Genetic Map of Sympatric Introgression in Hybridizing Colias Butterflies

硫蝶，Colias eurytheme和C. philodice，在北美大部分地区的田野和路边都很常见，因为它们广泛杂交而引人注目。高达10%的蝴蝶是杂交种，这种杂交率足以将它们混合成一个单一的物种。然而，它们仍然泾渭分明。许多其他物种对也表现出类似的杂交模式，包括达尔文雀和许多植物物种。这些案例挑战了我们对物种的传统定义，即物种通常不会杂交。1957年首次提出的一个未经验证的假设是，杂交物种实际上共享它们的部分基因组，而选择的作用是使基因组的其余部分保持不同。为了验证这一点，将使用新的方法来绘制这些蝴蝶的染色体的详细图谱。这张基因图谱将用于对基因在物种间传播速率的精细分析。如果表面上截然不同的杂交物种确实共享了它们基因组的大部分，那么它将导致生物学家重新思考什么是物种。这表明物种身份可以作为基因组复杂、稳定多态性的马赛克存在，维持在一个动态的、流动的基因组中。如果这种替代解释不被支持，该研究将为传统的物种观点提供有力的支持。

The sulfur butterflies, Colias eurytheme and C. philodice, common in fields and along roadsides across most of North America, are remarkable because they hybridize extensively. Up to 10% of the butterflies are hybrids, an interbreeding rate that is sufficient to blend them into a single species. Yet, they have remained distinct. Many other species pairs show similar patterns of hybridization, including Darwin's Finches and numerous plant species. These cases challenge our traditional definition of species, which do not normally interbreed.One untested hypothesis, first proposed in 1957, is that hybridizing species do in fact share part of their genome, and that selection acts to keep the remaining parts of the genomes distinct. To test this, new methods will be used to map the chromosomes of these butterflies in great detail. This genetic map will then be used for a fine-scale analysis of the rates that genes are able to spread between species. If superficially distinct, hybridizing species do share major portions of their genomes in common, then it will cause biologists to restructure their thinking about what species are. It would suggest that species identities can exist as a mosaic of genomically complex, stable polymorphisms, maintained in an otherwise dynamic, fluid genome. If this alternative explanation is not upheld, the study will provide strong support of the traditional view of species.