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7/14/2009 5:01:46 PM
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UCREFRP
UCREFRP Catalog Number
7861
Author
Douglas, M. E., W. L. Minckley and H. M. Tyus
Title
Qualitative Characters, Identification of Colorado River Chubs (Cyprinidae
USFW Year
1989
USFW - Doc Type
Genus
Copyright Material
YES
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<br /> <br />I ~~4 D o1lcv') t---C ~l. <br /> <br />Coptia. 1989(3). pp. 653-662 <br /> <br />Qualitative Characters, Identification of Colorado River <br />Chubs (Cyprinidae: Genus Gila) and the <br />"Art of Seeing Well" <br /> <br />MICHAEL E. DOUGLAS, W. L. MINCKLEY AND HAROLD M. TyUS <br /> <br />Qualitative scoring is frequently overlooked in preference to counts or mea- <br />surements of individual characters, particularly for species whose overlap in <br />morphology makes clear separation difficult. Quantitative measurements and <br />counts of single characters were compared to qualitative rankings of selected <br />morphological features of chubs (genus Gila) from the Yampa River, Colorado. <br />Data were collected by technicians with no specialized training in systematics. <br />A high degree of morphological variability confounded identification using the <br />quantitative data set, while principal components analysis of qualitative data <br />clearly separated Gila cypha (humpback chub) and G. robusta (roundtail chub). <br />Totals of 32 G. cypha and 336 G. robusta were identified; no intermediates were <br />indicated. We thus demonstrate tha1 scoring of complex characteristics is useful <br />for endangered fishes that must be minimally handled to insure uninjured re- <br />lease. The clean separation of syntopic G. cypha and G. robusta supports pro- <br />tection of the lower Yampa River, the only location in the upper Colorado River <br />basin in which apparent hybridization between the endangered G. cypha and its <br />congeners remains to be documented. <br /> <br />The art of seeing well, or of noticing and distinguishing with accuracy the objects <br />which we perceive, is a high faculty of the mind, unfolded in a few individuals, <br />and despised by those who can neither acquire it, nor appreciate its results. <br />Rafinesque (1820), Ichthyologia Ohioensis. <br /> <br />SYSTEMATISTS commonly make taxonom- <br />ic decisions on the basis of average quan- <br />titative features, plus such things as pattern and <br />extent of breeding colors and shape and con- <br />figuration of body parts, which are intentionally <br />or intuitively scored qualitatively. Visual rec- <br />ognition of subtle similarities and differences in <br />shape is a major component of "seeing well, or <br />of noticing and distinguishing with accuracy the <br />objects which we perceive" (Rafinesque, 1820). <br />However, when personnel from diverse back- <br />grounds are involved in collecting morpholog- <br />ical data, qualitative features (e.g., those scored <br />on a subjective basis) are rarely employed. In <br />practice, quantitative features are emphasized <br />on the assumption they can be enumerated un- <br />ambiguously and with little error. This fosters <br />dependence on values that, in fact, may rep- <br />resent species averages, but are often inter- <br />preted as non-varying characters. Individual <br />specimens that deviate from designated values <br />for measurement of a structure or a given count <br />for fin rays then become problematic, even <br /> <br />though such varIatIon is an innate feature of <br />the species. When two or more related forms <br />co-occur, and variation in an individual of one <br />tends toward that of another, questions of "pu- <br />rity" often arise. "Hybrids," "intergrades," or <br />"intermediates" are reported as a result, some- <br />times without the required rigors of analysis <br />(Neff and Smith, 1979). <br />Taxonomists have performed numerous ex- <br />periments in attempts to evaluate processes by <br />which diverse individuals classify or group <br />members of the same set of study organisms. <br />These studies are too involved to document here <br />and, in fact, would detract from the thrust of <br />our paper. However, results from one of them <br />(many of which bordered on the psychological <br />rather than systematic) are especially germane. <br />The experiment employed imaginary organ- <br />isms differing in size, shape, color, number and <br />position of appendages, etc. ("Camina1cules," <br />created by J. H. Camin). Observers were asked <br />to group Caminalcules by whatever taxonomic <br />principle seemed "natural" to them. All indi- <br /> <br />@ 1989 by the American Society of Ichthyologists and Herpetologists <br /> <br />l ~lol <br />
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