Modeling winter moth Operophtera brumata egg phenology: nonlinear effects of temperature and developmental stage on developmental rate

Abstract

Understanding the relationship between an insect's developmental rate and temperature is crucial to forecast insect phenology under climate change. In the winter moth Operophtera brumata timing of egg‐hatching has severe fitness consequences on growth and reproduction as egg‐hatching has to match bud burst of the host tree. In the winter moth, as in many insect species, egg development is strongly affected by ambient temperatures. Here we use laboratory experiments to show for the first time that the effect of temperature on developmental rate depends on the stage of development of the eggs. Building on this experimental finding, we present a novel physiological model to describe winter moth egg development in response to temperature. Our model, a modification of the existing Sharpe−Schoolfield biophysical model, incorporates the effect of developmental stage on developmental rate. Next we validate this model using a 13‐year data‐set from winter moth eggs kept under ambient conditions and compared this validation with a degree day model and with the Sharpe−Schoolfield model, which lacks the interaction between temperature and developmental stage on developmental rate. We show that accounting for the interaction between temperature and developmental stage improved the predictive power of the model and contributed to our understanding of annual variation in winter moth egg phenology. As climate change leads to unequal changes in temperatures throughout the year, a description of insect development in response to realistic patterns of temperature rather than an invariable degree‐day approach will help us to better predict future responses of insect phenology, and thereby insect fitness, to climate change.

Phytoplankton thermal responses adapt in the absence of hard thermodynamic constraints

“…Other factors besides enzyme thermodynamics might also be important, such as the transport of reaction products in the cell (Ritchie, 2018). Nevertheless, the Sharpe-Schoolfield model remains widely used because 174 it adequately captures the relationship between metabolic traits and temperature (e.g., see Padfield et al 2016;Salis et al 2016;Bestion et al 2018;Francis et al 2019).…”

Two-Year Bee, or Not Two-Year Bee? How Voltinism Is Affected by Temperature and Season Length in a High-Elevation Solitary Bee

“…Here, we expected that-regardless of experimental treatment-all bees would follow a similar developmental trajectory with respect to degree-day accumulation, provided degree-days were calculated with respect to the appropriate base (threshold) temperature. We recognize that this expectation may be simplistic, as responsiveness to temperature can vary over the course of development (Manel and Debouzie 1997;Salis et al 2016), and development rate can respond nonlinearly to temperature (Beck 1983); however, degreeday models are still widely used (e.g., Sato and Sato 2015;Uelmen et al 2016; Geng and Jung 2018) because they generally provide a good fit to insect phenology data, despite their limitations.…”

Age-Dependent Developmental Response to Temperature: An Examination of the Rarely Tested Phenomenon in Two Species (Gypsy Moth (Lymantria dispar) and Winter Moth (Operophtera brumata))

“…In a recent paper, Salis et al [ 10 ] examined the phenology of eggs of the winter moth ( Operophtera brumata L.) and proposed a phenology model in which developmental response is dependent on the “interactive effects of temperature and developmental stage” (p. 1777). However, the authors examined only one stage—the egg stage—and what they actually observed was the far more interesting phenomenon of age dependence, where age (defined below) must be dealt with as a continuous variable within the egg stage: 0 (at oviposition) to 1 (at egg hatch).…”

“…Other phenology models may be improved by including an age effect. I will examine the age-dependence observed in the Salis et al [ 10 ] experiment after establishing some basic terminology for the discussion.…”