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A Phenetic Study of the Suborder Lari (Aves) II. Phenograms, Discussion, and Conclusions

Gary D. Schnell
Systematic Zoology
Vol. 19, No. 3 (Sep., 1970), pp. 264-302
DOI: 10.2307/2412211
Stable URL: http://www.jstor.org/stable/2412211
Page Count: 39
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A Phenetic Study of the Suborder Lari (Aves) II. Phenograms, Discussion, and Conclusions
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Abstract

Phenetic affinities of the 93 species of skuas, gulls, terns, and skimmers in the suborder Lari (Charadriiformes: Aves) are described in detail. Methods and materials, as well as the results of principal components analyses, were given in Part I (Schnell, 1970). In this paper the 18 phenograms resulting from the use of different character suites (51 skeletal, 72 external, and both combined), transformations, and clustering methods are presented and analyzed. A classification of these resulting classifications (clustering basic similarity matrices or cophenetic values on the basis of correlations between classifications) is used to indicate which methods and character suites give similar results. The phenograms have also been compared with the classifications of Peters (1934) and Moynihan (1959) for the Lari. For analyses that included suites of highly correlated characters, correlation matrices were found to be relatively more robust than distances, being affected less by transformations or the use of different character suites. Also, when particularly divergent classifications occurred, this was partly due to divergent basic similarity matrices, but the clustering procedures added additional differences. The placing (or forcing) of OTUs into a hierarchical system of clusters (rather than just analyzing basic similarity matrices) resulted in an indication of relationships between OTUs more in accord with the opinions of previous workers, who also represented relationships in a hierarchy. The determination of the "best" overall phenetic classification, for use when one is in need of a single measure of similarity, is discussed and a set of guides is suggested to aid in the selection of such a classification. Some cladistic speculations are given and the relative positioning and stability of clusters is discussed. When analyzing data with high correlations between characters, the use of adaptive hierarchical clustering schemes that take into account possible trends in variation found within clusters is strongly recommended, and the value of multiple classifications to represent affinities is stressed. Principal component models, where no assumption is made that OTUs must fall into clusters, were particularly useful in representing relationships. The analysis of external characters resulted in phenograms that showed some similarity to those based on skeletal measurements. However, there were significant differences, indicating support for only a weak version of the nonspecificity hypothesis. A morphological description, using numerous characters, should be particularly valuable to current and future workers conducting various types of comparative studies (e.g., behavioral, ecological) within this taxon. It seems obvious that accurate and detailed morphometric description at the interspecific level is as important in the sound development of evolutionary theory as quantitative studies of intraspecific (e.g., geographic) variation.

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