Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/25/2011
Publication Date: 2/20/2012
Citation: Barman, A.K., Parajulee, M.N., Sansone, C.G., Suh, C.P., Medina, R.F. 2012. Geographic pattern of host-associated differentiation in Pseudatomoscelis seriatus (Reuter). Entomologia Experimentalis et Applicata. 43:31-41. Interpretive Summary: The cotton fleahopper prefers weed hosts such as horsemint and woolly croton, but will move to and feed on cotton as preferred weed hosts in the spring begin to mature and become less attractive. The weed host contributing the majority of fleahoppers in cotton is not known, but it is widely speculated that horsemint is a major source. We used Amplified Fragmented Length Polymorphism (AFLP) markers to examine the genetic structure of fleahopper populations occurring on horsemint, cotton, and woolly croton in five locations throughout Texas (Lubbock, San Angelo, College Station, Corpus Christi, and Weslaco). In three locations (Lubbock, San Angelo, and Weslaco), fleahopper populations occurring on horsemint were genetically distinct from those found on cotton. In contrast, the genetic structure of fleahopper populations occurring on horsemint, cotton, and woolly croton were similar in College Station as well as in Corpus Christi. These results suggest horsemint is a major contributor of fleahoppers in some production regions, but not in others. Interestingly, the geographic pattern of genetic differentiation among fleahopper populations matches a precipitation gradient among the five study locations. These precipitation differences affect the composition, distribution, and development of fleahopper host plants in the respective locations, which in combination may generate the observed pattern of genetic differentiation among fleahopper populations.
Technical Abstract: Host-associated differentiation (HAD) is the presence of genetically divergent, host-associated populations, and a phenomenon thought to promote diversity in parasitic organisms. HAD in phytophagous insects has mostly been documented in specialist, univoltine insects inhabiting feral ecosystems or in generalist, multivoltine, parthenogens in agro-ecosystem. Here we report HAD in the cotton fleahopper, Pseudatomoscelis seriatus Reuter (Hemiptera: Miridae), a generalist, multivoltine, non-parthenogentic insect pest of cotton (Gossypium hirsutum). We obtained cotton fleahoppers from cotton and two of its most preferred, non-cultivated host plant species, horsemint (Monarda punctata) and woolly croton (Croton capitatus). We used AFLP markers to examine the genetic differentiation of host-associated populations of P. seriatus in five locations within Texas, which are representative of distinct eco-zones. An overall Fixation Index of 0.10 indicates moderate genetic differentiation among the studied populations. We found a geographic pattern of genetic differentiation among the host-associated populations of P. seriatus. In three locations, two distinct genotypes of P. seriatus were found in association with horsemint and cotton/woolly croton, whereas in the two other locations, populations were panmictic regardless of their host-association. The geographic pattern of host-associated differentiation corresponds to a precipitation gradient among the study locations. We suggest that precipitation differences translate into heterogeneity in vegetation composition and distribution as well as in variation in allochrony among host plant phenologies at different locations, which in combination may generate the observed pattern of genetic differentiation among fleahopper populations.