Presentation Information
[POS-49]Theoretical analysis for the evolution of male diapause dimorphism in the butterfly, Eurema mandarina
*Sotaro Hirose1, Akiko Satake1 (1. Kyushu University (Japan))
Keywords:
evolutionary game theory,adaptive dynamics,seasonal polyphenism,diapause,butterfly
Winter is generally unsuitable for reproduction and growth in many organisms. Many insect species have evolved overwintering strategies involving diapause to cope with limited food resources, low temperatures, and snow during winter.
The Japanese common grass yellow (Eurema mandarina), found in temperate regions in Japan, exhibits seasonal polyphenism: a summer-form (non-diapause-form) butterfly that cannot enter the diapause, and an autumn-form (diapause-form) butterfly that can. The environmental cues such as temperature and day length during the last instar larvae and pupal stage determine these forms of adults in this species. Notably, the plasticity of this polyphenism differs between sexes, resulting in the coexistence of both forms in males and diapause-form females in late autumn. Previous studies have shown that the two male forms exhibit different mating timings: non-diapause-form males mate with females before diapause. In contrast, diapause-form males mate with females after diapause. However, the adaptive significance of the emergence of these dual forms in males and the occurrence of two mating periods in females–before and after diapause–remains unclear.
We developed an evolutionary game model in which the probability of a male developing into a diapause-form butterfly is treated as an evolutionary trait, to explore the conditions under which the coexistence of two male forms can evolve. Our analysis revealed that when male and female survival rates are low, male dimorphism–comprising diapause-form and non-diapause-form males–can evolve as the evolutionarily stable and convergence stable strategy, particularly when the survival probability of non-mated females is significantly lower than that of mated females and diapause-form males. Furthermore, the model suggests that male dimorphism can evolve even when females that mate both before and after diapause preferentially use the sperm of diapause-form males for fertilization. These results indicate that the evolution of male dimorphism may be favored even when mating with non-diapause-form males primarily serves to enhance female survival and females tend to fertilize more eggs with the sperm of diapause-form males.
This study not only advances our understanding of the evolution of sex-specific plasticity in seasonal polyphenism of E. mandarina but also provides insights into empirical studies on the roles of sperm precedence and pre-diapause mating in this butterfly.
The Japanese common grass yellow (Eurema mandarina), found in temperate regions in Japan, exhibits seasonal polyphenism: a summer-form (non-diapause-form) butterfly that cannot enter the diapause, and an autumn-form (diapause-form) butterfly that can. The environmental cues such as temperature and day length during the last instar larvae and pupal stage determine these forms of adults in this species. Notably, the plasticity of this polyphenism differs between sexes, resulting in the coexistence of both forms in males and diapause-form females in late autumn. Previous studies have shown that the two male forms exhibit different mating timings: non-diapause-form males mate with females before diapause. In contrast, diapause-form males mate with females after diapause. However, the adaptive significance of the emergence of these dual forms in males and the occurrence of two mating periods in females–before and after diapause–remains unclear.
We developed an evolutionary game model in which the probability of a male developing into a diapause-form butterfly is treated as an evolutionary trait, to explore the conditions under which the coexistence of two male forms can evolve. Our analysis revealed that when male and female survival rates are low, male dimorphism–comprising diapause-form and non-diapause-form males–can evolve as the evolutionarily stable and convergence stable strategy, particularly when the survival probability of non-mated females is significantly lower than that of mated females and diapause-form males. Furthermore, the model suggests that male dimorphism can evolve even when females that mate both before and after diapause preferentially use the sperm of diapause-form males for fertilization. These results indicate that the evolution of male dimorphism may be favored even when mating with non-diapause-form males primarily serves to enhance female survival and females tend to fertilize more eggs with the sperm of diapause-form males.
This study not only advances our understanding of the evolution of sex-specific plasticity in seasonal polyphenism of E. mandarina but also provides insights into empirical studies on the roles of sperm precedence and pre-diapause mating in this butterfly.