Expression of alternative developmental pathways in the cabbage butterfly, Pieris melete and their differences in life history traits

Abstract

The seasonal life cycle of the cabbage butterfly, Pieris melete is complicated because there are three options for pupal development: summer diapause, winter diapause, and nondiapause. In the present study, we tested the influence of temperature, day length, and seasonality on the expression of alternative developmental pathways and compared the differences in life history traits between diapausing and directly developing individuals under laboratory and field conditions. The expression of developmental pathway strongly depended on temperature, day length, and seasonality. Low temperatures induced almost all individuals to enter diapause regardless of day length; relatively high temperatures combined with intermediate and longer day lengths resulted in most individuals developing without diapause in the laboratory. The field data revealed that the degree of phenotypic plasticity in relation to developmental pathway was much higher in autumn than in spring. Directly developing individuals showed shorter development times and higher growth rates than did diapausing individuals. The pupal and adult weights for both diapausing and directly developing individuals gradually decreased as rearing temperature increased, with the diapausing individuals being slightly heavier than the directly developing individuals at each temperature. Female body weight was slightly lower than male body weight. The proportional weight losses from pupa to adult were almost the same in diapausing individuals and in directly developing individuals, suggesting that diapause did not affect weight loss at metamorphosis. Our results highlight the importance of the expression of alternative developmental pathways, which not only synchronizes this butterfly's development and reproduction with the growth seasons of the host plants but also exhibits the bet‐hedging tactic against unpredictable risks due to a dynamic environment.

Effects of temperature on life‐history traits of the newly invasive fall armyworm, Spodoptera frugiperda in Southeast China

“…We speculate whether an insect species follows the TSR or not may be related to its diapause traits. Those species with summer diapause may exhibit the TSR, as indicated by the cabbage beetle, Colaphellus bowringi (Tang et al., 2017) and the cabbage butterfly, Pieris melete (Tang et al., 2019) because their reproductive periods occur in the spring and autumn and they have experienced strong selection for body size under relatively low environmental temperatures during the process of evolution. Those species with winter diapause triggered by shortening day lengths combined with high autumn temperatures may exhibit the reverse TSR, as indicated by the Asian corn borer, O. furnacalis (He et al., 2019; Xia et al., 2019; Xiao et al., 2016), and the rice stem borer, Chilo suppressalis (Fu et al., 2016; Huang et al., 2018).…”