Research

Neotropical Fish

• Introduction
• Model
• Map
• Astyanax
• Brycon
• Bryconamericus
• Roeboides
• Hyphessobrycon
• Hoplias
• Piacubina
• Pimelodella
• Brachyhypopomus
• Aequidens

The published research presented on these pages comes from Bermingham and Martin (1998) and marks one chapter in our ongoing collaboration. Research on the other taxa pictured on these pages in progress. Additional publications and data sets based on our neotropical fish research can be found on this website. The photos on these pages were taken by Ascanio Castillo.

Introduction

Over the past 2-7 million years there has been extensive intercontinental exchange of flora and fauna between North and South America across the isthmian bridge of Panama, a phenomenon known as the Great American Interchange because of its importance for New World biogeography. Freshwater fishes participated in the Great American Interchange, although biogeographic studies of the regional fishes have been considerably less celebrated than the detailed and instructive studies of mammals. Yet, because the dispersal of freshwater fishes is dependent on direct connections between drainage basins, and because the history of river interconnections reflects the underlying geological development of landscapes, historical biogeographic analysis of freshwater fishes permit strong inference regarding the biotic and geologic evolution of the Panama isthmus. We have used mitochondrial DNA to infer the biogeographic history of ten genera of primary freshwater fishes that participated in the Great American Interchange. Rivers have provided a useful setting for our biogeographical analyses because they create repeated patterns of subdivision of taxa into discrete subpopulations and permit characterization of the dynamics of dispersal through a region and its influence on geographical differentiation and formation of new species. The mitochondrial gene trees pictured on this poster have focused attention on two issues. First they show that many of the distinct populations of LCA fishes diverged in a relatively brief period of time. Second, shared history across genera of freshwater fishes suggests two to three distinct waves of invasion into LCA from source populations in northwestern Colombia. The first probably happened in the late Miocene, prior to the final emergence of the Isthmus in the mid-Pliocene; the second was probably coincident with the rise of the Isthmus in the mid-Pliocene, and the third event occurred more recently. During each colonization wave the geographic scale of the dispersion of lineages was progressively more limited, a pattern we attribute to the continuing development of the Panama landscape due to mountain building and the consequent increase in the isolation of drainage basins. An important conclusion that can be drawn from our research is that the views of history afforded by historical biogeography have profound implications for understanding the composition of ecological communities and their stability over time. Our results suggest that the freshwater communities inhabiting contemporary, isolated drainage basins of Central America are not closed, equilibrium systems but are dynamic open systems subject to episodes of invasion and extinction.