assay specificity when there is missing information and it is not possible to assess assay specificity for each individual non-target confamilial. In this framework, we predict assay specificity against unsampled taxa (non-target taxa without sequence data available) using the sequence information that is available for other confamilials. We demonstrate this framework using four case study assays for: (1) An endemic, freshwater arthropod (meltwater stonefly; Lednia tumana), (2) a globally distributed, marine ascidian (Didemnum perlucidum), (3) a continentally distributed freshwater crustacean (virile crayfish; Faxonius virilis, deanae and nais species complex) and (4) a globally distributed freshwater teleost (common carp; Cyprinus carpio and its close relative C. rubrofuscus). We tested the robustness of our approach to missing information by simulating application of our framework for all possible subsamples of 20-all non-target taxa. Our results suggest that the modelling framework results in estimates which are largely concordant with observed levels of cross-amplification risk using all available sequence data, even when there are high levels of data missingness. We explore potential limitations and extensions of this approach for assessing assay specificity and provide users with an R Markdown template for generating reproducible reports to support their own assay validation efforts.

Validation of a species-specific probe-based qPCR assay for the threatened meltwater stonefly, Lednia tumana, in environmental samples

Validation of a species-specific probe-based qPCR assay for the threatened meltwater stonefly, Lednia tumana, in environmental samples

Warming undermines emergence success in a threatened alpine stonefly: A multi‐trait perspective on vulnerability to climate change

AbstractVulnerability to warming is often assessed using short‐term metrics such as the critical thermal maximum (CTMAX), which represents an organism's ability to survive extreme heat. However, the long‐term effects of sub‐lethal warming are an essential link to fitness in the wild, and these effects are not adequately captured by metrics like CTMAX.The meltwater stonefly,Lednia tumana, is endemic to high‐elevation streams of Glacier National Park, MT, USA, and has long been considered acutely vulnerable to climate‐change‐associated stream warming. As a result, in 2019, it was listed as Threatened under the U.S. Endangered Species Act. This presumed vulnerability to warming was challenged by a recent study showing that nymphs can withstand short‐term exposure to temperatures as high as ~27°C. But whether they also tolerate exposure to chronic, long‐term warming remained unclear.By measuring fitness‐related traits at several ecologically relevant temperatures over several weeks, we show thatL. tumanacannot complete its life‐cycle at temperatures only a few degrees above what some populations currently experience.The temperature at which growth rate was maximized appears to have a detrimental impact on other key traits (survival, emergence success and wing development), thus extending our understanding ofL. tumana's vulnerability to climate change.Our results call into question the use of CTMAXas a sole metric of thermal sensitivity for a species, while highlighting the power and complexity of multi‐trait approaches to assessing vulnerability.Read the freePlain Language Summaryfor this article on the Journal blog.

Cold Tolerance of Mountain Stoneflies (Plecoptera: Nemouridae) from the High Rocky Mountains

How aquatic insects cope with cold temperatures is poorly understood. This is particularly true for high-elevation species, which often experience a seasonal risk of freezing. In the Rocky Mountains, nemourid stoneflies (Plecoptera: Nemouridae) are a major component of mountain stream biodiversity and are typically found in streams fed by glaciers and snowfields, which are rapidly receding due to climate change. Predicting the effects of climate change on mountain stoneflies is difficult because their thermal physiology is largely unknown. We investigated cold tolerance of several alpine stoneflies (Lednia tumana, Lednia tetonica, and Zapada spp.) from the Rocky Mountains, USA. We measured the supercooling point (SCP) and tolerance to ice enclosure of late-instar nymphs collected from a range of thermal regimes. SCPs varied among species and populations, with the lowest SCP measured for nymphs from an alpine pond, which was much more likely to freeze solid in winter than flowing streams. We also show that L. tumana cannot survive being enclosed in ice, even for short periods of time (<3 h) at relatively mild temperatures (–0.5 °C). Our results indicate that high-elevation stoneflies at greater risk of freezing may have correspondingly lower SCPs, and despite their common association with glacial meltwater, these stoneflies appear to be living near their lower thermal limits.

Mountain stoneflies may tolerate warming streams: Evidence from organismal physiology and gene expression.

