Stockton Dara G, Wallingford Anna K, Loeb Gregory M
Department of Entomology, Cornell AgriTech and New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456, USA.
Invasive Insect Biocontrol and Behavior Laboratory, USDA⁻ARS, Beltsville, MD 20705, USA.
Insects. 2018 Aug 21;9(3):105. doi: 10.3390/insects9030105.
Spotted wing drosophila, Matsumura, is a major pest of small fruit worldwide in temperate and subtropical growing regions. In Northern climates, likely overwinters locally under leaf litter and snow pack, but our understanding of the factors affecting thermal susceptibility is limited. While previous investigations of thermal susceptibility in this species have employed conventional static acclimation protocols, we aimed to determine whether gradual cooling, or dynamic acclimation, may extend the limits of known thermal tolerance by more closely approximating naturally occurring shifts in temperature. First, we assessed survival among adult and pupal using static acclimation. Then, we re-assessed survival using a novel dynamic acclimation method. We found that while static acclimation was sufficient to induce cold tolerance, dynamic acclimation significantly improved survival at temperatures as low as -7.5 °C. Following static acclimation, the lower lethal limit of adult was -1.1 °C in winter morphotype (WM) adults compared to 1.7 °C in non-acclimated summer morphotype (SM) adults. Dynamic acclimation reduced the lower limit to -5 °C in SM flies. At the end of our study 50% of WM flies survived 72 h at -7.5 °C. Below 0 °C pupal survival declined significantly regardless of acclimation procedure. However, pupal acclimation improved survival outcomes significantly compared to non-acclimated pupae, suggesting that while juvenile diapause is unlikely, cold hardening likely benefits those flies which may develop into the overwintering WM population. These data suggest that the degree of cold hardening is proportional to the thermal environment, a finding previously unrecognized in this species. Given the economic impact of this pest, these data may have important implications for offseason population monitoring and management. We discuss how phenotypic plasticity may drive geographical range expansion, and the impact of climate change on the spread of this species.
铃木氏果蝇是全球温带和亚热带小水果种植区的主要害虫。在北方气候条件下，它可能在当地的落叶层和积雪下越冬，但我们对影响其热敏感性因素的了解有限。虽然此前对该物种热敏感性的研究采用了传统的静态驯化方案，但我们旨在确定逐渐降温或动态驯化是否能通过更接近自然发生的温度变化来扩展已知的耐热极限。首先，我们使用静态驯化评估成虫和蛹的存活率。然后，我们使用一种新的动态驯化方法重新评估存活率。我们发现，虽然静态驯化足以诱导耐寒性，但动态驯化显著提高了在低至-7.5°C温度下的存活率。经过静态驯化后，冬季形态型（WM）成虫的致死下限为-1.1°C，而非驯化的夏季形态型（SM）成虫为1.7°C。动态驯化将SM果蝇的下限降至-5°C。在我们研究结束时，50%的WM果蝇在-7.5°C下存活72小时。低于0°C时，无论驯化程序如何，蛹的存活率都会显著下降。然而，与未驯化的蛹相比，蛹的驯化显著改善了存活结果，这表明虽然幼虫滞育不太可能，但冷驯化可能有利于那些可能发育成越冬WM种群的果蝇。这些数据表明，冷驯化的程度与热环境成正比，这一发现此前在该物种中未被认识到。鉴于这种害虫的经济影响，这些数据可能对非生长季种群监测和管理具有重要意义。我们讨论了表型可塑性如何推动地理范围的扩大，以及气候变化对该物种传播的影响。
