Hybrid sterility and inviability in the parasitic fungal species complex Microbotryum |
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| Authors: | D M DE VIENNE G REFRÉGIER M E HOOD A GUIGUE B DEVIER E VERCKEN C SMADJA A DESEILLE T GIRAUD |
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| Institution: | 1. Both these authors contributed equally to this study and should be considered as sharing first authorship.;2. Department of Biology, Amherst College, Amherst, MA, USA;3. Ecologie, Systématique et Evolution, Université Paris‐Sud, Orsay Cedex, France;4. CNRS, Orsay Cedex, France;5. Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UK |
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| Abstract: | Microbotryum violaceum, the anther‐smut fungus, forms a complex of sibling species which specialize on different plants. Previous studies have shown the presence of partial ecological isolation and F1 inviability, but did not detect assortative mating apart from a high selfing rate. We investigated other post‐mating barriers and show that F1 hybrid sterility, the inability of gametes to mate, increased gradually with the increasing genetic distance between the parents. F2 hybrids showed a reduced ability to infect the plants that was also correlated with the genetic distance. The host on which the F2 hybrids were passaged caused a selection for alleles derived from the pathogen species originally isolated from that host, but this effect was not detectable for the most closely related species. The post‐mating barriers thus remain weak among the closest species pairs, suggesting that premating barriers are sufficient to initiate divergence in this system. |
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| Keywords: | Dobzhansky– Muller genetic incompatibilities extrinsic ecological isolation post‐zygotic reproductive isolation tempo of speciation mating type Silene selection arena |
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