Factors promoting genetic differentiation in cotton fleahopper (Pseudatomoscelis seriatus)

Evidence of population level genetic differentiation due to host association in phytophagous insects of agricultural importance is limited mostly to aphids, which reproduce parthenogentically and are relatively immobile. Here we report genetic differentiation in populations of the polyphagous, mobile, and non-parthenogenetic plant bug, cotton fleahopper (Pseudatomoscelis seriatus Hemiptera: Miridae) feeding on different host-plant species. Horsemint (Monarda spp.), cotton (Gossypium hirsutum), and woolly croton (Croton capitatus) are three host plant species with which cotton fleahopper intimately interact at different times of the year. Cotton fleahopper populations collected from these three host-plants in different cotton growing areas of Texas were screened with genetic markers (AFLP, amplified fragment length polymorphism). Results of genotype screening were analyzed by Bayesian method, using the software, STRUCTURE 2.2^®. The clustering pattern infers existence of differentiated genotypes of cotton fleahopper. There is a distinct genotype that corresponds to individuals collected from horsemint plants in western regions of Texas. However, behavioral assay results (olfactory response) of the cotton fleahopper associated with horsemint in western Texas were not significantly different from the ones obtained from their south eastern counterpart in terms of preference for horsemint over cotton. Considering genetic differences, it appears that cotton fleahopper populations associated with horsemint in the western parts of Texas (Lubbock, San Angelo) are experiencing host associated differentiation. The lower abundance of horsemint, its asynchronous existence with susceptible stages of cotton and the absence of a common winter host (woolly croton) in the western part of Texas may constitute factors promoting this differentiation.