title: Associations between sex-organ deployment and morph bias in related heterostylous taxa with different stylar polymorphisms.
abstract: OBJECTIVE
  Populations of heterostylous species are characterized by two or three floral morphs with reciprocal positioning of stigmas and anthers. Theoretical models predict equal morph frequencies (isoplethy) when disassortative mating is prevalent in populations, but biased morph ratios may occur when variation in the expression of heterostyly causes deviations from intermorph mating.
  
  
  METHODS
  We explore the role of sex-organ deployment in governing morph ratios in two closely related genera of Boraginaceae, exhibiting striking variation in floral traits associated with the heterostylous syndrome. We sampled 66 populations of six species of Glandora and 39 populations of three species of Lithodora across their distributional range in the Mediterranean. In each population we estimated morph ratios and measured several floral traits. We used phylogenetically corrected and noncorrected regressions to test the hypothesis that differences in sex-organ reciprocity and herkogamy are associated with deviations from isoplethy.
  
  
  RESULTS
  Biased morph ratios occurred in 24% of populations, particularly in Lithodora. Populations biased for the long-styled morph (L-morph) were more frequent than the short-styled morph (S-morph). Distylous species were less likely to exhibit biased ratios than species with stigma-height dimorphism. In Lithodora fruticosa, a species lacking reciprocity, decreased herkogamy in the S-morph was associated with increasing L-morph bias, perhaps resulting from self-interference.
  
  
  CONCLUSIONS
  Striking variation in the expression of heterostyly in Glandora and Lithodora is associated with biased morph ratios, which probably result from pollinator-mediated mating asymmetries within populations.
authors.affiliation: Department of Plant Biology and Soil Sciences, Faculty of Biology, University of Vigo, As Lagoas-Marcosende 36200 Vigo, Spain victoferrero@gmail.com.|CFE, Centre for Functional Ecology and Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
authors.forename: Victoria
authors.initials: V
authors.lastname: Ferrero
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
authors.forename: Spencer C H
authors.initials: SC
authors.lastname: Barrett
authors.affiliation: Department of Biology and Centre for Environmental and Marine Studies, University of Aveiro, 3810-193 Aveiro, Portugal.|Department of Ecology and Evolution, Stony Brook University, 650 Life Sciences Building Stony Brook, New York 11794 USA.
authors.forename: Danny
authors.initials: D
authors.lastname: Rojas
authors.affiliation: Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Apartado 1095 41080 Sevilla, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Arroyo
authors.affiliation: Department of Plant Biology and Soil Sciences, Faculty of Biology, University of Vigo, As Lagoas-Marcosende 36200 Vigo, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
mesh_terms: D005075:Biological Evolution; D028082:Boraginaceae / Q000033:anatomy & histology / Q000145:classification / Q000502:physiology*; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology*; D005843:Geography; D019083:Mediterranean Region; D008953:Models, Anatomic; D011058:Pollen / Q000033:anatomy & histology / Q000502:physiology*; D054817:Pollination / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D013045:Species Specificity
keywords: Glandora; Lithodora; Mediterranean plants; disassortative mating; distyly; floral morph ratios; heterostyly; stigma-height dimorphism