Rapid glacier recession is altering the physical conditions of headwater streams. Stream temperatures are predicted to rise and become increasingly variable, putting entire meltwater-associated biological communities at risk of extinction. Thus, there is a pressing need to understand how thermal stress affects mountain stream insects, particularly where glaciers are likely to vanish on contemporary timescales. In this study, we measured the critical thermal maximum (CTMAX ) of stonefly nymphs representing multiple species and a range of thermal regimes in the high Rocky Mountains, USA. We then collected RNA-sequencing data to assess how organismal thermal stress translated to the cellular level. Our focal species included the meltwater stonefly, Lednia tumana, which was recently listed under the U.S. Endangered Species Act due to climate-induced habitat loss. For all study species, critical thermal maxima (CTMAX >20°C) far exceeded the stream temperatures mountain stoneflies experience (<10°C). Moreover, while evidence for a cellular stress response was present, we also observed constitutive expression of genes encoding proteins known to underlie thermal stress (i.e., heat shock proteins) even at low temperatures that reflected natural conditions. We show that high-elevation aquatic insects may not be physiologically threatened by short-term exposure to warm temperatures and that longer-term physiological responses or biotic factors (e.g., competition) may better explain their extreme distributions.

Long-term alpine stream monitoring in the Teton Range: Investigating multi-year patterns and thermal physiology

Alpine streams and the biotic communities they contain are imperiled worldwide due to climate warming and the rapid decline of ice. The loss of glaciers and permanent snowpack may drive local populations to extinction, especially organisms with narrow habitat tolerances. We have been monitoring alpine streams in the Teton Range since 2015 that originate from three hydrological sources: surface glaciers, snowfields, or subterranean ice (e.g., rock glaciers). We call these stream types glacier-fed, snowmelt-fed, and icy seeps, respectively. We hypothesize that icy seeps may persist on the landscape longer than other hydrologic sources and that these features may act as a refuge for cold-adapted organisms such as the stoneflies Zapada glacier and Lednia tetonica. In November 2019, Z. glacier and a sister species of L. tetonica, Lednia tumana, were listed under the U.S. Endangered Species Act. This decision was based in part on work funded by the UW-NPS and highlights the pressing nature of our efforts. In 2019, we collected a 5th year of long-term data to begin investigating multi-year signals in the data. Our second 2019 objective was to further explore how thermal regimes affect tolerance of potentially imperiled insects. Because our annual data collection occurs in late summer with sample processing and analysis extending into the following year, this report will be a broad update on the project as whole, rather than 2019-specific. Through long-term monitoring of streams from different hydrological sources, we are building a dataset that will allow us to understand changes as air temperatures warm and permanent ice is lost in the alpine zone.&#x0D; &#x0D; Featured photo by Nicole Y-C on Unsplash. https://unsplash.com/photos/9XixVlnUCbk

Congruent population genetic structure but differing depths of divergence for three alpine stoneflies with similar ecology and geographic distributions

AbstractComparative population genetic studies provide a powerful means for assessing the degree to which evolutionary histories may be congruent among taxa while also highlighting the potential for cryptic diversity within existing species.In the Rocky Mountains, three confamilial stoneflies (Zapada glacier,Lednia tumana, andLednia tetonica; Plecoptera, Nemouridae) occupy cold alpine streams that are primarily fed by melting ice.Lednia tumanaandL. tetonicaare sister species diagnosed from systematic morphological differences, and they are endemic to areas surrounding Glacier National Park and Grand Teton National Park, respectively, in theU.S.Rocky Mountains.Zapada glacieris also present in alpine streams from Glacier National Park to the Teton Range, sometimes co‐occurring with eitherLedniaspecies.We used mitochondrial sequence data to clarify species boundaries, compare population genetic patterns, and test demographic models in a coalescent framework for the three stoneflies. We addressed four questions: (1) Is there genetic support for the morphology‐based species boundaries inLednia? (2) Is there genetic support for cryptic, or as‐yet undescribed, diversity withinZ. glacier? (3) Do similar geographic distributions and ecological requirements yield spatial congruence of genetic structure between high‐elevationLedniaandZ. glacierpopulations? (4) Is there evidence for contemporary gene flow among isolated populations in either group?Our results supported the existing taxonomy withZ. glacierand the twoLedniaspecies differing in their depths of divergence among study regions (e.g. maximum sequence divergence withinZ. glacier = 1.2% versus 5% betweenL. tumanaandL. tetonica). However, spatial population genetic patterns were broadly congruent, indicating stonefly populations isolated on mountaintop islands. Coalescent modelling supported the possibility of rare, extremely limited contemporary gene flow amongZ. glacierpopulations, with no support for gene flow betweenL. tumanaandL. tetonica.The focal stoneflies and associated assemblages occupy the highest elevation, coldest permanent alpine streams in the study region. This lotic habitat type faces an uncertain future under a diminishing alpine cryosphere. Given spatial congruence of genetic structure demonstrating unique biodiversity associated with individual alpine islands, we encourage conservation management strategies be developed and applied at corresponding spatial scales.

