In the present study, I demonstrated the ability of the xylem-feeding leafhopper, Carneocephala floridana, to discriminate between differentially fertilized Spartina alterniflora, which possessed varying levels of foliar nitrogen content. The hopper was capable of detecting, and preferentially fed upon, minimally fertilized plants, which did not differ in percent of foliar nitrogen from unfertilized control plants. / Chemical analyses of the xylem sap and performance data from another host plant, Borrichia frutescens, confirmed that amino acid levels in highly fertilized plants become very unbalanced and are either unusable, or toxic, to C. floridana. Highly fertilized plants had elevated levels of NH$\sb4\sp+$, and a nitrogen content, that is probably well above those found in naturally occurring B. frutescens. These results suggested that a threshold detection mechanism may be operating. C. floridana's host plants show seasonal trends in their nitrogen content. While, the field patterns of C. floridana did not suggest that the hopper switches host plants based solely on interspecific nitrogen content; intraspecific nitrogen content did show several trends that were consistent host plant usage. My results suggest that the spatial and temporal distribution natural populations of C. floridana may be influenced by host plant nitrogen, but crude nitrogen is not a good predictor of interspecific host plant preference. / In addition, egg mortality and parasitism rates were also higher on the grasses compared to the herbaceous species. It appears that host plant water content may be largely responsible for plant mediated egg mortality. In addition, high parasitism rates on the two grass species may be related to the orientation of eggs, which are laid in parallel packets just below the surface of the epidermis. Conversely, eggs laid on the two herbaceous species appear to be less accessible to searching parasitoids. / My data suggest that Carneocephala floridana should utilize the two grasses only when the two herbaceous species are unavailable. In the salt marshes of Florida's northern Gulf coast, this occurs during the winter when the herbaceous species experience a substantial dieback. / Source: Dissertation Abstracts International, Volume: 52-08, Section: B, page: 4007. / Major Professor: Donald R. Strong. / Thesis (Ph.D.)--The Florida State University, 1991.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76473 |
| Contributors | Rossi, Anthony Michael., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 212 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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