A model for the evolution of high frequencies of males in an androdioecious plant based on a cross-compatibility advantage of males.
Lloyd's (1975) and Charlesworth & Charlesworth's (1978) phenotypic selection models for the maintenance of androdioecy predict that males (female-sterile individuals) must have an advantage in fertility (K) of at least two in order to invade a hermaphroditic population, and that their equilibrium frequency (x(eq)=(K - 2)/2(K - 1)) is always less than 0.5. In this paper, we develop a model in which male fertility is frequency-dependent, a situation not investigated in the previous models, to explore the conditions under which a high frequency of males (i.e. more than 50%) could be maintained at equilibrium. We demonstrate that a gametophytic self-incompatibility (GSI) locus linked to a nuclear sex determination locus can favour rare alleles through male function, by causing frequency-dependent selection. Thus, the spread of a female-sterility allele in a hermaphroditic population may be induced. In contrast with the previous models, our model can explain male frequencies greater than 50% in a functionally androdioecious species, as long as there is (i) dominance of female-sterility at the sex locus, and (ii) a few alleles at the self-incompatibility locus, even if the advantage in fertility of male phenotype is lower than two.
Vassiliadis
C
C
Laboratoire de Génétique et Evolution des Populations Végétales, ESA-CNRS 8016, Bât SN2, Université de Lille 1, F-59655 Villeneuve d'Ascq cedex, France.
Valero
M
M
Saumitou-Laprade
P
P
Godelle
B
B
D005075:Biological Evolution; D003433:Crosses, Genetic; D005298:Fertility; D008957:Models, Genetic; D018521:Plant Physiological Phenomena; D010944:Plants / Q000235:genetics*