Voltine Ecotypes of the Asian Corn Borer and Their Response to Climate Warming.

William D Hutchison,Shu-Xiong Bai,Kai-Qiang Liu,Tian-Tao Zhang,Kang-Lai He,Ke-Qin Wang,Lian-Xia Wang,Zhen-Ying Wang

doi:10.3390/insects12030232

Abstract

Simple SummaryThe Asian corn borer (ACB), Ostrinia furnacalis, is an important economic pest of corn and other crops, and is widely distributed in China. Depending on the climate, ACB may have one or up to seven generations each year, from north to south, respectively. The degree of crop damage is closely related to its phenology and number of generations per year (voltinism). Climate warming may result in an alternation of voltinism in the ACB. In the present study, we investigated the voltinism of different populations under different simulated environments. From the diapause response, both the uni- and multivoltine ecotypes were coexisting in the Harbin (H) population collected from action sites of ACB moths in Harbin, Heilongjiang Province, China. Diapause incidence declined given the climate-warming scenario, which was temporally specific and could be overridden by significantly low daily average temperatures. Elevated CO2 did not directly impact voltinism. On the basis of voltinism, the H population reflected sympatric uni- and multivoltine ecotypes, with multivoltinism being dominant. The univoltinism trait was recessive. Climate warming could significantly override photoperiod effects. Warmer temperatures and declining latitude (reduced daylength), and their interaction, are estimated to drive ACB evolution to increased homogeneity and multivoltinism.In the Asian corn borer (ACB), Ostrinia furnacalis (Guenée), diapause is governed by a multigenetic constitution that responds to daylength and temperature with seasonality. The ACB displays uni- or multivoltinism, depending on its geographic specificity. Hence, warmer temperatures may result in alternation of voltinism in the ACB, which will help in understanding the ecological consequences of climate warming on insects. In the present study, we investigated the voltinism in two natural populations from Harbin (H) and Gongzhuling (G) as well as a laboratory (L) population (established from the H population in 2017) of the ACB, at ambient and elevated atmospheric CO2 (aCO2 390 μL/L and eCO2 750 μL/L) and temperature (aT and Et = At + 2 °C). From the diapause response, both the uni- and multivoltine ecotypes were coexisting in the H population. The neonate occurrence date of 50% individuals that induced diapause was ca. 10 days later in the G population than in the H population, but it was about 10 days earlier than in the L population. Comparing to the dates of onset and the peak of diapause induction, the G and L populations were less variable than the H population in response to a short and/or shortening daylength in the field. The univoltine individuals could not be eliminated completely after 19 generations of selection. Diapause incidence decreased with a climate-warming scenario, which was temporally specific and could be overridden by significantly low daily average temperatures. The eCO2 did not directly impact the voltinism. On the basis of voltinism, the H population was sympatric for uni- and multivoltine ecotypes, with multivoltinism being dominant. The univoltinism trait was recessive. Climate warming could significantly override the effect of photoperiod, which was yearly dependent. Warmer temperatures and a decreased latitude (shortened daylength), and their interaction, would drive ACB evolution toward diapause homogeneity for multivoltinism.

Highlights

Diapause is a highly adaptive trait that enables herbivorous insects to adapt to a tremendous diversity of climatic conditions, and harmonize phenology with seasonal host plant availability in temperate regions
The voltine ecotypes are virtually identical in morphology, both genetic and molecular differences have been documented in several insect species, such as the European corn borer, Ostrinia nubilalis (Hübner) [3,4]
In the laboratory, when larvae were reared at 28 ◦C with a long day (L: 16 h), larval diapause incidence was generally very low during the time of neonate occurrence of the H population in spring, indicating a typical long-day response species (Figure 2)

Summary

Introduction

Diapause is a highly adaptive trait that enables herbivorous insects to adapt to a tremendous diversity of climatic conditions, and harmonize phenology with seasonal host plant availability in temperate regions. Depending on the degree to which diapause is governed by environmental cues, diapause strategies are often distinguished as facultative and obligatory [1,2]. Insects with obligatory diapause will only exhibit one generation and enter diapause at a certain stage during development regardless of the photoperiod or temperature. In this case, the diapause is genetically preprogrammed. Insects with facultative diapause are induced by environmental factors, and usually exhibit multivoltinism along with an expansive geographical distribution. Voltinism plasticity is dependent on latitude, including the onset of diapause, which is induced by photoperiod. The voltine ecotypes are virtually identical in morphology, both genetic and molecular differences have been documented in several insect species, such as the European corn borer, Ostrinia nubilalis (Hübner) [3,4]

Results

Discussion

Conclusion