Spatial genetics of wild tomato species reveals roles of the Andean geography on demographic history.
Understanding the demographic history of natural populations in relation to the geographic features in their habitats is an important step toward deciphering the mechanisms of evolutionary processes in nature. This study investigates how the complex geographic and ecological features of the Andes play a role in demographic history, species divergence, dispersal patterns, and hybridization in wild tomato species. We investigated spatial genetics of two closely related wild tomato species, Solanum lycopersicum and S. pimpinellifolium, by integrating amplified fragment length polymorphism (AFLP) marker data and geographic information system (GIS)-derived geographic and climatic data. The two species represent genetically distinct lineages largely separated by the Andes, but hybridize extensively in central to northern Ecuador, likely mediated by the transitional climatic conditions between those of the two species. Solanum lycospericum has likely experienced a severe population bottleneck during the colonization of the eastern Andes followed by a rapid population expansion. The study demonstrates that the evolutionary patterns of the two wild tomatoes, including demographic history, dispersal patterns, interspecific divergence, and hybridization, are intimately related to the complex geographic and ecological features of the Andes. Integrating genetic data across the genome and GIS-derived environmental data can provide insights into the patterns of complex evolutionary processes in nature.