Genetic differentiation of three populations of the fall armyworm, <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae), in Mexico

Abstract The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important insect pest of maize and numerous other crops throughout the world. In this study, the genetic diversity and structure of three Mexican populations of S. frugiperda , collected from three maize-producing areas in the states of Sinaloa (Sf-SIN), Michoacán (Sf-MICH), and Chiapas (Sf-CHI), were evaluated using the mitochondrial cytochrome oxidase (COI) gene. Neighbor-joining analysis showed that the S. frugiperda sequences of our study were grouped, with 99 % branch support, with reference sequences from Canada, United States of America, and Mexico. Sf-SIN and Sf-CHI sequences were closely related to other Mexican reference sequences, while Sf-MICH sequences formed a well-supported separate clade. AMOVA analysis showed that most of the genetic variability was within populations. The highest correlation between genetic distance and haplotypical frequency was observed between Sf-CHI and Sf-MICH populations. Ten haplotypes were detected considering the three areas sampled and the haplotype diversity was higher in Sf-MICH and Sf-SIN populations. The haplotypic network indicates that two and one individuals from Sf-CHI and Sf-SIN populations, respectively, belonged to the same group. We concluded that the genetic diversity among S. frugiperda populations was more influenced by the variability within individuals of the same population than individuals of different populations. In addition, the presence of shared haplotypes between northwest (Sf-SIN) and southeast (Sf-CHI) individuals possibly indicate a moderate genetic exchange between populations. This diversity is essential for their ability to survive and adapt to environmental changes, which can influence how pest populations respond to control methods.