Journal Article

Among-individual variation in pollen limitation and inbreeding depression in a mixed-mating shrub

Juan P. González-Varo and Anna Traveset

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 106, issue 6, pages 999-1008
Published in print December 2010 | ISSN: 0305-7364
Published online October 2010 | e-ISSN: 1095-8290 | DOI: https://dx.doi.org/10.1093/aob/mcq200
Among-individual variation in pollen limitation and inbreeding depression in a mixed-mating shrub

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Variation in inbreeding depression (δ) among individual plants is considered to play a central role in mating system evolution and population genetics. Moreover, such variation could be linked to individual susceptibility to pollen limitation (PL) because those individuals strongly affected by δ for seed production will require more outcross pollen for setting a given number of fruits or seeds. However, no study has tested explicitly for associations between PL and δ at the individual plant level. This study assesses the extent of among-individual variation in PL and δ, the consistency of δ across life stages, and the relationships between individual PL and δ in the mixed-mating shrub Myrtus communis.

Methods

Controlled hand-pollinations were performed in a natural M. communis population. Marked flowers were monitored until fruit production and a greenhouse experiment was conducted with the seeds produced.

Key Results

Compared with selfing, outcross-pollination enhanced seed number per fruit, germination rate and seedling growth, but did not enhance fruit-set. Only seed number per fruit was pollen limited and, thus, cumulative pollen limitation depended more on pollen quality (outcross pollen) than on quantity. The effects of δ varied considerably across life stages and individual plants. Cumulative δ was high across individuals (mean δ = 0·65), although there were no positive correlations between δ values at different life stages. Interestingly, maternal plants showing stronger δ for seed production were more pollen limited, but they were also less affected by δ for seedling growth because of a seed size/number trade-off.

Conclusions

Results show a general inconsistency in δ across life stages and individuals, suggesting that different deleterious loci are acting at different stages. The association between δ and PL at the individual level corroborates the idea that pollen limitation may be ‘genotype-dependent’ regardless of other factors.

Keywords: Inbreeding depression; family level; mixed-mating systems; Myrtus communis; pollen limitation; progeny performance; seed number/seed size trade-off; seed production

Journal Article.  6869 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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