title: Floral display size, conspecific density and florivory affect fruit set in natural populations of Phlox hirsuta, an endangered species.
abstract: OBJECTIVE
  Natural variation in fruit and seed set may be explained by factors that affect the composition of pollen grains on stigmas. Self-incompatible species require compatible outcross pollen grains to produce seeds. The siring success of outcross pollen grains, however, can be hindered if self (or other incompatible) pollen grains co-occur on stigmas. This study identifies factors that determine fruit set in Phlox hirsuta, a self-sterile endangered species that is prone to self-pollination, and its associated fitness costs.
  
  
  METHODS
  Multiple linear regressions were used to identify factors that explain variation in percentage fruit set within three of the five known populations of this endangered species. Florivorous beetle density, petal colour, floral display size, local conspecific density and pre-dispersal seed predation were quantified and their effects on the ability of flowers to produce fruits were assessed.
  
  
  RESULTS
  In all three populations, percentage fruit set decreased as florivorous beetle density increased and as floral display size increased. The effect of floral display size on fruit set, however, often depended on the density of nearby conspecific plants. High local conspecific densities offset - even reversed - the negative effects of floral display size on percentage fruit set. Seed predation by mammals decreased fruit set in one population.
  
  
  CONCLUSIONS
  The results indicate that seed production in P. hirsuta can be maximized by selectively augmenting populations in areas containing isolated large plants, by reducing the population sizes of florivorous beetles and by excluding mammals that consume unripe fruits.
authors.affiliation: Department of Organismal and Environmental Biology, Christopher Newport University, 1 Avenue of the Arts, Newport News, VA 23606, USA.
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Ruane
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Rotzin
authors.forename: Philip H
authors.initials: PH
authors.lastname: Congleton
mesh_terms: D056727:Endangered Species; D035264:Flowers / Q000033:anatomy & histology; D020387:Food Chain; D014644:Genetic Variation; D019684:Magnoliopsida / Q000235:genetics / Q000502:physiology*; D011156:Population Density; D012098:Reproduction; D012639:Seeds / Q000254:growth & development
keywords: Allee effect; Phlox hirsuta; florivory; geitonogamous self-pollination; granivory; local conspecific density; outcross pollination; reproductive ecology; self interference; self-incompatible