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DISCRIMINATING GILA ROBUSTA AND GILA CYPHA : RISK ASSESSMENT AND THE ENDANGERED SPECIES ACT
Author(s) -
McElroy Douglas M.,
Shoemaker Julie A.,
Douglas Michael E.
Publication year - 1997
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/1051-0761(1997)007[0958:dgragc]2.0.co;2
Subject(s) - sympatric speciation , endangered species , biology , taxon , discriminant function analysis , context (archaeology) , ecology , threatened species , genus , zoology , habitat , statistics , paleontology , mathematics
Several sympatric Colorado River basin cyprinid fishes of the genus Gila are federally protected, yet difficulty in identifying individuals to species has limited recovery efforts. Using five characters easily scored in the field, we quantified morphological variation in G. robusta and G. cypha from eight localities, comparing discriminatory power of these data to that of a previous multivariate truss analysis of the same specimens. Significant between‐species differences existed in four characters; three displayed patterns consistent with typological differences between species. Success of post hoc identification of specimens exceeded 70% for these three characters and increased to >82% by incorporating variables into a discriminant function. Nevertheless, potentially diagnostic features were relatively uncorrelated within individuals, and little congruence existed between different characters. Multivariate analyses clearly discriminated between sympatric species pairs despite considerable variation among localities. None of these analyses generated patterns of phenetic relationships approximating those suggested by the prior truss analysis. Whereas field characters are broadly diagnostic, classification of a significant number of individuals from any sample will likely remain problematic. We explore the implications of this problem within the context of the “producer’s vs. consumer’s risk” gambit, arguing that management strategies for Gila should accept the “producer’s risk” and define endangered species broadly. We also advocate use of the risk gambit for the general problem of evaluating taxonomic distinctness of endangered taxa.