The planthopper Prokelisia marginata is the most common insect herbivore in the salt marshes of northwestern Florida, where it feeds and reproduces on smooth cordgrass, Spartina alterniflora Loisel. Relative to other sites where it has been studied, population densities of this planthopper in north Florida are low, despite high fecundity. Low nymphal survivorship, combined with high rates of adult mortality and dispersal, rapidly diminish the densities of local populations. Many factors act to alter the dynamics of planthopper populations. This study was designed to determine the magnitude of the effect of several of these factors on the demography and population dynamics of Prokelisia marginata at Apalachee Bay, Florida. / A field experiment looked at the impact of tides on planthopper populations. Artificial islands were used to create patches of the host plant. Floating islands were used to eliminate tidal inundation and waves, while populations on other islands experienced natural tidal conditions. Analysis showed that the populations did not differ significantly in size throughout the experiment and that they had similar dynamics. In the laboratory, simulated tidal inundation experiments showed that Prokelisia marginata is behaviorally adapted to withstand tidal submergence, either by retreating from the tide or by becoming submerged, and that the planthoppers are able to survive long periods under water. / A second field experiment examined the effects of spider predation on populations of Prokelisia marginata. Nymphal populations were significantly reduced in the presence of spiders, but adults were unaffected. Thus, spider predation had no effect on the population as a whole. A laboratory experiment showed that nymphs are more susceptible than adults to direct predation, and that the presence of spiders alters their life history. / The most important factor acting to reduce adult densities appears to be dispersal of the insects away from their populations. Because most of the dispersing insects probably fail to locate new sites on which to reproduce, dispersal is an important factor acting to reduce populations of Prokelisia marginata in northwestern Florida. / Source: Dissertation Abstracts International, Volume: 50-12, Section: B, page: 5443. / Major Professor: Donald R. Strong. / Thesis (Ph.D.)--The Florida State University, 1989.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78136 |
| Contributors | Throckmorton, Ann Elizabeth., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 238 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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