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Ecology of Cicindelidia haemorrhagica in the Extreme Environments of Thermal Pools in Yellowstone National Park
We noted a tiger beetle species, Cicindelidia haemorrhagica, walking and feeding in the thermal pools of Yellowstone National Park (YNP). Although this species was first recorded in YNP over 100 years ago (Hubbard, 1891), its distribution, ecology, and association with thermal features are not known. In this study, we examined the distribution, abundance, and habitat characteristics of YNP C. haemorrhagica to determine if they are exclusively associated with thermal springs and to determine the physical and chemical extremes in which these beetles can live. We transcribed their behavior using continuous focal sampling to determine if they use thermoregulatory behavior to cope with the high temperatures associated with thermal springs. Lastly, we studied their lethal thermal maxima to determine if they have an increased thermal tolerance, which indicates a structural or physiological adaptation. Our results show that C. haemorrhagica are seemingly exclusively associated with thermal springs. These springs range between pH 2.73 and 9.35, temperatures of 29.1 ˚C and 70 ˚C, and varying metal concentrations. However, all thermal springs were surrounded by barren soil with a gradual edge (gentle slope) towards the thermal water. We propose census and observations as the best methods to estimate the abundance for highly mobile species near thermal springs. Conservative population sizes of C. haemorrhagica ranged between 500–1500 individuals for thermal springs within YNP. Cicindelidia haemorrhagica populations inside YNP have a strong negative correlation between thermoregulatory behavior and temperature (Pearson Correlation Coefficient = −0.224, p = 0.0001), which contrasts studies performed C. haemorrhagica populations that are not associated with thermal springs. To our knowledge, there is no other example of dramatically different behaviors between two populations of insects in the same species. The lethal thermal maxima of C. haemorrhagica in YNP (50.41 °C ± 0.26) is only 1.08 °C higher than non-thermal spring C. haemorrhagica (49.33 °C ± 0.20) (Mixed model, p = 0.0023). Although these lethal thermal maxima are a new record for cicindelids and potentially all reproductive metazoans (at a maximum of 52.6 °C), it is not high enough to explain the beetles’ occurrence at thermal springs as high as 70 °C.
Willemssens, Kelly Ashley, "Ecology of Cicindelidia haemorrhagica in the Extreme Environments of Thermal Pools in Yellowstone National Park" (2019). ETD collection for University of Nebraska-Lincoln. AAI27667332.