Conserved and narrow temperature limits in alpine insects: Thermal tolerance and supercooling points of the ice-crawlers, Grylloblatta (Insecta: Grylloblattodea: Grylloblattidae)
[Display omitted] •Thermal limits are highly conserved among Grylloblatta populations.•Limits range from −4.0±0.8°C to 27.0±0.7°C, with an SCP of −3.9±1.0°C.•These limits are narrow compared to other insect taxa, with minimal plasticity.•The climate variability hypothesis is supported in Grylloblatt...
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| Published in: | Journal of insect physiology Vol. 78; pp. 55 - 61 |
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| Main Authors: | , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
England
Elsevier Ltd
01-07-2015
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | [Display omitted]
•Thermal limits are highly conserved among Grylloblatta populations.•Limits range from −4.0±0.8°C to 27.0±0.7°C, with an SCP of −3.9±1.0°C.•These limits are narrow compared to other insect taxa, with minimal plasticity.•The climate variability hypothesis is supported in Grylloblatta.•Grylloblatta depend on subterranean retreats to accommodate narrow thermal limits.
For many terrestrial species, habitat associations and range size are dependent on physiological limits, which in turn may influence large-scale patterns of species diversity. The temperature range experienced by individuals is considered to shape the breadth of the thermal niche, with species occupying temporally and/or geographically stable climates tolerating a narrow temperature range. High-elevation environments experience large temperature fluctuations, with frequent periods below 0°C, but Grylloblatta (Grylloblattodea: Grylloblattidae) occupy climatically stable microhabitats within this region. Here we test critical thermal limits and supercooling points for five Grylloblatta populations from across a large geographic area, to examine whether the stable microhabitats of this group are associated with a narrow thermal niche and assess their capacity to tolerate cold conditions. Thermal limits are highly conserved in Grylloblatta, despite substantial genetic divergence among populations spanning 1500m elevation and being separated by over 500km. Further, Grylloblatta show exceptionally narrow thermal limits compared to other insect taxa with little capacity to improve cold tolerance via plasticity. In contrast, upper thermal limits were significantly depressed by cold acclimation. Grylloblatta maintain coordinated movement until they freeze, and they die upon freezing. Convergence of the critical thermal minima, supercooling point and lower lethal limits point to adaptation to a cold but, importantly, constant thermal environment. These physiological data provide an explanation for the high endemism and patchy distribution of Grylloblatta, which relies on subterranean retreats to accommodate narrow thermal limits. These retreats are currently buffered from temperature fluctuations by snow cover, and a declining snowpack thus places Grylloblatta at risk of exposure to temperatures beyond its tolerance capacity. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0022-1910 1879-1611 |
| DOI: | 10.1016/j.jinsphys.2015.04.014 |