Stylar Polymorphisms and the Evolution of Heterostyly in Narcissus (Amaryllidaceae)

Abstract

In outcrossing hermaphrodite plants, the separate functions of pollen dispersal and pollen receipt may interfere with one another so that fitness as a paternal or maternal parent is compromised (van der Pijl, 1978; Bawa and Dpler, 1975; Lloyd and Yates, 1982; Lloyd and Webb, 1986; Webb and Lloyd, 1986; Bertin and Newman, 1993; Harder and Barrett, 1995), This is particularly likely in flowers in which the sex organs are close together and mature at the same time, Interference can potentially take several forms, including the obstruction by pistils of efficient pollen dispatch by pollinators, stamens restricting access by pollinators to stigmas, thus reducing pollen deposition, and the deleterious effects of self-pollination on maternal function due to stigmatic, stylar, or ovular clog- ging, Although there is some experimental evidence for self-pollen interference (Shore and Barrett, 1984; Barrett and Glover, 1985; Bertin and Sullivan, 1988; Palmer et aI., 1989; Waser and Price, 1991; Scribailo and Barrett, 994), the other two forms of pollen-pistil interference have seldom been in tigated (see, however, Barrett and Glover, 1985; Kohn and Barrett, 199 a ,