Holloway Alisha K, Cannatella David C, Gerhardt H Carl, Hillis David M
Section of Integrative Biology, University of Texas, Austin, Texas 78712, USA.
Am Nat. 2006 Apr;167(4):E88-101. doi: 10.1086/501079. Epub 2006 Mar 8.
Polyploidization is one of the few mechanisms that can produce instantaneous speciation. Multiple origins of tetraploid lineages from the same two diploid progenitors are common, but here we report the first known instance of a single tetraploid species that originated repeatedly from at least three diploid ancestors. Parallel evolution of advertisement calls in tetraploid lineages of gray tree frogs has allowed these lineages to interbreed, resulting in a single sexually interacting polyploid species despite the separate origins of polyploids from different diploids. Speciation by polyploidization in these frogs has been the source of considerable debate, but the various published hypotheses have assumed that polyploids arose through either autopolyploidy or allopolyploidy of extant diploid species. We utilized molecular markers and advertisement calls to infer the origins of tetraploid gray tree frogs. Previous hypotheses did not sufficiently account for the observed data. Instead, we found that tetraploids originated multiple times from extant diploid gray tree frogs and two other, apparently extinct, lineages of tree frogs. Tetraploid lineages then merged through interbreeding to result in a single species. Thus, polyploid species may have complex origins, especially in systems in which isolating mechanisms (such as advertisement calls) are affected directly through hybridization and polyploidy.
多倍体化是少数能够产生瞬时物种形成的机制之一。由相同的两个二倍体祖先多次起源四倍体系是常见的，但在此我们报告了首例已知的单个四倍体物种，它至少重复起源于三个二倍体祖先。灰树蛙四倍体系中求偶鸣叫的平行进化使得这些谱系能够杂交，尽管多倍体起源于不同的二倍体，但仍形成了一个单一的有性相互作用的多倍体物种。这些蛙类通过多倍体化形成物种一直是大量争论的源头，但各种已发表的假说都假定多倍体是通过现存二倍体物种的同源多倍体化或异源多倍体化产生的。我们利用分子标记和求偶鸣叫来推断四倍体灰树蛙的起源。先前的假说未能充分解释观测数据。相反，我们发现四倍体多次起源于现存的二倍体灰树蛙以及另外两个显然已灭绝的树蛙谱系。然后四倍体系通过杂交合并形成了一个单一物种。因此，多倍体物种可能有复杂的起源，尤其是在隔离机制（如求偶鸣叫）直接受杂交和多倍体影响的系统中。
