Reproductive barriers and their role in asymmetric Rhinanthus hybridization
(2013)
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- Authors
- Supervisors
- Wesselingh, Renate
- Abstract
- (en) We examined reproductive isolation between two hybridizing Rhinanthus species that are very similar in ecology and floral traits. The two species shared the same suite of pollinator species (bumblebees), but R. angustifolius was more attractive because of its higher rewards levels. Pollinator behaviour was highly sensitive to the relative Rhinanthus frequencies and site spatial configuration. When both species were in equal proportions, bumblebees preferred R. angustifolius, while at unbalanced frequencies, the more abundant species was preferred. Some bees foraged both Rhinanthus thus allowing interspecific pollen transfers. Pollen placement on bees was similar with both Rhinanthus, and cross-specific stigmatic pollen deposition was equal in both directions, thus interspecific pollen transfers were not mechanically limited. In case of mixed pollination, conspecific pollen grains have a siring advantage in both species, but hybrids seeds with R. angustifolius as maternal plant germinated poorly compared to those with R. minor as the maternal parent. At the flowering stage, bumblebees treated hybrids almost as equal to the background species. In a R. angustifolius background, bumblebees visited hybrids more often than R. minor, while visitation rates to the hybrids were equal to both parental species on a R. minor background. We used modelling to integrate these results, and showed that gene flow is directed towards R. angustifolius when its relative frequency in a mixed population is above 20-40%. However the two species seem unlikely to fuse over the short term. Interestingly, one of the two species and its genes are bound to disappear at any starting frequency over the long term. The combined action of the several leaky barriers seems to explain well the genetic patterns observed and the low introgression inferred at the European scale in molecular and phylogeographic studies.
- Affiliations
Citations
Natalis, L. (2013). Reproductive barriers and their role in asymmetric Rhinanthus hybridization. https://hdl.handle.net/2078.5/79051