RESUMO
PREMISE OF THE STUDY: Wild relatives of crop species have long been viewed as an important genetic resource for crop improvement, but basic information about the population biology of these species is often lacking. This study investigated the population structure, demographic history, and evolutionary patterns of a green-fruited relative of the cultivated tomato, Solanum peruvianum. METHODS: We investigated spatial genetics of S. peruvianum and screened for loci potentially under natural selection by integrating amplified fragment length polymorphism (AFLP) genotypes, phenotypic data, geography, and geographic information system (GIS)-derived climate data of 19 natural populations. KEY RESULTS: Solanum peruvianum had a moderate degree of population differentiation, likely reflecting partial geographic isolation between species. Populations had a distribution pattern consistent with north-to-south "stepping-stone" dispersal with significant isolation by distance (IBD), similar to other tomato species. Several AFLP loci showed evidence of selection and associated with climate variables. However, phenotypic traits generally did not correlate with climate variables. CONCLUSIONS: Geographic features of the coastal Andes is likely an important factor that determines the migration pattern and population structure of S. peruvianum, but climatic factors do not appear to be critical for its phenotypic evolution, perhaps due to a high degree of phenotypic plasticity. Spatial genetics of wild relatives of crop species is a powerful approach to understand their evolutionary patterns and to accelerate the discovery of their potential for crop improvements.
Assuntos
Evolução Molecular , Dispersão Vegetal , Solanum/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA de Plantas/genética , Geografia , Peru , Fenótipo , Seleção GenéticaRESUMO
PREMISE OF THE STUDY: 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. METHODS: 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. KEY RESULTS: 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. CONCLUSIONS: 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.
Assuntos
Solanum lycopersicum/crescimento & desenvolvimento , Solanum lycopersicum/genética , Solanum/crescimento & desenvolvimento , Solanum/genética , Alelos , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Evolução Biológica , Evolução Molecular , Especiação Genética , Genética Populacional , Geografia , Hibridização Genética , Dados de Sequência Molecular , Polimorfismo Genético , Dispersão de Sementes , Análise de Sequência de DNA , América do SulRESUMO
Environmental variation is widely viewed as a major force driving morphological change and speciation. Although many environmental attributes are potentially critical for adaptive responses within and between species, the individual and relative importance of these diverse attributes remain poorly understood. Here we combine a geographical information systems (GIS)-based analysis of environmental variation with a multipopulation analysis of phenotypic, physiological, and genetic variation, to generate and test hypotheses of environmental factors likely driving adaptive divergence within and between two wild Andean plant species. First, we document large environmental differences between population locations of the two species, and among regions within species. Second, we show evidence for inter- and intraspecific differences in genetically based phenotypic and physiological variation. Third, combining these data, we report evidence for trait-environment associations both among populations within species, and between species, that are strongly indicative of recent and rapid adaptive responses. Finally, we show that these trait-environment associations cannot be simply explained by genetic relatedness within species, reinforcing our inference that local, regional, and species-wide environmental conditions are responsible for phenotypic and physiological diversification. The strongest trait-environment associations involve temperature and precipitation gradients, suggesting these climatic factors are predominant drivers of adaptive diversification in these species.