title: Can floral display size compensate for Allee effects caused by low population abundance and density in Synthyris bullii (Plantaginaceae), a rare species?
abstract: OBJECTIVE
  Conservation seeks to address the issues of small population size, and the reproductive limitations confronting these populations. Sparse, small plant populations often suffer Allee effects such as pollinator limitation. However, some studies show that plants in sparse populations experience reduced resource competition. As a result, these plants may produce larger floral displays, which are also predicted to attract pollinators. The negative impacts from reduced floral quantity may thus be offset by improved floral quality.
  
  
  METHODS
  In a 2-yr field study, population abundance and density were quantified for 24 populations of Synthyris bullii (Plantaginaceae), a rare prairie endemic. In each population, data were collected on inflorescence size, fruit/seed set, and seed germination.
  
  
  RESULTS
  Inflorescence size had a positive relationship with population inflorescence abundance and density. Fruit set and germination responded positively to floral quality (i.e., flower density). In comparison, seed set showed a positive relationship with only floral quantity (i.e., population abundance).
  
  
  CONCLUSIONS
  Contrary to our predictions, inflorescence size and population size were not inversely related. While attractive floral displays in sparse populations potentially compensate in terms of fruit set, population abundance nevertheless plays an important role in seed set. Because floral quality and quantity differ in their ability to explain reproductive outcomes, studies should examine reproduction at several stages, otherwise the impacts of population size may be overlooked. Allee effects manifesting at a critical stage of reproduction, such as seed production, may act as a bottleneck impeding successful recruitment.
authors.affiliation: Department of Plant Biology, University of Illinois, 505 South Goodwin Avenue, 265 Morrill Hall, Urbana, Illinois 61801 USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Chi
authors.forename: Brenda
authors.initials: B
authors.lastname: Molano-Flores
mesh_terms: D003247:Conservation of Natural Resources; D003710:Demography; D017753:Ecosystem; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology*; D005638:Fruit / Q000033:anatomy & histology / Q000502:physiology; D018525:Germination; D056626:Inflorescence / Q000033:anatomy & histology / Q000502:physiology; D015146:Midwestern United States; D010943:Plantago / Q000033:anatomy & histology / Q000502:physiology*; D011058:Pollen / Q000033:anatomy & histology / Q000502:physiology; D054817:Pollination; D012098:Reproduction; D012639:Seeds / Q000033:anatomy & histology / Q000502:physiology; D013045:Species Specificity
keywords: conservation; demography; fitness; floral display; habitat fragmentation; population biology; reproductive ecology