Mutual Impacts on a Specialist Herbivore and its Host Plants: Variation in Insect Morphology and Plant Tolerance
MetadataShow full item record
In one study, a suite of host plants from the genus Zea L. (Poaceae) and the specialist herbivore Dalbulus maidis (DeLong and Wolcott) (Hemiptera: Cicadellidae) were used to address whether plant tolerance to direct damage by the herbivore and seedling morphometry were mediated by plant domestication and genetic improvement. Additionally, the role of shoot: root ratios in plant tolerance was included in this study. Plant tolerance was measured as regrowth rate, and a trade-off between plant tolerance and resistance was predicted based on (i) the increasing investment in growth and productivity with evolutionary history in Zea and, (ii) its negative correlation with plant resistance. The effects of the domestication transition were assessed by contrasting Balsas teosinte (Z. mays L. ssp. parviglumis Iltis & Doebley) and maize (Z. mays L. ssp. mays), while breeding transition by contrasting maize landraces and maize inbred lines. The results showed that domestication and breeding mediated changes in seedling morphometry, but did not mediate changes in plant tolerance, with Balsas teosinte, maize landraces, and maize inbred lines similarly tolerant to feeding damage by D. maidis. In contrast, domestication mediated changes in shoot: root ratios, with larger roots in the maizes, suggesting increased storage capability in domesticated taxa. In another study, morphometrics analyses were performed on D. maidis specimens collected from Perennial teosinte [Zea diploperennis Iltis (Doebley & Guzman)] and maize in western Mexico, to determine whether a correlation existed between previously documented genetic differentiation and morphological (morphometrical) differentiation. Traditional morphometrics was used to analyze body differences, and geometric morphometrics was applied for wing analysis. The results suggested that genetic and morphological differentiation are correlated in D. maidis, with individuals associated to Perennial teosinte exhibiting larger body size compared to individuals associated to maize. A strong host plant effect and a moderate habitat effect were detected, and body size was found to be as the variable explaining most of the variance between individuals. Wing differentiation between individuals associated with Perennial teosinte and maize was detected, but it was strongly correlated with allometry. It was hypothesized that different selection forces are acting on morphological and genetic differentiation because while morphological differentiation is maintained in locations where Perennial teosinte and maize coexist, genetic differentiation is lost in those locations. Overall, the study’s results suggested that evolutionary transitions in Zea have exerted changes in both the plant morphometry and insect morphology, with changes in the plant related to increased storage and productivity in roots, and changes in the insect related to overall body size.
Chinchilla-Ramirez, Milena (2014). Mutual Impacts on a Specialist Herbivore and its Host Plants: Variation in Insect Morphology and Plant Tolerance. Master's thesis, Texas A & M University. Available electronically from