Phenetic Taxonomy at the Species Level and Above

Summary Phenetic analyses are valuable at all taxonomic ranks. A review of work at higher ranks is presented, and certain difficulties are discussed: these are just as serious for traditional studies, though often glossed over. Difficulties include determination of homologies, incompleteness of data and shortage of constant characters. It is also necessary to employ similarity coefficients and cluster methods that are not too sensitive, respectively, to effects of gross size and numbers of OTU's. The number of OTU's required to represent a homogeneous cluster is apt to be underestimated: even with a simplified model of phenetic variation this number should be at least 10 and preferably 25 or more. Some newer developments in numerical analysis of phytogeny are briefly reviewed.