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灭绝造成的损失之间的平衡。虽然人们对物种灭绝给予了极大的关注，但关于物种形成的方式的许多问题仍然没有解决。恩斯特·迈尔提请人们注意研究所谓环状物种的价值。环状物种由一系列围绕着地理屏障的种群组成。在环中的某一点上，两个种群相遇，但不进行杂交。由于生殖隔离的种群关系非常密切，它们提供了一个研究物种形成过程的模型系统。环状物种很少见，需要特殊的地理和历史安排。普莱斯博士已经确定了一种可能的环物种，并将进行研究，以调查其形成。正在研究的物种是一种小型雀形目鸟类，其歌声似乎是用于物种识别的主要特征。人们正在围绕着戒指研究歌曲的变异和识别，以了解生殖隔离是如何在其末端出现的。对种群间DNA变异的研究被用来询问它们在多大程度上仍与基因流动水平有关，并追踪范围扩大和碎片化的历史模式。这种方法应该使普赖斯博士能够追踪从种群内变异到繁殖隔离的共生物种的完整的连续体。对这一连续体的透彻理解对于理解物种形成以及最终控制物种数量的因素至关重要。

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.