An experimental evaluation of self-interference in Narcissus assoanus: functional and evolutionary implications.
Floral traits that reduce self-pollination in hermaphroditic plants have usually been interpreted as mechanisms that limit the genetic consequences of self-fertilization. However, the avoidance of sexual conflict between female and male function (self-interference) may also represent an important selection pressure for the evolution of floral traits, particularly in self-incompatible species. Here, we use experimental manipulations to investigate self-interference in Narcissus assoanus, a self-incompatible species with a stigma-height dimorphism in which the degree of spatial separation between sex organs (herkogamy) differs strikingly between the long- and short-styled morphs (hereafter L- and S-morphs). We predicted that weak herkogamy in the L-morph would cause greater self-pollination and hence self-interference. Experimental self-pollination reduced seed set when it occurred prior to, or simultaneously with, cross-pollination in the L-morph, but only if it occurred prior to cross-pollination in the S-morph. In the field, autonomous self-pollination was greater in the L-morph than the S-morph, but we found no evidence that self-interference reduced maternal or paternal fitness in either morph. One-day-old flowers of the L-morph have reduced stigma receptivity and hence exhibit protandry, whereas stigma receptivity and anther dehiscence are concurrent in the S-morph. This suggests that the two style morphs have alternative strategies for reducing self-interference: dichogamy in the L-morph and herkogamy in the S-morph. These results provide insight into the mechanisms that reduce sexual conflict in hermaphrodite plants and are of significance for understanding the evolution and maintenance of sexual polymorphisms.
Cesaro
A C
AC
Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Montpellier Cedex 5, France.
Barrett
S C H
SC
Maurice
S
S
Vaissiere
B E
BE
Thompson
J D
JD
D000704:Analysis of Variance; D035264:Flowers / Q000033:anatomy & histology*; D005602:France; D007178:Inbreeding; D031427:Narcissus / Q000033:anatomy & histology / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D012641:Selection, Genetic; D012727:Sex Characteristics; D013997:Time Factors