Anthropogenic activities have highly impacted aquatic ecosystems. The developments of urbanization like dams, channels, industries taking oil and gas has greatly affected river systems. This paper of “Patterns of genetic divergence in the Rio Grande cooter (pseudemys gorzugi), a riverine turtle inhabiting an arid and anthropogenically modified system” caught my attention because it talks about urbanization impacts on wildlife genetics. Especially how a well-known persistent long-lived turtle such as the Rio Grande Cooter (pseudemys gorzugi) is even experiencing conservation concerns. Genetics is interesting to look at when thinking about being able to adapt to new challenges and the population’s fitness in survivability.

This study was conducted in the Southwest region of the United States. Specifically, looking at the river systems of the Rio Grande and Pecos River. Methods consisted of sample collection, DNA preparation, sequencing, mapping, population structure, genetic diversity measurements, migration inference, and demographic inferences. Either tissue or blood was collected and surveyed through snorkeling or hoop-net traps. The DNA was collected using QIAGEN DNest Blood and Tissue Kit. There was the process of determining which cross-reference genome to map and address genotype uncertainty using ANGSD 0.94. Population structure was done by using the NGSadmix that estimated “admixture proportions of individuals”. For genetic diversity measurements the data was split in 5 groups: Pecos River North/South, Black River, Devils River, and the Rio Grande. Migration inference was analyzed through pairwise genetic distances and used EEMS for migration surfaces in locating corridors and barriers to gene flow. There were plenty of other resources used to visualize the data better and account for errors, but the above are the main points.

The author’s findings found that there was lower heterozygosity, diminished nucleotide diversity, and a reduced effective population (Ne). The modified river confluences have caused challenges in the migration patterns that have caused isolations in the original population. Which has created two distinct populations discovered through population genetic analysis one residing in the Pecos and the other in the Black Rivers of New Mexico. The population in New Mexico was found to have a greater decline and harder bounce back then Texas’ population. These findings were done with 150 samples that had fit analysis criteria and 141 were sequenced.

I like how the study mentioned other effects on chelonians since turtles have survived many extinctions. Yet are being detrimentally impacted by the Anthropocene. The other studies mentioned in the paper have found loss in connectivity, reduced gene flow in the Rio Grande endemic Trachemys gaigeae in New Mexico and Texas populations. Then other freshwater turtle species: Terrapene caohulia, Trachemys taylori, and Apalone atra in Coahulia, Mexico have suffered reduced genetic diversity, connectivity, and isolation from drying environments. This emphasizes how urbanization has deeply affected even the most known enduring animal. Highlighting the urgency for understanding conservation needs and implementation plans.

Although the study was well-developed and looked at many variables, I would suggest a few things that I think could have been considered. Additional variables that should have been added are having gone the extra mile and gone ahead to inflate the number of singletons. The data analysis could improve in having been able to observe more sites such as the Rio Grande tributaries that had not been permitted to do so but maybe in the future. The discussion of findings in my opinion is well-rounded it emphasizes how Rio Grande cooter (pseudemys gorzugi may not receive attention for federal protection but aids in how that should be re-evaluated with the new findings and then moves on to be more general on the climate change and urbanization effects on freshwater turtles. The future research directions are to utilize the findings to aid in conservation efforts and re-establishing populations of Rio Grande Cooter (pseudemys gorzugi). There is still a gap to identify the distinctive demands for the two populations.

Citation: Michael W Vandewege, Javier Gutierrez, Drew R Davis, Michael R J Forstner, Ivana Mali, Patterns of genetic divergence in the Rio Grande cooter (Pseudemys gorzugi), a riverine turtle inhabiting an arid and anthropogenically modified system, Journal of Heredity, Volume 115, Issue 3, May 2024, Pages 253–261, https://doi.org/10.1093/jhered/esae011