Cold tolerance of different adult elytral color morphs inHarmonia axyridis (Coleoptera: Coccinellidae)
Author of the article:ZHAO Jing1, 2** XIAO Da3 LI Xiao-Li1 XU Yong-Yu2*** WANG Su3***
Author's Workplace：1. College of Weifang Science & technology, Shouguang, Shandong 262700, China; 2. College of Plant Protection, Shandong Agricultural University, Tai’an, Shandong 271018, China; 3. Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Science, Beijing 100089, China
Key Words：Harmonia axyridis, elytral color morphs, SCP, cold survival ability, overwintering strategy
Abstract： [Objectives] To investigate the adaptive significance of seasonal changes in different adult elytral color morphs of Harmonia axyridis (Pallas). [Methods] We measured the supercooling point (SCP) and cold survival rate of different elytral color morphs. [Results] There was no significant difference in the SCP and cold survival rate of melanic and non- melanic adults from experimental populations reared at the same temperature (P > 0.05). However, the survival rate of adults reared at 25℃ decreased more severely with duration of cold-exposure. In addition, the SCP of melanic and non- melanic adults from natural populations displayed obvious seasonal variation. SCPs were highest in July (﹣8.2℃and ﹣7.5℃, respectively) and lowest in January (﹣16.8℃ and ﹣18.2℃, respectively). At the beginning of overwintering, the SCP of melanic adults was lower than that of non- melanic adults, but the SCP of non-melanic adults was lower than that of overwintering melanic adults . However, there was no significant difference in survival rate between melanic and non-melanic overwintering adults. [Conclusion] The SCP of non-melanic adults was lower than melanic adults during overwintering which could help to prevent freezing damage through body fluids supercooling and enhance the cold tolerance of overwintering adults. This was one of the important reasons that the proportion of non-melanic adults markedly increased during overwintering.