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DFC PROCEEDINGS -ABSTRACTS AND CONTRIBUTED PAPERS IN ORDER PRESENTED <br />REIMUS,C.R. m pa u l azoniogy, Arizona state university) <br />Morphological changes related to growth in razorback sucker, Xyrauchen texanus <br />Cambios morfol6gicos relacionados al crecimiento en el matalote jorobado Xyrauchen texanus <br />KEYWORDS: morphometrics; allometry; razorback sucker; thin-plate splines <br />ABSTRACT <br />Allometric responses in organisms may have extensions to many ecological and evolutionary questions. In <br />catostomids, information regarding allometric changes associated with large size and great age are essentially <br />lacking. Allometric responses in razorback sucker, Xyrauchen texanus, have been quantified. Preliminary analyses <br />have indicated marked sexual dimorphic and ontogenetic shape change in this species. Geometric morphometric <br />techniques have been used to clarify and provide directionality to these changes. Analyses involved thin-plate spline <br />functions to quantify neurocranial and vertebral shape change in razorback suckers. Ecological and evolutionary <br />ramifications are discussed. <br />CLAVES: morfom€tricos; alometria; matalote jorobado; thin-plate splines <br />RESUMEN <br />Las respuestas alom6tricas en organismos pueden resultar en algunas preguntas ecologicas y evolutivas. En <br />catost6midos, la informati6n referente a cambios alom6tricos asociados con gran tamafio y edad son esencialmente <br />escasos. Las respuestas alometricas en el matalote jorobado, Xyrauchen texanus, han sido cuantificados. Analisis <br />preliminares indican, marcas de dimorfismo sexual y cambio en la forma ontog6nica en estas especies. T6cnicas de <br />morfometrfa geom6trica han sido usadas para clarificar y dar direccionalidad a estos cambios. Los anfilisis implican <br />funciones de "thin-plate spline" para cuantificar cambios en la forma neurocranial y vertebral en el matalote <br />jorobado. Las consecuencias ecologicas y evolutivas son discutidas. <br />(HUBBS STUDENT PAPER COMPETITOR] <br />BUTH,D.G.s; HAGLUND,T.R.; DRILL, . (Dept. of Biology, Univ. of California (UCLA), Los Angeles, CA 90014-1606) <br />Allozyme variation and population structure in the razorback sucker, Xyrauchen texanus <br />Variaci6n alozimatica y estructura de poblaci6n en matalote jorobado, Xyrauchen texanus <br />KEYWORDS: propagation; allozyines; population structure; razorback sucker <br />ABSTRACT <br />The management and recovery of the razorback sucker is going to have to include large-scale propagation. <br />Choice of breeding stock and decisions about release sites must be made from an informed perspective. If <br />genetically divergent stocks exist, they may have to be managed and propagated separately. To address this <br />question, non-lethal tissue samples (muscle and fin) were obtained from razorback suckers from locations <br />throughout its remaining native range in the Colorado River system. Allozyme variation was assessed for the gene <br />products of 38 loci; 17 loci were polyalleleic. All populations were in equilibrium, expressed some heterozygote <br />excess, and had levels of heterozygosity comparable to other catostomid fishes. No obvious pattern of major allelic <br />variation was revealed, although the metapopulation is not in equilibrium. Direct comparison of our extreme <br />geographic samples, Upper Basin Green River vs. Lower Basin Lake Mojave, reveals a low F(st) = 0.029 but with <br />variant alleles shared at only 3 of 10 polyallelic loci. Stock sources could include Green-Yampa Rivers and/or Lake <br />Powell and/or Lake Mojave. We recommend against using the few remaining razorbacks from the Upper Colorado <br />population in a breeding program because of its reduced variation due to genetic drift, which may also have <br />enhanced its proportion of genes introgressed from hybridization with flannelmouth suckers. <br />CLAVES: propagaci6n; alozimas; estructura de la poblaci6n; matalote jorobado <br />RESUMEN <br />El manejo y recuperaci6n del matalote jorobado tiende a incluir la propagaci6n a gran escala. La elecci6n del <br />linaje reproductivo y las decisions acerca de los sitios de liberaci6n deben de ser hechas desde una perspective <br />informada. Si existen linajes divergentes gen6ticamente, estos pueden tener que ser manejados y propagados <br />separadamente. Para contestar esta pregunta, muestras no letales de tejido (mdsculo y aleta) fueron obtenidos de <br />matalotes jorobados en localidades remanentes de su rango distribucional original en el sistema del Rio Colorado. <br />La variacion alozimfitica file evaluada mediante los productos de los genes de 38 loci; 17 loci fueron polial6licos. <br />Todas las poblaciones que estuvieron en equilibrio expresaron algo de exceso heterocig6tico, y tuvieron niveles <br />de heterocigocidad comparable a otros catostomidos. No fueron revelados patrons obvios de variacion al61ica <br />mayor, aunque la metapoblaci6n no esta en equilibrio. La comparaci6n directa de muestras geograficas extremas, <br />Cuenca Alta del Rfo Green vs Cuenca Baja del Lago Mohave, revelan un bajo F(st)=0.029 pero con alelos variantes <br />repartidos en solamente 3 de 10 loci polial6licos. Las fuentes de los linajes podrfan incluir los rfos Green-Yampa <br />28