Frequency-dependent fitness in gynodioecious Lobelia siphilitica

Selection is frequency dependent when an individual's fitness depends on the frequency of its phenotype. Frequency-dependent selection should be common in gynodioecious plants, where individuals are female or hermaphroditic; if the fitness of females is limited by the availability of pollen to...

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Bibliographic Details
Published in:Evolution 2015-05, Vol.69 (5), p.1232-1243
Main Authors: Rivkin, L. Ruth, Case, Andrea L., Caruso, Christina M.
Format: Article
Language:English
Subjects:
Availability
Ecological competition
Evolution
Female animals
Females
Fitness
Flowers
Flowers & plants
Flowers - genetics
Frequency distribution
Frequency-dependent selection
Fruits
Genetic Fitness
Genotype & phenotype
Hermaphroditism
Lobelia - genetics
Lobelia - physiology
Lobelia siphilitica
Models, Genetic
Ovules
Phenotypes
Plant reproduction
Plants
Pollen
Pollen - genetics
pollen limitation
Pollination
polymorphism
Seeds
Seeds - genetics
Selection, Genetic
Sex ratio
sexual system
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Summary:Selection is frequency dependent when an individual's fitness depends on the frequency of its phenotype. Frequency-dependent selection should be common in gynodioecious plants, where individuals are female or hermaphroditic; if the fitness of females is limited by the availability of pollen to fertilize their ovules, then they should have higher fitness when rare than when common. To test whether the fitness of females is frequency dependent, we manipulated the sex ratio in arrays of gynodioecious Lobelia siphilitica. To test whether fitness was frequency dependent because of variation in pollen availability, we compared open-pollinated and supplemental hand-pollinated plants. Open-pollinated females produced more seeds when they were rare than when they were common, as expected if fitness is negatively frequency dependent. However, hand-pollinated females also produced more seeds when they were rare, indicating that variation in pollen availability was not the cause of frequency-dependent fitness. Instead, fitness was frequency dependent because both hand- and open-pollinated females opened more flowers when they were rare than when they were common. This plasticity in the rate of anthesis could cause fitness to be frequency dependent even when reproduction is not pollen limited, and thus expand the conditions under which frequency-dependent selection operates in gynodioecious species.
ISSN:0014-3820
1558-5646
DOI:10.1111/evo.12654