Karrenberg Sophie, Edelist Cécile, Lexer Christian, Rieseberg Loren
Plant Ecological Genetics, Institute of Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland.
New Phytol. 2006;170(3):615-29. doi: 10.1111/j.1469-8137.2006.01687.x.
To contribute to the understanding of ecological differentiation in speciation, we compared salinity responses of the halophytic diploid hybrid species Helianthus paradoxus and its glycophytic progenitors Helianthus annuus and Helianthus petiolaris. Plants of three populations of each species were subjected to a control (nonsaline) and three salinity treatments, including one simulating the ion composition in the habitat of H. paradoxus. Relative to the control, saline treatments led to a 17% biomass increase in H. paradoxus while its progenitors suffered 19-33% productivity reductions and only in H. paradoxus, leaf contents of potassium, calcium, and magnesium were strongly reduced. Under all treatments, H. paradoxus allocated more resources to roots, was more succulent, and had higher leaf contents of sodium (> 200 mmol l(-1) tissue water) and sulfur than its progenitor species. These results suggest that salt tolerance and thus speciation of H. paradoxus is related to sodium replacing potassium, calcium and magnesium as vacuolar osmotica. The evolutionary and genetic mechanisms likely to be involved are discussed.
为了促进对物种形成过程中生态分化的理解，我们比较了盐生二倍体杂交种向日葵（Helianthus paradoxus）及其甜土植物祖先向日葵（Helianthus annuus）和糙叶向日葵（Helianthus petiolaris）对盐分的响应。每个物种的三个种群的植株分别接受对照（非盐）和三种盐分处理，其中一种处理模拟了向日葵栖息地的离子组成。相对于对照，盐分处理使向日葵的生物量增加了17%，而其祖先物种的生产力则降低了19%-33%，并且只有向日葵的叶片钾、钙和镁含量大幅降低。在所有处理条件下，向日葵比其祖先物种将更多资源分配到根部，肉质更厚，叶片钠含量（组织水>200 mmol l(-1)）和硫含量更高。这些结果表明，向日葵的耐盐性以及物种形成与钠取代钾、钙和镁作为液泡渗透剂有关。文中还讨论了可能涉及的进化和遗传机制。
