Overwintering Larval Cold Tolerance of Sirex noctilio (Hymenoptera: Siricidae): Geographic Variation in Northeast China
by
and
Chengcheng Li
1,2, 
Jiahe Pei
1,2,
Jiale Li
1,2,
Xiaobo Liu
1,2,
Lili Ren
1,2,*
and
Youqing Luo
1,2,* 1
Beijing Key Laboratory for Forest Pest Control, School of Forestry, Beijing Forestry University, Beijing 100083, China
2
Sino-French Joint Laboratory for Invasive Forest Pests in Eurasia, Beijing Forestry University—INRAE, Beijing 100083, China
*
Authors to whom correspondence should be addressed.
Insects 2021, 12(2), 116; https://doi.org/10.3390/insects12020116
Submission received: 6 December 2020
/
Revised: 26 January 2021
/
Accepted: 26 January 2021
/
Published: 28 January 2021
(This article belongs to the Section Insect Physiology, Reproduction and Development)
Simple Summary
The cold tolerance strategy of Sirex noctilio overwintering larvae was freeze-avoidance and their supercooling points adjusted seasonally to avoid icing damage. The cold hardiness between different populations varied on a spatiotemporal scale; specifically, the harsher the environment, the stronger the cold tolerance of overwintering Sirex noctilio larvae. A tunnel played a certain protective role but did not affect the low temperature parameters limiting the distribution of S. noctilio. We provide experimentally determined low temperature limiting parameters of Sirex noctilio and prove it has the opportunity to spread and colonize in other regions.
Abstract
Sirex noctilio (Hymenoptera: Siricidae) is an invasive pest that has spread and established in many regions worldwide. However, its cold tolerance strategy is still unclear. We measured the supercooling point (SCP) and the lower lethal temperature (LLT) of overwintering S. noctilio larvae during three overwintering periods in four geographically separated populations in China. In addition, using the statistical analysis of the local historical temperature data, we also conducted comprehensive studies of S. noctilio cold tolerance variations and strategies. We measured the SCP of all samples as S. noctilio could survive at its SCP during a short period of exposure (<48 h) and its cold tolerance strategy was freeze-avoidance. The average SCPs of the groups in different spatiotemporal scales were significantly related to average temperature variation with most individuals exhibiting stronger cold hardiness at low ambient temperatures. S. noctilio exhibited a strong cold tolerance and it has the ability to withstand lower temperatures in cold environments. The geographic population showed a positive tendency as the ambient temperature decreased, which would increase its chance of developing in cold regions.
