Mettler-Cherry, Paige , Smith, Marian , Keevin, Thomas .
Effects of Psyllid parasitism on growth and reproduction of Boltonia decurrens, a threatened species.
BOLTONIA decurrens (Asteraceae)(Torrey and Wood, Gray) is a facultative perennial endemic to the Illinois River floodplain. The species was placed on the federal list of threatened species in 1988 by the USFWS, and is currently threatened in Illinois and endangered in Missouri. During population visits in 2000, many plants in the Horseshoe Lake (Madison County, IL) population were observed to have stunted growth and malformed leaves. Damage to the plants was caused by the larval stage of an insect species from the family Psyllidae. To determine the effects of the parasite on growth and reproduction of B. decurrens, 50 parasitized plants (25 seedlings and 25 rosettes) and 50 non-parasitized plants (25 seedlings and 25 rosettes) were identified and tagged. At anthesis, plant height was measured and inflorescences counted. After seeds ripened, four inflorescences from each plant were randomly selected, weighed and individual seeds counted and tested for viability. Plant biomass was harvested; roots and shoots were separated, dried and weighed. One-way analysis of variance (ANOVA) was calculated to determine if there were significant differences between parasitized and non-parasitized plants, both seedlings and rosettes. Parasitized rosettes had significantly greater biomass (root, shoot and total) than non-parasitized plants and seedlings. There was no significant difference between parasitized and non-parasitized seedling biomass. Rosettes were significantly taller than seedlings at anthesis and had more inflorescences; however, there were no significant difference between parasitized and non-parasitized rosettes and seedlings. Parasitized plants had significantly fewer seeds per inflorescence, fewer viable seeds and lower inflorescence mass than non-parasitized plants. Although Psyllid parasitism did not negatively impact growth in terms of biomass, it does appear to reduce reproduction. Populations of B. decurrens are ephemeral and establishment depends on adequate seed dispersal; therefore, reduction is seed production could be especially damaging for a species whose existence is already precarious.
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1 - Lindenwood University, Biology Department, 209 S. Kingshighway, St. Charles, Missouri, 63301-1695, USA
2 - Southern Illinois University, Department of Biological Sciences, Box 1651, Edwardsville, Illinois, 62026-1651, USA
3 - US Army Corps of Engineers, St. Louis District, Environmental Analysis Branch, 1222 Spruce St., St. Louis, Missouri, 63103-2833, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, August 1st, 2006
Time: 2:00 PM