A Single Hot Event That Does Not Affect Survival but Decreases Reproduction in the Diamondback Moth, Plutella xylostella

Abstract

Extremely hot events (usually involving a few hours at extreme high temperatures in summer) are expected to increase in frequency in temperate regions under global warming. The impact of these events is generally overlooked in insect population prediction, since they are unlikely to cause widespread mortality, however reproduction may be affected by them. In this study, we examined such stress effects in the diamondback moth, Plutella xylostella. We simulated a single extreme hot day (maximum of 40°C lasting for 3, 4 or 5 h) increasingly experienced under field conditions. This event had no detrimental effects on immediate mortality, copulation duration, mating success, longevity or lifetime fecundity, but stressed females produced 21% (after 3 or 4 h) fewer hatched eggs because of a decline in the number and hatching success of eggs laid on the first two days. These negative effects on reproduction were no longer evident in the following days. Male heat exposure led to a similar but smaller effect on fertile egg production, and exposure extended pre-mating period in both sexes. Our results indicate that a single hot day can have detrimental effects on reproduction, particularly through maternal effects on egg hatching, and thereby influence the population dynamics of diamondback moth.

Stage-specific heat effects: timing and duration of heat waves alter demographic rates of a global insect pest

“…the proportion and total number of eggs laid per day. Consistent with previous studies, we found that high temperatures generally led to a reduction in maximum egg production at the start of the oviposition period (Krebs and Loeschcke 1994;Janowitz and Fischer 2011;Zhang et al 2013). However, we also found that high temperatures led on average, to a faster decline in egg production with age (Fig.…”

“…62N, 114.13E) in Wuhan, China. The captive population was reared on an artificial diet at 25 ± 1 °C, 30-40 % relative humidity (RH) and a photoperiod of 15:9 h (light:dark), as described by Zhang et al (2013).…”

“…However, persistent carry-over effects of exposure to hot temperature at early life-stages do not always occur (Huey et al 1995;Potter et al 2011;Xing et al 2014). Exposure to high temperatures during the adult stage may also limit mating performances (Katsuki and Miyatake 2009;Mironidis and Savopoulou-Soultani 2010), egg maturation (Berger et al 2008) and oviposition pattern (Berger et al 2008;Zhang et al 2013), which in turn could alter the temperature effects during early life-stages.…”

Daily temperature extremes play an important role in predicting thermal effects

“…This suggests that T max will reduce fitness to 0 when it reaches a critical threshold. During the daytime, episodic high temperatures can lead to a series of severe physiological and developmental problems in organisms (Denlinger and Yocum, 1998;Karl et al, 2011;Zhang et al, 2013) and further result in mass mortality (Welbergen et al, 2008).…”

“…While average temperatures in temperate regions are rarely expected to exceed optimum temperatures for many organisms (Deutsch et al, 2008), T max on summer days is often predicted to surpass critical thermal maxima (Kearney et al, 2009;Bale and Hayward, 2010), resulting in stressful conditions for many midlatitude ectotherms Zhang et al, 2013;Vasseur et al, 2014). Even small increases in maximum temperature may impact organism phenology (Semenov, 2009), species distribution (Overgaard et al, 2014), population dynamics (Welbergen et al, 2008) and community structure (Ma et al, 2015).…”