Pollen performance decreases with plant age for outcrosser but not selfer: evidence for cost of male performance

Premise Declines in reproductive capabilities with increasing age are common across the tree of life. However, in plants, mating system traits have rarely been tested for signs of senescence. Since reproduction is often resource limited, we might expect outcrossing and selfing taxa to allocate these...

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Bibliographic Details
Published in:American journal of botany 2019-09, Vol.106 (9), p.1271-1278
Main Authors: Malagon, Daniel A., Roche, Morgan D., McElderry, Robert M., Kalisz, Susan
Format: Article
Language:English
Subjects:
Age
BRIEF COMMUNICATION
Collinsia
Flowering
Flowers
Germinability
Growth chambers
male reproductive senescence
Ovule
Ovules
Performance measurement
Phenotype
plant mating systems
Pollen
pollen germinability
Pollination
Pollinators
Reproduction
selfing syndrome
Senescence
sex allocation
Sibling species
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Summary:Premise Declines in reproductive capabilities with increasing age are common across the tree of life. However, in plants, mating system traits have rarely been tested for signs of senescence. Since reproduction is often resource limited, we might expect outcrossing and selfing taxa to allocate these resources differently, especially as a plant ages. Compared with selfers, outcrossers are expected to produce showy, rewarding flowers that attract pollinators and high‐quality pollen that can successfully compete for ovules. Yet, this resource‐intensive strategy of outcrossers may result in declines in floral allocation and pollen performance metrics, relative to selfers. Methods To explore age‐related changes in reproduction, we measured flower size and pollen germinability over the flowering period for multiple populations of an annual sister species pair, Collinsia linearis (outcrosser) and C. rattanii (selfer), in a growth chamber experiment. Results We found that flower size decreased significantly with age in both species. The outcrosser expressed a significant and dramatic (88%) decline in pollen germinability with age, while the selfer's pollen germinability decline was non‐significant and low (17%). Conclusions Our results support the idea that the higher total cost of reproduction in outcrossers can deplete available resources more rapidly than in selfers, manifesting as a decline in male performance with plant age.
ISSN:0002-9122
1537-2197
1537-2197
DOI:10.1002/ajb2.1346