Assessing thermal tolerance of vulnerable alpine stream insects as part of a long-term monitoring project in the Teton Range, Wyoming

Alpine streams are predicted to decline as air temperatures warm and their water sources dry. Stream temperatures are expected to increase as glaciers and permanent snowfields decrease in size. For aquatic insects that are cold-adapted and restricted to small, high elevation streams fed by glaciers or snowfields, warmer water temperatures could be lethal. Conversely, less water in streams may increase the likelihood of insects freezing during winter months. We measured the critical thermal maximum (CTMAX) – the highest non-lethal temperature an insect can survive, and supercooling temperature – the temperature at which an insect freezes, of three alpine stoneflies, Zapada sp., Lednia tetonica and Lednia tumana, collected in Grant Teton and Glacier National Parks. CTMAX and supercooling point varied among species and with stream source (glacier-fed, snowmelt-fed and icy seep) and population (seven populations). Supercooling temperature was lowest in an alpine tarn and highest in glacier- and snowmelt-fed streams. Zapada sp. had the lowest CTMAX of the three species. Stoneflies from icy seeps had lower CTMAX than individuals from glacier- or snowmelt-fed streams. Individuals that likely experience the coldest winter temperatures had the lowest supercooling temperature. Similarly, stoneflies that experienced warmer water temperatures also had higher CTMAX values. Investigating the thermal tolerances of alpine stoneflies allows us to predict how these insects may respond to future climate change scenarios.&#x0D; &#x0D; Featured photo by Nicole Y-C on Unsplash. https://unsplash.com/photos/9XixVlnUCbk

Climate-induced glacier and snow loss imperils alpine stream insects.

Climate warming is causing rapid loss of glaciers and snowpack in mountainous regions worldwide. These changes are predicted to negatively impact the habitats of many range-restricted species, particularly endemic, mountaintop species dependent on the unique thermal and hydrologic conditions found only in glacier-fed and snow melt-driven alpine streams. Although progress has been made, existing understanding of the status, distribution, and ecology of alpine aquatic species, particularly in North America, is lacking, thereby hindering conservation and management programs. Two aquatic insects - the meltwater stonefly (Lednia tumana) and the glacier stonefly (Zapada glacier) - were recently proposed for listing under the U.S. Endangered Species Act due to climate-change-induced habitat loss. Using a large dataset (272 streams, 482 total sites) with high-resolution climate and habitat information, we describe the distribution, status, and key environmental features that limit L.tumana and Z.glacier across the northern Rocky Mountains. Lednia tumana was detected in 113 streams (175 sites) within Glacier National Park (GNP) and surrounding areas. The probability of L.tumana occurrence increased with cold stream temperatures and close proximity to glaciers and permanent snowfields. Similarly, densities of L.tumana declined with increasing distance from stream source. Zapada glacier was only detected in 10 streams (24 sites), six in GNP and four in mountain ranges up to ~600km southwest. Our results show that both L.tumana and Z.glacier inhabit an extremely narrow distribution, restricted to short sections of cold, alpine streams often below glaciers predicted to disappear over the next two decades. Climate warming-induced glacier and snow loss clearly imperils the persistence of L.tumana and Z.glacier throughout their ranges, highlighting the role of mountaintop aquatic invertebrates as sentinels of climate change in mid-latitude regions.

Thermal tolerance of meltwater stoneflyLednia tumananymphs from an alpine stream in Waterton–Glacier International Peace Park, Montana, USA

AbstractGlobal climate change threatens to affect negatively the structure, function, and diversity of aquatic ecosystems worldwide. In alpine systems, the thermal tolerances of stream invertebrates can be assessed to understand better the potential effects of rising ambient temperatures and continued loss of glaciers and snowpack on alpine stream ecosystems. We measured the critical thermal maximum (CTM) and lethal temperature maximum (LTM) of the meltwater stonefly (Lednia tumana), a species limited to glacial and snowmelt-driven alpine streams in the Waterton–Glacier International Peace Park area and a candidate for listing under the US Endangered Species Act. We collected L. tumana nymphs from Lunch Creek in Glacier National Park, Montana (USA) and transported them to a laboratory at the University of Montana Flathead Lake Biological Station, Polson, Montana. We placed nymphs in a controlled water bath at 1 of 2 acclimation temperatures, 8.5 and 15°C. We increased water temperature at a constant rate ...