Black Bass Diversity: Multidisciplinary Science for Conservation

Genetic Analysis and Conservation Status of Native Populations of Largemouth Bass in Northeastern Mexico

Francisco J. García De León, Rocío I. Rodríguez-Martínez, and Dean A. Hendrickson

doi: https://doi.org/10.47886/9781934874400.ch45

Abstract.—Largemouth Bass Micropterus salmoides ranges naturally in Mexico from the binational Rio Grande basin, including Cuatro Ciénegas valley in the state of Coahuila, southward and eastward through two adjacent Gulf Coast drainages, the Río San Fernando and Río Soto La Marina in Nuevo León and Tamaulipas. Within this range, Florida Bass M. floridanus has been introduced into reservoirs in at least the Río Grande and Soto La Marina basins. To assess the conservation status of native Mexican bass, we study genetic variability within and among Largemouth Bass populations and the degree of genetic introgression by Florida Bass within them. We sampled numerous localities in Cuatro Ciénegas, the San Fernando and Río Soto La Marina basins, and Vicente Guerrero Reservoir, where Florida Bass was introduced. We examined restriction-fragment polymorphisms within the 12S and 16S ribosomal RNA mitochondrial DNA genes and genotypes at two allozyme and five microsatellite DNA loci. Levels of introgression were quantified by Bayesian assignment testing using the nuclear data. Largemouth Bass specimens possessed generally lower nuclear diversity, but higher mitochondrial diversity, than those of Florida Bass. Populations from Cuatro Ciénegas differed from those in the San Fernando and Soto La Marina basins. Nuclear analyses revealed three genetically pure populations in Cuatro Ciénegas (Charcos Prietos, Las Playitas, and Canal del Tío Julio), but hybrids in Río Garabatal and Mojarral Este. Another presumably pure Largemouth Bass population was found in Río El Tigre of the Soto La Marina drainage. Our results could be explained by geographic barriers, sex-biased dispersion, hybrid disadvantage, or selection for coadapted gene complexes. More extensive surveys are needed to fully assess the conservation status of native Largemouth Bass populations in México. We anticipate that these will reveal additional native diversity. Meanwhile, the remnant native populations delineated herein are important to protect and we advocate that their ranges be managed as genetic conservation areas.