Evidence of restoration cost in the annual gynodioecious Phacelia dubia.
A negative pleiotropic effect on fitness of nuclear sex-determining genes (cost of restoration) could explain nuclear-cytoplasmic gynodioecy but rarely has been demonstrated empirically. In a gynodioecious Phacelia dubia population, maternal lineages produce only hermaphroditic progenies irrespective of the pollen parent (N) or can segregate females (S). Natural progenies of N maternal plants had lower seed viability than that of S. Full-sib progenies of unrelated hermaphrodites from all possible matings between N and S lineages had similar pollen filling but differed in sporophyte performance, mainly at seed germination stage. A discrete multivariate analysis reveals that the performance of N(female symbol) x S(male symbol) progeny at early stages of development was significantly lower than that of the other three types of mating in agreement with the silent-cost-of-restoration hypothesis, affecting the sporophyte. The restoration cost and male sterility appear to be dominant and consequence of nuclear-cytoplasmic incompatibilities that may maintain nuclear-cytoplasmic polymorphism by frequency-dependent selection.
Del Castillo
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CIIDIR Oaxaca, Instituto Politécnico Nacional, Santa Cruz Xoxocotlán, Oaxaca, Mexico. rdelcast@yahoo.com
Trujillo
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S
D000704:Analysis of Variance; D018525:Germination / Q000235:genetics; D029522:Hydrophyllaceae / Q000235:genetics / Q000502:physiology*; D011058:Pollen / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D012641:Selection, Genetic; D016019:Survival Analysis