title: Preferences of pollinators and herbivores in gynodioecious Geranium sylvaticum.
abstract: OBJECTIVE
  For the maintenance of gynodioecy (i.e. the coexistence of female and hermaphroditic plants), females need to compensate for the lack of pollen production through higher seed production or better progeny quality compared to hermaphrodites. In Geranium sylvaticum, females produce more seeds per flower than hermaphrodites. This difference in seed production might be modified by biological interactions with pollinators and herbivores that may favour one sex and thus affect the maintenance of gynodioecy.
  
  
  METHODS
  Sexual dimorphism in flower size and flowering phenology, and in attractiveness to pollinators, pre-dispersal seed predators and floral herbivores were examined in natural populations of G. sylvaticum.
  
  
  RESULTS
  Pollinators preferred hermaphrodites 25 % more often than females in two of the three study populations, and floral herbivores attacked hermaphrodites 15 % more often than females in two of the six study populations. These preferences might be explained by the larger flower size of hermaphrodites. In contrast, seed predators did not prefer either sex.
  
  
  CONCLUSIONS
  The data suggest that pollinator preference does not benefit females, whereas the higher floral herbivory of hermaphrodites might enhance the maintenance of females in G. sylvaticum. Thus, although the data support the view that ecological factors may contribute to the maintenance of gynodioecy, they also suggest that these contributions may vary across populations and that they may function in opposite directions.
authors.affiliation: Section of Ecology, Department of Biology, University of Turku, FIN-20014 Turku, Finland.
authors.forename: Eija
authors.initials: E
authors.lastname: Asikainen
authors.forename: Pia
authors.initials: P
authors.lastname: Mutikainen
mesh_terms: D000222:Adaptation, Physiological; D000704:Analysis of Variance; D035264:Flowers / Q000502:physiology*; D031315:Geranium / Q000502:physiology*; D011058:Pollen / Q000502:physiology*; D012098:Reproduction; D012639:Seeds / Q000502:physiology; D012727:Sex Characteristics