Geographic variation in developmental duration of the Asian corn borer, Ostrinia furnacalis (Guené) (Lepidoptera: Crambidae) in China

Abstract

Insect species with broad geographic distributions can phenologically adjust their life cycles to adapt to different habitats, for example by altering their growth, development, and reproduction periods to better match their emergence times with local conditions, such as food availability, optimum temperature, rainfall, etc.). These adjustments are very important for such widespread species to be able to reproduce in different habitats. The Asian corn borer, Ostrinia furnacalis (Guené) (Lepidoptera: Crambidae) is a major pest insect of Zea mays L., that poses a serious economic threat to corn production in China. Its distribution ranges from north to south in China, through Southeast Asia, and into Australia, and the pest has recently been found in isolated regions of the United States. Because of its wide distribution, the Asian corn borer encounters great variation in climatic conditions across its range and exhibits considerable diversity in its life-history parameters among geographic populations. Populations differ distinctly in voltinism, critical photoperiod, post-diapause emergence time, body size, fecundity, and cold hardiness. However, little is known about whether the developmental duration of O. furnacalis populations varies with geographic origin. In the present study, we systematically investigated the developmental duration of the egg, larval, and pupal phases at five different temperatures (20, 22, 25, 28 and 31℃) using insects collected from five different populations of the Asian corn borer. Each population inhabited a different latitude: Yangshuo, Guangxi (YS, 24.8°N, 110.5°E); Nanchang, Jiangxi (NC, 28.8°N, 115.9°E); Taian, Shandong (TA, 36.2°N, 117.1°E); Langfang, Hebei (LF, 39.5°N, 116.7°E) and Haerbin, Heilongjiang (HEB, 44.9°N, 127.2°E). Although at any given temperature the duration of the egg phase did not differ significantly among populations, the length of this phase increased slightly from south to north at 20, 22, and 25℃ and had a highly significant positive correlation with the latitudinal origin of the populations at these three temperatures. However, the egg phase lasted about the same amount of time in all populations at 28℃, with no significant correlation to latitudinal origin. The duration of the larval phase was not significantly different among the five populations at 31℃, but it differed significantly at 20, 22, 25, and 28℃. The larval- phase duration had a significant positive correlation with the latitudinal origin of the populations at 22, 25, and 28℃. However, these two parameters were negatively correlated at 20 and 31℃. The duration of the larval phase varied little with temperature in the HEB population, but it decreased significantly as temperature increased in the YS, NC, TA, and LF populations. The developmental durations of female pupae at 20℃, male pupae at 28℃, and all pupae at 31℃did not differ significantly among populations, but all other pupal categories had significantly different durations among the five populations. The pupal-phase duration had a positive relationship with the latitudinal origin of the population at any given temperature. These results indicate that a single widespread species of insect may adapt to varying environmental conditions across its geographic range by altering the developmental duration of its life-history stages in different ways in each population.