title: Mutualists and antagonists mediate frequency-dependent selection on floral display.
abstract: Theory predicts that, with conflicting selection pressures mediated by mutualists and antagonists, alternative reproductive strategies can be maintained by negative frequency-dependent selection if it results in rare-morph advantage. We combined field experiments and surveys of natural populations to determine whether selection on floral display is frequency dependent in the self-incompatible herb Primula farinosa, which is polymorphic for inflorescence height and occurs in a short-scaped and a long-scaped morph. Among short-scaped plants, both pollination success, quantified as initiation of fruits and seeds, and seed predation were positively correlated with the relative frequency of the long-scaped morph. The relative strength of these effects and the direction of the resulting frequency-dependent selection on scape morph varied among years and populations. The results suggest that both mutualists and antagonists may mediate frequency-dependent selection and that frequency dependence may vary from positive to negative with rare-morph advantage, depending on the relative strength of these interactions.
authors.affiliation: Department of Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden. Per.Torang@ebc.uu.se
authors.forename: Per
authors.initials: P
authors.lastname: Toräng
authors.forename: Johan
authors.initials: J
authors.lastname: Ehrlén
authors.forename: Jon
authors.initials: J
authors.lastname: Agren
mesh_terms: D000818:Animals; D005247:Feeding Behavior / Q000502:physiology; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology*; D005638:Fruit; D009036:Moths / Q000502:physiology; D031825:Primula / Q000254:growth & development* / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D012641:Selection, Genetic; D013997:Time Factors