Chi, Katherine , Molano-Flores, Brenda .
Environmental and demographic effects on reproduction in the rare species Besseya bullii (Plantaginaceae).
Besseya bullii (Plantaginaceae) is a prairie-savanna forb endemic to the Midwestern United States, where it is considered rare throughout its range. During species assessments in the 1980s, woody encroachment was frequently cited as a potential cause of B. bullii's decline. In addition, declining populations of B.bullii may be subject to problems associated with demographic factors (i.e., Allee effects). The objective of this study was to determine if environmental (i.e., shading) and demographic (i.e., number of flowering individuals) factors affect reproduction in this species and contribute to its rarity. Sites were selected from across the range of B. bullii, resulting in 25 populations that were then assigned to one of the following habitat categories: open, semi-shaded, and shaded. Populations were visited from April to June, and data was collected on population size and the percent of flowering individuals. At each population, 20 infructescences were randomly collected to estimate fruit and seed set. The mean percent of flowering individuals was highest in open habitats and lowest for shaded habitats, with many shaded sites having completely sterile populations. Seed set was found to correlate positively with increasing population size, and increase in open habitats compared to shaded habitats. These results show that woody encroachment has a negative effect on reproduction in B.bullii, and confirm traditional conservation theory regarding the importance of maintaining large population sizes.
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1 - University of Illinois, Illinois Natural History Survey, 1816 S. Oak St., Champaign, IL, 61820, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Forsyth Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 11:00 AM