# Population Genetics, Demographic History, and Potential Distributions of the New Important Pests Monolepta signata (Coleoptera: Chrysomelidae) on Corn in China

## TL;DR

This study explores the genetic diversity, population history, and future distribution of the corn pest Monolepta signata in China to aid in its management.

## Contribution

The study provides new insights into the population genetics and potential future distribution of Monolepta signata in China.

## Key findings

- M. signata populations show high genetic differentiation and weak gene flow between most populations.
- The pest's population has undergone rapid expansion in recent history.
- Northeast and north China are predicted to remain high suitability areas for M. signata in the future.

## Abstract

The adults of Monolepta signata mainly feed on corn silks, anther and kernels at the filling stage, which result in great loss of yield and quality. Herein, we studied the population genetics and demographic history of M. signata based on mitochondrial genes (COI) and nuclear genes (ITS2, EF-1α). Based on the data of environmental factors and known sample points, the fitness of M. signata was also analyzed according to mathematical statistics and ecological niche theory. The distribution of the suitable habitat of M. signata in China and center-of-mass transfer under different climatic scenarios in the present and future time periods were predicted. The areas of potential serious damage in the future were also predicted. The population of M. signata has also experienced rapid expansion. The damage caused by M. signata in Xinjiang will be worse and more attention should be paid on.

Monolepta signata are polyphagous pest widely distributed in China, and the damage as well as economic losses it caused were increasing in recent years. Knowledge of species diversity, population structure and habitat suitability could enhance the efforts of pest control. Here, we sampled the populations of M. signata in almost all of China’s major corn-producing regions. A total of 568 sequences were obtained from each gene. There were 48, 29, and 30 haplotypes of COI, ITS2 and EF-1α, respectively. The genetic distance between the HuangHuaiHai population and other populations was the largest. There were 61.90%, 71.43% and 61.90% of Nm values smaller than 1 in COI, ITS2 and EF-1α, respectively, which indicated that gene flow between most populations was weak. The degree of differentiation in most populations of M. signata was relatively high. The population of M. signata has also experienced rapid expansion. Population history dynamic analysis showed that the effective population size of M. signata remained relatively stable before 0.075 Ma. There was a slow contraction trend from 0.075 to 0.010 Ma. It has been rapidly and continuously expanding since 0.010 Ma. Among the investigated geographical populations, the “yellow-spot type” was only present in the populations of southern and southwestern regions, while the “two-spot type” and “four-spot type” were widely distributed in all other geographical populations. Predictions of the potential distribution areas of M. signata indicated that the northeast and north China regions will remain being the high suitability areas of M. signata in the future. Our results will not only facilitate studies on the phylogeography of M. signata but also benefit the effective monitoring and management of this agricultural pest.