Signal Evolution and the Origins of Biodiversity in African Mormyridae Fishes

在NSF国际计划资助的一个试点项目中，康奈尔大学的研究人员在西非中部的加蓬工作，发现了一个新的物种群，属于Mormyridae科的Brienomyrus属。 到目前为止，他们已经发现了大约34个新物种。 所有这些新的鱼类都是在两次实地考察西非赤道雨林加蓬河流域时发现的。 它们通常在形态上是神秘的，因此它们不容易区分。 能够识别不同形式的是它们独特的电器官放电（EOD），这有助于在现场进行识别。 EOD对于物种识别和生殖隔离是必不可少的。 研究计划有三个目标。 首先，研究人员希望继续在非洲的成功实地工作，在加蓬，象牙海岸和刚果进行新的研究，以便更广泛地记录这一物种群的生物多样性。 他们将收集标本，绘制地理分布图，进行爆炸物处理记录，并收集组织样本进行DNA分析。第二，他们将研究这些鱼类的物种特异性EOD波形的感觉处理的性质，通过从电感受器进行电生理记录，当受体呈现自然放电时。 最后，他们将使用回放技术进行行为研究，以探索雌性对同种和异种个体的电鱼EOD的刺激偏好。 研究人员将使用来自多个基因座的DNA序列，包括线粒体和核基因，为新发现的加蓬Brienomyrus分支产生物种水平的同源性。 他们建议使用多位点DNA指纹技术与扩增片段长度多态性（AFLP），以提供数百个二元等位基因特征的系统发育分析。 物种水平的进化将被用来重建这些分支中的电器官的进化。 研究这一物种群的进化的核心是对现有形式的进化关系的良好分子理解。 由此，可以探索信号分集的演变模式。 除了物种水平的遗传学，现场数据将提供这些电鱼的地理分布模式的第一个详细信息。集成的EEODs和EOD波形的地理变异的生殖特征位移的EOD和EEOD波形的物种内的一个详细的分析。 一个完整的分类学修订属Brienomyrus将做承认的34个pueromyrus新类群在一组，目前只列出11个。 认识到国际合作的重要性，康奈尔大学的研究人员将开始与加蓬鱼类研究人员合作。 由于电信号在丝光鱼系统生物学中的核心重要性，研究人员还将创建一个电子器官放电的网站数据库，研究人员可以访问该数据库，以获得凭证标本的EOD现场记录。 该数据库将用于对20多年来在非洲实地工作中收集的数千个类似EOD进行存档和编目，并将为记录与系统收集有关的信号制定国家标准。 这些研究应该对从事进化和系统生物学的研究人员产生广泛的兴趣。 发现一个新物种群具有内在的兴趣，特别是当它涉及到一个众所周知的脊椎动物群体时，但是这个特定的群体对比较感觉和运动系统生物学感兴趣的神经生物学家具有潜在的兴趣。 通过对加蓬分支类的行为学、神经生物学、系统学和进化等方面的研究，将有助于我们更好地理解新物种的进化机制。

During a pilot project funded by the NSF International Program, researchers at Cornell University, working in Gabon in Central West Africa, have discovered a new species flock of weakly electric fishes in the genus Brienomyrus of the family Mormyridae. So far they have discovered approximately 34 new species. All of these new fishes were uncovered during two field trips to the river basins of Gabon, in West Africa's equatorial rainforests. They are often morphologically cryptic, so they cannot be easily distinguished. What makes it possible to recognize different forms is their distinctive electric organ discharges (EODs) that facilitate identification in the field. EODs are essential for species recognition and reproductive isolation. There are three goals for the research program. First, the researchers hope to continue the successful fieldwork in Africa with new studies in Gabon, Ivory Coast, and the Congo in order to more extensively document the biodiversity of this species flock. They will collect specimens, make biogeographic distribution maps, make EOD recordings, and collect tissue samples for DNA analysis. Second, they will study the nature of sensory processing of the species-specific EOD waveforms of these fishes by making electrophysiological recordings from electroreceptors, when the receptors are presented with naturalistic electric discharges. Finally, they will do behavioral studies using the technique of playback to explore the stimulus preferences of females to EODs of electric fishes from conspecific and heterospecific individuals.Proposed Research. The researchers will use DNA sequences derived from multiple loci including both mitochondrial and nuclear genes to produce a species-level phylogeny for the newly discovered Gabon clade of Brienomyrus. They propose using multi-locus DNA fingerprinting techniques with amplified fragment length polymorphisms (AFLP) to provide hundreds of binary allelic characters for phylogenetic analysis. The species-level phylogenies will be used to reconstruct the evolution of the electric organs within these clades. A centerpiece of the study of the evolution of this species flock is a good molecular understanding of the evolutionary relationships of existing forms. From this, patterns in the evolution of signal diversity can be explored. In addition to the species-level phylogenies the field data will provide the first detailed information on geographical distribution patterns of these electric fishes. Integration of biogeography with phylogeny and electrical recordings will permit a detailed analysis of reproductive character displacement in EODs and geographic variation in EOD waveforms within species. A complete taxonomic revision of the genus Brienomyrus will be done to recognize the 34 putatively new taxa in a group that currently lists only 11. Recognizing the importance of international cooperation, the Cornell researchers will initiate collaboration with Gabonese fish researchers. Because of the central importance of electric signals in the systematic biology of mormyrids, the researchers will also create a web-site database of electric organ discharges that researchers can access to obtain field recordings of EODs from voucher specimens. The database will be used to archive and catalogue thousands of similar EODs collected during more than 20 years of field work in Africa, and it will set a national standard for recording signals tied to a systematic collection.Impact. These studies should have broad interest to researchers working in evolutionary and systematic biology. To discover a new species flock has intrinsic interest, especially when it concerns a well-known vertebrate group, but this particular group has potential interest to neurobiologists interested in comparative sensory and motor systems biology. The studies of behavior, neurobiology, systematics, and evolution of the Gabon-clade mormyrids will give us a better understanding of the mechanisms of evolution of new species.