Comparison of upper sublethal and lethal temperatures in three species of rice planthoppers

Pei Li,Asad Ali,Maolin Hou,Shahbaz Ali

doi:10.1038/s41598-019-52034-7

Abstract

Temperature is an important environmental factor for ectotherms’ fitness and survival. The upper sublethal and lethal temperatures were compared between adults of three closely related destructive planthopper species, the small brown planthopper (Laodelphax striatellus, SBPH), the brown planthopper (Nilaparvata lugens, BPH), and the white-backed planthopper (Sogatella furcifera, WBPH) in the absence and presence of the host plant (Oryza sativa, var. Taichong1). Values of the critical thermal maxima (CTmax) were higher in SBPH than in both BPH and WBPH and higher in BPH than in WBPH, and values of the heat coma temperatures (HCT) were higher in both BPH and SBPH than in WBPH. CTmax and HCT values were higher in the presence than in the absence of plant material. Between sexes, females generally showed higher CTmax and HCT than males. The upper lethal temperatures (ULT50) measured in the absence of plant material were not significantly different among the planthopper species. The planthoppers also exhibited different behaviors in an increasing temperature regime, with fewer insects dropping-off from the plant in SBPH than in BPH and WBPH. These results indicate that SBPH and BPH are more heat tolerant than WBPH. The findings highlight the biological divergence in closely related planthopper species and the importance of performing the heat tolerance measurement in an ecologically relevant setting, which serves to predict seasonal and spatial occurrence patterns of the destructive planthopper species.

Highlights

Temperature is an important environmental factor for ectotherms’ fitness and survival
When an insect is exposed to increasing temperatures for a certain duration, different observable and measurable events occur[7]: when the exposed organism shows uncoordinated movement until motionless, it reaches the critical thermal maximum (CTmax); when the appendages are incapable of movement and the organism enters a ‘heat coma’ state, it comes to the heat coma temperature (HCT)[8]
Mean CTmax values were higher in small brown planthopper (SBPH) than in both brown planthopper (BPH) and white-backed planthopper (WBPH) (Tukey test, P < 0.001), and higher in BPH than in WBPH (Tukey test, P = 0.038; Fig. 1B)

Summary

Introduction

Temperature is an important environmental factor for ectotherms’ fitness and survival. The upper sublethal and lethal temperatures were compared between adults of three closely related destructive planthopper species, the small brown planthopper (Laodelphax striatellus, SBPH), the brown planthopper (Nilaparvata lugens, BPH), and the white-backed planthopper (Sogatella furcifera, WBPH) in the absence and presence of the host plant The planthoppers exhibited different behaviors in an increasing temperature regime, with fewer insects dropping-off from the plant in SBPH than in BPH and WBPH. These results indicate that SBPH and BPH are more heat tolerant than WBPH. Piyaphongkul et al.[8] measured CTmax, HCT and ULT of BPH and found that thermal tolerance differed between developmental stages They indicated that acclimation increases heat tolerance in BPH14. These results question the validity of measuring heat tolerance in the absence of the host plant for predictions and decisions concerning pest species (e.g., timing and severity of pest outbreaks, efficiency and establishment potential of invasive species, implications of climate change)[16]

Methods

Results

Conclusion