Introduction:
Changemaker Catalyst Award recipient, Abigail Heck continued her research in Dr. Henry Bart’s
lab at Tulane University, investigating the phylogenetic relationships of freshwater fish in genus
Enteromius. She uses DNA sequencing techniques to describe differences in genetic markers of
fish collected from Kenya. As she continues her work with Dr. Bart and PhD student Godservice
Eziefule, she prepares to present her findings that clarify the evolutionary relationships between
numerous Enteromius species by studying both nuclear and mitochondrial genes at the Tulane
Research, Innovation, and Creativity Summit in April 2025, and eventually co-authoring a
publication.
Abigail is a senior, Class of 2025, majoring in Ecology & Evolutionary Biology with a minor in
Marine Biology.
The lakes and rivers of the African Rift Valley hold one of the most abundant and
biodiverse fish populations in the world. There have been many adaptive radiations in this
freshwater habitat causing unmatched species diversity, the evolution of species found only in
the Rift Valley, and the potential for numerous research projects in biodiversity and species
conservation. In the Summer of 2024, I was fortunate to experience the wealth of fish diversity
of the African Rift Valley during the IRES Expedition to Kenya with Dr. Henry Bart’s Lab at
Tulane, sponsored by the National Science Foundation. Over the course of the Expedition, our
team of researchers from Tulane University, Randolph Macon College, and the University of
Nairobi caught hundreds of fish for morphological and genetic research. While morphological
research assesses the unique shape and structure of a species and its hypothesized relatives,
genetic analysis allows researchers to investigate differences in the nucleotide sequences that
construct code in highly conserved genes. These small differences in conserved genes are often
unique to a species group, allowing researchers to identify species.
As an undergraduate field assistant, my responsibilities included catching fishes with a
seine net, tagging fishes with identification numbers, taking tissue samples for genetic analysis,
and organizing fishes into species groupings. Our main species of interest were those in genus
Enteromius– these fishes are endemic to the rivers and lakes of Africa, with many of their
representative species hypothesized to be undescribed and relatedness unclear. With photos of
their body form and tissues for genetic analysis, we would analyze this information to create a
phylogeny– an accurate tree of life depicting the relatedness and evolution of species.
Upon returning to Tulane University after the IRES expedition, I began working in the lab
under the supervision of Dr. Bart and PhD student Godservice Eziefule as an undergraduate lab
assistant. I was tasked with generating nucleotide sequences for three highly conserved genes
used to identify species– mitochondrial gene cytochrome B and nuclear genes GH-intron and
RAG-1. Sequencing cytochrome B allows us to identify distinct species from tissue samples
extracted from fishes caught in Kenya. The resulting sequences act as a barcode, similar to those
found at supermarkets, that scan for a distinct species in a phylogeny rather than a food item in a
store catalogue. The two nuclear genes allow us to investigate crossbreeding between species.
This combination of information allows us to construct an accurate phylogeny for Enteromius,
while describing hybridization patterns in the Kenyan Enteromius complex.
There are many steps to produce sequences from tissue samples. The tissue samples
are organized, prepared with primers, processed in a thermocycler for a polymerase chain
reaction to isolate the genes, cleaned to allow observations, and checked for quality and quantity
of DNA after each step using a fluorometer and gel electrophoresis. Godservice and I sequenced
tissues for over one hundred fish from Kenya to barcode each individual. The barcodes allow us
to accurately organize the fish on a phylogeny, showing how each species is related to one
another.
Although much of our project focused on quantifying the genetic differences between fishes
within genus Enteromius, our research also aimed to refine cost-effective genetic investigation
methods for use in the study of vertebrates. Our methods also used nuclear genes typically not
studied to clarify the hybrid relationships in Enteromius species from Lake Victoria.
For our research with Enteromius, we aimed to mimic field conditions in a lab
environment to perfect our methods of sequencing with aquatic vertebrates in the field. Applying
past methods to our system of interest has been one of our lab’s greatest accomplishments over
the source of this project. By adapting methods of this cost effective and efficient sequencing
fish research, we are making genetic barcoding and taxonomic research more accessible.
Decreasing the cost of producing sequences, decreasing the time and number of people needed
to produce barcodes, and eliminating the need for a designated lab space by allowing
sequencing to take place in the field makes barcoding more accessible to labs worldwide. With
more labs taking part in genetic analysis, the taxonomic field will have a better understanding of
which species are found where, helping to advance conservation efforts in our rapidly changing
world. As we begin preparing to present our work at conferences and in a paper, our lab aims to
increase awareness about the effectiveness of this barcoding method.
Reflecting on this experience, catching fish in the field was both exciting and challenging.
Prior to the IRES expedition, I did not have experience fishing with a seine net or identifying
freshwater fish in Kenya. I am grateful for all I learned in the field, and I have since had the
opportunity to apply my fishing skills to projects in Louisiana. The lab commitments of this
project have been challenging, but I am pleased with the skills and lessons I have taken from
this experience. Many of the protocols for this project require 7 hour cycles repeated tens of
times over, but the repetitive nature of genetics protocols has increased my confidence in lab
work. I have learned to be patient with myself when I make mistakes and with the process of
genomics research when the work feels grueling and time consuming. Most importantly, I
learned that I enjoy working in the lab and field. I am deeply curious about questions
surrounding speciation, genomics, and biodiversity. This project has allowed me to explore my
curiosities, and I look forward to continuing my research in genomics.