Artificial Selections for Life-History Traits Affect Effective Cumulative Temperature and Developmental Zero Point in Zeugoducus cucurbitae

Effective cumulative temperature and developmental zero point are important indicators for estimating the timing of organism development and the area of distribution. These indicators are generally considered to have unique values for different species of organisms and are also important for predicting the distribution range of animals and plants, especially insect pests. These values generally are species-specific, but there is variation within populations in traits having a genetic component. However, there are no studies on what kind of selection pressure affects these indicator values. To address this issue, it would be worthwhile to compare these values using individuals of strains that have been artificially selected for life-history traits by rearing them at various temperatures and calculating these indicators from developmental days and temperatures. In the present study, eggs were taken from adults of strains with many generations of artificial selection on two life-history traits (age at reproduction and developmental period) of the melon fly, Zeugodacus cucurbitae, under constant temperature conditions. Eggs were reared at five different temperatures, and the effective cumulative temperatures and developmental zero points of the larval and developmental periods were compared. The results demonstrate that artificial selection on life-history traits in Z. cucurbitae induces evolutionary changes in both the effective cumulative temperature and the developmental zero point across successive generations.