Weibel Amy C, Dowling Thomas E, Turner Bruce J
Department of Biological Sciences, Wayne State University, Detroit, Michigan, 48212.
Department of Biology, Arizona State University, Tempe, Arizona, 85287.
Evolution. 1999 Aug;53(4):1217-1225. doi: 10.1111/j.1558-5646.1999.tb04534.x.
Rivulus marmoratus is the only known vertebrate with obligate, synchronous hermaphroditic fertilization. Males can be experimentally induced in the laboratory and are rare or absent in most populations, but at the isolated Twin Cays, Belize, locality, males are relatively abundant. At this locality, evidence of outcrossing has been documented in this otherwise automictic cloning species. Phylogenetic analysis of restriction sites and sequence characters revealed that all Florida and Belize western Caribbean populations (including Twin Cays) are phyletically indistinguishable yet divergent from eastern populations in Brazil and the Bahamas. Further, these western lineages shared a common ancestor more recently than all other populations. Therefore, the Twin Cays population is not a remnant ancestral outcrossing population. Outcrossing is suspected to have evolved as a phenotypically plastic character, and its expression in R. marmoratus may be dormant unless triggered by some ecological factor that is not well understood.
线纹鳉是唯一已知的具有专性、同步雌雄同体受精的脊椎动物。在实验室中可以通过实验诱导出雄性，并且在大多数种群中雄性稀少或不存在，但在伯利兹孤立的双礁岛地区，雄性相对较多。在这个地区，在这个原本进行自体融合克隆的物种中已经记录到了杂交的证据。对限制性位点和序列特征的系统发育分析表明，所有佛罗里达和伯利兹西加勒比海种群（包括双礁岛）在系统发育上无法区分，但与巴西和巴哈马的东部种群不同。此外，这些西部谱系比所有其他种群更近地拥有一个共同祖先。因此，双礁岛种群不是残余的祖传杂交种群。杂交被怀疑是作为一种表型可塑性特征进化而来的，并且它在线纹鳉中的表达可能处于休眠状态，除非受到某种尚未完全了解的生态因素的触发。
