Analysis of a Ring Species

价格9806692 地球上物种的数量取决于新物种的产生和物种灭绝之间的平衡。 虽然人们对物种灭绝给予了极大的关注，但关于物种形成方式的许多问题仍然没有得到解决。 恩斯特·迈尔提请注意研究所谓的环物种的价值。 环形物种由一系列围绕地理屏障的种群组成。 在环中的某一点，两个种群相遇但不杂交。 由于生殖隔离的种群是非常密切相关的，他们提供了一个模型系统，在其中检查的过程中的物种形成。 环物种是罕见的，需要一个特殊的安排的地理和历史。 普莱斯博士已经确定了一个可能的环物种，并将进行研究，以调查其形成。被研究的物种是一种小型雀形目鸟类，其歌曲似乎是用于物种识别的主要特征。 人们正在研究环内的歌曲变异和歌曲识别，以了解环端如何出现生殖隔离。对不同种群之间DNA变异的研究被用来询问它们在多大程度上仍然通过基因流水平联系在一起，并追踪范围扩张和分裂的历史模式。这种方法应该使普赖斯博士能够追踪一个完整的连续体，从种群内的变化到繁殖隔离的同域物种。 彻底理解这一连续体对于理解物种形成至关重要，最终是什么控制了物种数量。

Price 9806692 The number of species on earth depends on a balance between the production of new species and their loss through extinction. While great attention is being paid to extinction, many questions about the way in which species form remain unresolved. Ernst Mayr drew attention to the value of studying so-called ring species. Ring species consist of a chain of populations encircling a geographical barrier. At one point in the ring two populations meet but do not interbreed. Because the reproductively isolated populations are very closely related, they offer a model system in which to examine the process of speciation. Ring species are rare, requiring a special arrangement of geography and history. Dr. Price has identified a probable ring species and will conduct research to investigate its formation. The species being studied is a small passerine bird for which song appears to be the main trait used in species recognition. Song variation and recognition of songs are being studied around the ring in order to understand how reproductive isolation has arisen at its ends. Studies of DNA variation across the populations are being used to ask to what extent they are still connected by levels of gene flow, and to trace historical patterns of range expansion and fragmentation. This approach should enable Dr. Price to trace a complete continuum from within-population variation up to reproductively isolated sympatric species. A thorough understanding of that continuum is crucial to understanding speciation, and ultimately what controls species number.