title: Intraspecific variation in gender strategies in Lycium (Solanaceae): associations with ploidy and changes in floral form following the evolution of gender dimorphism.
abstract: •
  
  
  OBJECTIVE
  An association between polyploidy and gender dimorphism has been noted in several plant lineages. Whereas the majority of Lycium species are diploid and have hermaphroditic flowers in cosexual populations, gender dimorphism (gynodioecy, dioecy) has been shown to be uniformly associated with polyploidy in previous studies. Preliminary field observations suggested that some populations of Lycium carolinianum were dimorphic, providing a test of this association.•
  
  
  METHODS
  We assessed sexual systems and cytotype variation (to infer ploidy) across 17 populations of L. carolinianum. Comparison of flowers in cosexual and dimorphic populations were used to infer changes in reproductive morphology associated with the evolution of gynodioecy.•
  
  
  RESULTS
  The majority of populations were cosexual in gender expression, but dimorphism was present in the Yucatán and in some populations in Hawaii. Populations varied in ploidy and were either diploid or tetraploid. Floral sexual dimorphism was present in all gynodioecious populations, though the magnitude differed and was cryptic in some cases. Our results are consistent with the hypothesis that following the evolution of gynodioecy, flowers on hermaphrodites increased in size.•
  
  
  CONCLUSIONS
  Dimorphic sexual systems have likely evolved convergently in L. carolinianum. In contrast to previous studies, dimorphism is not perfectly associated with polyploidy. Although our sample from the Yucatán was both tetraploid and dimorphic, all populations in Hawaii were diploid regardless of sexual system. Ongoing phylogeographic and mating system studies will contribute to our understanding of reproductive evolution in this widespread, polymorphic species.
authors.affiliation: Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA.
authors.forename: Caitlin M
authors.initials: CM
authors.lastname: Blank
authors.affiliation: Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Levin
authors.affiliation: Department of Biology, Amherst College, Amherst, Massachusetts 01002 USA.
authors.forename: Jill S
authors.initials: JS
authors.lastname: Miller
mesh_terms: D005075:Biological Evolution; D035264:Flowers / Q000033:anatomy & histology*; D014644:Genetic Variation; D006254:Hawaii; D032305:Lycium / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology; D008800:Mexico; D011123:Polyploidy; D012098:Reproduction
keywords: DNA content; Lycium; Lycium carolinianum; Solanaceae; floral evolution; gender dimorphism; gynodioecy; male sterility; polyploidy; sexual dimorphism