Interspecific seed discounting and the fertility cost of hybridization in an endangered species

Hybrid fertilizations can have negative demographic effects on taxa by usurping ovules that would otherwise give rise to nonhybrid offspring. The consequent reduction in conspecific matings may be exaggerated in rare taxa and constitutes a fertility cost that has rarely been quantified. Here, the ef...

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Bibliographic Details
Published in:The New phytologist 2008-01, Vol.177 (1), p.276-284
Main Authors: Burgess, Kevin S, Morgan, Martin, Husband, Brian C
Format: Article
Language:English
Subjects:
Conservation of Natural Resources
Culling
culling experiment
demographic swamping
Discounting
Fruits
Genetic hybridization
Hybridity
Hybridization, Genetic
minority disadvantage
Morus
Morus - genetics
Morus - physiology
paternity
Plants
Pollen
Population mean
Reproduction - genetics
Reproduction - physiology
Seeds
small populations
Taxa
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Summary:Hybrid fertilizations can have negative demographic effects on taxa by usurping ovules that would otherwise give rise to nonhybrid offspring. The consequent reduction in conspecific matings may be exaggerated in rare taxa and constitutes a fertility cost that has rarely been quantified. Here, the effect of interspecific mating was estimated on the fecundity of locally rare red mulberry (Morus rubra), which hybridizes with introduced white mulberry (Morus alba) and red [yen sign] white hybrids. First, the asymmetry in pollen production among red, white and hybrid mulberry in two sympatric populations was quantified. The fertility cost of hybridization was then assessed experimentally by estimating seed production and rates of interspecific mating in red mulberry trees from plots where white and hybrid mulberry trees were selectively removed. On average, the percentage of mulberry pollen per plot produced by red mulberry (8%) was significantly lower than the mean for white and hybrid mulberry combined (92%). Experimentally removing white and hybrid mulberry increased the siring fertility of red mulberry by 14% but produced no change in seed set. Results indicate that seeds of red mulberry, ordinarily sired by conspecific pollen, are being discounted through fertilization of ovules by heterospecific pollen, which may contribute to local decline of red mulberry.
ISSN:0028-646X
1469-8137
DOI:10.1111/j.1469-8137.2007.02244.x