Effects of temperature during successive generations on life-history traits in a seed beetle Callosobruchus chinensis (Chrysomelidae: Coleoptera)

Temperature is an important environmental factor for life-history traits in poikilothermic animals. Many of experiments on evolution have been conducted using Drosophila species, and effects on life-history traits vary depending on the study. On the other hand, few studies have been conducted on the effects of temperature on life-history traits in the other insect species. In the present study, we reared adzuki bean beetles under two different temperatures, high and low, for 2 years (20 generations), and compared life-history traits including body size of females, fecundity, egg size, rate of egg hatching, emergence rate, development time, and wing length. No differences in responses were found in these traits between selection strains, except the rate of egg hatching. That is, the rates of egg hatching in high-temperature (32 degrees C) selection strains were significantly higher than those in low-temperature (24 degrees C) selection strains. We discuss the cause of change in egg hatchability during successive generations under different temperature treatments from the following viewpoints including evolutionary adaptation to high temperature and the experimental protocol.