Pat Bedinger & Amanda Broz on Dynamics of reproductive barriers in wild tomato species
Abstract. The tomato clade (Solanum section Lycopersicon) is particularly amenable to the study of reproductive barriers (RB), as it contains both self-compatible (SC) and self-incompatible (SI) populations and species, with numerous examples of sympatry. We surveyed 12 sympatric sites and identified post-pollination, pre-zygotic and post-zygotic barriers, which were often linked to mating system type. Viable hybrid seeds were formed between sympatric pairs in only three of 28 interspecific crosses. To better understand how changes in mating system impact interspecific and inter-population interactions, we characterized the dynamics of RBs in Solanum habrochaites, which has undergone SI to SC transitions at the species margins. We found that loss of S-RNase was associated with SC in most marginal northern populations, and that subsequent loss of additional pistil factors weakened interspecific barriers. In addition, pollen from a subset of these northern SC populations was rejected by pistils of central SI populations, demonstrating the formation of an inter-population RB due to loss of pollen side factors. This suggests that mating system transitions are followed by additional loss of function mutations that influence both interspecific and inter-population RBs, and that these mutations can promote speciation by limiting gene flow between diverging and ancestral populations.
Watch this talk here: https://youtu.be/WSrZvzo0gSw
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