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THE EVOLUTIONARY HISTORY OF THE GENUS RHINICHTHYS: HYPOTHESES AND TESTS
Abstract
The genus Rhinichthys is a group consisting of seven species of North American cyprinids, collectively distributed almost all over the continent. As conventionally described, this genus comprised two groups, the sub-genus Apocope consisting of the species R. falcatus and R. osculus and the cataractae group consisting of the species R. atratulus and the sister species R. evermanni and R. cataractae. These relationships were proposed on the basis of overall similarity, and without out-group comparison. The relationships within the genus have been redefined using cladistic methodology with rigorous out-group comparisons. Characters states present in the in-group and the out-group were plesiomorphic and inappropriate for the analysis. This was not a compatibility analysis in that all derived character states were used in the determination of the phylogeny. Eight species of cyprinids were used as the out-group. Fifty-four osteological and myological characters were considered initially. Of these, 11 characters were polarizable and 7 were used to generate a completely resolved cladogram. The remaining characters were 'discarded' since objective decisions regarding their homology could not be made. The monotypic genera Agosia and Tiaroga are considered invalid and are included within the genus Rhinichthys based upon a shared derived similarity. Within the genus the species R. falcatus and R. osculus are not considered sister-species. Consequently, the sub-genus Apocope is considered a paraphyletic group. The species R. cataractae and R. evermanni are considered sister species. The cataractae group is not real given that R. falcatus is the sister-species of R. cataractae + R. evermanni. Based on the systematic results obtained in this study and data available in the literature, the common assumption that hybridization studies could serve to evaluate the relative nearness of relationship between species was examined. This concept, proposed by Ernst Mayr (implicitly), and Clark Hubbs (more explicitly), has generally been accepted as one of the paradigms of Biology. It is shown that the ability to hybridize is plesiomorphic and hence unsuitable for the determination of the relationships between species.
Subject Area
Zoology
Recommended Citation
WOODMAN, DAVID A, "THE EVOLUTIONARY HISTORY OF THE GENUS RHINICHTHYS: HYPOTHESES AND TESTS" (1987). ETD collection for University of Nebraska-Lincoln. AAI8717269.
https://digitalcommons.unl.edu/dissertations/AAI8717269