CONSERVATION GENETICS OF AN UNDESCRIBED SPECIES OF DIONDA (TELEOSTEI: CYPRINIDAE) IN THE RIO GRANDE DRAINAGE IN WESTERN TEXAS
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The systematic and conservation-genetic status of a population of the cyprinid genus Dionda in Alamito Creek, a tributary of the Rio Grande in Big Bend Ranch State Park, Presidio County, Texas, was assessed using mtDNA sequences and nuclear-encoded microsatellites. Phylogenetic analyses of the mitochondrial cytochrome b (cytb) gene revealed that the Dionda in Alamito Creek likely is conspecific with an undescribed species (Dionda species 1) known only from the Ro Conchos and Ro Nazas basins of Mexico and in the USA from Cibolo Creek, a small tributary of the Rio Grande drainage. Genetic variation of Dionda in Alamito Creek is extremely low. All 18 fish assayed for 1,533 base pairs of mitochondrial mtDNA (cytb and ND5 sequences) had the same haplotype, and 40 fish assayed for 34 nuclear-encoded microsatellites (25 monomorphic) averaged only 1.44 alleles/microsatellite (HE = 0.12). Estimates of current effective size (Ne) and effective number of breeders (Nb) were 22 and 28, respectively. Bayesian coalescent analysis indicated that the population has undergone a greater than three-orders-of-magnitude decline in effective size. Low genetic diversity and low estimates of Ne and Nb indicate that the population is compromised genetically and warrants monitoring and attention to its official conservation status.