Schwarz Dietmar, Matta Benjamin M, Shakir-Botteri Nicole L, McPheron Bruce A
Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, Pennsylvania 16803, USA.
Nature. 2005 Jul 28;436(7050):546-9. doi: 10.1038/nature03800.
Speciation in animals is almost always envisioned as the split of an existing lineage into an ancestral and a derived species. An alternative speciation route is homoploid hybrid speciation in which two ancestral taxa give rise to a third, derived, species by hybridization without a change in chromosome number. Although theoretically possible it has been regarded as rare and hence of little importance in animals. On the basis of molecular and chromosomal evidence, hybridization is the best explanation for the origin of a handful of extant diploid bisexual animal taxa. Here we report the first case in which hybridization between two host-specific animals (tephritid fruitflies) is clearly associated with the shift to a new resource. Such a hybrid host shift presents an ecologically robust scenario for animal hybrid speciation because it offers a potential mechanism for reproductive isolation through differential adaptation to a new ecological niche. The necessary conditions for this mechanism of speciation are common in parasitic animals, which represent much of animal diversity. The frequency of homoploid hybrid speciation in animals may therefore be higher than previously assumed.
动物物种形成几乎总是被设想为一个现有谱系分裂为一个祖先物种和一个衍生物种。另一种物种形成途径是同倍体杂交物种形成，即两个祖先类群通过杂交产生第三个衍生物种，而染色体数目不变。虽然理论上有可能，但它被认为很罕见，因此在动物中不太重要。基于分子和染色体证据，杂交是少数现存二倍体双性动物类群起源的最佳解释。在此，我们报告了首例两个宿主特异性动物（实蝇科果蝇）之间的杂交与转向新资源明显相关的案例。这种杂交宿主转移为动物杂交物种形成提供了一个生态上稳固的情景，因为它通过对新生态位的差异适应提供了一种生殖隔离的潜在机制。这种物种形成机制的必要条件在寄生动物中很常见，而寄生动物占动物多样性的很大一部分。因此，动物中同倍体杂交物种形成的频率可能比之前设想的要高。
