Sexual specialization and inbreeding avoidance in the evolution of dioecy

Dioecy has evolved independently, many times, among unrelated taxa. It also appears to have evolved along two contrasting pathways: (1) from hermaphroditism via monoecy to dioecy and (2) from hermaphroditism via gynodioecy to dioecy. Most dioecious plants have close cosexual relatives with some mean...

Full description

Saved in:
Bibliographic Details
Published in:The Botanical review 1997-01, Vol.63 (1), p.65-92
Main Authors: Freeman, D.C. (Wayne State University, Detroit, MI.), Doust, J.L, El-Keblawy, A, Miglia, K.J, McArthur, E.D
Format: Article
Language:English
Subjects:
Dimorphism (Biology)
Dimorphism (Plants)
Dioecy
ENDOGAMIA
EVOLUCION
EVOLUTION
Female animals
FISIOLOGIA VEGETAL
Flowers
Gynodioecy
Hermaphrodites
Hermaphroditism
INBREEDING
Incompatibility
INSECTA
Intermediates
Lability
LITERATURE REVIEWS
Male animals
Monoecy
Outbreeding
PHYSIOLOGIE VEGETALE
PLANT PHYSIOLOGY
Plant reproduction
Plants
POLINIZACION
POLINIZADORES
Pollen
POLLINATION
POLLINATORS
POLLINISATEUR
POLLINISATION
Self-incompatibility
SEX
Sex (Botany)
Sex in plants
SEXE
SEXO
Sexual dimorphism
Specialization
Species
VENT
VIENTO
WINDS
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Dioecy has evolved independently, many times, among unrelated taxa. It also appears to have evolved along two contrasting pathways: (1) from hermaphroditism via monoecy to dioecy and (2) from hermaphroditism via gynodioecy to dioecy. Most dioecious plants have close cosexual relatives with some means of promoting outcrossing (e.g., herkogamy, dichogamy, self-incompatibility, or monoecy). To the extent that these devices prevent inbreeding, the evolution of dioecy in these species cannot logically be attributed to selection for outcrossing. In these cases, the evolution of dioecy is, we believe, due to selection for sexual specialization. However, in other species, that lack outbreeding close relatives, dioecy may have evolved from gynodioecy (males and hermaphrodites) as an outbreeding device. Subsequent disruptive selection and selection for sexual specialization may have also shaped the evolution of dioecy from gynodioecy in these species, resulting in two genetically determined, constant sex morphs. Both pathways for the evolution of dioecy require the operation of disruptive selection, though the gynodioecy route involves more restrictive disruptive selection and a genetic designation of gender. In contrast, the monoecy route is not dependent on the genetic designation of two sex morphs, but, rather, allows the possibility of sexual intermediates and sexual lability. Both pathways produce one morph in which maleness is suppressed and another in which the female function is negligible or nonexistent-the reproductive mode recognized as dioecy. Evidence is presented here to support the thesis that instances of sexual lability, the presence of an array of sexual intermediates, sex-switching, and sexual niche segregation can be explained in terms of the pathway that was taken in the evolution of a particular dioecious species. In addition, the degree of sexual dimorphism seen in dioecious species is correlated with mode of pollination (insect- or wind-pollinated) and other ecological factors.
ISSN:0006-8101
1874-9372
DOI:10.1007/bf02857918