Not all cicadas increase thermal tolerance in response to a temperature gradient in metropolitan Seoul

Hoa Quynh Nguyen, Hortense Serret, Yoonhyuk Bae, Seongmin Ji, Soyeon Chae, Ye Inn Kim, Jeongjoo Ha, Yikweon Jang

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9 Scopus citations

Abstract

Rapid anthropogenic alterations caused by urbanization are increasing temperatures in urban cores, a phenomenon known as the urban heat island (UHI) effect. Two cicada species, Cryptotympana atrata and Hyalessa fuscata (Hemiptera: Cicadidae), are abundant in metropolitan Seoul where their population densities correlate strongly with UHI intensities. Such a positive correlation between cicada density and UHI intensity may be possible if cicada abundance is linked to a certain thermal tolerance. We tested this hypothesis by investigating variation in morphology and thermal responses of two cicada species along a thermal gradient in Seoul and surrounding areas. The morphological responses were measured by metrics such as length, thorax width and depth, and mass. The thermal responses were measured in terms of minimum flight temperature, maximum voluntary temperature and heat torpor temperature. First, we observed a species-specific variation in thermal responses, in which C. atrata displayed a higher thermal threshold for maximum voluntary and heat torpor temperatures than H. fuscata. Second, a positive association between temperature conditions and body sizes were displayed in females H. fuscata, but not in either conspecific males or C. atrata individuals. Third, C. atrata exhibited similar thermal responses regardless of habitat temperature, while H. fuscata in warmer areas showed an increase in heat tolerance. In addition, H. fuscata individuals with bigger thorax sizes were more heat-tolerant than those with smaller thoraxes. Overall, our research is the first to detect a variation in thermal responses and body size of H. fuscata individuals at a local scale. More investigations would be needed to better understand the adaptation mechanisms of insects linked to UHI effects.

Original languageEnglish
Article number1343
JournalScientific Reports
Volume10
Issue number1
DOIs
StatePublished - 1 Dec 2020

Bibliographical note

Funding Information:
We thank Jeong Hyunsuu for her assistance in sample collection and the experiments, and Desiree Anderson for the heat map construction. This work was supported by the National Research Foundation of Korea (Grant Number: 2015R1A4A1041997). H.S. was funded by the Korea Research Fellowship Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (KRF project grant number: 2016H1D3A1938095).

Publisher Copyright:
© 2020, The Author(s).

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