Evolution of Species and Electric Signal Diversity
in the Neotropical Electric Fish Gymnotus

Project Description | Gymnotus | Personnel | Photographs | Signal Analysis | Bibliography | Website Team

Overview | Color Figures

Overview

This website will present the ongoing progress of an international collaborative investigation of the evolution of species and signal diversity in the weakly electric banded knife-fishes of South and Central America.

          
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Gymnotus obscura, a rare species of banded knife fish from the Brazilian Amazon (left) with Electric Organ Discharge (EOD) waveform (right).

We will study the evolution of species and signal diversity in the widespread and species-rich Neotropical electric fish genus Gymnotus. Patterns of diversity in this taxon are typical of Neotropical fishes, which with some 6,000 species, represents the richest vertebrate fauna on earth (c. 10% of all vertebrates). Like most Neotropical fish groups, Gymnotus is diverse, widely distributed, has ancient origins, and occurs in non-monophyletic regional species assemblages. A pattern of unexpected antiquity is now also emerging for many elements of the Neotropical terrestrial biota, including amphibians, reptiles, birds, mammals and some plants. This pattern of long-term accumulation of species diversity at a continental-scale probably accounts for the greatest part of animal species diversity in tropical environments and yet studies of diversification in the tropics have traditionally focused on explosive, in-situ, speciation events in localized, insular circumstances. Gymnotus is ideally suited to the study of evolutionary processes operating at a broader temporal and geographical scale. In particular, it generates stereotyped species-specific electric organ discharges (EODs). These signals are easy to observe and quantify, and also facilitate the identification of morphologically cryptic species, and. The electric signals of Gymnotus provide an unparalleled window on communication and species recognition that is simply unavailable in most other fish groups. Gymnotus is also unique among Neotropical electric fishes in that a well-developed functional model for electrogenesis has been developed. To generate and test hypotheses about diversification we will: 1, undertake a monographic revision of the alpha taxonomy and geographical distribution of Gymnotus based on existing museum material and new collections in remote regions; 2, generate phylogenetic hypotheses of Gymnotus species relationships using morphological and molecular data; 3, conduct biogeographical analyses and test hypotheses regarding the role of geomorphology in the origin and accumulation of species diversity in Gymnotus; 4, catalogue intra- and inter-specific electric signal diversity of Gymnotus and test alternative hypotheses for the role of electric signals in the maintenance of species diversity, and; 5, investigate the diversity of electric organ morphology and cellular physiology that underlie EOD diversity in Gymnotus.


Project Objectives

We propose a thorough, integrated investigation of the alpha taxonomy, phylogenetic systematics, biogeography, electric organ diversity and electric signal diversity of Gymnotus. An international team comprising two PIs (W. Crampton and J. Albert, U. Florida), two Senior Investigators (N. Lovejoy, U. Manitoba; Angel Caputi, U. Montevideo) and eight Collaborating Investigators from seven Central and South American countries will achieve the following specific project objectives.

Objective 1 : Undertake a monographic revision of the alpha taxonomy, species diversity and geographical distribution of Gymnotus based on an exhaustive survey of existing museum materials and from newly collected materials. Up to 30 new species will be described.

Objective 2: Generate phylogenetic hypotheses of Gymnotus species relationships using morphological and molecular data.

Objective 3: Conduct descriptive and historical biogeographical analyses of Gymnotus and test hypotheses regarding the role of geography in the origin and accumulation of species diversity.

Objective 4: Catalogue intra- and inter-specific electric signal diversity of Gymnotus and test alternative hypotheses for the role of communication signals in maintaining reproductive isolation.

Objective 5. Investigate the diversity of electric organ morphology and cellular physiology that underlie EOD diversity in Gymnotus.

Objective 6. Construct a web-based guide to the biology of Gymnotus, with photographs, EOD waveforms, identification keys, and locality data.


Expected Significance

The data and analysis arising from this international collaborative project will result in synthetic publications on the evolution of species and electric signal diversity, and will generate new and refreshing perspectives on the origins and maintenance of tropical biodiversity. The published and web-accessible results of this project will represent used toan unusual and valuable resource for researchers from several areas of expertise, including molecular and traditional systematics, evolutionary ecology, ichthyology, animal communication, biogeography, ecology, neurophysiology and anatomy. We will combine expertise from several disciplines to gain a unique perspective on the genesis and maintenance of species diversity in an important tropical fish taxon. Gymnotus is a model representative of the Neotropical fish fauna and many elements of the terrestrial fauna in four principal regards. The genus is species rich, of great antiquity, utilizes communication signals for mate choice, and is characterized by polyphyletic regional assemblages. During this project several students will be trained, and long-term collaborations fostered between institutes in the US, Canada and eight South and Central American countries. Finally, the project will include collections in very remote and little explored regions where many species other than Gymnotus are likely to be new to science. We will conduct general collections of all fishes encountered (with tissue samples) and make these available to Neotropical ichthyologists.