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Morphological and genetic characters from cyprinid fishes of the genus Gila were examined to assess a hypothesized hybrid origin of Gila seminuda from the Virgin River, Arizona-Nevada-Utah. The presumed parents, Gila robusta robusta and Gila elegans, are clearly differentiated from one another based on morphology, allozymes, and mtDNA haplotypes. G. seminuda is morphologically intermediate and polymorphic at allozyme loci diagnostic for the parental species. Restriction endonuclease analysis of mtDNA showed G. seminuda nearly identical to G. elegans. These results support an origin of the bisexual taxon G. seminuda through introgressive hybridization. The Gila population in the Moapa River, Nevada, also appears...
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Southwestern Fishes and the Enigma of "Endangered Species": Man's invasion of deserts creates problems for native animals, especially for freshwater fishes, credited to Deacon, James E, published in 1968. Published in Science, volume 159, issue 3822, on pages 1424 - 1432, in 1968.
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Qualitative scoring is frequently overlooked in preference to counts or measurements of individual characters, particularly for species whose overlap in morphology makes clear separation difficult. Quantitative measurements and counts of single characters were compared to qualitative rankings of selected morphological features of chubs (genus Gila) from the Yampa River, Colorado. Data were collected by technicians with no specialized training in systematics. A high degree of morphological variability confounded identification using the quantitative data set, while principal components analysis of qualitative data clearly separated Gila cypha (humpback chub) and G. robusta (roundtail chub). Totals of 32 G. cypha...
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T.-Thraez orbacks uckerp opulation of the lower ColoradoR iver basin is now reduced to scatteredi ndividuals in all but Lake Mohave, Arizona-NevadaT. hat population consists of large, slowly-growing fish, which are proposed to be nearly 30 years old, presumably having hatchedw hen the reservoirw as filling in the early 1950s.T he speciesc ompriseda bout 12.5%o f all fishes taken by trammel netting in Lake Mohave in the period 1974-82. No recruitment into the population has been detected in that period, despite repeated observations of spawning and records of fertilized eggs and hatched larvae. Sex ratios, sexual dimorphism, and fecundity all indicate the fish to be reproductivelyc apable despite a high incidenceo...
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The endangered Sonoran topminnow Poeciliopsis occidentalis has steadily declined in distribution and abundance in the past several decades, and currently survives in the United States only in several isolated localities in southern Arizona. This reduction is correlated with, and primarily attributed to, habitat destruction, and introduction and establishment of mosquitofish Gambusia affinis and other exotic fishes. Topminnows have characteristically been reduced in number or replaced within a year or two of introduction of non-native fishes. Other native fishes have experienced similar declines after introduction of exotics, and much of the endemic western ichthyofauna may be vulnerable to extirpation in this manner....
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