@article {gallant2011signal,
	title = {Signal variation and its morphological correlates in Paramormyrops kingsleyae provide insight into the evolution of electrogenic signal diversity in mormyrid electric fish},
	journal = {Journal of Comparative Physiology A},
	volume = {197},
	year = {2011},
	pages = {799{\textendash}817},
	publisher = {Springer-Verlag},
	abstract = {<p>We describe patterns of geographic variation in electric signal waveforms among populations of the mormyrid electric fish species Paramormyrops kingsleyae. This analysis includes study of electric organs and electric organ discharge (EOD) signals from 553 specimens collected from 12 localities in Gabon, West-Central Africa from 1998 to 2009. We measured time, slope, and voltage values from nine defined EOD \&ldquo;landmarks\&rdquo; and determined peak spectral frequencies from each waveform; these data were subjected to principal components analysis. The majority of variation in EODs is explained by two factors: the first related to EOD duration, the second related to the magnitude of the weak head-negative pre-potential, P0. Both factors varied clinally across Gabon. EODs are shorter in eastern Gabon and longer in western Gabon. Peak P0 is slightly larger in northern Gabon and smaller in southern Gabon. P0 in the EOD is due to the presence of penetrating-stalked (Pa) electrocytes in the electric organ while absence is due to the presence of non-penetrating stalked electrocytes (NPp). Across Gabon, the majority of P. kingsleyae populations surveyed have only individuals with P0-present EODs and Pa electrocytes. We discovered two geographically distinct populations, isolated from others by barriers to migration, where all individuals have P0-absent EODs with NPp electrocytes. At two sites along a boundary between P0-absent and P0-present populations, P0-absent and P0-present individuals were found in sympatry; specimens collected there had electric organs of intermediate morphology. This pattern of geographic variation in EODs is considered in the context of current phylogenetic work. Multiple independent paedomorphic losses of penetrating stalked electrocytes have occurred within five Paramormyrops species and seven genera of mormyrids. We suggest that this key anatomical feature in EOD signal evolution may be under a simple mechanism of genetic control, and may be easily influenced by selection or drift throughout the evolutionary history of mormyrids.</p>
},
	doi = {10.1007/s00359-011-0643-8},
	url = {https://doi.org/10.1007/s00359-011-0643-8},
	author = {Jason R. Gallant and Matthew E Arnegard and John P Sullivan and Bruce A Carlson and Carl D Hopkins}
}
@article {Carlson:2011gd,
	title = {Brain Evolution Triggers Increased Diversification of Electric Fishes},
	journal = {Science},
	volume = {332},
	number = {6029},
	year = {2011},
	pages = {583{\textendash}586},
	abstract = {<p>Communication can contribute to the evolution of biodiversity by promoting speciation and reinforcing reproductive isolation between existing species. The evolution of species-specific signals depends on the ability of individuals to detect signal variation, which in turn relies on the capability of the brain to process signal information. Here, we show that evolutionary change in a region of the brain devoted to the analysis of communication signals in mormyrid electric fishes improved detection of subtle signal variation and resulted in enhanced rates of signal evolution and species diversification. These results show that neural innovations can drive the diversification of signals and promote speciation.</p>
},
	doi = {10.1126/science.1201524},
	url = {http://www.sciencemag.org/cgi/doi/10.1126/science.1201524},
	author = {Bruce A Carlson and Hasan, S M and Hollmann, M and Miller, D B and Luke J. Harmon and Matthew E Arnegard}
}
