Phylogeography and Population Structure of the Imperiled Redtail Splitfin (Goodeidae: Xenotoca eiseni): Implications for Conservation
The river drainages of Central Mexico have a high degree of freshwater diversity, and are subsequently a focal point for many freshwater fish conservation studies. The livebearing subfamily Goodeinae (Teleostomi: Goodeidae) is a diverse endemic group, under threat from many anthropogenic factors. Xenotoca eiseni, the Redtail Splitfin, a member of this subfamily, has a fragmented distribution in the western basins of the Pacific Coast including the Ríos Grande de Santiago, Compostela, Ayuquila, Coahuayana, and the endorheic Lago de Magdalena and Etzatlán-San Marcos basins. Previous studies have noted high levels of genetic differentiation between the endorheic Lago de Magdalena and Etzatlán-San Marcos basins and surrounding areas which may be indicative of more taxonomic diversity within X. eiseni than currently recognized. The objectives of this study were to use mitochondrial (cytochrome b) and nuclear (ITS-1) DNA sequences and microsatellite data to assess phylogeography, genetic differentiation, and population structure between and within populations of this species. Analysis of the sequence data resulted in two deeply divergent clades, with a mean nucleotide difference of 2.51% within cytochrome b and 0.88% within ITS-1 between populations in the endorheic Lago de Magdalena and Etzatlán-San Marcos basins and all other locations. Microsatellite data also found significant structuring within these two clades of X. eiseni and identified multiple operational conservation units (OCUs). Each of these units contains a proportion of the total variation within the species and requires conservation attention and protection.
Map showing the historical distribution of Xenotoca eiseni within the Mesa Central of Mexico based on fishnet records (Accessed through the Fishnet2 Portal, www.fishnet2.org, April 2014) and collection localities for specimens used in this study. Historical localities are indicated by black circles, whereas collection sites are indicated by stars.
Phylogram of relationships of Xenotoca eiseni based upon cytochrome b sequence data inferred from Bayesian Inference analysis. The numbers above the branches represent posterior probabilities. Asterisks represent values ≥95. Bars represent the two deeply divergent (2.51%) clades of this species.
Network phylogram of relationships within Xenotoca eiseni based upon ITS-1 sequence data inferred from Bayesian Inference analysis. The numbers above the branches represent posterior probabilities. Asterisks represent values ≥95.
STRUCTURE plots depicting results from the microsatellite analysis of Xenotoca eiseni. Colors represent the probability of ancestry to each cluster inferred from K = 3, following the methods of Evanno et al. (2005).
Contributor Notes
Associate Editor: T. J. Near.