New Paper! Convergence in Barbs

Post date: Dec 9, 2015 10:12:47 PM

During a 2013 expedition to Cameroon, my co-authors, Jon Armbruster and Carla Stout, collected a large number of small minnows.

They caught many fish in the Dja River, clipped their fins for DNA analysis, preserved the rest of the specimen, and brought them back to Auburn University. Once the fish were stateside, I helped Jon sort the different species out from one another. While doing this, we noticed that two different species of fish kept getting mistaken for one another: Enteromius aspilus and E. guirali (see the picture below). This led us to consider why these fish looked so similar.

Some examples of the Enteromius of the Dja River.

a Enteromius aspilus, b E. camptacanthus, c E. guirali, d E. castrasibutum.

Photos by J. W. Armbruster

Did the fish look the same because they were closely related to each other? To answer that question, we used DNA evidence. Using the DNA from those fin clippings taken in the field, we were able to construct a phylogenetic tree to see how these species were related. Although they are in the same genus, the E. aspilus and E. guirali were not each other's closest relatives, and the other species in the group looked very different!

We then looked at the whole fish specimens that were brought back to Auburn University's Museum of Natural History. The specimens were photographed, digitized, and analyzed using geometric morphometrics. This analysis showed that all the other minnows in the Dja River could be differentiated from one another, but E. aspilus and E. guirali overlapped in their physical measurements.

Since the species are similarly colored as well as similarly shaped, this led us to think the convergence is likely due to many factors. The fish could be similar to each other to avoid predators. One fish (E. guirali) has a spine to keep them out of bigger fish's mouths, maybe the other is mimicking that. Another explanation is that E. aspilus can feel predators coming faster than E. guirali because it has more sensory pores on its body.

Direct observations of behavior will need to be done to confirm these hypotheses, but we can at least put forth some explanations for their similarity.

Read the paper here:

An empirical test for convergence using African barbs (Cypriniformes: Cyprinidae) by J. W. Armbruster, C. C. Stout, and M. M. Hayes