title: The role of inbreeding depression and mating system in the evolution of heterostyly.
abstract: We investigated the role of morph-based differences in the expression of inbreeding depression in loss of the mid-styled morph from populations of tristylous Oxalis alpina. The extent of self-compatibility (SC) of reproductive morphs, the degree of self-fertilization, and the magnitude of inbreeding depression were investigated in three populations of O. alpina differing in their tristylous incompatibility relationships. All three populations exhibited significant inbreeding depression. In two populations with highly modified tristylous incompatibility, manifested as increased reciprocal compatibility between short- and long-styled morphs, substantial SC and self-fertilization of mid-styled morphs were detected, and expected to result in expression of inbreeding depression in the progeny of mid-styled morphs in the natural populations. In contrast, significant self-fertility of the mid-styled morph was absent from the population with typical tristylous incompatibility, and no self-fertilization could be detected. Although self-fertilization and expression of inbreeding depression should result in selection against the mid-styled morph in the later stages of the transition from tristyly to distyly, in O. alpina selection against the mid-styled morph in the early phases of the evolution of distyly is likely due to genic selection against mid-alleles associated with modified tristylous incompatibility, rather than expression of inbreeding depression.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697, USA. jenniferjuneweber@gmail.com
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Weber
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Weller
authors.forename: Ann K
authors.initials: AK
authors.lastname: Sakai
authors.forename: Olga V
authors.initials: OV
authors.lastname: Tsyusko
authors.forename: Travis C
authors.initials: TC
authors.lastname: Glenn
authors.forename: César A
authors.initials: CA
authors.lastname: Domínguez
authors.forename: Francisco E
authors.initials: FE
authors.lastname: Molina-Freaner
authors.forename: Juan
authors.initials: J
authors.lastname: Fornoni
authors.forename: Mike
authors.initials: M
authors.lastname: Tran
authors.forename: Nhu
authors.initials: N
authors.lastname: Nguyen
authors.forename: Karen
authors.initials: K
authors.lastname: Nguyen
authors.forename: Lien-Khuong
authors.initials: LK
authors.lastname: Tran
authors.forename: Greg
authors.initials: G
authors.lastname: Joice
authors.forename: Ellen
authors.initials: E
authors.lastname: Harding
mesh_terms: D005075:Biological Evolution; D018533:Biomass; D018744:DNA, Plant / Q000235:genetics; D035264:Flowers / Q000502:physiology; D007178:Inbreeding; D019684:Magnoliopsida / Q000235:genetics* / Q000502:physiology; D057945:Self-Fertilization
chemical_list: D018744:DNA, Plant
keywords: Breeding systems; Oxalidaceae; distyly; self-incompatibility; tristyly