Biology subjects

Finn, D. S.

Publications and source records attributed to Finn, D. S..

3 recordsLinked to original sources

bioRxiv2020

Cold tolerance of mountain stoneflies (Plecoptera: Nemouridae) from the high Rocky Mountains

ABSTRACTHow aquatic insects cope with cold temperatures is poorly understood. This is particularly true for high-elevation species that 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 due to climate change, are rapidly receding. 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 is 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 (less than three hours) 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, they appear to be living near their lower thermal limits.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2019

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 tested 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{degrees}C) far exceeded the stream temperatures mountain stoneflies experience (< 10{degrees}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.

physiology↗

bioRxiv2019

Headwaters fed by subterranean ice: potential climate refugia for mountain stream communities?

Near-term extirpations of macroinvertebrates are predicted for mountain streams worldwide as a warming climate drives the recession of high-elevation ice and snow. However, hydrological sources likely vary in their resistance to climate change and thus streams fed by more resistant sources could persist as climate refugia for imperiled biota. In 2015-2016, we measured habitat characteristics and quantified macroinvertebrate community structure along six alpine streams in the Teton Range, Wyoming, USA. Strong differences in habitat characteristics (e.g., temperature, bed stability, conductivity) confirmed three major stream sources: surface glaciers, perennial snowfields, and subterranean ice. Subterranean ice-fed streams - termed "icy seeps" - appear common in the Teton Range and elsewhere yet are globally understudied. Midges in the family Chironomidae dominated our study sites, representing 78.6% of all specimens sampled, with nematodes, caddisflies (Neothremma), and mayflies (Epeorus) also common. At the community-scale, glacier-and snowmelt-fed streams differed significantly in multivariate space, with icy-seep communities intermediate between them, incorporating components of both assemblages. Because the thermal environment of subterranean ice, including rock glaciers, is decoupled from large-scale climatic conditions, we predict that icy seeps will remain intact longer than streams fed by surface ice and snow. Furthermore, our results suggest that icy seeps are suitable habitat for many macroinvertebrates occupying streams fed by vulnerable hydrological sources. Thus, icy seeps may act as key climate refugia for mountain stream biodiversity, an idea in need of further investigation.

ecology↗