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<br />Mitochondrial DNA Variability in the Endangered
<br />Razorback Sucker (Xyrauchen texanus): Analysis of
<br />Hatchery Stocks and Implications for Captive
<br />Propagation
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<br />THOMAS E. DOWLING,* W. 1. MINCKLEY,* PAUL C. MARSH, t
<br />AND ELUOIT s. GOLDSTEINt
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<br />.Department of Zoology, Arizona State University, Tempe, AZ 85287, U.S.A., email atted@asuvm.inre.asu.edu
<br />tCenter for Environmental Studies, Arizona State University, Tempe, AZ 85287, U.S.A.
<br />*Department of Zoology, Arizona State University, Tempe, AZ 85287, U.S.A.
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<br />Abstract: The razorback sucker (Xyrauchen texanus) is a large, long-lived catostomid fish endemic to the Col-
<br />orado River drainage of western North America, endangered because of recruitment failure. Efforts to pre-
<br />serve the species have emphasized artificial propagation and reintroduction. Given the importance of main-
<br />taining genetic diversity in such a program, we examined mitochondrial DNA diversity in a Source
<br />POPulation (Lake Mohave, Arizona-Nevada) and three hatchery-produced year classe! (1987, 1989, 1990).
<br />The source contained considerable variation, indicated by high haplotype diversity (h = p.97) and a large
<br />number of unique haplotypes (17 in 25 individuals). Diversity also .was high in the 1987 (h = 0.89,6 haplo-
<br />types in 10 individuals) a.nd 1989 hatchery-produced year classes (h = 0.91, 7 in 11), but significantly lower
<br />in the 1990 year class (h = 0.71, 4 in 10). Low diversity in the last class was likely because of differences
<br />among females in fecundity, viability of progeny, or both. Because natural populations have collapsed
<br />throughout the species' range, we must identify methods that preserve the most diversity. We examined three
<br />potential alternatives: standard hatchery propagation, natural spawning in predator-Jree environments, and
<br />protective custody of larvae collected from the lake with reintroduction after growth to a size likely to survive.
<br />The last is the preferred alternative and shOuld be pursued as the most cost-effective option for preserving ge-
<br />netic diversity in the razorback sucker.
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<br />Variabilidad del ADN mitocondrial en Xyrauchen texanus, una especie en peligro: An31isis de los stocks de las
<br />granjas de cria y su implicacion en la propagacion de animales criados en cautiverio
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<br />Resumen: Xyrauchen texanus es un pez catostomido longevo endemico al drenaje del rio Colorado en el
<br />oeste de Norte America, que se encuentra en peligro debido a fracasos en el recrutamiento. Los esfuerzos para
<br />presen/ar la especie han enJatizado la propagaci6n artificial y la reintroducci6n. Dada la importancia que
<br />liene el mantenimiento de la diversidad genetica en tales programas, hemos examinado la diversidad del
<br />AD.V mitOCOndrlal en una poblaci6n fuente ([ago Mohave, Arizona-Nevada) y en tres clases anuales produci-
<br />das en estadones de crianza 0987, 1989, 1990). Lafuente tuvo una considerable variaci6n genetica eviden-
<br />ciada por una aita diversidad haplotfpica (h = 0.97) Y un gran numero de haplotipos unicos (17 en 25 indi-
<br />rUJuos). La divenidad tambienfue alta en las clases anuales producidas en las estaciones de cria de 1987 (h =
<br />0.89. 6 baplOlipos en 10 individuos) y 1989 (h = 0.91, 7 en 11) pero significativamente menor en la clase de
<br />/ ryJ() (b = 0.7/, 4 en 10). La baja diversidad en la ultima clase era esperada debido a diferencias en la fecun-
<br />didod rntrr /as bembras, la viabilidad de la progenie, 0 ambas. Dado que las poblaciones naturales se han
<br />cnla~=~ /aTgo Y ancho del area de distribuci6n, debemos identificar metodos que preserven la mayoria
<br />tk /Q Nosotros examinamos tres alernativas: la propagaci6n estandard de las estaciones de cria,
<br />la rrJ1roducn6n natural en ambientes libres desde predadores y la custodia protectora de larvas recolectadas
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<br />1.IIhI DrcftJJber
<br />2, /993; revised manUScript accepted March 9. 1995.
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<br />,- ..,.. ........,. 1996
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