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Mitochondrial DNA Variability in the Endangered
<br />Razorback Sucker (Xyrauchen texanus): Analysis of
<br />Hatchery Stocks and Implications for Captive
<br />Propagation
<br />THOMAS E. DOWLING,* W. L. MINCKLEY,* PAUL C. MARSH,t
<br />AND ELLIOTT S. GOLDSTEIN$
<br />*Department of Zoology, Arizona State University, Tempe, AZ 85287, U.S.A., email attedQasuvm.inre.asu.edu
<br />(Center 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.
<br />Abstract: The razorback sucker (Xyrauchen texanus) is a large, long-lived cetostomid 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 classes (1987, 1989, 1990).
<br />The source contained considerable variation, indicated by high haplotype diversity (h = 0.97) 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 1 D individuals) and 1989 hatcheryproducedyeer classes (h = 0.91, 7 in I Z), 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 free 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.
<br />Vari~bilidad del ADN mitocondrial en Xyrauchen texanus, una especie en peligro: Analisis de los stocks de las
<br />granjas de cria y su implication en la propagacion de animales criados en cautiverio
<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 pare
<br />preserver la especie hen enfatizado la propagacion artificial y la reintroducti6n. Dada la importancia que
<br />tiene el mantenimiento de la diversidad genetica en tales programas, hemos examinado la diversidad del
<br />ADN mitocondrial en una poblacion fuente (lago Mohave, Arizona Nevada) y en tres claws anuales produci-
<br />das en estaciones de crianza (1987, 1989, 1990). La fuente tuvo una considerable variation genetica eviden-
<br />ciada por una alts diversidad haplotipica (h = 0.97) y un gran numeeo de haplotipos unicos (17 en 25 indi-
<br />viduos), La diversidad tambien fue alts en las claws anuales producidas en las estaciones de cria de 1987 (h =
<br />0.89, 6 haplotipos en IO individuos) y 1989 (h = 0.91, 7 en 11) Pero significativamente menor en la claw de
<br />1990 (h = 0.71, 4 en 10). La baja diversidad en la tiltima claw era esperada debido a diferencias en la fecun-
<br />didad entre las hembras, la viabilidad de lct progenie, o ambas. Dado que las poblaciones naturales se hen
<br />colapsado a to largo y ancho del area de distribution, debemos identificar metooos que preserven la mayoria
<br />de la diversidad. Nosotros examinamos tres alernativas: la propagacion ettandard de las estaciones de cris, '
<br />la reproduction natural en ambientes libres desde predadores y la custodia protectors de larval recolectadas
<br />v
<br />Paper submitted .December 2, 1993; revised manuscript accepted March 9, 1995.
<br />120
<br />Conservation Biology, Pages ]20-127
<br />Volume 10, No. i, February 1996
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