Genetic & genomic advances on the analysis of hybridization & introgression in the Yaqui catfish, Ictalurus pricei (Rutter, 1896)

Authors: Alexsandre Gutiérrez-Barragán, Alejandro Varela-Romero, Francisco Leon, Mariana Mateos, Carlos Ballesteros-Córdova, José Grijalva-Chon, John Garza, José Romo-León

Year: 2023

Abstract

The Yaqui catfish Ictalurus pricei is a native species of the northwestern Mexico and southwestern United States and is endangered due to loss of most of its historical recorded populations. Furthermore, hybridization with the exotic channel catfish I. punctatus threatens the few native remaining populations, increasing the risk of extinction. In the present work, mitochondrial Cytb and COXI and nuclear RAG1 and RAG2 genes were analyzed to detect hybridization evidence with channel catfish. Also, 23 individuals from Arroyo Cajón Bonito (Río Yaqui basin) were subjected to Whole Genome Sequencing (WGS) to detect evidence of introgression based on 1 million Single Nucleotide Polymorphisms (SNPs). Based on mitochondrial and two nuclear genes, hybridization was detected in Río Yaqui and Río Fuerte basins, as well as possible genetic introgression in the Río Tutuaca (Yaqui basin). Specimens sampled from the Río Mayo (following >20 years hiatus of Yaqui catfish collections), shown the presence of both Yaqui and channel catfish mitochondrial genes, indicating the presence of both species and/or their hybrids. Admixture results showed that 20 of 23 Arroyo Cajón Bonito individuals have 100% ancestry of Yaqui catfish, 17 of which are being kept alive in a stock for future reproduction. Of the remaining three individuals, the first was a pure channel catfish, the second was an F1 hybrid (50% ancestry of both species), and the third had 70% Yaqui and 30% channel catfish ancestries, indicating its status as a backcross. Thus, evidence of introgression at two localities of the Río Yaqui basin was detected using genes and WGS, demonstrating that hybrids are fertile and interbreed with the parental species, and thereby posing a major threat to the integrity of the Yaqui catfish. Further sampling and WGS analysis should be performed to better understand the negative impact of the introgression in the entire Yaqui catfish distribution, and to promote accurately informed management decisions and conservation plans between México and USA.